1,925 results on '"A. Comerón"'
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2. Geometrical and optical properties of cirrus clouds in Barcelona, Spain: analysis with the two-way transmittance method of 4 years of lidar measurements
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C. Gil-Díaz, M. Sicard, A. Comerón, D. C. F. dos Santos Oliveira, C. Muñoz-Porcar, A. Rodríguez-Gómez, J. R. Lewis, E. J. Welton, and S. Lolli
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Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
In this paper a statistical study of cirrus geometrical and optical properties based on 4 years of continuous ground-based lidar measurements with the Barcelona (Spain) Micro Pulse Lidar (MPL) is analysed. First, a review of the literature on the two-way transmittance method is presented. This method is a well-known lidar inversion method used to retrieve the optical properties of an aerosol–cloud layer between two molecular (i.e. aerosol and cloud-free) regions below and above, without the need to make any a priori assumptions about their optical and/or microphysical properties. Second, a simple mathematical expression of the two-way transmittance method is proposed for both ground-based and spaceborne lidar systems. This approach of the method allows the retrieval of the cloud optical depth, the cloud column lidar ratio and the vertical profile of the cloud backscatter coefficient. The method is illustrated for a cirrus cloud using measurements from the ground-based MPL and from the spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Third, the database is then filtered with a cirrus identification criterion based on (and compared to) the literature using only lidar and radiosonde data. During the period from November 2018 to September 2022, 367 high-altitude cirrus clouds were identified at 00:00 and 12:00 UTC, of which 203 were successfully inverted with the two-way transmittance method. The statistical results of these 203 high-altitude cirrus clouds show that the cloud thickness is 1.8 ± 1.1 km, the mid-cloud temperature is −51 ± 8 ∘C and the linear cloud depolarization ratio is 0.32 ± 0.13. The application of the transmittance method yields an average cloud optical depth (COD) of 0.36 ± 0.45 and a mean effective column lidar ratio of 30 ± 19 sr. Statistical results of the errors associated with the two-way transmittance method retrievals are also provided. The highest occurrence of cirrus is observed in spring and the majority of cirrus clouds (48 %) are visible (0.03 < COD < 0.3), followed by opaque (COD > 0.3) with a percentage of 38 %. Together with results from other sites, possible latitudinal dependencies have been analysed together with correlations between cirrus cloud properties. For example, we noted that in Barcelona the COD correlates positively with the cloud base temperature, effective column lidar ratio and linear cloud depolarization ratio and negatively with the cloud base height.
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- 2024
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3. Combined sun-photometer–lidar inversion: lessons learned during the EARLINET/ACTRIS COVID-19 campaign
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A. Tsekeri, A. Gialitaki, M. Di Paolantonio, D. Dionisi, G. L. Liberti, A. Fernandes, A. Szkop, A. Pietruczuk, D. Pérez-Ramírez, M. J. Granados Muñoz, J. L. Guerrero-Rascado, L. Alados-Arboledas, D. Bermejo Pantaleón, J. A. Bravo-Aranda, A. Kampouri, E. Marinou, V. Amiridis, M. Sicard, A. Comerón, C. Muñoz-Porcar, A. Rodríguez-Gómez, S. Romano, M. R. Perrone, X. Shang, M. Komppula, R.-E. Mamouri, A. Nisantzi, D. Hadjimitsis, F. Navas-Guzmán, A. Haefele, D. Szczepanik, A. Tomczak, I. S. Stachlewska, L. Belegante, D. Nicolae, K. A. Voudouri, D. Balis, A. A. Floutsi, H. Baars, L. Miladi, N. Pascal, O. Dubovik, and A. Lopatin
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Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
The European Aerosol Research Lidar Network (EARLINET), part of the Aerosols, Clouds and Trace gases Research Infrastructure (ACTRIS), organized an intensive observational campaign in May 2020, with the objective of monitoring the atmospheric state over Europe during the COVID-19 lockdown and relaxation period. Besides the standard operational processing of the lidar data in EARLINET, for seven EARLINET sites having collocated sun-photometric observations in the Aerosol Robotic Network (AERONET), a network exercise was held in order to derive profiles of the concentration and effective column size distributions of the aerosols in the atmosphere, by applying the GRASP/GARRLiC (from Generalized Aerosol Retrieval from Radiometer and Lidar Combined data – GARRLiC – part of the Generalized Retrieval of Atmosphere and Surface Properties – GRASP) inversion algorithm. The objective of this network exercise was to explore the possibility of identifying the anthropogenic component and of monitoring its spatial and temporal characteristics in the COVID-19 lockdown and relaxation period. While the number of cases is far from being statistically significant so as to provide a conclusive description of the atmospheric aerosols over Europe during this period, this network exercise was fundamental to deriving a common methodology for applying GRASP/GARRLiC to a network of instruments with different characteristics. The limits of the approach are discussed, in particular the missing information close to the ground in the lidar measurements due to the instrument geometry and the sensitivity of the GRASP/GARRLiC retrieval to the settings used, especially for cases with low aerosol optical depth (AOD) like the ones we show here. We found that this sensitivity is well-characterized in the GRASP/GARRLiC products, since it is included in their retrieval uncertainties.
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- 2023
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4. An explicit formulation for the retrieval of the overlap function in an elastic and Raman aerosol lidar
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A. Comerón, C. Muñoz-Porcar, A. Rodríguez-Gómez, M. Sicard, F. Dios, C. Gil-Díaz, D. C. F. dos Santos Oliveira, and F. Rocadenbosch
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Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
We derive an explicit (i.e., non-iterative) formula for the retrieval of the overlap function in an aerosol lidar with both elastic and Raman N2 and/or O2 channels used for independent measurements of aerosol backscatter and extinction coefficients. The formula requires only the measured, range-corrected elastic and the corresponding Raman signals, plus an assumed lidar ratio. We assess the influence of the lidar ratio error in the overlap function retrieval and present retrieval examples.
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- 2023
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5. Vertical characterization of fine and coarse dust particles during an intense Saharan dust outbreak over the Iberian Peninsula in springtime 2021
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M. Á. López-Cayuela, C. Córdoba-Jabonero, D. Bermejo-Pantaleón, M. Sicard, V. Salgueiro, F. Molero, C. V. Carvajal-Pérez, M. J. Granados-Muñoz, A. Comerón, F. T. Couto, R. Barragán, M.-P. Zorzano, J. A. Bravo-Aranda, C. Muñoz-Porcar, M. J. Costa, B. Artíñano, A. Rodríguez-Gómez, D. Bortoli, M. Pujadas, J. Abril-Gago, L. Alados-Arboledas, and J. L. Guerrero-Rascado
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
An intense and long-lasting Saharan dust outbreak crossed the Iberian Peninsula (IP) from the southwest (SW) to the northeast (NE) from 25 March until 7 April 2021. This work aims to assess the optical and mass contribution of both fine and coarse dust particles along their transport. Five Iberian lidar stations were monitoring the transport and evolution of the Saharan dust particles, i.e. El Arenosillo/Huelva, Granada, Torrejón/Madrid and Barcelona in Spain, and Évora in Portugal. The particular meteorological conditions determined the aerosol scenario along the overall dust event, differing in the first part of the event (25–31 March), in which the strongest dust incidence occurred on 29–31 March at the south and central stations and 1 April at Barcelona, from the second one (1–7 April). The use of the two-step POLIPHON algorithm showed the relevance of using polarized lidar measurements for separating the aerosol properties of dust fine and coarse particles as an added value. Both the fine dust (Df) and coarse dust (Dc) components of the total particle backscatter coefficient (total dust, DD = Dc + Df) were separately derived. The dust plume was well-mixed with height and no significant differences were found in the vertical structure of both the Dc and Df particle backscatter coefficients. From the beginning of the dust outbreak until 1 April, the vertical Df / DD mass ratio was nearly constant in time at each station and also in altitude with values of ∼ 10 %. Moreover, the mean dust optical depth at 532 nm was decreasing along that dust pathway, reporting values from SW to NE stations of 0.34 at El Arenosillo/Huelva, 0.28 at Granada, 0.20 at Évora, 0.28 at Torrejón/Madrid, and 0.14 at Barcelona, although its Df / DD ratio remained almost constant (28 %–30 %). A similar pattern was found for the total dust mass loading and its Df / DD ratio, i.e. mostly decreasing mean mass values were reported, being constant in its Df / DD ratio (∼ 10 %) along the SW–NE dust pathway. In addition, the episode-mean centre-of-mass height increased with latitude overall, showing a high variability, being greater than 0.5 km at the southern sites (El Arenosillo/Huelva, Granada, Évora) and ∼ 1.0 km at Torrejón/Madrid and Barcelona. However, despite the relatively high intensity of the dust intrusion, the expected ageing of the dust particles was hardly observed, by taking into account the minor changes found in the contribution and properties of the coarse and fine dust particles. This is on the basis that the IP is relatively close to the Saharan dust sources and then, under certain dust transport conditions, any potential ageing processes in the dust particles remained unappreciated. The following must be highlighted: the different relative contribution of the fine dust particles to the total dust found for their optical properties (∼ 30 %) associated with the radiative effect of dust, with respect to that for the mass features (∼ 10 %) linked to air quality issues, along the overall dust event by crossing the IP.
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- 2023
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6. Measurement report: Spectral and statistical analysis of aerosol hygroscopic growth from multi-wavelength lidar measurements in Barcelona, Spain
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M. Sicard, D. C. Fortunato dos Santos Oliveira, C. Muñoz-Porcar, C. Gil-Díaz, A. Comerón, A. Rodríguez-Gómez, and F. Dios Otín
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
This paper presents the estimation of the hygroscopic growth parameter of atmospheric aerosols retrieved with a multi-wavelength lidar, a micro-pulse lidar (MPL) and daily radiosoundings in the coastal region of Barcelona, Spain. The hygroscopic growth parameter, γ, parameterizes the magnitude of the scattering enhancement in terms of the backscatter coefficient following Hänel parameterization. After searching for time-colocated lidar and radiosounding measurements (performed twice a day, all year round at 00:00 and 12:00 UTC), a strict criterion-based procedure (limiting the variations of magnitudes such as water vapor mixing ratio (WMVR), potential temperature, wind speed and direction) is applied to select only cases of aerosol hygroscopic growth. A spectral analysis (at the wavelengths of 355, 532 and 1064 nm) is performed with the multi-wavelength lidar, and a climatological one, at the wavelength of 532 nm, with the database of both lidars. The spectral analysis shows that below 2 km the regime of local pollution and sea salt γ decreases with increasing wavelengths. Since the 355 nm wavelength is sensitive to smaller aerosols, this behavior could indicate slightly more hygroscopic aerosols present at smaller size ranges. Above 2 km (the regime of regional pollution and residual sea salt) the values of γ at 532 nm are nearly the same as those below 2 km, and its spectral behavior is flat. This analysis and others from the literature are put together in a table presenting, for the first time, a spectral analysis of the hygroscopic growth parameter of a large variety of atmospheric aerosol hygroscopicities ranging from low (pure mineral dust, γ γ > 1.0) hygroscopicity. The climatological analysis shows that, at 532 nm, γ is rather constant all year round and has a large monthly standard deviation, suggesting the presence of aerosols with different hygroscopic properties all year round. The annual γ is 0.55 ± 0.23. The height of the layer where hygroscopic growth was calculated shows an annual cycle with a maximum in summer and a minimum in winter. Former works describing the presence of recirculation layers of pollutants injected at various heights above the planetary boundary layer (PBL) may explain why γ, unlike the height of the layer where hygroscopic growth was calculated, is not season-dependent. The subcategorization of the whole database into No cloud and Below-cloud cases reveals a large difference of γ in autumn between both categories (0.71 and 0.33, respectively), possibly attributed to a depletion of inorganics at the point of activation into cloud condensation nuclei (CCN) in the Below-cloud cases. Our work calls for more in situ measurements to synergetically complete such studies based on remote sensing.
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- 2022
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7. Aerosol radiative impact during the summer 2019 heatwave produced partly by an inter-continental Saharan dust outbreak – Part 2: Long-wave and net dust direct radiative effect
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M. Sicard, C. Córdoba-Jabonero, M.-Á. López-Cayuela, A. Ansmann, A. Comerón, M.-P. Zorzano, A. Rodríguez-Gómez, and C. Muñoz-Porcar
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
This paper is the companion paper of Córdoba-Jabonero et al. (2021). It deals with the estimation of the long-wave (LW) and net dust direct radiative effect (DRE) during the dust episode that occurred between 23 and 30 June 2019 and was paired with a mega-heatwave. The analysis is performed at two European sites where polarized micro-pulse lidars ran continuously to retrieve the vertical distribution of the dust optical properties: Barcelona, Spain, 23–30 June, and Leipzig, Germany, 29–30 June. The radiative effect is computed with the GAME (global atmospheric model) radiative transfer model separately for the fine- and coarse-mode dust. The instantaneous and daily radiative effect and radiative efficiency (DREff) are provided for the fine-mode, coarse-mode and total dust at the surface, top of the atmosphere (TOA) and in the atmosphere. The fine-mode daily LW DRE is low (< 6 % of the short-wave (SW) component), which makes the coarse-mode LW DRE the main modulator of the total net dust DRE. The coarse-mode LW DRE starts exceeding (in absolute values) the SW component in the middle of the episode, which produces positive coarse-mode net DRE at both the surface and TOA. Such an unusual tendency is attributed to increasing coarse-mode size and surface temperature throughout the episode. This has the effect of reducing the SW cooling in Barcelona up to the point of reaching total net positive dust DRE (+0.9 W m−2) on one occasion at the surface and quasi-neutral (−0.6 W m−2) at TOA. When adding the LW component, the total dust SW radiative efficiency is reduced by a factor of 1.6 at both surface (on average over the episode the total dust net DREff is −54.1 W m−2 τ−1) and TOA (−37.3 W m−2 τ−1). A sensitivity study performed on the surface temperature and the air temperature in the dust layer, both linked to the heatwave and upon which the LW DRE strongly depends, shows that the heatwave contributed to reducing the dust net cooling effect at the surface and that it had nearly no effect at TOA. Its subsequent effect was thus to reduce the heating of the atmosphere produced by the dust particles.
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- 2022
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8. Statistical validation of Aeolus L2A particle backscatter coefficient retrievals over ACTRIS/EARLINET stations on the Iberian Peninsula
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J. Abril-Gago, J. L. Guerrero-Rascado, M. J. Costa, J. A. Bravo-Aranda, M. Sicard, D. Bermejo-Pantaleón, D. Bortoli, M. J. Granados-Muñoz, A. Rodríguez-Gómez, C. Muñoz-Porcar, A. Comerón, P. Ortiz-Amezcua, V. Salgueiro, M. M. Jiménez-Martín, and L. Alados-Arboledas
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The Global Observing System (GOS) has encountered some limitations due to a lack of worldwide real-time wind measurements. In this context, the European Space Agency (ESA) has developed the Aeolus satellite mission, based on the ALADIN (Atmospheric Laser Doppler Instrument) Doppler wind lidar; this mission aims to obtain near-real-time wind retrievals at the global scale. As spin-off products, the instrument retrieves aerosol optical properties such as particle backscatter and extinction coefficients. In this work, a validation of Aeolus reprocessed (baseline 10) co-polar backscatter coefficients (βAeoluspart) is presented through an intercomparison with analogous ground-based measurements taken at the ACTRIS (Aerosols, Clouds and Trace gases Research InfraStructure Network)/EARLINET (European Aerosol Research Lidar Network) stations of Granada (Spain), Évora (Portugal) and Barcelona (Spain) over the period from July 2019 until October 2020. Case studies are first presented, followed by a statistical analysis. The stations are located in a hot spot between Africa and the rest of Europe, which guarantees a variety of aerosol types, from mineral dust layers to continental/anthropogenic aerosol, and allows us to test Aeolus performance under different scenarios. The so called Aeolus-like profiles (βAeoluslike,355part) are obtained from total particle backscatter coefficient and linear particle depolarization ratio (δlinearpart) profiles at 355 and 532 nm measured from the surface, through a thorough bibliographic review of dual-polarization measurements for relevant aerosol types. Finally, the study proposes a relation for the spectral conversion of δlinearpart, which is implemented in the Aeolus-like profile calculation. The statistical results show the ability of the satellite to detect and characterize significant aerosol layers under cloud-free conditions, along with the surface effect on the lowermost measurements, which causes the satellite to largely overestimate co-polar backscatter coefficients. Finally, the Aeolus standard correct algorithm middle bin (SCAmb) shows a better agreement with ground-based measurements than the standard correct algorithm (SCA), which tends to retrieve negative and meaningless coefficients in the clear troposphere. The implementation of Aeolus quality flags entails a vast reduction in the number of measurements available for comparison, which affects the statistical significance of the results.
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- 2022
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9. Measurement report: Characterization of the vertical distribution of airborne Pinus pollen in the atmosphere with lidar-derived profiles – a modeling case study in the region of Barcelona, NE Spain
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M. Sicard, O. Jorba, J. J. Ho, R. Izquierdo, C. De Linares, M. Alarcón, A. Comerón, and J. Belmonte
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
This paper investigates the mechanisms involved in the dispersion, structure, and mixing in the vertical column of atmospheric pollen. The methodology used employs observations of pollen concentration obtained from Hirst samplers (we will refer to this as surface pollen) and vertical distribution (polarization-sensitive lidar), as well as nested numerical simulations with an atmospheric transport model and a simplified pollen module developed especially for this study. The study focuses on the predominant pollen type, Pinus, of the intense pollination event which occurred in the region of Barcelona, Catalonia, NE Spain, during 27–31 March 2015. First, conversion formulas are expressed to convert lidar-derived total backscatter coefficient and model-derived mass concentration into pollen grains concentration, the magnitude measured at the surface by means of aerobiological methods, and, for the first time ever, a relationship between optical and mass properties of atmospheric pollen through the estimation of the so-called specific extinction cross section is quantified in ambient conditions. Second, the model horizontal representativeness is assessed through a comparison between nested pollen simulations at 9, 3, and 1 km horizontal resolution and observed meteorological and aerobiological variables at seven sites around Catalonia. Finally, hourly observations of surface and column concentration in Barcelona are analyzed with the different numerical simulations at increasing horizontal resolution and varying sedimentation/deposition parameters. We find that the 9 or 3 km simulations are less sensitive to the meteorology errors; hence, they should be preferred for specific forecasting applications. The largest discrepancies between measured surface (Hirst) and column (lidar) concentrations occur during nighttime, where only residual pollen is detected in the column, whereas it is also present at the surface. The main reason is related to the lidar characteristics which have the lowest useful range bin at ∼ 225 m, above the usually very thin nocturnal stable boundary layer. At the hour of the day of maximum insolation, the pollen layer does not extend up to the top of the planetary boundary layer, according to the observations (lidar), probably because of gravity effects; however, the model simulates the pollen plume up to the top of the planetary boundary layer, resulting in an overestimation of the pollen load. Besides the large size and weight of Pinus grains, sedimentation/deposition processes have only a limited impact on the model vertical concentration in contrast to the emission processes. For further modeling research, emphasis is put on the accurate knowledge of plant/tree spatial distribution, density, and type, as well as on the establishment of reliable phenology functions.
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- 2021
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10. Gas-Phase metallicity for the Seyfert galaxy NGC 7130
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Amiri, Amirnezam, Knapen, Johan H., Comerón, Sébastien, Marconi, Alessandro, and Lehmer, Bret. D.
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Astrophysics - Astrophysics of Galaxies - Abstract
Metallicity measurements in galaxies can give valuable clues about galaxy evolution. One of the mechanisms postulated for metallicity redistribution in galaxies is gas flows induced by AGN, but the details of this process remain elusive. We report the discovery of a positive radial gradient in the gas-phase metallicity of the narrow line region of the Seyfert 2 galaxy NGC 7130, which is not found when considering the star-forming components in the galaxy disk. To determine gas-phase metallicities for each kinematic component, we use both active galactic nuclei (AGN) and star-forming (SF) strong-line abundance relations, as well as BPT diagnostic diagrams. These relations involve sensitive strong emission lines, namely [OIII]5007, [NII]6584, H$\alpha$, H$\beta$, [SII]6716, and [SII]6731, observed with the adaptive-optics-assisted mode of the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT). The presence of a positive radial metallicity gradient only in the AGN ionized component suggests that metals may be transported from central areas to its purlieus by AGN activity., Comment: Accepted for publication in Astronomy & Astrophysics (A&A)
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- 2024
11. Aerosol radiative impact during the summer 2019 heatwave produced partly by an inter-continental Saharan dust outbreak – Part 1: Short-wave dust direct radiative effect
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C. Córdoba-Jabonero, M. Sicard, M.-Á. López-Cayuela, A. Ansmann, A. Comerón, M.-P. Zorzano, A. Rodríguez-Gómez, and C. Muñoz-Porcar
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The short-wave (SW) direct radiative effect (DRE) during the summer 2019 heatwave produced partly by a moderate, long-lasting Saharan dust outbreak over Europe is analysed in this study. Two European sites (periods) are considered: Barcelona, Spain (23–30 June), and Leipzig, Germany (29 and 30 June), 1350 km apart from each other. Major data are obtained from AERONET and polarised Micro-Pulse Lidar (P-MPL) observations. Modelling is used to describe the different dust pathways, as observed at both sites. The coarse dust (Dc) and fine dust (Df) components (with total dust, DD = Dc + Df) are identified in the profiles of the total particle backscatter coefficient using the POLIPHON (POlarisation LIdar PHOtometer Networking) method in synergy with P-MPL measurements. This information is used to calculate the relative mass loading and the centre-of-mass height, as well as the contribution of each dust mode to the total dust DRE. Several aspects of the ageing of dust are put forward. The mean dust optical depth and its Df/DD ratios are, respectively, 0.153 and 24 % in Barcelona and 0.039 and 38 % in Leipzig; this Df increase in Leipzig is attributed to a longer dust transport path in comparison to Barcelona. The dust produced a cooling effect on the surface with a mean daily DRE of −9.1 and −2.5 W m−2, respectively, in Barcelona and Leipzig, but the Df/DD DRE ratio is larger for Leipzig (52 %) than for Barcelona (37 %). Cooling is also observed at the top of the atmosphere (TOA), although less intense than on the surface. However, the Df/DD DRE ratio at the TOA is even higher (45 % and 60 %, respectively, in Barcelona and Leipzig) than on the surface. Despite the predominance of Dc particles under dusty conditions, the SW radiative impact of Df particles can be comparable to, even higher than, that induced by the Dc ones. In particular, the Df/DD DRE ratio in Barcelona increases by +2.4 % d−1 (surface) and +2.9 % d−1 (TOA) during the dusty period. This study is completed by a second paper about the long-wave and net radiative effects. These results are especially relevant for the next ESA EarthCARE mission (planned in 2022) as it is devoted to aerosol–cloud–radiation interaction research.
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- 2021
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12. Star formation in the high-extinction Planck cold clump PGCC G120.69+2.66
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Djupvik, Anlaug Amanda, Yun, João L., and Comerón, Fernando
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics - Abstract
We investigate the star formation occurring in the Planck Galactic cold clump PGCC 120.69+2.66. Near-infrared JHKs images and K-band spectroscopy obtained with NOTCam at the Nordic Optical Telescope complemented with archive data are used to study the stellar content. In addition, millimetre line CO and CS spectra were obtained with the Onsala 20 m telescope, and sub-millimetre continuum SCUBA archive data are used to characterise the host molecular cloud. We identify a molecular cloud core traced by CO and CS emission at a distance of 1.1 kpc. In the region studied, we identify 5 submm continuum cores. Embedded in and around these dense submm cores, we find 38 young stellar objects, classified as 9 Class I, 8 Class II, and 21 near-IR excess or variability sources, accompanied by bipolar nebulosities and signs of protostellar jets. Furthermore, a very bright and reddened source is found towards this molecular cloud core. Even though its location appears to suggest its association to the star formation region, its infrared spectral type is compatible with a red supergiant, hidden behind 36 mag of visual extinction., Comment: 12 pages, 9 figures
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- 2024
13. Assessing the accuracy of the star formation rate measurements by direct star count in molecular clouds
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Dib, Sami, Zhou, Jian Wen, Comerón, Sébastien, Garduño, Luis E., Kravtsov, Valery V., Clark, Paul C., Li, Guang-Xing, Lara-López, Maritza A., Liu, Tie, Shadmehri, Mohsen, and Doughty, James R.
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics - Abstract
Star formation estimates based on the counting of YSOs is commonly applied to nearby star-forming regions in the Galaxy. With this method, the SFRs are measured using the counts of YSOs in a particular protostellar Class, a typical protostellar mass, and the lifetime associated with this Class. However, the assumptions underlying the validity of the method such as that of a constant star formation history (SFH) and whether the method is valid for all protostellar Classes has never been fully tested. In this work, we use Monte Carlo models to test the validity of the method. We build synthetic clusters in which stars form at times that are randomly drawn from a specified SFH. The latter is either constant or time-dependent with a burst like behavior. The masses of the protostars are randomly drawn from an IMF which can be either similar to that of the Milky Way field or be variable . For each star in every cluster, the lifetimes associated with the different protostellar classes are also randomly drawn from Gaussian distribution functions centered around their most likely value as suggested by the observations. We find that only the SFR derived using the Class 0 population can reproduce the true SFR at all epochs, and this is true irrespective of the shape of the SFH. For a constant SFH, the SFR derived using the more evolved populations of protostars (Classes I, F, II, and III) reproduce the real SFR only at later epochs which correspond to epochs at which their numbers have reached a steady state. For a time-dependent burst-like SFH, all SFR estimates based on the number counts of the evolved populations fail to reproduce the true SFR. We also show how the offsets between Class I and Class II based SFRs and the true SFR plotted as a function of the number ratios of Class I and Class II versus Class III YSOs can be used in order to constrain the SFH of observed molecular clouds., Comment: Submitted. Comments are welcome
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- 2024
14. First detection of the [CII] 158 micron line in the intermediate-velocity cloud Draco
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Schneider, N., Ossenkopf-Okada, V., Keilmann, E., Roellig, M., Kabanovic, S., Bonne, L., Csengeri, T., Klein, B., Simon, R., and Comeron, F.
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Astrophysics - Astrophysics of Galaxies - Abstract
High-latitude intermediate-velocity clouds (IVCs) are part of the Milky Way's HI halo and originate from either a galactic fountain process or extragalactic gas infall. They are partly molecular and can most of the time be identified in CO. Some of these regions also exhibit high-velocity cloud (HVC) gas, which is mostly atomic, and gas at local velocities (LVCs), which is partly atomic and partly molecular. We conducted a study on the IVCs Draco and Spider, both were exposed to a very weak UV field, using the receiver upGREAT on SOFIA. The 158 micron line of ionized carbon (CII) was observed, and the results are as follows: In Draco, the CII line was detected at intermediate velocities (but not at local or high velocities) in four out of five positions. No CII emission was found at any velocity in the two observed positions in Spider. To understand the excitation conditions of the gas in Draco, we analyzed complementary CO and HI data as well as dust column density and temperature maps from Herschel. The observed CII intensities suggest the presence of shocks in Draco that heat the gas and subsequently emit in the CII cooling line. These shocks are likely caused by the fast cloud's motion toward the Galactic plane that is accompanied by collisions between HI clouds. The nondetection of CII in the Spider IVC and LVC as well as in other low-density clouds at local velocities that we present in this paper (Polaris and Musca) supports the idea that highly dynamic processes are necessary for CII excitation in UV-faint low-density regions., Comment: in press Astronomy and Astrophysics
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- 2024
15. An EARLINET early warning system for atmospheric aerosol aviation hazards
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N. Papagiannopoulos, G. D'Amico, A. Gialitaki, N. Ajtai, L. Alados-Arboledas, A. Amodeo, V. Amiridis, H. Baars, D. Balis, I. Binietoglou, A. Comerón, D. Dionisi, A. Falconieri, P. Fréville, A. Kampouri, I. Mattis, Z. Mijić, F. Molero, A. Papayannis, G. Pappalardo, A. Rodríguez-Gómez, S. Solomos, and L. Mona
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
A stand-alone lidar-based method for detecting airborne hazards for aviation in near real time (NRT) is presented. A polarization lidar allows for the identification of irregular-shaped particles such as volcanic dust and desert dust. The Single Calculus Chain (SCC) of the European Aerosol Research Lidar Network (EARLINET) delivers high-resolution preprocessed data: the calibrated total attenuated backscatter and the calibrated volume linear depolarization ratio time series. From these calibrated lidar signals, the particle backscatter coefficient and the particle depolarization ratio can be derived in temporally high resolution and thus provide the basis of the NRT early warning system (EWS). In particular, an iterative method for the retrieval of the particle backscatter is implemented. This improved capability was designed as a pilot that will produce alerts for imminent threats for aviation. The method is applied to data during two diverse aerosol scenarios: first, a record breaking desert dust intrusion in March 2018 over Finokalia, Greece, and, second, an intrusion of volcanic particles originating from Mount Etna, Italy, in June 2019 over Antikythera, Greece. Additionally, a devoted observational period including several EARLINET lidar systems demonstrates the network's preparedness to offer insight into natural hazards that affect the aviation sector.
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- 2020
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16. The unprecedented 2017–2018 stratospheric smoke event: decay phase and aerosol properties observed with the EARLINET
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H. Baars, A. Ansmann, K. Ohneiser, M. Haarig, R. Engelmann, D. Althausen, I. Hanssen, M. Gausa, A. Pietruczuk, A. Szkop, I. S. Stachlewska, D. Wang, J. Reichardt, A. Skupin, I. Mattis, T. Trickl, H. Vogelmann, F. Navas-Guzmán, A. Haefele, K. Acheson, A. A. Ruth, B. Tatarov, D. Müller, Q. Hu, T. Podvin, P. Goloub, I. Veselovskii, C. Pietras, M. Haeffelin, P. Fréville, M. Sicard, A. Comerón, A. J. Fernández García, F. Molero Menéndez, C. Córdoba-Jabonero, J. L. Guerrero-Rascado, L. Alados-Arboledas, D. Bortoli, M. J. Costa, D. Dionisi, G. L. Liberti, X. Wang, A. Sannino, N. Papagiannopoulos, A. Boselli, L. Mona, G. D'Amico, S. Romano, M. R. Perrone, L. Belegante, D. Nicolae, I. Grigorov, A. Gialitaki, V. Amiridis, O. Soupiona, A. Papayannis, R.-E. Mamouri, A. Nisantzi, B. Heese, J. Hofer, Y. Y. Schechner, U. Wandinger, and G. Pappalardo
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EARLINET) from August 2017 to January 2018 are presented. The decay phase of an unprecedented, record-breaking stratospheric perturbation caused by wildfire smoke is reported and discussed in terms of geometrical, optical, and microphysical aerosol properties. Enormous amounts of smoke were injected into the upper troposphere and lower stratosphere over fire areas in western Canada on 12 August 2017 during strong thunderstorm–pyrocumulonimbus activity. The stratospheric fire plumes spread over the entire Northern Hemisphere in the following weeks and months. Twenty-eight European lidar stations from northern Norway to southern Portugal and the eastern Mediterranean monitored the strong stratospheric perturbation on a continental scale. The main smoke layer (over central, western, southern, and eastern Europe) was found at heights between 15 and 20 km since September 2017 (about 2 weeks after entering the stratosphere). Thin layers of smoke were detected at heights of up to 22–23 km. The stratospheric aerosol optical thickness at 532 nm decreased from values > 0.25 on 21–23 August 2017 to 0.005–0.03 until 5–10 September and was mainly 0.003–0.004 from October to December 2017 and thus was still significantly above the stratospheric background (0.001–0.002). Stratospheric particle extinction coefficients (532 nm) were as high as 50–200 Mm−1 until the beginning of September and on the order of 1 Mm−1 (0.5–5 Mm−1) from October 2017 until the end of January 2018. The corresponding layer mean particle mass concentration was on the order of 0.05–0.5 µg m−3 over these months. Soot particles (light-absorbing carbonaceous particles) are efficient ice-nucleating particles (INPs) at upper tropospheric (cirrus) temperatures and available to influence cirrus formation when entering the tropopause from above. We estimated INP concentrations of 50–500 L−1 until the first days in September and afterwards 5–50 L−1 until the end of the year 2017 in the lower stratosphere for typical cirrus formation temperatures of −55 ∘C and an ice supersaturation level of 1.15. The measured profiles of the particle linear depolarization ratio indicated a predominance of nonspherical smoke particles. The 532 nm depolarization ratio decreased slowly with time in the main smoke layer from values of 0.15–0.25 (August–September) to values of 0.05–0.10 (October–November) and < 0.05 (December–January). The decrease of the depolarization ratio is consistent with aging of the smoke particles, growing of a coating around the solid black carbon core (aggregates), and thus change of the shape towards a spherical form. We found ascending aerosol layer features over the most southern European stations, especially over the eastern Mediterranean at 32–35∘ N, that ascended from heights of about 18–19 to 22–23 km from the beginning of October to the beginning of December 2017 (about 2 km per month). We discuss several transport and lifting mechanisms that may have had an impact on the found aerosol layering structures.
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- 2019
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17. An automatic observation-based aerosol typing method for EARLINET
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N. Papagiannopoulos, L. Mona, A. Amodeo, G. D'Amico, P. Gumà Claramunt, G. Pappalardo, L. Alados-Arboledas, J. L. Guerrero-Rascado, V. Amiridis, P. Kokkalis, A. Apituley, H. Baars, A. Schwarz, U. Wandinger, I. Binietoglou, D. Nicolae, D. Bortoli, A. Comerón, A. Rodríguez-Gómez, M. Sicard, A. Papayannis, and M. Wiegner
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
We present an automatic aerosol classification method based solely on the European Aerosol Research Lidar Network (EARLINET) intensive optical parameters with the aim of building a network-wide classification tool that could provide near-real-time aerosol typing information. The presented method depends on a supervised learning technique and makes use of the Mahalanobis distance function that relates each unclassified measurement to a predefined aerosol type. As a first step (training phase), a reference dataset is set up consisting of already classified EARLINET data. Using this dataset, we defined 8 aerosol classes: clean continental, polluted continental, dust, mixed dust, polluted dust, mixed marine, smoke, and volcanic ash. The effect of the number of aerosol classes has been explored, as well as the optimal set of intensive parameters to separate different aerosol types. Furthermore, the algorithm is trained with literature particle linear depolarization ratio values. As a second step (testing phase), we apply the method to an already classified EARLINET dataset and analyze the results of the comparison to this classified dataset. The predictive accuracy of the automatic classification varies between 59 % (minimum) and 90 % (maximum) from 8 to 4 aerosol classes, respectively, when evaluated against pre-classified EARLINET lidar. This indicates the potential use of the automatic classification to all network lidar data. Furthermore, the training of the algorithm with particle linear depolarization values found in the literature further improves the accuracy with values for all the aerosol classes around 80 %. Additionally, the algorithm has proven to be highly versatile as it adapts to changes in the size of the training dataset and the number of aerosol classes and classifying parameters. Finally, the low computational time and demand for resources make the algorithm extremely suitable for the implementation within the single calculus chain (SCC), the EARLINET centralized processing suite.
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- 2018
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18. Constraining the top-light initial mass function in the extended ultraviolet disk of M83
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Rautio, R. P. V., Watkins, A. E., Salo, H., Venhola, A., Knapen, J. H., and Comerón, S.
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Astrophysics - Astrophysics of Galaxies - Abstract
The universality or non-universality of the initial mass function (IMF) has significant implications for determining star formation rates and star formation histories from photometric properties of stellar populations. We reexamine whether the IMF is deficient in high-mass stars (top-light) in the low-density environment of the outer disk of M83 and constrain the shape of the IMF therein. Using archival Galaxy Evolution Explorer (GALEX) far ultraviolet (FUV) and near ultraviolet (NUV) data and new deep OmegaCAM narrowband H$\alpha$ imaging, we constructed a catalog of FUV-selected objects in the outer disk of M83. We counted H$\alpha$-bright clusters and clusters that are blue in FUV$-$NUV in the catalog, measured the maximum flux ratio $F_{\mathrm{H}\alpha}/f_{\lambda \mathrm{FUV}}$ among the clusters, and measured the total flux ratio $\Sigma F_{\mathrm{H}\alpha}/\Sigma f_{\lambda \mathrm{FUV}}$ over the catalog. We then compared these measurements to predictions from stellar population synthesis models made with a standard Salpeter IMF, truncated IMFs, and steep IMFs. We also investigated the effect of varying the assumed internal extinction on our results. We are not able to reproduce our observations with models using the standard Salpeter IMF or the truncated IMFs. It is only when assuming an average internal extinction of $0.10 < A_{\mathrm{V}} < 0.15$ in the outer disk stellar clusters that models with steep IMFs ($\alpha > 3.1$) simultaneously reproduce the observed cluster counts, the maximum observed $F_{\mathrm{H}\alpha}/f_{\lambda \mathrm{FUV}}$, and the observed $\Sigma F_{\mathrm{H}\alpha}/\Sigma f_{\lambda \mathrm{FUV}}$. Our results support a non-universal IMF that is deficient in high-mass stars in low-density environments., Comment: 18 pages, 15 figures, accepted to Astronomy & Astrophysics
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- 2023
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19. The Tully-Fisher relation and the Bosma effect
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Labini, Francesco Sylos, De Marzo, Giordano, Straccamore, Matteo, and Comerón, Sébastien
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Astrophysics - Astrophysics of Galaxies - Abstract
We show that the rotation curves of 16 nearby disc galaxies in the THINGS sample and the Milky Way can be described by the NFW halo model and by the Bosma effect at approximately the same level of accuracy. The latter effect suggests that the behavior of the rotation curve at large radii is determined by the rescaled gas component and thus that dark matter and gas distributions are tightly correlated. By focusing on galaxies with exponential decay in their gas surface density, we can normalize their rotation curves to match the exponential thin disc model at large enough radii. This normalization assumes that the galaxy mass is estimated consistently within this model, assuming a thin disc structure. We show that this rescaling allows us to derive a new version of the Tully-Fisher (TF) relation, the Bosma TF relation that nicely fit the data. In the framework of this model, the connection between the Bosma Tully-Fisher (TF) relation and the baryonic TF relation can be established by considering an additional empirical relation between the baryonic mass and the total mass of the disc, as measured in the data., Comment: 21 pages, 12 figures. Monthly Notices of the Royal Astronomical Society, in the press
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- 2023
20. Roman Early-Definition Astrophysics Survey Opportunity: Galactic Roman Infrared Plane Survey (GRIPS)
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Paladini, Roberta, Zucker, Catherine, Benjamin, Robert, Nataf, David, Minniti, Dante, Zasowski, Gail, Peek, Joshua, Carey, Sean, Allen, Lori, Alonso-Garcia, Javier, Alves, Joao, Anders, Friederich, Athanassoula, Evangelie, Beers, Timothy C., Bird, Jonathan, Bland-Hwathorn, Joss, Brown, Anthony, Buder, Sven, Casagrande, Luca, Casey, Andrew, Cassisi, Santi, Catelan, Marcio, Chary, Ranga-Ram, Chene, Andre-Nicolas, Ciardi, David, Comeron, Fernando, Cohen, Roger, Dame, Thomas, Drimmel, Ronald, Trincado, Jose Fernandez, Finkbeiner, Douglas, Geisler, Douglas, Gennaro, Mario, Goodman, Alyssa, Green, Gregory, Hajdu, Gergely, Henderson, Calen, Hora, Joseph, Ivanov, Valentin D., Kirkpatrick, Davy, Kobayashi, Chiaki, Kuhn, Michael, Kunder, Andres, Lu, Jessica, Lucas, Philip W., Majaess, Daniel, Megeath, S. Thomas, Meisner, Aaron, Molinari, Sergio, Mroz, Przemek, Ness, Meliss, Neumayer, Nadine, Nogueras-Lara, Francisco, Noriega-Crespo, Alberto, Poleski, Radek, Rix, Hans-Walter, Rebull, Luisa, Reggiani, Henrique, Rejkuba, Marina, Saito, Roberto K., Schoenrich, Ralph, Saydjari, Andrew, Schisano, Eugenio, Schlafly, Edward, Schlaufman, Keving, Smith, Leigh, Speagle, Joshua, Wisz, Dan, Wyse, Rosemary, and Zakamska, Nadia
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
A wide-field near-infrared survey of the Galactic disk and bulge/bar(s) is supported by a large representation of the community of Galactic astronomers. The combination of sensitivity, angular resolution and large field of view make Roman uniquely able to study the crowded and highly extincted lines of sight in the Galactic plane. A ~1000 deg2 survey of the bulge and inner Galactic disk would yield an impressive dataset of ~120 billion sources and map the structure of our Galaxy. The effort would foster subsequent expansions in numerous dimensions (spatial, depth, wavelengths, epochs). Importantly, the survey would benefit from early defintion by the community, namely because the Galactic disk is a complex environment, and different science goals will require trade offs., Comment: Submitted to the Roman Project on October 22 2021 in response to a call for white papers on early-definition Astrophysics opportunity
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- 2023
21. The AMIGA sample of isolated galaxies. XIV. Disc breaks and interactions through ultra-deep optical imaging
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Sánchez-Alarcón, P. M., Román, J., Knapen, J. H., Verdes-Montenegro, L., Comerón, S., Rich, R. M., Beckman, J. E., Argudo-Fernández, M., Ramírez-Moreta, P., Blasco, J., Unda-Sanzana, E., Garrido, J., and Sánchez-Exposito, S.
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Astrophysics - Astrophysics of Galaxies - Abstract
In the standard cosmological model of galaxy evolution, mergers and interactions play a fundamental role in shaping galaxies. Galaxies that are currently isolated are thus interesting, allowing us to distinguish between internal and external processes affecting the galactic structure. However, current observational limits may obscure crucial information in the low-mass or low-brightness regime. We use optical imaging of a subsample of the AMIGA catalogue of isolated galaxies to explore the impact of different factors on the structure of these galaxies. We study the type of disc break as a function of the degree of isolation and the presence of interaction indicators like tidal streams or plumes only detectable in the low surface brightness regime. We present deep optical imaging of a sample of 25 isolated galaxies. Through careful data processing and analysis techniques, the surface brightness limits achieved are comparable to those to be obtained on the 10-year LSST coadds. The extreme depth of our imaging allows us to study the interaction signatures of 20 galaxies, given that the presence of Galactic cirrus is a strong limiting factor in the characterisation of interactions for the remaining 5 of them. We detect previously unreported interaction features in 8 (40%) galaxies in our sample. We identify 9 galaxies (36%) showing an exponential disc (Type I), 14 galaxies (56%) with down-bending (Type II) profile and only 2 galaxies (8%) with up-bending (Type III) profiles. Isolated galaxies have considerably more purely exponential discs and fewer up-bending surface brightness profiles than field or cluster galaxies. We suggest that major mergers produce up-bending profiles while a threshold in star formation probably forms down-bending profiles. Unperturbed galaxies, evolving slowly with a low star formation rate could cause the high rate of Type I discs in isolated galaxies observed., Comment: 20 pages, 7 figures, and 2 tables (incl. 2 appendix). Accepted for publication in A&A. Images and profiles will be made publicly available upon publication
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- 2023
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22. The truncation of the disk of NGC 4565: Detected up to z=4 kpc, with star formation, and affected by the warp
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Martinez-Lombilla, Cristina, Infante-Sainz, Raul, Jimenez-Ibarra, Felipe, Knapen, Johan H., Trujillo, Ignacio, Comeron, Sebastien, Borlaff, Alejandro S., and Roman, Javier
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Astrophysics - Astrophysics of Galaxies - Abstract
Context: The hierarchical model of galaxy formation suggests that galaxies are continuously growing. However, our position inside the Milky Way prevents us from studying the disk edge. Truncations are low surface brightness features located in the disk outskirts of external galaxies. They indicate where the disk brightness abruptly drops and their location is thought to change dynamically. In previous analyses of Milky Way-like galaxies, truncations were detected up to 3 kpc above the mid-plane but whether they remain present beyond that height remains unclear. Aims: Our goal is to determine whether truncations can be detected above 3 kpc height in the Milky Way-like galaxy NGC 4565, thus establishing the actual disk thickness. We also aim to study how the truncation relates to disk properties such as star formation activity or the warp. Methods: We perform a vertical study of the disk of NGC 4565 edge in unprecedented detail. We explore the truncation radius at different heights above/below the disk mid-plane (0
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- 2023
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23. Profiling of aerosol microphysical properties at several EARLINET/AERONET sites during the July 2012 ChArMEx/EMEP campaign
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M. J. Granados-Muñoz, F. Navas-Guzmán, J. L. Guerrero-Rascado, J. A. Bravo-Aranda, I. Binietoglou, S. N. Pereira, S. Basart, J. M. Baldasano, L. Belegante, A. Chaikovsky, A. Comerón, G. D'Amico, O. Dubovik, L. Ilic, P. Kokkalis, C. Muñoz-Porcar, S. Nickovic, D. Nicolae, F. J. Olmo, A. Papayannis, G. Pappalardo, A. Rodríguez, K. Schepanski, M. Sicard, A. Vukovic, U. Wandinger, F. Dulac, and L. Alados-Arboledas
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The simultaneous analysis of aerosol microphysical properties profiles at different European stations is made in the framework of the ChArMEx/EMEP 2012 field campaign (9–11 July 2012). During and in support of this campaign, five lidar ground-based stations (Athens, Barcelona, Bucharest, Évora, and Granada) performed 72 h of continuous lidar measurements and collocated and coincident sun-photometer measurements. Therefore it was possible to retrieve volume concentration profiles with the Lidar Radiometer Inversion Code (LIRIC). Results indicated the presence of a mineral dust plume affecting the western Mediterranean region (mainly the Granada station), whereas a different aerosol plume was observed over the Balkans area. LIRIC profiles showed a predominance of coarse spheroid particles above Granada, as expected for mineral dust, and an aerosol plume composed mainly of fine and coarse spherical particles above Athens and Bucharest. Due to the exceptional characteristics of the ChArMEx database, the analysis of the microphysical properties profiles' temporal evolution was also possible. An in-depth analysis was performed mainly at the Granada station because of the availability of continuous lidar measurements and frequent AERONET inversion retrievals. The analysis at Granada was of special interest since the station was affected by mineral dust during the complete analyzed period. LIRIC was found to be a very useful tool for performing continuous monitoring of mineral dust, allowing for the analysis of the dynamics of the dust event in the vertical and temporal coordinates. Results obtained here illustrate the importance of having collocated and simultaneous advanced lidar and sun-photometer measurements in order to characterize the aerosol microphysical properties in both the vertical and temporal coordinates at a regional scale. In addition, this study revealed that the use of the depolarization information as input in LIRIC in the stations of Bucharest, Évora, and Granada was crucial for the characterization of the aerosol types and their distribution in the vertical column, whereas in stations lacking depolarization lidar channels, ancillary information was needed. Results obtained were also used for the validation of different mineral dust models. In general, the models better forecast the vertical distribution of the mineral dust than the column-integrated mass concentration, which was underestimated in most of the cases.
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- 2016
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24. Near-surface and columnar measurements with a micro pulse lidar of atmospheric pollen in Barcelona, Spain
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M. Sicard, R. Izquierdo, M. Alarcón, J. Belmonte, A. Comerón, and J. M. Baldasano
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
We present for the first time continuous hourly measurements of pollen near-surface concentration and lidar-derived profiles of particle backscatter coefficients and of volume and particle depolarization ratios during a 5-day pollination event observed in Barcelona, Spain, between 27 and 31 March 2015. Daily average concentrations ranged from 1082 to 2830 pollen m−3. Platanus and Pinus pollen types represented together more than 80 % of the total pollen. Maximum hourly pollen concentrations of 4700 and 1200 m−3 were found for Platanus and Pinus, respectively. Every day a clear diurnal cycle caused by the vertical transport of the airborne pollen was visible on the lidar-derived profiles with maxima usually reached between 12:00 and 15:00 UT. A method based on the lidar polarization capabilities was used to retrieve the contribution of the pollen to the total aerosol optical depth (AOD). On average the diurnal (09:00–17:00 UT) pollen AOD was 0.05, which represented 29 % of the total AOD. Maximum values of the pollen AOD and its contribution to the total AOD reached 0.12 and 78 %, respectively. The diurnal means of the volume and particle depolarization ratios in the pollen plume were 0.08 and 0.14, with hourly maxima of 0.18 and 0.33, respectively. The diurnal mean of the height of the pollen plume was found at 1.24 km with maxima varying in the range of 1.47–1.78 km. A correlation study is performed (1) between the depolarization ratios and the pollen near-surface concentration to evaluate the ability of the former parameter to monitor pollen release and (2) between the depolarization ratios as well as pollen AOD and surface downward solar fluxes, which cause the atmospheric turbulences responsible for the particle vertical motion, to examine the dependency of the depolarization ratios and the pollen AOD upon solar fluxes. For the volume depolarization ratio the first correlation study yields to correlation coefficients ranging 0.00–0.81 and the second to correlation coefficients ranging 0.49–0.86.
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- 2016
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25. EARLINET instrument intercomparison campaigns: overview on strategy and results
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U. Wandinger, V. Freudenthaler, H. Baars, A. Amodeo, R. Engelmann, I. Mattis, S. Groß, G. Pappalardo, A. Giunta, G. D'Amico, A. Chaikovsky, F. Osipenko, A. Slesar, D. Nicolae, L. Belegante, C. Talianu, I. Serikov, H. Linné, F. Jansen, A. Apituley, K. M. Wilson, M. de Graaf, T. Trickl, H. Giehl, M. Adam, A. Comerón, C. Muñoz-Porcar, F. Rocadenbosch, M. Sicard, S. Tomás, D. Lange, D. Kumar, M. Pujadas, F. Molero, A. J. Fernández, L. Alados-Arboledas, J. A. Bravo-Aranda, F. Navas-Guzmán, J. L. Guerrero-Rascado, M. J. Granados-Muñoz, J. Preißler, F. Wagner, M. Gausa, I. Grigorov, D. Stoyanov, M. Iarlori, V. Rizi, N. Spinelli, A. Boselli, X. Wang, T. Lo Feudo, M. R. Perrone, F. De Tomasi, and P. Burlizzi
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Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
This paper introduces the recent European Aerosol Research Lidar Network (EARLINET) quality-assurance efforts at instrument level. Within two dedicated campaigns and five single-site intercomparison activities, 21 EARLINET systems from 18 EARLINET stations were intercompared between 2009 and 2013. A comprehensive strategy for campaign setup and data evaluation has been established. Eleven systems from nine EARLINET stations participated in the EARLINET Lidar Intercomparison 2009 (EARLI09). In this campaign, three reference systems were qualified which served as traveling standards thereafter. EARLINET systems from nine other stations have been compared against these reference systems since 2009. We present and discuss comparisons at signal and at product level from all campaigns for more than 100 individual measurement channels at the wavelengths of 355, 387, 532, and 607 nm. It is shown that in most cases, a very good agreement of the compared systems with the respective reference is obtained. Mean signal deviations in predefined height ranges are typically below ±2 %. Particle backscatter and extinction coefficients agree within ±2 × 10−4 km−1 sr−1 and ± 0.01 km−1, respectively, in most cases. For systems or channels that showed larger discrepancies, an in-depth analysis of deficiencies was performed and technical solutions and upgrades were proposed and realized. The intercomparisons have reinforced confidence in the EARLINET data quality and allowed us to draw conclusions on necessary system improvements for some instruments and to identify major challenges that need to be tackled in the future.
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- 2016
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26. EARLINET: potential operationality of a research network
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M. Sicard, G. D'Amico, A. Comerón, L. Mona, L. Alados-Arboledas, A. Amodeo, H. Baars, J. M. Baldasano, L. Belegante, I. Binietoglou, J. A. Bravo-Aranda, A. J. Fernández, P. Fréville, D. García-Vizcaíno, A. Giunta, M. J. Granados-Muñoz, J. L. Guerrero-Rascado, D. Hadjimitsis, A. Haefele, M. Hervo, M. Iarlori, P. Kokkalis, D. Lange, R. E. Mamouri, I. Mattis, F. Molero, N. Montoux, A. Muñoz, C. Muñoz Porcar, F. Navas-Guzmán, D. Nicolae, A. Nisantzi, N. Papagiannopoulos, A. Papayannis, S. Pereira, J. Preißler, M. Pujadas, V. Rizi, F. Rocadenbosch, K. Sellegri, V. Simeonov, G. Tsaknakis, F. Wagner, and G. Pappalardo
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Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
In the framework of ACTRIS (Aerosols, Clouds, and Trace Gases Research Infrastructure Network) summer 2012 measurement campaign (8 June–17 July 2012), EARLINET organized and performed a controlled exercise of feasibility to demonstrate its potential to perform operational, coordinated measurements and deliver products in near-real time. Eleven lidar stations participated in the exercise which started on 9 July 2012 at 06:00 UT and ended 72 h later on 12 July at 06:00 UT. For the first time, the single calculus chain (SCC) – the common calculus chain developed within EARLINET for the automatic evaluation of lidar data from raw signals up to the final products – was used. All stations sent in real-time measurements of a 1 h duration to the SCC server in a predefined netcdf file format. The pre-processing of the data was performed in real time by the SCC, while the optical processing was performed in near-real time after the exercise ended. 98 and 79 % of the files sent to SCC were successfully pre-processed and processed, respectively. Those percentages are quite large taking into account that no cloud screening was performed on the lidar data. The paper draws present and future SCC users' attention to the most critical parameters of the SCC product configuration and their possible optimal value but also to the limitations inherent to the raw data. The continuous use of SCC direct and derived products in heterogeneous conditions is used to demonstrate two potential applications of EARLINET infrastructure: the monitoring of a Saharan dust intrusion event and the evaluation of two dust transport models. The efforts made to define the measurements protocol and to configure properly the SCC pave the way for applying this protocol for specific applications such as the monitoring of special events, atmospheric modeling, climate research and calibration/validation activities of spaceborne observations.
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- 2015
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27. Mapping non-axisymmetric velocity fields of external galaxies
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Labini, Francesco Sylos, Straccamore, Matteo, De Marzo, Giordano, and Comerón, Sébastien
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Astrophysics - Astrophysics of Galaxies - Abstract
Disk galaxies are typically in a stable configuration where matter moves in almost closed circular orbits. However, non-circular motions caused by distortions, warps, lopsidedness, or satellite interactions are common and leave distinct signatures on galaxy velocity maps. We develop an algorithm that uses an ordinary least square method for fitting a non-axisymmetric model to the observed two-dimensional line-of-sight velocity map of an external galaxy, which allows for anisotropic non-circular motions. The method approximates a galaxy as a flat disk, which is an appropriate assumption for spiral galaxies within the optical radius where warps are rare. In the outer parts of HI distributions, which may extend well into the warp region, we use this method in combination with a standard rotating tilted ring model to constrain the range of radii where the flat disk assumption can be conservatively considered valid. Within this range, the transversal and radial velocity profiles, averaged in rings, can be directly reconstructed from the velocity map. The novelty of the algorithm consists in using arc segments in addition to rings: in this way spatial velocity anisotropies can be measured in both components, allowing for the reconstruction of angularly resolved coarse-grained two-dimensional velocity maps. We applied this algorithm to 25 disk galaxies from the THINGS sample for which we can provide 2D maps of both velocity components., Comment: 42 pages, 37 figures, Monthly Notices of the Royal Astronomical Society Main Journal in the press (2023)
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- 2023
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28. A methodology for investigating dust model performance using synergistic EARLINET/AERONET dust concentration retrievals
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I. Binietoglou, S. Basart, L. Alados-Arboledas, V. Amiridis, A. Argyrouli, H. Baars, J. M. Baldasano, D. Balis, L. Belegante, J. A. Bravo-Aranda, P. Burlizzi, V. Carrasco, A. Chaikovsky, A. Comerón, G. D'Amico, M. Filioglou, M. J. Granados-Muñoz, J. L. Guerrero-Rascado, L. Ilic, P. Kokkalis, A. Maurizi, L. Mona, F. Monti, C. Muñoz-Porcar, D. Nicolae, A. Papayannis, G. Pappalardo, G. Pejanovic, S. N. Pereira, M. R. Perrone, A. Pietruczuk, M. Posyniak, F. Rocadenbosch, A. Rodríguez-Gómez, M. Sicard, N. Siomos, A. Szkop, E. Terradellas, A. Tsekeri, A. Vukovic, U. Wandinger, and J. Wagner
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Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
Systematic measurements of dust concentration profiles at a continental scale were recently made possible by the development of synergistic retrieval algorithms using combined lidar and sun photometer data and the establishment of robust remote-sensing networks in the framework of Aerosols, Clouds, and Trace gases Research InfraStructure Network (ACTRIS)/European Aerosol Research Lidar Network (EARLINET). We present a methodology for using these capabilities as a tool for examining the performance of dust transport models. The methodology includes considerations for the selection of a suitable data set and appropriate metrics for the exploration of the results. The approach is demonstrated for four regional dust transport models (BSC-DREAM8b v2, NMMB/BSC-DUST, DREAMABOL, DREAM8-NMME-MACC) using dust observations performed at 10 ACTRIS/EARLINET stations. The observations, which include coincident multi-wavelength lidar and sun photometer measurements, were processed with the Lidar-Radiometer Inversion Code (LIRIC) to retrieve aerosol concentration profiles. The methodology proposed here shows advantages when compared to traditional evaluation techniques that utilize separately the available measurements such as separating the contribution of dust from other aerosol types on the lidar profiles and avoiding model assumptions related to the conversion of concentration fields to aerosol extinction values. When compared to LIRIC retrievals, the simulated dust vertical structures were found to be in good agreement for all models with correlation values between 0.5 and 0.7 in the 1–6 km range, where most dust is typically observed. The absolute dust concentration was typically underestimated with mean bias values of -40 to -20 μg m−3 at 2 km, the altitude of maximum mean concentration. The reported differences among the models found in this comparison indicate the benefit of the systematic use of the proposed approach in future dust model evaluation studies.
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- 2015
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29. Assimilation of lidar signals: application to aerosol forecasting in the western Mediterranean basin
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Y. Wang, K. N. Sartelet, M. Bocquet, P. Chazette, M. Sicard, G. D'Amico, J. F. Léon, L. Alados-Arboledas, A. Amodeo, P. Augustin, J. Bach, L. Belegante, I. Binietoglou, X. Bush, A. Comerón, H. Delbarre, D. García-Vízcaino, J. L. Guerrero-Rascado, M. Hervo, M. Iarlori, P. Kokkalis, D. Lange, F. Molero, N. Montoux, A. Muñoz, C. Muñoz, D. Nicolae, A. Papayannis, G. Pappalardo, J. Preissler, V. Rizi, F. Rocadenbosch, K. Sellegri, F. Wagner, and F. Dulac
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
This paper presents a new application of assimilating lidar signals to aerosol forecasting. It aims at investigating the impact of a ground-based lidar network on the analysis and short-term forecasts of aerosols through a case study in the Mediterranean basin. To do so, we employ a data assimilation (DA) algorithm based on the optimal interpolation method developed in the Polair3D chemistry transport model (CTM) of the Polyphemus air quality modelling platform. We assimilate hourly averaged normalised range-corrected lidar signals (PR2) retrieved from a 72 h period of intensive and continuous measurements performed in July 2012 by ground-based lidar systems of the European Aerosol Research Lidar Network (EARLINET) integrated into the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) network and an additional system in Corsica deployed in the framework of the pre-ChArMEx (Chemistry-Aerosol Mediterranean Experiment)/TRAQA (TRAnsport à longue distance et Qualité de l'Air) campaign. This lidar campaign was dedicated to demonstrating the potential operationality of a research network like EARLINET and the potential usefulness of assimilation of lidar signals to aerosol forecasts. Particles with an aerodynamic diameter lower than 2.5 μm (PM2.5) and those with an aerodynamic diameter higher than 2.5 μm but lower than 10 μm (PM10–2.5) are analysed separately using the lidar observations at each DA step. First, we study the spatial and temporal influences of the assimilation of lidar signals on aerosol forecasting. We conduct sensitivity studies on algorithmic parameters, e.g. the horizontal correlation length (Lh) used in the background error covariance matrix (50 km, 100 km or 200 km), the altitudes at which DA is performed (0.75–3.5 km, 1.0–3.5 km or 1.5–3.5 km a.g.l.) and the assimilation period length (12 h or 24 h). We find that DA with Lh = 100 km and assimilation from 1.0 to 3.5 km a.g.l. during a 12 h assimilation period length leads to the best scores for PM10 and PM2.5 during the forecast period with reference to available measurements from surface networks. Secondly, the aerosol simulation results without and with lidar DA using the optimal parameters (Lh = 100 km, an assimilation altitude range from 1.0 to 3.5 km a.g.l. and a 12 h DA period) are evaluated using the level 2.0 (cloud-screened and quality-assured) aerosol optical depth (AOD) data from AERONET, and mass concentration measurements (PM10 or PM2.5) from the French air quality (BDQA) network and the EMEP-Spain/Portugal network. The results show that the simulation with DA leads to better scores than the one without DA for PM2.5, PM10and AOD. Additionally, the comparison of model results to evaluation data indicates that the temporal impact of assimilating lidar signals is longer than 36 h after the assimilation period.
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- 2014
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30. The massive relic galaxy NGC 1277 is dark matter deficient. From dynamical models of integral-field stellar kinematics out to five effective radii
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Comerón, Sébastien, Trujillo, Ignacio, Cappellari, Michele, Buitrago, Fernando, Garduño, Luis E., Zaragoza-Cardiel, Javier, Zinchenko, Igor A., Lara-López, Maritza A., Ferré-Mateu, Anna, and Dib, Sami
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Astrophysics - Astrophysics of Galaxies - Abstract
According to the $\Lambda$CDM cosmology, present-day galaxies with stellar masses $M_\star>10^{11} {\rm M}_\odot$ should contain a sizable fraction of dark matter within their stellar body. Models indicate that in massive early-type galaxies (ETGs) dark matter should account for $\sim60\%$ of the dynamical mass within five effective radii ($5 R_{\rm e}$). Most massive ETGs have been shaped through a two-phase process: the rapid growth of a compact core was followed by the accretion of an extended envelope through mergers. The exceedingly rare galaxies that have avoided the second phase, the so-called relic galaxies, are thought to be the frozen remains of the massive ETG population at $z\gtrsim2$. The best relic galaxy candidate discovered to date is NGC 1277, in the Perseus cluster. We used deep integral field GCMS data to revisit NGC 1277 out to an unprecedented radius of 6 kpc (corresponding to $5 R_{\rm e}$). By using Jeans anisotropic modelling we find a negligible dark matter fraction within $5 R_{\rm e}$ ($f_{\rm DM}(5 R_{\rm e})<0.05$; two-sigma confidence level), which is in tension with the expectation. Since the lack of an extended envelope would reduce dynamical friction and prevent the accretion of an envelope, we propose that NGC 1277 lost its dark matter very early or that it was dark matter deficient ab initio. We discuss our discovery in the framework of recent proposals suggesting that some relic galaxies may result from dark matter stripping as they fell in and interacted within galaxy clusters. Alternatively, NGC 1277 might have been born in a high-velocity collision of gas-rich proto-galactic fragments, where dark matter left behind a disc of dissipative baryons. We speculate that the relative velocities of $\approx2000 {\rm km/s}$ required for the latter process to happen were possible in the progenitors of the present-day rich galaxy clusters., Comment: Accepted for publication in A&A
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- 2023
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31. Gaia-ESO Survey: massive stars in the Carina Nebula. A new census of OB stars
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Berlanas, S. R., Apellániz, J. Maíz, Herrero, A., Mahy, L., Blomme, R., Negueruela, I., Dorda, R., Comerón, F., Gosset, E., González, M. Pantaleoni, Lera, J. A. Molina, Sota, A., Furst, T., Alfaro, E. J., Bergemann, M., Carraro, G., Drew, J. E., Morbidelli, L., and Vink, J. S.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
The Gaia-ESO survey sample of massive OB stars in the Carina Nebula consists of 234 stars. The addition of brighter sources from the Galactic O-Star Spectroscopic Survey and additional sources from the literature allows us to create the most complete census of massive OB stars done so far in the region. It contains a total of 316 stars, being 18 of them in the background and four in the foreground. Of the 294 stellar systems in Car OB1, 74 are of O type, 214 are of non-supergiant B type and 6 are of WR or non-O supergiant (II to Ia) spectral class. We identify 20 spectroscopic binary systems with an O-star primary, of which 6 are reported for the first time, and another 18 with a B-star primary, of which 13 are new detections. The average observed double-lined binary fraction of O-type stars in the surveyed region is 0.35, which represents a lower limit. We find a good correlation between the spectroscopic n-qualifier and the projected rotational velocity of the stars. The fraction of candidate runaways among the stars with and without the n-qualifier is 4.4% and 2.4%, respectively, although non resolved double-lined binaries can be contaminating the fast rotators sample., Comment: Accepted for publication in A&A, 62 pages, 8 figures
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- 2023
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32. The HH 24 Complex: Jets, Multiple Star Formation, and Orphaned Protostars
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Reipurth, Bo, Bally, J., Yen, Hsi-Wei, Arce, H. G., Rodriguez, L. -F., Raga, A. C., Geballe, T. R., Rao, R., Comeron, F., Mikkola, S., Aspin, C. A., and Walawender, J.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
The HH 24 complex harbors five collimated jets emanating from a small protostellar multiple system. We have carried out a multi-wavelength study of the jets, their driving sources, and the cloud core hosting the embedded stellar system, based on data from the HST, Gemini, Subaru, APO 3.5m, VLA, and ALMA telescopes. The data show that the multiple system, SSV 63, contains at least 7 sources, ranging in mass from the hydrogen-burning limit to proto-Herbig Ae stars. The stars are in an unstable non-hierarchical configuration, and one member, a borderline brown dwarf, is moving away from the protostellar system with 25 km/s, after being ejected about 5,800 yr ago as an orphaned protostar. Five of the embedded sources are surrounded by small, possibly truncated, disks resolved at 1.3 mm with ALMA. Proper motions and radial velocities imply jet speeds of 200-300 km/s. The two main HH 24 jets, E and C, form a bipolar jet system which traces the innermost portions of parsec-scale chains of Herbig-Haro and H2 shocks with a total extent of at least 3 parsec. H2CO and C18O observations show that the core has been churned and continuously fed by an infalling streamer. 13CO and 12CO trace compact, low-velocity, cavity walls carved by the jets and an ultra-compact molecular outflow from the most embedded object. Chaotic N-body dynamics likely will eject several more of these objects. The ejection of stars from their feeding zones sets their masses. Dynamical decay of non-hierarchical systems can thus be a major contributor to establishing the initial mass function., Comment: 57 pages, 61 figures, 12 tables; accepted to Astron.J
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- 2023
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33. Estimation of mineral dust long-wave radiative forcing: sensitivity study to particle properties and application to real cases in the region of Barcelona
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M. Sicard, S. Bertolín, M. Mallet, P. Dubuisson, and A. Comerón
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The aerosol radiative effect in the long-wave (LW) spectral range is sometimes not taken into account in atmospheric aerosol forcing studies at local scale because the LW aerosol effect is assumed to be negligible. At regional and global scale this effect is partially taken into account: aerosol absorption is taken into account but scattering is still neglected. However, aerosols with strong absorbing and scattering properties in the LW region, like mineral dust, can have a non-negligible radiative effect in the LW spectral range (both at surface and top of the atmosphere) which can counteract their cooling effect occurring in the short-wave spectral range. The first objective of this research is to perform a sensitivity study of mineral dust LW radiative forcing (RF) as a function of dust microphysical and optical properties using an accurate radiative transfer model which can compute vertically resolved short-wave and long-wave aerosol RF. Radiative forcing simulations in the LW range have shown an important sensitivity to the following parameters: aerosol load, radius of the coarse mode, refractive index, aerosol vertical distribution, surface temperature and surface albedo. The scattering effect has been estimated to contribute to the LW RF up to 18% at the surface and up to 38% at the top of the atmosphere. The second objective is the estimation of the short-wave and long-wave dust RF for 11 dust outbreaks observed in Barcelona. At the surface, the LW RF varies between +2.8 and +10.2 W m−2, which represents between 11 and 26% (with opposite sign) of the SW component, while at the top of the atmosphere the LW RF varies between +0.6 and +5.8 W m−2, which represents between 6 and 26% (with opposite sign) of the SW component.
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- 2014
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34. Monitoring of the Eyjafjallajökull volcanic aerosol plume over the Iberian Peninsula by means of four EARLINET lidar stations
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M. Sicard, J. L. Guerrero-Rascado, F. Navas-Guzmán, J. Preißler, F. Molero, S. Tomás, J. A. Bravo-Aranda, A. Comerón, F. Rocadenbosch, F. Wagner, M. Pujadas, and L. Alados-Arboledas
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Lidar and sun-photometer measurements were performed intensively over the Iberian Peninsula (IP) during the eruption of the Eyjafjallajökull volcano (Iceland) in April–May 2010. The volcanic plume reached all the IP stations for the first time on 5 May 2010. A thorough study of the event was conducted for the period 5–8 May. Firstly, the spatial and temporal evolution of the plume was described by means of lidar and sun-photometer measurements supported with backtrajectories. The volcanic aerosol layers observed over the IP were rather thin (−3 during the whole event.
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- 2012
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35. Seasonal variability of aerosol optical properties observed by means of a Raman lidar at an EARLINET site over Northeastern Spain
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M. Sicard, F. Rocadenbosch, M. N. M. Reba, A. Comerón, S. Tomás, D. García-Vízcaino, O. Batet, R. Barrios, D. Kumar, and J. M. Baldasano
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The annual and seasonal variability of aerosol optical properties observed by means of a Raman lidar over Northeastern Spain has been assessed. The lidar representativeness has first been checked against sun-photometer measurements in terms of aerosol optical thickness. Then the annual cycle and the seasonal variability of the planetary boundary layer aerosol optical thickness and its fraction compared to the columnar optical thickness, the lidar ratio, the backscatter-related Ångström exponent and the planetary boundary layer height are analyzed and discussed. Winter and summer mean profiles of extinction, backscatter and lidar ratio retrieved with the Raman algorithm are presented. The analysis shows the impact of most of the natural events (Saharan dust intrusions, wildfires, etc.) and meteorological situations (summer anticyclonic situation, the formation of the Iberian thermal low, winter long-range transport from North Europe and/or North America, re-circulation flows, etc.) occurring in the Barcelona area. A detailed study of a special event including a combined intrusion of Saharan dust and biomass-burning particles proves the suitability of combining the retrieval of aerosol optical properties from Raman and pure elastic lidar measurements to discriminate spatially different types of aerosols and to follow their spatial and temporal evolution.
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- 2011
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36. Linking star formation thresholds and truncations in the thin and thick disks of the low-mass galaxy UGC 7321
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Díaz-García, Simón, Comerón, Sébastien, Courteau, Stéphane, Watkins, Aaron E., Knapen, Johan H., and Román, Javier
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Astrophysics - Astrophysics of Galaxies - Abstract
Thin and thick disks are found in most spiral galaxies, yet their formation scenarios remain uncertain. Whether thick disks form through slow or fast, internal or environmental, processes is unclear. The physical origin of outer truncations in thin and thick disks, observed as a drop in optical and near-infrared (NIR) surface brightness profiles, is also a much debated topic. These truncations have been linked to star formation (SF) thresholds in Milky-Way type galaxies, but no such connection has been made for their low-mass counterparts or in thick disks. Our photometric analysis of the edge-on galaxy UGC 7321 offers a possible breakthrough. This well-studied diffuse, isolated, bulgeless, ultra-thin galaxy is thought to be under-evolved both dynamically and in SF. It is an ideal target to disentangle internal effects in the formation of thick disks and truncations. Our axial light profiles from deep far- and near-ultraviolet (UV; GALEX) images, tracing recent SF, and optical (DESI grz) and NIR (Spitzer 3.6 microns) images, tracing old stellar populations, enable a detailed identification of an outer truncation in all probed wavelengths in both the thin and thick disks. After deprojecting to a face-on view, a sharp truncation signature is found at a stellar density of roughly 1.5 solar masses per square parsec, in agreement with theoretical expectations of gas density SF thresholds. The redder colours beyond the truncation radius are indicative of stellar migration towards the outer regions. We thus show that thick disks and truncations can form via internal mechanisms alone, given the pristine nature of UGC 7321. We report the discovery of a truncation at and above the mid-plane of a diffuse galaxy that is linked to a SF threshold; this poses a constraint on physically-motivated disk size measurements among low-mass galaxies., Comment: Accepted for publication in A&A (August 29, 2022). 7 pages, 3 figures
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- 2022
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37. Star formation in two irradiated globules around Cygnus OB2
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Comerón, F., Schneider, N., and Djupvik, A. A.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We investigate the young stellar populations associated with DR 18 and ECX 6-21, which are two isolated globules irradiated by the O-type stars of the Cygnus OB2 association. Both are HII regions containing obvious tracers of recent and ongoing star formation. We also study smaller isolated molecular structures in their surroundings. Both globules contain their own embedded populations, with a higher fraction of the less-evolved classes. Masses and temperatures are estimated under the assumption of a common age of 1 Myr, which has been found to appropriately represent the general Cygnus OB2 YSO population but is most probably an overestimate for both globules, especially ECX 6-21. The early-B star responsible for the erosion of DR 18 is found to be part of a small aggregate of intermediate-mass stars still embedded in the cloud, which probably contains a second site of recent star formation, also with intermediate-mass stars. We confirm the two main star forming sites embedded in ECX 6-21 described in previous works, with the southern site being more evolved than the northern site. We also discuss the small globule ECX 6-21-W ($= G79.8+1.2$), and propose that its non thermal radio spectrum is due to synchrotron emission from an embedded jet, whose existence is suggested by our observations. The extreme youth of some of the YSOs suggests that star formation in both globules started after they became externally irradiated. The populations of both globules are not found to be particularly rich, but they contain stars with estimated masses similar or above that of the Sun in numbers that hint at some differences with respect to the star formation process taking place in more quiescent regions where low-mass stars dominate, which deeper observations may confirm., Comment: Accepted for publication by Astronomy and Astrophysics
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- 2022
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38. The extended population associated with W40
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Comerón, F., Djupvik, A. A., and Schneider, N.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
W40 is a heavily obscured bipolar HII region projected in the direction of the Aquila Rift and ionized by hot stars in a central, partly embedded cluster. The study of the cluster and its surroundings has been greatly hampered thus far by the strong extinction in the region. We use the Gaia eDR3 catalog to establish astrometric membership criteria based on the population of the W40 central cluster, reassess the distance of the region, and identify in this way new members, both inside and outside the cluster. We obtain visible spectroscopy in the red spectral region to classify both known and new members, complemented with Gaia and Spitzer photometry to assess the evolutionary status of the stellar population. We derive a high-confidence geometric distance to the W40 region of 502 pc $\pm$ 4 pc and confirm the presence of a comoving extended population of stars at the same distance, spreading over the whole projected area of the HII region and beyond. Spectral classifications are presented for 21 members of the W40 region, 10 of them belonging to the central cluster. One of the newly identified B stars in the extended population is clearly interacting with the shell surrounding the HII region, giving rise to a small arc-shaped nebula that traces a bow shock. The infrared excess properties suggest that the extended population is significantly older ($\sim 3$ Myr) than the W40 central cluster ($< 1$ Myr). The area currently occupied by the W40 HII region and its surroundings has a history of star formation extending at least several million years in the past, of which the formation of the W40 central cluster and the subsequent HII region is one of the latest episodes. The newly determined distance suggests that W40 is behind, and physically detached from, a pervasive large dust layer which is some 60 pc foreground to it as determined by previous studies., Comment: Submitted to Astronomy and Astrophysics
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- 2022
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39. The nature of the Cygnus extreme B-supergiant 2MASS J20395358+4222505
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Herrero, A., Berlanas, S. R., de Paz, A. Gil, Comerón, F., Puls, J., Alegría, S. Ramírez, García, M., Lennon, D. J., Najarro, F., Simón-Díaz, S., Urbaneja, M. A., Gallego, J., Carrasco, E., Iglesias, J., Cedazo, R., Vargas, M. L. García, Castillo-Morales, A., Pascual, S., Cardiel, N., Pérez-Calpena, A., Gómez-Alvarez, P., and Martínez-Delgado, I.
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Astrophysics - Solar and Stellar Astrophysics - Abstract
2MASS J20395358+4222505 is an obscured early B supergiant near the massive OB star association Cyg OB2. Despite its bright infrared magnitude (K$_{s}$=5.82) it has remained largely ignored because of its dim optical magnitude (B=16.63, V=13.68). In a previous paper we classified it as a highly reddened, potentially extremely luminous, early B-type supergiant. We obtained its spectrum in the U, B and R spectral bands during commissioning observations with the instrument MEGARA@GTC. It displays a particularly strong H$\alpha$ emission for its spectral type, B1 Ia. The star seems to be in an intermediate phase between super- and hypergiant, a group that it will probably join in the near (astronomical) future. We observe a radial velocity difference between individual observations and determine the stellar parameters, obtaining T$_{eff}$ = 24000 K, logg$_{c}$= 2.88 $\pm$ 0.15. The rotational velocity found is large for a B-supergiant, vsini= 110 $\pm$ 25 km s$^{-1}$. The abundance pattern is consistent with solar, with a mild C underabundance (based on a single line). Assuming that J20395358+4222505 is at the distance of Cyg OB2 we derive the radius from infrared photometry, finding R= 41.2 $\pm$ 4.0 R$_{\odot}$, log(L/L$_{\odot}$)= 5.71 $\pm$ 0.04 and a spectroscopic mass of 46.5 $\pm$ 15.0 M$_{\odot}$. The clumped mass-loss rate (clumping factor 10) is very high for the spectral type, $\dot{M}$ = 2.4x10$^{-6}$ M$_{\odot}$ a$^{-1}$. The high rotational velocity and mass-loss rate place the star at the hot side of the bi-stability jump. Together with the nearly solar CNO abundance pattern, they may also point to evolution in a binary system, J20395358+4222505 being the initial secondary., Comment: Accepted for publication in MNRAS, 13 pages, 9 figures
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- 2022
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40. Stellar masses, sizes, and radial profiles for 465 nearby early-type galaxies: an extension to the Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G)
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Watkins, A. E., Salo, H., Laurikainen, E., Díaz-García, S., Comerón, S., Janz, J., Su, A. H., Buta, R., Athanassoula, E., Bosma, A., Ho, L. C., Holwerda, B. W., Kim, T., Knapen, J. H., Laine, S., Menéndez-Delmestre, K., Peletier, R. F., Sheth, K., and Zaritsky, D.
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Astrophysics - Astrophysics of Galaxies - Abstract
The Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G) is a detailed study of over 2300 nearby galaxies in the near-infrared (NIR), which has been critical to our understanding of the detailed structures of nearby galaxies. Because the sample galaxies were selected only using radio-derived velocities, however, the survey favored late-type disk galaxies over lenticulars and ellipticals. A follow-up Spitzer survey was conducted to rectify this bias, adding 465 early-type galaxies (ETGs) to the original sample, to be analyzed in a manner consistent with the initial survey. We present the data release of this ETG extension, up to the third data processing pipeline (P3): surface photometry. We produce curves of growth and radial surface brightness profiles (with and without inclination corrections) using reduced and masked Spitzer IRAC 3.6$\mu$m and 4.5$\mu$m images produced through Pipelines 1 and 2, respectively. From these profiles, we derive the following integrated quantities: total magnitudes, stellar masses, concentration parameters, and galaxy size metrics. We showcase NIR scaling relations for ETGs among these quantities. We examine general trends across the whole S$^{4}$G and ETG extension among our derived parameters, highlighting differences between ETGs and late-type galaxies (LTGs). ETGs are, on average, more massive and more concentrated than LTGs, and also show subtle distinctions among ETG morphological sub-types. We also derive the following scaling relations and compare with previous results in visible light: mass--size (both half-light and isophotal), mass--concentration, mass--surface brightness (central, effective, and within 1 kpc), and mass--color. We find good agreement with previous works, though some relations (e.g., mass--central surface brightness) will require more careful multi-component decompositions to be fully understood., Comment: 25 pages, 17 figures, accepted for publication in A&A
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- 2022
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41. The multifarious ionization sources and disturbed kinematics of extraplanar gas in five low-mass galaxies
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Rautio, R. P. V., Watkins, A. E., Comerón, S., Salo, H., Díaz-García, S., and Janz, J.
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Astrophysics - Astrophysics of Galaxies - Abstract
We investigate the origin of the extraplanar diffuse ionized gas (eDIG) and its predominant ionization mechanisms in five nearby (17-46 Mpc) low-mass ($10^9\text{-}10^{10}$ $M_{\odot}$) edge-on disk galaxies: ESO 157-49, ESO 469-15, ESO 544-27, IC 217, and IC 1553. We acquired Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy and deep narrowband H$\alpha$ imaging of our sample galaxies. To investigate the connection between in-plane star formation and eDIG, we perform a photometric analysis of our narrowband H$\alpha$ imaging. We measure eDIG scale heights of $h_{z\text{eDIG}} = 0.59 \text{-} 1.39$ kpc and find a positive correlation between them and specific star formation rates. In all galaxies, we also find a strong correlation between extraplanar and midplane radial H$\alpha$ profiles. Using our MUSE data, we investigate the origin of eDIG via kinematics. We find ionized gas rotation velocity lags above the midplane with values between 10 and 27 km s$^{-1}$ kpc$^{-1}$. While we do find hints of an accretion origin for the ionized gas in ESO 157-49, IC 217, and IC 1553, overall the ionized gas kinematics of our galaxies do not match a steady galaxy model or any simplistic model of accretion or internal origin for the gas. We also construct standard diagnostic diagrams and emission-line maps (EW(H$\alpha$), [NII]/H$\alpha$, [SII]//H$\alpha$, [OIII]/H$\beta$) and find regions consistent with mixed OB star and hot low-mass evolved stars (HOLMES) ionization, and mixed OB-shock ionization. Our results suggest that OB stars are the primary driver of eDIG ionization, while both HOLMES and shocks may locally contribute to the ionization of eDIG to a significant degree. Despite our galaxies' similar structures and masses, we find a surprisingly composite image of ionization mechanisms and a multifarious origin for the eDIG., Comment: 21 pages, 14 figures, accepted to Astronomy & Astrophysics
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- 2022
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42. Globules and pillars in Cygnus X III. Herschel and upGREAT/SOFIA far-infrared spectroscopy of the globule IRAS 20319+3958 inCygnus X
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Schneider, N., Roellig, M., Polehampton, E. T., Comeron, F., Djupvik, A. A., Makai, Z., Buchbender, C., Simon, R., Bontemps, S., Guesten, R., White, G., Okada, Y., Parikka, A., and Rothbart, N.
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Astrophysics - Astrophysics of Galaxies - Abstract
IRAS 20319+3958 in Cygnus X South is a rare example of a free-floating globule (mass ~240 Msun, length ~1.5 pc) with an internal HII region created by the stellar feedback of embedded intermediate-mass stars, in particular, one Herbig Be star. Here, we present a Herschel/HIFI CII 158 mu map of the whole globule and a large set of other FIR lines (mid-to high-J CO lines observed with Herschel/PACS and SPIRE, the OI 63 mu line and the CO 16-15 line observed with upGREAT on SOFIA), covering the globule head and partly a position in the tail. The CII map revealed that the whole globule is probably rotating. Highly collimated, high-velocity CII emission is detected close to the Herbig Be star. We performed a PDR analysis using the KOSMA-tau PDR code for one position in the head and one in the tail. The observed FIR lines in the head can be reproduced with a two-component model: an extended, non-clumpy outer PDR shell and a clumpy, dense, and thin inner PDR layer, representing the interface between the HII region cavity and the external PDR. The modelled internal UV field of ~2500 Go is similar to what we obtained from the Herschel FIR fluxes, but lower than what we estimated from the census of the embedded stars. External illumination from the ~30 pc distant Cyg OB2 cluster, producing an UV field of ~150-600 G0 as an upper limit, is responsible for most of the CII emission. For the tail, we modelled the emission with a non-clumpy component, exposed to a UV-field of around 140 Go., Comment: accepted by Astronomy & Astrophysics
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- 2021
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43. A MUSE Spectro-imaging Study of the Th 28 Jet: Precession in the Inner Jet
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Murphy, A., Dougados, C., Whelan, E. T., Bacciotti, F., Coffey, D., Comerón, F., Eislöffel, J., and Ray, T. P.
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Astrophysics - Solar and Stellar Astrophysics - Abstract
Context: Th 28 is a Classical T Tauri star in the Lupus 3 cloud which drives an extended bipolar jet. Previous studies of the inner jet identified signatures of rotation around the outflow axis, a key result for theories of jet launching. Thus this is an important source in which to investigate the poorly understood jet launching mechanism. We investigate the morphology and kinematics of the Th 28 micro-jets with the aim of characterizing their structure and outflow activity, using optical integral-field spectroscopy observations obtained with VLT/MUSE. We use spectro-imaging and position-velocity maps to investigate the kinematic and morphological features of the jet, and obtain a catalogue of emission lines in which the jet is visible. A Lucy-Richardson deconvolution procedure is used to differentiate the structure of the inner micro-jet region. Spatial profiles extracted perpendicular to the jet axis are fitted to investigate the jet width, opening angle and the evolution of the jet axis. We confirm the previously identified knot HHW$_{2}$ within the red-shifted jet and identify three additional knots in each lobe for the first time. We also find [O III]$\lambda$5007 emission from the blue-shifted micro-jet including the knot closest to the star. Proper motions for the innermost knots on each side are estimated and we show that new knots are ejected on an approximate timescale of 10-15 years. The jet axis centroids show a point-symmetric wiggle within the inner portion of both micro-jets indicating precession. We use the jet shape to measure a precession period of 8 years, with a half-opening angle < 0.6$^{\circ}$. This may provide an alternative explanation for the rotation signatures previously reported. We find the jet shape to be compatible with precession due to a brown dwarf companion orbiting at a separation $\leq$ 0.3 au., Comment: Accepted by Astronomy & Astrophysics; 21 pages, 23 figures
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- 2021
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44. First Results of Inverted Aerosol Properties Through GRASP Algorithm, Using Polarized Data from the Multiwavelength Sun-Sky-Lunar Photometer in Barcelona, Spain
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Oliveira, D. C. F. S., Rodriguéz-Gomez, A., Comerón, A., Muñoz-Porcar, C., Dubovik, O., Lopatin, A., Herrera, M. E., Sicard, M., Sullivan, John T., editor, Leblanc, Thierry, editor, Tucker, Sara, editor, Demoz, Belay, editor, Eloranta, Edwin, editor, Hostetler, Chris, editor, Ishii, Shoken, editor, Mona, Lucia, editor, Moshary, Fred, editor, Papayannis, Alexandros, editor, and Rupavatharam, Krishna, editor
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- 2023
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45. Performance Simulation of a Spaceborne Raman Lidar for ATLAS
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Franco, Noemi, Di Girolamo, Paolo, Behrendt, Andreas, Wulfmeyer, Volker, Comerón, Adolfo, Summa, Donato, Whiteman, David N., Sullivan, John T., editor, Leblanc, Thierry, editor, Tucker, Sara, editor, Demoz, Belay, editor, Eloranta, Edwin, editor, Hostetler, Chris, editor, Ishii, Shoken, editor, Mona, Lucia, editor, Moshary, Fred, editor, Papayannis, Alexandros, editor, and Rupavatharam, Krishna, editor
- Published
- 2023
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46. A prediction on the age of thick discs as a function of the stellar mass of the host galaxy
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Comerón, S.
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Astrophysics - Astrophysics of Galaxies - Abstract
One of the suggested thick disc formation mechanisms is that they were born quickly and in situ from a turbulent clumpy disc. Subsequently, thin discs formed slowly within them from leftovers of the turbulent phase and from material accreted through cold flows and minor mergers. In this letter, I propose an observational test to verify this hypothesis. By combining thick disc and total stellar masses of edge-on galaxies with galaxy stellar mass functions calculated in the redshift range of $z\leq3.0$, I derived a positive correlation between the age of the youngest stars in thick discs and the stellar mass of the host galaxy; galaxies with a present-day stellar mass of $\mathcal{M}_\star(z=0)<10^{10}\,\mathcal{M}_\odot$ have thick disc stars as young as $4-6\,{\rm Gyr}$, whereas the youngest stars in the thick discs of Milky-Way-like galaxies are $\sim10\,{\rm Gyr}$ old. I tested this prediction against the scarcely available thick disc age estimates, all of them are from galaxies with $\mathcal{M}_\star(z=0)\gtrsim10^{10}\,\mathcal{M}_\odot$, and I find that field spiral galaxies seem to follow the expectation. On the other hand, my derivation predicts ages that are too low for the thick discs in lenticular galaxies, indicating a fast early evolution for S0 galaxies. I propose the idea of conclusively testing whether thick discs formed quickly and in situ by obtaining the ages of thick discs in field galaxies with masses of $\mathcal{M}_\star(z=0)\sim10^{9.5}\,\mathcal{M}_\odot$ and by checking whether they contain $\sim5\,{\rm Gyr}$-old stars., Comment: Letter accepted for publication in A&A
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- 2021
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47. ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds
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Santamaría-Miranda, A., de Gregorio-Monsalvo, I., Plunkett, A. L., Huélamo, N., López, C., Ribas, Á., Schreiber, M. R., Mužić, K., Palau, A., Knee, L. B. G., Bayo, A., Comerón, F., and Hales, A.
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics - Abstract
The dominant mechanism leading to the formation of brown dwarfs (BDs) remains uncertain. The most direct keys to formation, which are obtained from younger objects (pre-BD cores and proto-BDs), are limited by the very low number statistics available. We aim to identify and characterize a set of pre- and proto-BDs as well as Class II BDs in the Lupus 1 and 3 molecular clouds to test their formation mechanism. We performed ALMA band 6 (1.3 mm) continuum observations of a selection of 64 cores previously identified from AzTEC/ASTE data (1.1 mm), along with previously known Class II BDs in the Lupus 1 and 3 molecular clouds. Surveyed archival data in the optical were used to complement these observations. We expect these ALMA observations prove efficient in detecting the youngest sources in these regions, since they probe the frequency domain at which these sources emit most of their radiation. We detected 19 sources from 15 ALMA fields. Considering all the pointings in our observing setup, the ALMA detection rate was $\sim$23% and the derived masses of the detected sources were between $\sim$0.18 and 124 $\mathrm{M_{Jup}}$. We classified these sources according to their spectral energy distribution as 5 Class II sources, 2 new Class I/0 candidats, and 12 new possible pre-BD or deeply embedded protostellar candidates. We detected a promising candidate for a Class 0/I proto-BD source and inferred the disk dust mass of a bona fide Class II BD. The pre-BD cores might be the byproduct of an ongoing process of large-scale collapse. The Class II BD disks follow the correlation between disk mass and the mass of the central object that is observed at the low-mass stellar regime. We conclude that it is highly probable that the sources in the sample are formed as a scaled-down version of low-mass star formation, although disk fragmentation may be responsible for a considerable fraction of BDs., Comment: 21 pages, 10 figures, 13 tables, 3 Appendixes. Accepted in A&A
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- 2020
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48. The complex multi-component outflow of the Seyfert galaxy NGC 7130
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Comerón, S., Knapen, J. H., Almeida, C. Ramos, and Watkins, A. E.
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Astrophysics - Astrophysics of Galaxies - Abstract
AGN are a key ingredient for understanding galactic evolution. AGN-driven outflows are one of the manifestations of feedback. The AO mode for MUSE at the VLT permits to study the innermost tens of parsecs of nearby AGN in the optical. We present a detailed analysis of the ionised gas in the central regions of NGC 7130, an archetypical composite Seyfert and nuclear starburst galaxy. We achieve an angular resolution of 0.17$^{\prime\prime}$ (50 pc). We performed a multi-component analysis of the main ISM lines and identified nine kinematic components, six of which correspond to the outflow. The outflow is biconic and has velocities of a few $100\,{\rm km\,s^{-1}}$ with respect to the disc. We decompose the approaching side of the outflow into a broad and a narrow component with typical velocity dispersions below and above $\sim200\,{\rm km\,s^{-1}}$, respectively. The blueshifted narrow component has substructure, in particular a collimated plume aligned with the radio jet, indicating that it may be jet-powered. The redshifted lobe is composed of two Narrow Components and a Broad Component. An additional redshifted component is seen outside the main outflow axis. Line ratio diagnostics indicate that the outflow gas in the main axis is AGN-powered whereas the off-axis component has LINER properties. The ionised gas mass outflow rate is $\dot{M}=1.2\pm0.7\,M_{\odot}\,{\rm yr^{-1}}$ and the kinetic power is $\dot{E}_{\rm kin}=(2.7\pm2.0)\times10^{41}\,{\rm erg\,s^{-1}}$, which corresponds to $F_{\rm kin}=0.12\pm0.09\%$ of the bolometric AGN power. The combination of high angular resolution integral field spectroscopy and a careful multi-component decomposition allows a uniquely detailed view of the outflow in NGC 7130, illustrating that AGN kinematics are more complex than traditionally derived from less sophisticated data and analyses. (abridged), Comment: Published in A&A. This version of the preprint has been corrected with the modifications appearing in the A&A corrigendum
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- 2020
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49. The historical record of massive star formation in Cygnus
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Comerón, F., Djupvik, A. A., Schneider, N., and Pasquali, A.
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics - Abstract
The Cygnus region, which dominates the local spiral arm of the Galaxy, is one of the nearest complexes of massive star formation. Its massive stellar content, regions of ongoing star formation, and molecular gas have been studied in detail. However, little is known of the history of the region beyond the past 10 Myr. The brightness and spectroscopic characteristics of red supergiants make it easy to identify them and build up a virtually complete sample of such stars at the distance of the Cygnus region, thus providing a record of massive star formation extending several tens of Myr into the past, a period inaccessible through the O and early B stars observable at present. We have made a selection of a sample of bright, red stars in an area of 84 square degrees covering the whole present extension of the Cygnus region. We have obtained spectroscopy in the red visible range allowing an accurate, homogeneous spectral classification as well as a reliable separation between supergiants and other cool stars. Our data are complemented with Gaia Data Release 2 astrometric data. We have identified 29 red supergiants in the area, 17 of which had not been previously classified as supergiants. Twenty-four of the 29 most likely belong to the Cygnus region and four of the remaining to the Perseus arm. We have used their derived luminosities and masses to infer the star formation history of the region. Intense massive star formation activity is found to have started approximately 15 Myr ago, and we find evidence for two other episodes, one taking place between 20 and 30 Myr ago and another one having ended approximately 40 Myr ago. There are small but significant differences between the kinematic properties of red supergiants younger or older then 20 Myr, hinting that stars of the older group were formed outside the precursor of the present Cygnus complex, possibly in the Sagittarius-Carina arm., Comment: Accepted for publication in Astronomy and Astrophysics
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- 2020
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50. Launching the VASCO citizen science project
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Villarroel, Beatriz, Pelckmans, Kristiaan, Solano, Enrique, Laaksoharju, Mikael, Souza, Abel, Dom, Onyeuwaoma Nnaemeka, Laggoune, Khaoula, Mimouni, Jamal, Guergouri, Hichem, Mattsson, Lars, García, Aurora Lago, Soodla, Johan, Castillo, Diego, Shultz, Matthew E., Aworka, Rubby, Comerón, Sébastien, Geier, Stefan, Marcy, Geoffrey, Gupta, Alok C., Bergstedt, Josefine, Bär, Rudolf E., Buelens, Bart, Enriquez, Emilio, Mellon, Christopher K., Prieto, M. Almudena, Wamalwa, Dismas Simiyu, de Souza, Rafael S., and Ward, Martin J.
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
The Vanishing & Appearing Sources during a Century of Observations (VASCO) project investigates astronomical surveys spanning a time interval of 70 years, searching for unusual and exotic transients. We present herein the VASCO Citizen Science Project, which can identify unusual candidates driven by three different approaches: hypothesis, exploratory, and machine learning, which is particularly useful for SETI searches. To address the big data challenge, VASCO combines three methods: the Virtual Observatory, user-aided machine learning, and visual inspection through citizen science. Here we demonstrate the citizen science project and its improved candidate selection process, and we give a progress report. We also present the VASCO citizen science network led by amateur astronomy associations mainly located in Algeria, Cameroon, and Nigeria. At the moment of writing, the citizen science project has carefully examined 15,593 candidate image pairs in the data (ca. 10% of the candidates), and has so far identified 798 objects classified as "vanished". The most interesting candidates will be followed up with optical and infrared imaging, together with the observations by the most potent radio telescopes., Comment: 16 pages, 7 figures, contribution to IAC 2020 conference
- Published
- 2020
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