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The history of gas assembly in early galaxies is reflected in their complex kinematics. While a considerable fraction of galaxies at z~5 are consistent with rotating disks, current studies indicate that the dominant galaxy assembly mechanism corresponds to mergers. Despite the important progress, the dynamical classification of galaxies at these epochs is still limited by observations' resolution. We present a detailed morphological and kinematic analysis of the far-infrared bright main sequence galaxy HZ10 at z=5.65, making use of new high-resolution ($\lesssim0.3$") [CII] 158$\mu$m ALMA and rest-frame optical JWST/NIRSpec observations. These observations reveal a previously unresolved complex morphology and kinematics of the HZ10. We confirm that HZ10 is not a single galaxy but consists of at least three components in close projected separation along the east-to-west direction. We find a [CII] bright central component (C), separated by 1.5 and 4 kpc from the east (E) and west (W) components, respectively. Our [CII] observations resolve the HZ10-C component resulting in a velocity gradient, produced by either rotation or a close-in merger. We test the rotating disk possibility using DysmalPy kinematic modeling and propose three dynamical scenarios for the HZ10 system: (i) a double merger, in which the companion galaxy HZ10-W merges with the disturbed clumpy rotation disk formed by the HZ10-C and E components; (ii) a triple merger, where the companion galaxies, HZ10-W and HZ10-E, merge with the rotation disk HZ10-C; and (iii) a quadruple merger, in which the companion galaxies HZ10-W and HZ10-E merge with the close double merger HZ10-C. Comparing [CII] with JWST/NIRSpec data, we find that [CII] emission closely resembles the broad [OIII] 5007{\AA} emission. The latter reflects the interacting nature of the system and suggests that ionized and neutral gas phases in HZ10 are well mixed., Comment: Submitted to A&A, 16 pages, 17 figures, 1 table

We study the importance of several processes that influence the evolution of dust and its grain size distribution on spatially resolved scales in nearby galaxies. Here, we compiled several multi-wavelength observations for the nearby galaxies NGC628(M74), NGC5457(M101), NGC598(M33), and NGC300. We applied spatially resolved spectral energy distribution fitting to the latest iteration of infrared data to get constraints on the galaxy dust masses and the small-to-large grain abundance ratio. For comparison, we took the radial profiles of the stellar mass and gas mass surface density for NGC628 combined with its metallicity gradient in the literature to calibrate a single-galaxy simulation using the GADGET4-OSAKA code. The simulations include a parametrization to separate the dense and diffuse phases of the ISM where different dust-evolution mechanisms are in action. We find that our simulation can reproduce the radial profile of dust mass surface density but overestimates the SLR in NGC628. Changing the dust-accretion timescale has little impact on the dust mass or SLR, as most of the available metals are accreted onto dust grains at early times (< 3Gyr), except in the outer regions of the galaxy. This suggests we can only constrain the accretion timescale of galaxies at extremely low metallicities where accretion still competes with other mechanisms controlling the dust budget. The overestimation of the SLR likely results from (i) overly efficient shattering processes in the diffuse interstellar medium, which were calibrated to reproduce Milky Way-type galaxies and/or (ii) our use of a diffuse and dense gas density subgrid model that does not entirely capture the intricacies of the small-scale structure present in NGC628., Comment: Accepted on October 12th 2024 16 pages, 13 figures

We present a spatially resolved analysis of four star-forming galaxies at $z = 4.44-5.64$ using data from the JWST PRIMER and ALMA-CRISTAL surveys to probe the stellar and inter-stellar medium properties on the sub-kpc scale. In the $1-5\,\mu{\rm m}$ JWST NIRCam imaging we find that the galaxies are composed of multiple clumps (between $2$ and $\sim 8$) separated by $\simeq 5\,{\rm kpc}$, with comparable morphologies and sizes in the rest-frame UV and optical. Using BAGPIPES to perform pixel-by-pixel SED fitting to the JWST data we show that the SFR ($\simeq 25\,{\rm M}_{\odot}/{\rm yr}$) and stellar mass (${\rm log}_{10}(M_{\star}/{\rm M}_{\odot}) \simeq 9.5$) derived from the resolved analysis are in close ($ \lesssim 0.3\,{\rm dex}$) agreement with those obtained by fitting the integrated photometry. In contrast to studies of lower-mass sources, we thus find a reduced impact of outshining of the older (more massive) stellar populations in these normal $z \simeq 5$ galaxies. Our JWST analysis recovers bluer rest-frame UV slopes ($\beta \simeq -2.1$) and younger ages ($\simeq 100\,{\rm Myr}$) than archival values. We find that the dust continuum from ALMA-CRISTAL seen in two of these galaxies correlates, as expected, with regions of redder rest-frame UV slopes and the SED-derived $A_{\rm V}$, as well as the peak in the stellar mass map. We compute the resolved IRX-$\beta$ relation, showing that the IRX is consistent with the local starburst attenuation curve and further demonstrating the presence of an inhomogeneous dust distribution within the galaxies. A comparison of the CRISTAL sources to those from the FirstLight zoom-in simulation of galaxies with the same $M_{\star}$ and SFR reveals similar age and colour gradients, suggesting that major mergers may be important in the formation of clumpy galaxies at this epoch., Comment: 16 pages, 8 figures, 3 tables, plus 4 page appendix. Submitted to MNRAS

In stars, metallicity is usually traced using Fe, while in nebulae, O serves as the preferred proxy. Both elements have different nucleosynthetic origins and are not directly comparable. Additionally, in ionized nebulae, Fe is heavily depleted onto dust grains. We investigate the distribution of Fe gas abundances in a sample of 452 star-forming nebulae with \feiii~$\lambda 4658$ detections and their relationship with O and N. Additionally, we analyze the depletion of Fe onto dust grains in photoionized environments. We homogeneously determine the chemical abundances with direct determinations of electron temperature ($T_e$), considering the effect of possible internal variations of this parameter. We adopt a sample of 300 Galactic stars to interpret the nebular findings. We find a moderate linear correlation ($r=-0.59$) between Fe/O and O/H. In turn, we report a stronger correlation ($r=-0.80$) between Fe/N and N/H. We interpret the tighter correlation as evidence of Fe and N being produced on similar timescales while Fe-dust depletion scales with the Fe availability. The apparently flat distribution between Fe/N and N/H in Milky Way stars supports this interpretation. We find that when 12+log(O/H)<7.6, the nebulae seem to reach a plateau value around $\text{log(Fe/O)} \approx -1.7$. If this trend is confirmed, it would be consistent with a very small amount of Fe-dust in these systems, similar to what is observed in high-z galaxies discovered by the James Webb Space Telescope (JWST). We derive a relationship that allows us to approximate the fraction of Fe trapped into dust in ionized nebulae. If the O-dust scales in the same way, its possible contribution in low metallicity nebulae would be negligible. After analyzing the Fe/O abundances in J0811+4730 and J1631+4426, we do not see evidence of the presence of very massive stars with $M_\text{init}>300M_{\odot}$ in these systems., Comment: Accepted for publication in A&A

Galaxy protoclusters are sites of rapid growth, with a high density of massive galaxies driving elevated rates of star formation and accretion onto supermassive black holes. Here, we present new JWST/NIRSpec IFU observations of the J1000+0234 group at $z=4.54$, a dense region of a protocluster hosting a massive, dusty star forming galaxy (DSFG). The new data reveal two extended, high-equivalent-width (EW$_0>1000\r{A}$) [O III] nebulae that appear at both sides of the DSFG along its minor axis (namely O3-N and O3-S). On one hand, the spectrum of O3-N shows a broad and blueshifted component with a full width at half maximum (FWHM) of 1300 km/s, suggesting an outflow origin. On the other hand, O3-S stretches over 8.6 kpc, and has a velocity gradient that spans 800 km/s, but shows no evidence of a broad component. However, both sources seem to be powered by an active galactic nucleus (AGN), so we classified them as extended emission-line regions (EELRs). The strongest evidence comes from the detection of the high-ionization [Ne V] $\lambda 3427$ line toward O3-N, which paired with the lack of hard X-rays implies an obscuring column density above the Compton-thick regime. The [Ne V] line is not detected in O3-S, but we measure a He II $\lambda 4687$/H$\beta$=0.25, which is well above the expectation for star formation. Despite the remarkable alignment of O3-N and O3-S with two radio sources, we do not find evidence of shocks from a radio jet that could be powering the EELRs. We interpret this as O3-S being externally irradiated by the AGN, akin to the famous Hanny's Voorwerp object in the local Universe. In addition, classical line ratio diagnostics (e.g., [O III]/H$\beta$ vs [N II]/H$\alpha$) put the DSFG itself in the AGN region of the diagrams, and therefore suggest it to be the most probable AGN host. These results showcase the ability of JWST to unveil obscured AGN at high redshifts., Comment: 13 pages, 10 figures, and one table. Accepted for publication in A&A on November 12th 2024

We present new $\lambda_{\rm rest}=77$ $\mu$m dust continuum observations from the ALMA of HZ10 (CRISTAL-22), a dusty main-sequence galaxy at $z$=5.66 as part of the [CII] Resolved Ism in STar-forming Alma Large program, CRISTAL. The high angular resolution of the ALMA Band 7 and new Band 9 data($\sim{0}''.4$) reveals the complex structure of HZ10, which comprises two main components (HZ10-C and HZ10-W) and a bridge-like dusty emission between them (the Bridge). We model the dust spectral energy distribution (SED) to constrain the physical conditions of the interstellar medium (ISM) and its variations among the different components identified in HZ10. We find that HZ10-W (the more UV-obscured component) has an SED dust temperature of $T_{\rm SED}$$\sim$51.2$\pm13.1$ K; this is $\sim$5 K higher (although still consistent) than that of the central component and previous global estimations for HZ10. Our new ALMA data allow us to reduce by a factor of $\sim$2.3 the uncertainties of global $T_{\rm SED}$ measurements compared to previous studies. Interestingly, HZ10-W shows a lower [CII]/FIR ratio compared to the other two components (although still within the uncertainties), suggesting a harder radiation field destroying polycyclic aromatic hydrocarbon associated with [CII] emission (e.g., active galactic nuclei or young stellar populations). While HZ10-C appears to follow the tight IRX-$\beta_{\rm UV}$ relation seen in local UV-selected starburst galaxies and high-$z$ star-forming galaxies, we find that both HZ10-W and the Bridge depart from this relation and are well described by dust-screen models with holes in front of a hard UV radiation field. This suggests that the UV emission (likely from young stellar populations) is strongly attenuated in the more dusty components of the HZ10 system.

We have learnt in the last decades that the majority of galaxies belong to high density regions interconnected in a sponge-like fashion. This large-scale structure is characterised by clusters, filaments, walls, where most galaxies concentrate, but also under-dense regions, called voids. The void regions and the galaxies within represent an ideal place for the study of galaxy formation and evolution as they are largely unaffected by the complex physical processes that transform galaxies in high-density environments. These void galaxies can hold the key as well to answer current challenges to the $\Lambda$CDM paradigm. The Calar Alto Void Integral-field Treasury surveY (CAVITY) is a Legacy project approved by the Calar Alto Observatory to obtain spatially resolved spectroscopic information of $\sim300$ void galaxies in the Local Universe (0.005 < z < 0.050) covering from -17.0 to -21.5 in $\rm r$ band absolute magnitude. It officially started in January 2021 and has been awarded 110 useful dark observing nights at the 3.5 m telescope using the PMAS spectrograph. Complementary follow-up projects including deep optical imaging, integrated, as well as resolved CO data, and integrated HI spectra, have joint the PMAS observations and naturally complete the scientific aim of characterising galaxies in cosmic voids. The extension data has been denominated CAVITY+. The data will be available to the whole community in different data releases, the first of which is planned for July 2024, and it will provide the community with PMAS data cubes for around 100 void galaxies through a user friendly, and well documented, database platform. We present here the survey, sample selection, data reduction, quality control schemes, science goals, and some examples of the scientific power of the CAVITY and CAVITY+ data., Comment: 19 pages, 11 figures. Accepted for publication in A&A - Replacement after A&A minor language edition

The ALMA [CII] Resolved Ism in STar-forming gALaxies (CRISTAL) survey is a Cycle 8 ALMA Large Programme that studies the cold gas component of high-redshift galaxies. Its sub-arcsecond resolution observations are key to disentangling physical mechanisms that shape galaxies during cosmic dawn. In this paper, we explore the morphology and kinematics of the cold gas, star-forming, and stellar components in the star-forming main-sequence galaxy CRISTAL-05/HZ3, at z = 5.54. Our analysis includes 0.3" spatial resolution (~2 kpc) ALMA observations of the [CII] line. While CRISTAL-05 was previously classified as a single source, our observations reveal that the system is a close interacting pair surrounded by an extended component of carbon-enriched gas. This is imprinted in the disturbed elongated [CII] morphology and the separation of the two components in the position-velocity diagram (~100 km/s). The central region is composed of two components, named C05-NW and C05-SE, with the former being the dominant one. A significant fraction of the [CII] arises beyond the close pair up to 10 kpc, while the regions forming new massive stars and the stellar component seem compact (r_[CII] ~ 4 r_UV), as traced by rest-frame UV and optical imaging obtained with the Hubble Space Telescope and the James Webb Space Telescope. Our kinematic model, using the DYSMALpy software, yields a minor contribution of dark matter of C05-NW within a radius of ~2x Reff. Finally, we explore the resolved [CII]/FIR ratios as a proxy for shock-heating produced by this merger. We argue that the extended [CII] emission is mainly caused by the merger, which could not be discerned with lower-resolution observations. Our work emphasizes the need for high-resolution observations to fully characterize the dynamic stages of infant galaxies and the physical mechanisms that drive the metal enrichment of the circumgalactic medium., Comment: Submitted to A&A - comments are welcome! - 19 pages, 13 figures

Massive star-forming galaxies in the high-redshift universe host large reservoirs of cold gas in their circumgalactic medium (CGM). Traditionally, these reservoirs have been linked to diffuse H I Lyman-$\alpha$ (Ly$\alpha)$ emission extending beyond $\approx 10$ kpc scales. In recent years, millimeter/submillimeter observations are starting to identify even colder gas in the CGM through molecular and/or atomic tracers such as the [C II] $158\,\mu$m transition. In this context, we study the well-known J1000+0234 system at $z=4.54$ that hosts a massive dusty star-forming galaxy (DSFG), a UV-bright companion, and a Ly$\alpha$ blob. We combine new ALMA [C II] line observations taken by the CRISTAL survey with data from previous programs targeting the J1000+0234 system, and achieve a deep view into a DSFG and its rich environment at a 0.2" resolution. We identify an elongated [C II]-emitting structure with a projected size of 15 kpc stemming from the bright DSFG at the center of the field, with no clear counterpart at any other wavelength. The plume is oriented $\approx 40^{\circ}$ away from the minor axis of the DSFG, and shows significant spatial variation of its spectral parameters. In particular, the [C II] emission shifts from 180 km/s to 400 km/s between the bottom and top of the plume, relative to the DSFG's systemic velocity. At the same time, the line width starts at 400-600 km/s but narrows down to 190 km/s at top end of the plume. We discuss four possible scenarios to interpret the [C II] plume: a conical outflow, a cold accretion stream, ram pressure stripping, and gravitational interactions. While we cannot strongly rule out any of these with the available data, we disfavor the ram pressure stripping scenario due to the requirement of special hydrodynamic conditions., Comment: 17 pages (14 main text, 2 for references and 1 appendix page), 7 figures and 4 tables. Submitted to A&A

Galaxies in the Universe are distributed in a web-like structure characterised by different large-scale environments: dense clusters, elongated filaments, sheetlike walls, and under-dense regions, called voids. The low density in voids is expected to affect the properties of their galaxies. Indeed, previous studies have shown that galaxies in voids are on average bluer and less massive, and have later morphologies and higher current star formation rates than galaxies in denser large-scale environments. However, it has never been observationally proved that the star formation histories (SFHs) in void galaxies are substantially different from those in filaments, walls, and clusters. Here we show that void galaxies have had, on average, slower SFHs than galaxies in denser large-scale environments. We also find two main SFH types present in all the environments: 'short-timescale' galaxies are not affected by their large-scale environment at early times but only later in their lives; 'long-timescale' galaxies have been continuously affected by their environment and stellar mass. Both types have evolved slower in voids than in filaments, walls, and clusters., Comment: Published in Nature. 27 pages, 4 Figures, 7 Extended Data Figures, and 1 Extended Data Table

The evolution of the dust grain size distribution has been studied in recent years with great detail in cosmological hydrodynamical simulations taking into account all the channels under which dust evolves in the interstellar medium. We present a systematic analysis of the observed spectral energy distribution of a large sample of galaxies in the local universe in order to derive not only the total dust masses but also the relative mass fraction between small and large dust grains (DS/DL). Simulations reproduce fairly well the observations except for the high stellar mass regime where dust masses tend to be overestimated. We find that ~45% of galaxies exhibit DS/DL consistent with the expectations of simulations, while there is a sub-sample of massive galaxies presenting high DS/DL (log(DS/DL)~-0.5), and deviating from the prediction in simulations. For these galaxies, which also have high molecular gas mass fractions and metallicities, coagulation is not an important mechanism affecting the dust evolution. Including diffusion, transporting large grains from dense regions to a more diffuse medium where they can be easily shattered, would explain the observed high DS/DL values in these galaxies. With this study we reinforce the use of the small-to-large grain mass ratio to study the relative importance of the different mechanisms in the dust life cycle. Multi-phase hydrodynamical simulations with detailed feedback prescriptions and more realistic subgrid models for the dense phase could help to reproduce the evolution of the dust grain size distribution traced by observations., Comment: 32 pages, 22 figures, 4 tables. Accepted in MNRAS

Scaling laws of dust, HI gas and metal mass with stellar mass, specific star formation rate and metallicity are crucial to our understanding of the buildup of galaxies through their enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass ($M_{\text{HI}}$/$M_{\star}$) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) - incluidng stellar dust production, grain growth, and dust destruction - within a Bayesian framework to enable a rigorous search of the multi-dimensional parameter space. We find that these scaling laws for galaxies with $-1.0\lesssim \log M_{\text{HI}}$/$M_{\star}\lesssim0$ can be reproduced using closed-box models with high fractions (37-89$\%$) of supernova dust surviving a reverse shock, relatively low grain growth efficiencies ($\epsilon$=30-40), and long dus lifetimes (1-2\,Gyr). The models have present-day dust masses with similar contributions from stellar sources (50-80\,$\%$) and grain growth (20-50\,$\%$). Over the entire lifetime of these galaxies, the contribution from stardust ($>$90\,$\%$) outweighs the fraction of dust grown in the interstellar medium ($<$10$\%$). Our results provide an alternative for the chemical evolution models that require extremely low supernova dust production efficiencies and short grain growth timescales to reproduce local scaling laws, and could help solving the conundrum on whether or not grains can grow efficiently in the interstellar medium., Comment: 56 pages, 30 figures, accepted for publication in MNRAS

Dust is formed out of stellar material and is constantly affected by different mechanisms occurring in the ISM. Dust grains behave differently under these mechanisms depending on their sizes, and therefore the dust grain size distribution also evolves as part of the dust evolution itself. Following how the grain size distribution evolves is a difficult computing task that is just recently being overtaking. Smoothed particle hydrodynamic (SPH) simulations of a single galaxy as well as cosmological simulations are producing the first predictions of the evolution of the dust grain size distribution. We compare for the first time the evolution of the dust grain size distribution predicted by the SPH simulations with the results provided by the observations. We analyse how the radial distribution of the small to large grain mass ratio (D(S)/D(L)) changes over the whole discs in three galaxies: M 101, NGC 628 and M 33. We find good agreement between the observed radial distribution of D(S)/D(L) and what is obtained from the SPH simulations of a single galaxy. The central parts of NGC 628, at high metallicity and with a high molecular gas fraction, are mainly affected not only by accretion but also by coagulation of dust grains. The centre of M 33, having lower metallicity and lower molecular gas fraction, presents an increase of D(S)/D(L), showing that shattering is very effective in creating a large fraction of small grains. Observational results provided by our galaxies confirm the general relations predicted by the cosmological simulations based on the two grain size approximation. However, we present evidence that the simulations could be overestimating the amount of large grains in high massive galaxies., Comment: 11 pages, 6 Figures, to be published in A&A

Dust and starlight are modeled for the KINGFISH project galaxies. With data from 3.6 micron to 500 micron, models are strongly constrained. For each pixel in each galaxy we estimate (1) dust surface density; (2) q_PAH, the dust mass fraction in PAHs; (3) distribution of starlight intensities heating the dust; (4) luminosity emitted by the dust; and (5) dust luminosity from regions with high starlight intensity. The models successfully reproduce both global and resolved spectral energy distributions. We provide well-resolved maps for the dust properties. As in previous studies, we find q_PAH to be an increasing function of metallicity, above a threshold Z/Z_sol approx 0.15. Dust masses are obtained by summing the dust mass over the map pixels; these "resolved" dust masses are consistent with the masses inferred from model fits to the global photometry. The global dust-to-gas ratios obtained from this study correlate with galaxy metallicities. Systems with Z/Z_sol > 0.5 have most of their refractory elements locked up in dust, whereas when Z/Z_sol < 0.3 most of these elements tend to remain in the gas phase. Within galaxies, we find that q_PAH is suppressed in regions with unusually warm dust with nu L_nu(70 um) > 0.4L_dust. With knowledge of one long-wavelength flux density ratio (e.g., f_{160}/f_{500}), the minimum starlight intensity heating the dust (U_min) can be estimated to within ~50%. For the adopted dust model, dust masses can be estimated to within ~0.07 dex accuracy using the 500 micron luminosity nu L_nu(500) alone. There are additional systematic errors arising from the choice of dust model, but these are hard to estimate. These calibrated prescriptions may be useful for studies of high-redshift galaxies., Comment: ApJ, accepted

We present a spatially resolved study of the relation between dust and metallicity in the nearby spiral galaxies M101 (NGC 5457) and NGC 628 (M74). We explore the relation between the chemical abundances of their gas and stars with their dust content and their chemical evolution. The empirical spatially resolved oxygen effective yield and the gas to dust mass ratio (GDR) across both disc galaxies are derived, sampling one dex in oxygen abundance. We find that the metal budget of the NGC 628 disc and most of the M101 disc appears consistent with the predictions of the simple model of chemical evolution for an oxygen yield between half and one solar, whereas the outermost region (R<0.8R25) of M101 presents deviations suggesting the presence of gas flows. The GDR-metallicity relation shows a two slopes behaviour, with a break at 12+log(O/H)~8.4, a critical metallicity predicted by theoretical dust models when stardust production equals grain growth. A relation between GDR and the fraction of molecular to total gas, Sigma(H2)/Sigma(gas) is also found. We suggest an empirical relationship between GDR and the combination of 12+log(O/H), for metallicity, and Sigma(H2)/Sigma(gas), a proxy for the molecular clouds fraction. The GDR is closely related with metallicity at low abundance and with Sigma(H2)/Sigma(gas) for higher metallicities suggesting ISM dust growth. The ratio Sigma(dust)/Sigma(star) correlates well with 12 + log(O/H) and strongly with log(N/O) in both galaxies. For abundances below the critical one, the 'stardust' production gives us a constant value suggesting a stellar dust yield similar to the oxygen yield., Comment: 16 pages, 14 Figures, accepted in MNRAS

We have fit the far-ultraviolet (FUV) to sub-millimeter (850 micron) spectral energy distributions (SEDs) of the 61 galaxies from the "Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel" (KINGFISH). The fitting has been performed using three models: the Code for Investigating GALaxy Evolution (CIGALE), the GRAphite-SILicate approach (GRASIL), and the Multi-wavelength Analysis of Galaxy PHYSical properties (MAGPHYS). We have analyzed the results of the three codes in terms of the SED shapes, and by comparing the derived quantities with simple "recipes" for stellar mass (Mstar), star-formation rate (SFR), dust mass (Mdust), and monochromatic luminosities. Although the algorithms rely on different assumptions for star-formation history, dust attenuation and dust reprocessing, they all well approximate the observed SEDs and are in generally good agreement for the associated quantities. However, the three codes show very different behavior in the mid-infrared regime, in particular between 25 and 70 micron where there are no observational constraints for the KINGFISH sample. We find that different algorithms give discordant SFR estimates for galaxies with low specific SFR, and that the standard "recipes" for calculating FUV absorption overestimate the extinction compared to the SED-fitting results. Results also suggest that assuming a "standard" constant stellar mass-to-light ratio overestimates Mstar relative to the SED fitting, and we provide new SED-based formulations for estimating Mstar from WISE W1 (3.4 micron) luminosities and colors. From a Principal Component Analysis of Mstar, SFR, Mdust, and O/H, we reproduce previous scaling relations among Mstar, SFR, and O/H, and find that Mdust can be predicted to within roughly 0.3 dex using only Mstar and SFR., Comment: 42 pages, 23 figures, 8 tables, 2 appendices: updated to v2, A&A, accepted

The relative abundance of the dust grain types in the interstellar medium (ISM) is directly linked to physical quantities that trace the evolution of galaxies. We study the dust properties of the whole disc of M33 at spatial scales of ~170 pc. This analysis allows us to infer how the relative dust grain abundance changes with the conditions of the ISM, study the existence of a submillimetre excess and look for trends of the gas-to-dust mass ratio (GDR) with other physical properties of the galaxy. For each pixel in the disc of M33 we fit the infrared SED using a physically motivated dust model that assumes an emissivity index beta close to 2. We derive the relative amount of the different dust grains in the model, the total dust mass, and the strength of the interstellar radiation field (ISRF) heating the dust at each spatial location. The relative abundance of very small grains tends to increase, and for big grains to decrease, at high values of Halpha luminosity. This shows that the dust grains are modified inside the star-forming regions, in agreement with a theoretical framework of dust evolution under different physical conditions. The radial dependence of the GDR is consistent with the shallow metallicity gradient observed in this galaxy. The strength of the ISRF derived in our model correlates with the star formation rate in the galaxy in a pixel by pixel basis. Although this is expected it is the first time that a correlation between both quantities is reported. We produce a map of submillimetre excess in the 500 microns SPIRE band for the disc of M33. The excess can be as high as 50% and increases at large galactocentric distances. We further study the relation of the excess with other physical properties of the galaxy and find that the excess is prominent in zones of diffuse ISM outside the main star-forming regions, where the molecular gas and dust surface density are low., Comment: Accepted to Astronomy and Astrophysics, 19 pages, 18 figures plus appendix

ABRIGED: Quantifying the number, type and distribution of W-R stars is a key component in the context of galaxy evolution, since they put constraints on the age of the star formation bursts. Nearby galaxies (d<5 Mpc) are particularly relevant in this context since they fill the gap between studies in the Local Group, where individual stars can be resolved, and galaxies in the Local Volume and beyond. We intend to characterize the W-R star population in NGC625, a low-metallicity dwarf galaxy suffering a currently declining burst of star formation. Optical IFS data have been obtained with the VIMOS-IFU covering the starburst region. We estimate the number of W-R stars using a linear combination of 3 W-R templates: 1 early-type nitrogen (WN) star, 1 late-type WN star and 1 carbon-type (WC) star (or oxygen-type (WO) star). Fits using several ensembles of templates were tested. Results were confronted with: i) high spatial resolution HST photometry; ii) numbers of W-R stars in nearby galaxies; iii) model predictions. The W-R star population is spread over the main body of the galaxy, not necessarily coincident with the overall stellar distribution. Our best estimation for the number of W-R stars yields a total of 28 W-R stars in the galaxy, out of which 17 are early- type WN, 6 are late-type WN and 5 are WC stars. The width of the stellar features nicely correlates with the dominant W-R type found in each aperture. The distribution of the different types of WR in the galaxy is roughly compatible with the way star formation has propagated in the galaxy, according to previous findings using HST images. Fits using templates at the metallicity of the LMC yield more reasonable number of W-R than those using templates at the metallicity of the SMC. Given the metallicity of NGC 625, this suggests a non-linear relation between the metallicity and the luminosity of the W-R spectral features., Comment: 13 pages, 6 figures, accepted by A&A; Labels in the axes of some figures are not displayed properly after the compilation on arXiv. Another version with the proper figures can be found here: https://www.dropbox.com/s/u2bx2li5jogmfkp/manuscript_astroph.pdf?dl=0

The conversion of the IR emission into star formation rate can be strongly dependent on the physical properties of the dust, which are affected by the environmental conditions where the dust is embedded. We study here the dust properties of a set of HII regions in the Local Group Galaxy M33 presenting different spatial configurations between the stars, gas and dust to understand the dust evolution under different environments. We model the SED of each region using the DustEM tool and obtain the mass relative to hydrogen for Very Small Grains (YVSG), Polycyclic Aromatic Hydrocarbons (YPAH) and Big Grains (YBG). The relative mass of the VSGs (YVSG/YTOT) is a factor of 1.7 higher for HII regions classified as filled and mixed than for regions presenting a shell structure. The enhancement of VSGs within NGC 604 and NGC 595 is correlated to expansive gas structures with velocities greater than 50 km/s. The gas-to-dust ratio derived for the HII regions in our sample exhibits two regimes related to the HI-H2 transition of the ISM. Regions corresponding to the HI diffuse regime present a gas-to-dust ratio compatible with the expected value if we assume that the gas-to-dust ratio scales linearly with metallicity, while regions corresponding to a H2 molecular phase present a flatter dust-gas surface density distribution. The fraction of VSGs can be affected by the conditions of the interstellar environment: strong shocks of 50-90 km/s existing in the interior of the most luminous HII regions can lead to fragmentation of BGs into smaller ones, while the more evolved shell and clear shell objects provide a more quiescent environment where reformation of dust BG grains might occur. The gas-to-dust variations found in this analysis might imply that grain coagulation and/or gas-phase metals incorporation to the dust mass is occurring in the interior of the HII regions in M33., Comment: Accepted for publication in A&A, 29 pages, 16 figures

To compute the SFR of galaxies from the rest-frame UV it is essential to take into account the obscuration by dust. To do so, one of the most popular methods consists in combining the UV with the emission from the dust itself in the IR. Yet, different studies have derived different estimators, showing that no such hybrid estimator is truly universal. In this paper we aim at understanding and quantifying what physical processes drive the variations between different hybrid estimators. Doing so, we aim at deriving new universal UV+IR hybrid estimators to correct the UV for dust attenuation, taking into account the intrinsic physical properties of galaxies. We use the CIGALE code to model the spatially-resolved FUV to FIR SED of eight nearby star-forming galaxies drawn from the KINGFISH sample. This allows us to determine their local physical properties, and in particular their UV attenuation, average SFR, average specific SFR (sSFR), and their stellar mass. We then examine how hybrid estimators depend on said properties. We find that hybrid UV+IR estimators strongly depend on the stellar mass surface density (in particular at 70 and 100 micron) and on the sSFR (in particular at 24 micron and the TIR). Consequently, the IR scaling coefficients for UV obscuration can vary by almost an order of magnitude. This result contrasts with other groups who found relatively constant coefficients with small deviations. We exploit these variations to construct a new class of hybrid estimators based on observed UV to near-IR colours and near-IR luminosity densities per unit area. We find that they can reliably be extended to entire galaxies. The new estimators provide better estimates of attenuation-corrected UV emission than classical hybrid estimators. Naturally taking into account the variable impact of dust heated by old stellar populations, they constitute a step towards universal estimators., Comment: 25 pages, 12 figures, 8 tables. Accepted for publication in A&A

Previous studies have shown the existence of an excess of emission at submillimeter (submm) and millimeter (mm) wavelengths in the spectral energy distribution (SED) of many low-metallicity galaxies. The goal of the present study is to model separately the emission from the star forming (SF) component and the emission from the diffuse interstellar medium (ISM) in the nearby spiral galaxy M33. We decomposed the observed SED of M33 into its SF and diffuse components. Mid-infrared (MIR) and far-infrared (FIR) fluxes were extracted from Spitzer and Herschel data. At submm and mm wavelengths, we used ground-based observations from APEX to measure the emission from the SF component and data from the Planck space telescope to estimate the diffuse emission. Both components were separately fitted using radiation transfer models based on standard dust properties and a realistic geometry. Both modeled SEDs were combined to build the global SED of M33. In addition, the radiation field necessary to power the dust emission in our modeling was compared with observations from GALEX, Sloan, and Spitzer. Our modeling is able to reproduce the observations at MIR and FIR wavelengths, but we found a strong excess of emission at submm and mm wavelengths, where the model expectations severely underestimate the LABOCA and Planck fluxes. We also found that the ultraviolet (UV) radiation escaping the galaxy is 70% higher than the model predictions. We determined a gas-to-dust mass ratio Gdust~100, significantly lower than the value expected from the sub-solar metallicity of M33. We discussed different hypotheses to explain the discrepancies found in our study (i.e., excess of emission at submm and mm wavelengths, deficit of UV attenuation, and abnormally low value of Gdust), concluding that different dust properties in M33 is the most plausible explanation., Comment: accepted by A&A, 22 pages

Context. Measuring star formation at a local scale is important to constrain star formation laws. Yet, it is not clear whether and how the measure of star formation is affected by the spatial scale at which a galaxy is observed. Aims. We want to understand the impact of the resolution on the determination of the spatially resolved star formation rate (SFR) and other directly associated physical parameters such as the attenuation. Methods. We have carried out a multi-scale, pixel-by-pixel study of the nearby galaxy M33. Assembling FUV, Halpha, 8, 24, 70, and 100 micron maps, we have systematically compared the emission in individual bands with various SFR estimators from a resolution of 33 pc to 2084 pc. Results. We have found that there are strong, scale-dependent, discrepancies up to a factor 3 between monochromatic SFR estimators and Halpha+24 micron. The scaling factors between individual IR bands and the SFR show a strong dependence on the spatial scale and on the intensity of star formation. Finally, strong variations of the differential reddening between the nebular emission and the stellar continuum are seen, depending on the specific SFR (sSFR) and on the resolution. At the finest spatial scales, there is little differential reddening at high sSFR. The differential reddening increases with decreasing sSFR. At the coarsest spatial scales the differential reddening is compatible with the canonical value found for starburst galaxies. Conclusions. Our results confirm that monochromatic estimators of the SFR are unreliable at scales smaller than 1 kpc. Furthermore, the extension of local calibrations to high redshift galaxies presents non-trivial challenges as the properties of these systems may be poorly known., Comment: 15 pages, 9 figures, 1 table. Accepted for publication in A&A

Over the past decade, 3D optical spectroscopy has become the preferred tool for understanding the properties of galaxies and is now increasingly used to carry out galaxy surveys. Low redshift surveys include SAURON, DiskMass, ATLAS3D, PINGS and VENGA. At redshifts above 0.7, surveys such as MASSIV, SINS, GLACE, and IMAGES have targeted the most luminous galaxies to study mainly their kinematic properties. The on-going CALIFA survey ($z\sim0.02$) is the first of a series of upcoming Integral Field Spectroscopy (IFS) surveys with large samples representative of the entire population of galaxies. Others include SAMI and MaNGA at lower redshift and the upcoming KMOS surveys at higher redshift. Given the importance of spatial scales in IFS surveys, the study of the effects of spatial resolution on the recovered parameters becomes important. We explore the capability of the CALIFA survey and a hypothetical higher redshift survey to reproduce the properties of a sample of objects observed with better spatial resolution at lower redshift. Using a sample of PINGS galaxies, we simulate observations at different redshifts. We then study the behaviour of different parameters as the spatial resolution degrades with increasing redshift., Comment: 20 pages, 16 figures. Accepted for publication in A&A

We study the wavelength dependence of the dust emission as a function of position and environment across the disk of M33 at a linear resolution of 160 pc using Spitzer and Herschel photometric data. Expressing the emissivity of the dust as a power law, the power-law exponent (beta) is estimated from two independent approaches designed to properly treat the degeneracy between beta and the dust temperature. Both beta and the dust temperature are higher in the inner disk than in the outer disk, contrary to reported beta-T anti-correlations found in other sources. In the cold + warm dust model, the warm component and the ionized gas (Halpha) have a very similar distribution across the galaxy, demonstrating that the model separates the components in an appropriate fashion. The flocculent spiral arms and the dust lanes are evident in the map of the cold component. Both cold and warm dust column densities are high in star forming regions and reach their maxima toward the giant star forming complexes NGC604 and NGC595. beta declines from close to 2 in the center to about 1.3 in the outer disk. beta is positively correlated with star formation and with molecular gas column, as traced by Halpha and CO emission. The lower dust emissivity index in the outer parts of M33 is likely related to the reduced metallicity (different grain composition) and possibly different size distribution. It is not due to the decrease in stellar radiation field or temperature in a simple way because the FIR-bright regions in the outer disk also have a low beta. Like most spirals, M33 has a (decreasing) radial gradient in star formation and molecular-to-atomic gas ratio such that the regions bright in Halpha or CO tend to trace the inner disk, making it difficult to distinguish between their effects on the dust., Comment: 18 pages, 16 figures, Accepted for Publication in Astronomy & Astrophysics Journal

We aim to better understand the heating of the gas by observing the prominent gas cooling line [CII] at 158um in the low-metallicity environment of the Local Group spiral galaxy M33 at scales of 280pc. In particular, we aim at describing the variation of the photoelectric heating efficiency with galactic environment. In this unbiased study, we used ISO/LWS [CII] observations along the major axis of M33, in combination with Herschel PACS and SPIRE continuum maps, IRAM 30m CO 2-1 and VLA HI data to study the variation of velocity integrated intensities. The ratio of [CII] emission over the far-infrared continuum is used as a proxy for the heating efficiency, and models of photon-dominated regions are used to study the local physical densities, FUV radiation fields, and average column densities of the molecular clouds. The heating efficiency stays constant at 0.8% in the inner 4.5kpc radius of the galaxy where it starts to increase to reach values of ~3% in the outskirts at about 6kpc radial distance. The rise of efficiency is explained in the framework of PDR models by lowered volume densities and FUV fields, for optical extinctions of only a few magnitudes at constant metallicity. In view of the significant fraction of HI emission stemming from PDRs, and for typical pressures found in the Galactic cold neutral medium (CNM) traced by HI emission, the CNM contributes ~15% to the observed [CII] emission in the inner 2kpc radius of M33. The CNM contribution remains largely undetermined in the south, while positions between 2 and 7.3kpc radial distance in the north of M33 show a contribution of ~40%+-20%., Comment: (16 pages, a version with higher resolution figures may be downloaded from http://www.iram.es/IRAMES/hermesWiki/HermesPublications)

Within the framework of the Herschel M 33 extended survey HerM33es we study the Spectral Energy Distribution (SED) of a set of HII regions in M 33 as a function of the morphology. We present a catalogue of 119 HII regions morphologically classified: 9 filled, 47 mixed, 36 shell, and 27 clear shell HII regions. For each object we extract the photometry at twelve available wavelength bands (from FUV-1516A to IR-250mi) and obtain the SED. We also obtain emission line profiles across the regions to study the location of the stellar, ionised gas, and dust components. We find trends for the SEDs related to the morphology, showing that the star and gas-dust configuration affects the ratios of the emission in different bands. The mixed and filled regions show higher emission at 24mi than the shells and clear shells, which could be due to the proximity of the dust to the stellar clusters in the case of mixed and filled regions. The FIR peak for shells and clear shells seems to be located towards longer wavelengths, indicating that the dust is colder for this type of objects.The logarithmic 100/70mi ratio for filled and mixed regions remains constant over one order of magnitude in Halpha and FUV surface brightness, while the shells and clear shells exhibit a wider range of values of almost two orders of magnitude. We derive dust masses and temperatures fitting the individual SEDs with dust models proposed in the literature. The derived dust mass range is between 10^2-10^4 Msun and the cold dust temperature spans T(cold)~12-27 K. The spherical geometrical model proposed for the Halpha clear shells is confirmed by the emission profile obtained from the observations and is used to infer the electron density within the envelope: the typical electron density is 0.7+-0.3 cm^-3, while filled regions can reach values two to five times higher., Comment: 21 pages, 19 figures. Accepted to A&A

We study the far-infrared emission from the nearby spiral galaxy M33 in order to investigate the dust physical properties such as the temperature and the luminosity density across the galaxy. Taking advantage of the unique wavelength coverage (100, 160, 250, 350 and 500 micron) of the Herschel Space Observatory and complementing our dataset with Spitzer-IRAC 5.8 and 8 micron and Spitzer-MIPS 24 and 70 micron data, we construct temperature and luminosity density maps by fitting two modified blackbodies of a fixed emissivity index of 1.5. We find that the 'cool' dust grains are heated at temperatures between 11 and 28 K with the lowest temperatures found in the outskirts of the galaxy and the highest ones in the center and in the bright HII regions. The infrared/submillimeter total luminosity (5 - 1000 micron) is estimated to be 1.9x10^9 Lsun. 59% of the total luminosity of the galaxy is produced by the 'cool' dust grains (~15 K) while the rest 41% is produced by 'warm' dust grains (~55 K). The ratio of the cool-to-warm dust luminosity is close to unity (within the computed uncertainties), throughout the galaxy, with the luminosity of the cool dust being slightly enhanced in the center of the galaxy. Decomposing the emission of the dust into two components (one emitted by the diffuse disk of the galaxy and one emitted by the spiral arms) we find that the fraction of the emission in the disk in the mid-infrared (24 micron) is 21%, while it gradually rises up to 57% in the submillimeter (500 micron). We find that the bulk of the luminosity comes from the spiral arm network that produces 70% of the total luminosity of the galaxy with the rest coming from the diffuse dust disk. The 'cool' dust inside the disk is heated at a narrow range of temperatures between 18 and 15 K (going from the center to the outer parts of the galaxy)., Comment: 12 pages, 14 figures, accepted for publication in A&A

We present observational evidence that leakage of ionising photons from star-forming regions can affect the quantification of the star formation rate (SFR) in galaxies. This effect could partially explain the differences between the SFR estimates using the far ultraviolet (FUV) and the Halpha emission. We find that leakage could decrease the SFR(Ha)/SFR(FUV) ratio by up to a 25 per cent. The evidence is based on the observation that the SFR(Ha)/SFR(FUV) ratio is lower for objects showing a shell Halpha structure than for regions exhibiting a much more compact morphology. The study has been performed on three object samples: low luminosity dwarf galaxies from the Local Volume Legacy survey and star-forming regions in the Large Magellanic Cloud and the nearby Local Group galaxy M33. For the three samples we find differences (1.1-1.4sigma) between the SFR(Ha)/SFR(FUV) for compact and shell objects. Although leakage cannot entirely explain the observed trend of SFR(Ha)/SFR(FUV) ratios for systems with low SFR, we show the mechanism can lead to different SFR estimates when using Halpha and FUV luminosities. Therefore, further study is needed to constrain the contribution of leakage to the low SFR(Ha)/SFR(FUV) ratios observed in dwarf galaxies and its impact on the Halpha flux as a SFR indicator in such objects., Comment: 8 pages, 7 figures; accepted for publication in MNRAS

Power spectra of de-projected images of late-type galaxies in gas and/or dust emission are very useful diagnostics of the dynamics and stability of their interstellar medium. Previous studies have shown that the power spectra can be approximated as two power-laws, a shallow one at large scales (larger than 500 pc) and a steeper one at small scales, with the break between the two corresponding to the line-of-sight thickness of the galaxy disk. We present a thorough analysis of the power spectra of the dust and gas emission at several wavelengths in the nearby galaxy M33. In particular, we use the recently obtained images at five wavelengths by PACS and SPIRE onboard Herschel. The large dynamical range (2-3 dex in scale) of most images allow us to determine clearly the change in slopes from -1.5 to -4, with some variations with wavelength. The break scale is increasing with wavelength, from 100 pc at 24 and 100micron to 350 pc at 500micron, suggesting that the cool dust lies in a thicker disk than the warm dust, may be due to star formation more confined to the plane. The slope at small scale tends to be steeper at longer wavelength, meaning that the warmer dust is more concentrated in clumps. Numerical simulations of an isolated late-type galaxy, rich in gas and with no bulge, like M33, are carried out, in order to better interpret these observed results. Varying the star formation and feedback parameters, it is possible to obtain a range of power-spectra, with two power-law slopes and breaks, which nicely bracket the data. The small-scale power-law is indeed reflecting the 3D behaviour of the gas layer, steepening strongly while the feedback smoothes the structures, by increasing the gas turbulence. M33 appears to correspond to a fiducial model with an SFR of $\sim$ 0.7 Mo/yr, with 10% supernovae energy coupled to the gas kinematics., Comment: 11 pages, 24 figures, accepted in Astronomy & Astrophysics

We have carried out a detailed modelling of the dust heating and emission in the nearby, starbursting dwarf galaxy NGC 4214. Due to its proximity and the great wealth of data from the UV to the millimeter range (from GALEX, HST, {\it Spitzer}, Herschel, Planck and IRAM) it is possible to separately model the emission from HII regions and their associated photodissociation regions (PDRs) and the emission from diffuse dust. Furthermore, most model parameters can be directly determined from the data leaving very few free parameters. We can fit both the emission from HII+PDR regions and the diffuse emission in NGC 4214 with these models with "normal" dust properties and realistic parameters., Comment: 4pages, 3 figures. To appear in 'The Spectral Energy Distribution of Galaxies' Proceedings IAU Symposium No 284, 2011

We have carried out a detailed modeling of the dust Spectral Energy Distribution (SED) of the nearby, starbursting dwarf galaxy NGC 4214. A key point of our modeling is that we distinguish the emission from (i) HII regions and their associated photodissociation regions (PDRs) and (ii) diffuse dust. For both components we apply templates from the literature calculated with a realistic geometry and including radiation transfer. The large amount of existing data from the ultraviolet (UV) to the radio allows the direct measurement of most of the input parameters of the models. We achieve a good fit for the total dust SED of NGC 4214. In the present contribution we describe the available data, the data reduction and the determination of the model parameters, whereas a description of the general outline of our work is presented in the contribution of Lisenfeld et al. in this volume., Comment: 3 pages, 1 figure. To appear in 'The Spectral Energy Distribution of Galaxies' Proceedings IAU Symposium No 284, 2011

Within the framework of the HerM33es Key Project for Herschel and in combination with multi-wavelength data, we study the Spectral Energy Distribution (SED) of a set of HII regions in the Local Group Galaxy M33. Using the Halpha emission, we perform a classification of a selected HII region sample in terms of morphology, separating the objects in filled, mixed, shell and clear shell objects. We obtain the SED for each HII region as well as a representative SED for each class of objects. We also study the emission distribution of each band within the regions. We find different trends in the SEDs for each morphological type that are related to properties of the dust and their associated stellar cluster. The emission distribution of each band within the region is different for each morphological type of object., Comment: 3pages, 4 figures. To appear in 'The Spectral Energy Distribution of Galaxies' Proceedings IAU Symposium No 284, 2011

We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction.We summarize the survey goals and design, including sample selection and observational strategy.We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of $\sim600$ galaxies in the Local Universe (0.005< z <0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK Integral Field Unit (IFU), with a hexagonal field-of-view of $\sim1.3\sq\arcmin'$, with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 {\AA}, using two overlapping setups (V500 and V1200), with different resolutions: R\sim850 and R\sim1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfill the expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis. We conclude from this first look at the data that CALIFA will be an important resource for archaeological studies of galaxies in the Local Universe., Comment: 32 pages, 29 figures, Accepted for publishing in Astronomy and Astrophysics

Dust emission is one of the main windows to the physics of galaxies and to star formation as the radiation from young, hot stars is absorbed by the dust and reemitted at longer wavelengths. The recently launched Herschel satellite now provides a view of dust emission in the far-infrared at an unequaled resolution and quality up to 500 \mu m. In the context of the Herschel HERM33ES open time key project, we are studying the moderately inclined Scd local group galaxy M33 which is located only 840 kpc away. In this article, using Spitzer and Herschel data ranging from 3.6 \mu m to 500 \mu m, along with HI, H\alpha\ maps, and GALEX ultraviolet data we have studied the emission of the dust at the high spatial resolution of 150 pc. Combining Spitzer and Herschel bands, we have provided new, inclination corrected, resolved estimators of the total infrared brightness and of the star formation rate from any combination of these bands. The study of the colors of the warm and cold dust populations shows that the temperature of the former is, at high brightness, dictated by young massive stars but, at lower brightness, heating is taken over by the evolved populations. Conversely, the temperature of the cold dust is tightly driven by the evolved stellar populations., Comment: 29 pages, 12 figures, accepted for publication in AJ

Context: The emission line of [CII] at 158 micron is one of the strongest cooling lines of the interstellar medium (ISM) in galaxies. Aims: Disentangling the relative contributions of the different ISM phases to [CII] emission, is a major topic of the HerM33es program, a Herschel key project to study the ISM in the nearby spiral galaxy M33. Methods: Using PACS, we have mapped the emission of [CII] 158 micron, [OI] 63 micron, and other FIR lines in a 2'x2' region of the northern spiral arm of M33, centered on the HII region BCLMP302. At the peak of H-alpha emission, we have observed in addition a velocity resolved [CII] spectrum using HIFI. We use scatterplots to compare these data with PACS 160 micron continuum maps, and with maps of CO and HI data, at a common resolution of 12 arcsec or 50 pc. Maps of H-alpha and 24 micron emission observed with Spitzer are used to estimate the SFR. We have created maps of the [CII] and [OI] 63 micron emission and detected [NII] 122 micron and NIII 57 micron at individual positions. Results: The [CII] line observed with HIFI is significantly broader than that of CO, and slightly blue-shifted. In addition, there is little spatial correlation between [CII] observed with PACS and CO over the mapped region. There is even less spatial correlation between [CII] and the atomic gas traced by HI. Detailed comparison of the observed intensities towards the HII region with models of photo ionization and photon dominated regions, confirms that a significant fraction, 20--30%, of the observed [CII] emission stems from the ionized gas and not from the molecular cloud. The gas heating efficiency, using the ratio between [CII] and the TIR as a proxy, varies between 0.07 and 1.5%, with the largest variations found outside the HII region., Comment: Accepted for publication in A&A. 12 pages, 12 figures

Within the key project "Herschel M33 extended survey" (HerM33es), we are studying the physical and chemical processes driving star formation and galactic evolution in the nearby galaxy M33, combining the study of local conditions affecting individual star formation with properties only becoming apparent on global scales. Here, we present recent results obtained by the HerM33es team. Combining Spitzer and Herschel data ranging from 3.6um to 500um, along with HI, Halpha, and GALEX UV data, we have studied the dust at high spatial resolutions of 150pc, providing estimators of the total infrared (TIR) brightness and of the star formation rate. While the temperature of the warm dust at high brightness is driven by young massive stars, evolved stellar populations appear to drive the temperature of the cold dust. Plane-parallel models of photon dominated regions (PDRs) fail to reproduce fully the [CII], [OI], and CO maps obtained in a first spectroscopic study of one 2'x2' subregion of M33, located on the inner, northern spiral arm and encompassing the HII region BCLMP302., Comment: 6 pages, to appear in the proceedings of the 5th Zermatt ISM Symposium "Conditions and impact of star formation: New results with Herschel and beyond"

(ABRIDGED) We present an analysis of NGC588 based on IFS data with PMAS, together with Spitzer images at 8 mi and 24 mi. The extinction distribution in the optical shows complex structure, with maxima correlating in position with those of the emission at 24 mi and 8 mi. The Ha luminosity absorbed by the dust within the GHIIR reproduces the structure observed in the 24 mi image, supporting the use of this band as a tracer of recent star formation. A velocity difference of ~50 km/s was measured between the areas of high and low surface brightness, which would be expected if NGC588 were an evolved GHIIR. Line ratios used in the BPT diagnostic diagrams show a larger range of variation in the low surface brightness areas. The ranges are ~0.5 to 1.2 dex for [NII]/Ha, 0.7 to 1.7 dex for [SII]/Ha, and 0.3 to 0.5 dex for [OIII]/Hb. Ratios corresponding to large ionization parameter (U) are found between the peak of the emission in Hb and the main ionizing source decreasing radially outwards within the region. Differences between the integrated and local values of the U tracers can be as high as ~0.8 dex. [OII]/Hb and [OIII]/[OII] yield similar local values for U and consistent with those expected from the integrated spectrum of an HII region ionized by a single star. The ratio [SII]/Ha departs significantly from the range predicted by this scenario, indicating the complex ionization structure in GHIIRs. There is a significant scatter in derivations of Z using strong line tracers as a function of position, caused by variations in the degree of ionization. The scatter is smaller for N2O3 which points to this tracer as a better Z tracer than N2. The comparison between integrated and local line ratio values indicates that measurements of the line ratios of GHIIR in galaxies at distances >~25 Mpc may be dominated by the ionization conditions in their low surface brightness areas., Comment: accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal, 2010 January 5; 18 pages; 15 figures

We present an analysis of the first space-based far-IR-submm observations of M 33, which measure the emission from the cool dust and resolve the giant molecular cloud complexes. With roughly half-solar abundances, M33 is a first step towards young low-metallicity galaxies where the submm may be able to provide an alternative to CO mapping to measure their H$_2$ content. In this Letter, we measure the dust emission cross-section $\sigma$ using SPIRE and recent CO and \HI\ observations; a variation in $\sigma$ is present from a near-solar neighborhood cross-section to about half-solar with the maximum being south of the nucleus. Calculating the total H column density from the measured dust temperature and cross-section, and then subtracting the \HI\ column, yields a morphology similar to that observed in CO. The H$_2$/\HI\ mass ratio decreases from about unity to well below 10% and is about 15% averaged over the optical disk. The single most important observation to reduce the potentially large systematic errors is to complete the CO mapping of M 33., Comment: 5 pages, 5 figures Accepted for publication in Astronomy and Astrophysics

Within the framework of the HERM33ES key project, we are studying the star forming interstellar medium in the nearby, metal-poor spiral galaxy M33, exploiting the high resolution and sensitivity of Herschel. We use PACS and SPIRE maps at 100, 160, 250, 350, and 500 micron wavelength, to study the variation of the spectral energy distributions (SEDs) with galacto-centric distance. Detailed SED modeling is performed using azimuthally averaged fluxes in elliptical rings of 2 kpc width, out to 8 kpc galacto-centric distance. Simple isothermal and two-component grey body models, with fixed dust emissivity index, are fitted to the SEDs between 24 and 500 micron using also MIPS/Spitzer data, to derive first estimates of the dust physical conditions. The far-infrared and submillimeter maps reveal the branched, knotted spiral structure of M33. An underlying diffuse disk is seen in all SPIRE maps (250-500 micron). Two component fits to the SEDs agree better than isothermal models with the observed, total and radially averaged flux densities. The two component model, with beta fixed at 1.5, best fits the global and the radial SEDs. The cold dust component clearly dominates; the relative mass of the warm component is less than 0.3% for all the fits. The temperature of the warm component is not well constrained and is found to be about 60K plus/minus 10K. The temperature of the cold component drops significantly from about 24K in the inner 2 kpc radius to 13K beyond 6 kpc radial distance, for the best fitting model. The gas-to-dust ratio for beta=1.5, averaged over the galaxy, is higher than the solar value by a factor of 1.5 and is roughly in agreement with the subsolar metallicity of M33., Comment: 5 pages, 3 figures, accepted for publication in the A&A Herschel Special Issue

Within the framework of the HERM33ES Key Project, using the high resolution and sensitivity of the Herschel photometric data, we study the compact emission in the Local Group spiral galaxy M33 to investigate the nature of the compact SPIRE emission sources. We extracted a catalogue of sources at 250um in order to investigate the nature of this compact emission. Taking advantage of the unprecedented Herschel resolution at these wavelengths, we also focus on a more precise study of some striking Halpha shells in the northern part of the galaxy. We present a catalogue of 159 compact emission sources in M33 identified by SExtractor in the 250um SPIRE band that is the one that provides the best spatial resolution. We also measured fluxes at 24um and Halpha for those 159 extracted sources. The morphological study of the shells also benefits from a multiwavelength approach including Halpha, far-UV from GALEX, and infrared from both Spitzer IRAC 8um and MIPS 24um in order to make comparisons. For the 159 compact sources selected at 250um, we find a very strong Pearson correlation coefficient with the MIPS 24um emission (r24 = 0.94) and a rather strong correlation with the Halpha emission, although with more scatter (rHa = 0.83). The morphological study of the Halpha shells shows a displacement between far-ultraviolet, Halpha, and the SPIRE bands. The cool dust emission from SPIRE clearly delineates the Halpha shell structures. The very strong link between the 250um compact emission and the 24um and Halpha emissions, by recovering the star formation rate from standard recipes for HII regions, allows us to provide star formation rate calibrations based on the 250um compact emission alone. The different locations of the Halpha and far-ultraviolet emissions with respect to the SPIRE cool dust emission leads to a dynamical age of a few Myr for the Halpha shells and the associated cool dust., Comment: 4 pages, 3 figures, Accpeted for publication in the A&A Herschel Special Issue

Over the past few years several studies have provided estimates of the SFR (star-formation rate) or the total infrared luminosity from just one infrared band. However these relations are generally derived for entire galaxies, which are known to contain a large scale diffuse emission that is not necessarily related to the latest star-formation episode. We provide new relations to estimate the SFR from resolved star-forming regions at 100 mum and 160 mum. We select individual star-forming regions in the nearby (840 kpc) galaxy M33. We estimate the SFR combining the emission in Halpha and at 24 mum to calibrate the emission at 100 mum and 160 mum as SFR estimators, as mapped with PACS/Herschel. The data are obtained in the framework of the HERM33ES open time key project. There is less emission in the HII regions at 160 mum than at 100 mum. Over a dynamic range of almost 2 dex in Sigma(SFR) we find that the 100 mum emission is a nearly linear estimator of the SFR, whereas that at 160 mum is slightly superlinear. The behaviour of individual star-forming regions is surprisingly similar to that of entire galaxies. At high Sigma(SFR), star formation drives the dust temperature, whereas uncertainties and variations in radiation-transfer and dust-heated processes dominate at low Sigma(SFR). Detailed modelling of both galaxies and individual star forming regions will be needed to interpret similarities and differences between the two and assess the fraction of diffuse emission in galaxies., Comment: 5 pages, 3 figures, accepted for publication in the A&A Herschel special issue

We present Integral Field Spectroscopy (IFS) of NGC 595, one of the most luminous HII regions in M33. This type of observations allows studying the variation of the principal emission-line ratios across the surface of the nebula. At each position of the field of view, we fit the main emission-line features of the spectrum within the spectral range 3650-6990A, and create maps of the principal emission-line ratios for the total surface of the region. The extinction map derived from the Balmer decrement and the absorbed H-alpha luminosity show good spatial correlation with the 24 micron emission from Spitzer. We also show here the capability of the IFS to study the existence of Wolf-Rayet (WR) stars, identifying the previously catalogued WR stars and detecting a new candidate towards the north of the region. The ionization structure of the region nicely follows the H-alpha shell morphology and is clearly related to the location of the central ionizing stars. The electron density distribution does not show strong variations within the HII region nor any trend with the H-alpha emission distribution. We study the behaviour within the HII region of several classical emission-line ratios proposed as metallicity calibrators: while [NII]/Ha and [NII]/[OIII] show important variations, the R23 index is substantially constant across the surface of the nebula, despite the strong variation of the ionization parameter as a function of the radial distance from the ionizing stars. These results show the reliability in using the R23 index to characterize the metallicity of HII regions even when only a fraction of the total area is covered by the observations., Comment: 16 pages, 12 figures, published in MNRAS (replaced to match the journal version). Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, (MPIA and IAA-CSIC)

We present a study of the extinction, traced by the Balmer decrement, in HII regions in the dwarf galaxies NGC 1569 and NGC 4214. We find that the large-scale extinction around the most prominent HII regions in both galaxies forms a shell in which locally the intrinsic extinction can adopt relatively high values ($A_V = 0.8 - 0.9$ mag) despite the low metallicity and thus the low overall dust content. The small-scale extinction (spatial resolution $\sim$0.3'') shows fluctuations that are most likely due to variations in the dust distribution. We compare the distribution of the extinction to that of the dust emission, traced by Spitzer emission at 8 and 24 \mi, and to the emission of cold dust at 850 \mi. We find in general a good agreement between all tracers, expect for the 850 \mi emission in NGC 4214 which is more extended than the extinction and the other emissions. Whereas in NGC 1569 the dust emission at all wavelengths is very similar, NGC 4214 shows spatial variations in the 24-to-850 \mi ratio. We furthermore compared the 24 \mi and the extinction-corrected Halpha emission from HII regions in a sample of galaxies with a wide range of metallicities and found a good correlation between both emissions, independent of metallicity. We suggest that this lack of dependence on metallicity might be due to the formation of dust shells with a relatively constant opacity, like the ones observed here, around ionizing stars., Comment: 5 pages, to appear in proceeding of IAU Symposition 255 "Low-metallicity star formation", ed. L. Hunt, S. Madden, & R. Schneider (Cambridge: CUP)

GH$\alpha$FaS a new Fabry-Perot system, is now available at the William Herschel Telescope. It was mounted, for the first time, at the Nasmyth focus of the 4.2 meter WHT on La Palma in July 2007. Using modern technology, with a spectral resolution of the order R$\sim$15000, and with a seeing limited spatial resolution, GH$\alpha$FaS will provide a new look at the H$\alpha$ -emitting gas over a 4.8 arcminutes circular field in the nearby universe. Many science programs can be done on a 4.2 metre class telescope in world class seeing conditions with a scanning Fabry-Perot. Not only galaxies but HII regions, planetary nebulae, supernova remnants and the diffuse interstellar medium are subjects for which unique data can be aquired rapidly. Astronomers from the Laboratoire d'Astrophysique Exp\'erimentale (LAE) in Montr\'eal, the Laboratoire d'Astrophysique de Marseille (LAM-OAMP), and the Instituto de Astrof\'isica de Canarias (IAC), have inaugurated GH$\alpha$FaS by studying in detail the dynamics of some nearby spiral galaxies. A robust set of state-of-the-arts tools for reducing and analyzing the data cubes obtained with GH$\alpha$FaS has also been developed., Comment: 29 pages, 10 figures. Accepted for publication in PASP

We investigate the use of the rest-frame 24microns luminosity as an indicator of the star formation rate (SFR) in galaxies with different metallicities by comparing it to the (extinction corrected) Halpha luminosity. We carry out this analysis in 2 steps: First, we compare the emission from HII regions in different galaxies with metallicities between 12+log(O/H) = 8.1 and 8.9. We find that the 24microns and the extinction corrected Halpha luminosities from individual HII regions follow the same correlation for all galaxies, independent of their metallicity. Second, the role of metallicity is explored further for the integrated luminosity in a sample of galaxies with metallicities in the range of 12+log(O/H) = 7.2 - 9.1. For this sample we compare the 24microns and Halpha luminosities integrated over the entire galaxies and find a lack of the 24microns emission for a given Halpha luminosity for low metallicity objects, likely reflecting a low dust content. These results suggest that the 24microns luminosity is a good metallicity independent tracer for the SFR in individual HII regions. On the other hand, metallicity has to be taken into account when using the 24microns luminosity as a tracer for the SFR of entire galaxies., Comment: accepted for publication in ApJ Letters

Large HI shells, with diameters of hundreds of pc and expansion velocities of 10-20kms-1 are well observed features of local gas rich galaxies. These shells could well be predicted as a result of the impact of OB associations on the ISM, but doubt has been cast on this scenario by the apparent absence of OB stars close to the centres of a large fraction of these shells in recent observations of the SMC. Using Fabry-Perot scanned Halpha emission line mapping of nearby galaxy discs we have detected, in all the HII regions where the observations yield sufficient angular resolution and S:N ratio, dominant Halpha shells with radii a few tens of pc, expanding at velocities of 50-100kms-1. We have applied a simple dynamically consistent framework in which we can extrapolate the properties of the observed Halpha shells to a few 10^7yr after the formation of the OB stars. The framework includes the dynamical inputs of both winds and SNe on the surrounding ISM. The results give quantitative statistical support to the hypothesis that the Halpha emitting shells are generic progenitors of the HI shells. During the time taken for an expanding shell to reach the size of a typical HI shell, the OB association may well lose its most luminous stars so the absence of such stars near the centres of many of the HI shells is well explained in this scenario., Comment: 8 pages, 4 figures, accepted for publication in Astronomy and Astrophysics

We investigate the distribution of the intrinsic extinction in NGC1569 using an extinction map derived from the H_alpha/H_beta emission line ratio. We compare the extinction distribution to that of the dust emission traced by SPITZER IRAC(8microns) and MIPS (24microns) maps. The intrinsic extinction shows spatial variations, from zones with negligible extinction to zones with values up to A(V)=0.8mag. We find an extinction shell and establish a relation between this shell and the interstellar expanding structure produced by the stellar winds comig from the Super Star Cluster (SSCs) A and B in the center of the galaxy. We suggest that the extinction shell has been produced by the accumulation of dust at the border of the shell. Although we find a good spatial correlation between the Balmer extinction and infrared emission, there is a spatial displacement between the 8microns and 24microns maxima and the maximum in Balmer extinction which needs further investigation., Comment: 4 pages, presented at the Spitzer Conference Infrared Diagnostics of Galaxy Evolution, 14-16 November 2005

We investigate spatial the distribution of the intrinsic extinction in the starburst dwarf galaxy NGC1569 creating an extinction map of the whole galaxy derived from the Halpha/Hbeta emission line ratio. We differentiate the extinction in the HII regions from the extinction of the diffuse gas. The intrinsic extinction shows considerable variations over the plane of the galaxy, from negligible extinction up to highest values of A(V)=0.8mag. The extinction map shows small scale clumpy structures possibly due to a clumpy dust distribution. We also identify in this map a shell structure, for which we establish a causal relation with the expanding gas structure produced by the stellar winds coming from the Super Star Clusters (SSC) in the center of the galaxy. The comparison of the spatial profiles of the extinction, dust and gaseous emissions crossing the border of the shell shows a layered structure; the peak of this Halpha distribution lying closest to the SSC A, followed outwards by the peak of the extinction and at a still larger distances by the bulk of the atomic gas. We suggest that the extinction shell has been produced by the SSCs and that it can be explained by the accumulation of dust at the border of this ionized gas structure., Comment: Accepted for publication in Astronomy & Astrophysics. Paper with full resolution figures is available from http://www.ugr.es/~ute/ngc1569_accepted.ps.gz

We present an analysis of the integrated Halpha emission line profiles for the HII region population of the spiral galaxies NGC 1530, NGC 6951 and NGC 3359. We show that 70% of the line profiles show two or three Gaussian components. The relations between the Halpha luminosity and non-thermal line width for the HII regions of the three galaxies are studied and compared with the relation found taken all the HII regions of the three galaxies as a single distribution. A clearer envelope in non-thermal line width is found when only those HII regions with non-thermal line width bigger than 13kms are considered. The linear fit for the envelope is logL=36.8+2.0*log(sigma). The masses of the HII regions on the envelope using the virial theorem and the mass estimates from the Halpha luminosity are comparable, which offers evidence that the HII regions on the envelope are virialized systems, while the remaining regions, the majority, are not in virial equilibrium., Comment: 19 pages, 10 figures,accepted for publication in A&A

We study the presence of low intensity high velocity components, which we have termed wing features in the integrated Halpha emission line profiles of the HII region populations of the spiral barred galaxies NGC 1530, NGC 3359 and NGC 6951. We find that more than a third of the HII region line profiles in each galaxy show these components. The highest fraction is obtained in the galaxy whose line profiles show the best S:N, which suggests that wing features of this type may well exist in most, if not all, HII region line profiles. Applying selection criteria to the wing features, we obtain a sample of HII regions with clearly defined high velocity components in their profiles. Deconvolution of a representative sample of the line profiles eliminates any doubt that the wing features could possibly be due to instrumental effects. We present an analysis of the high velocity low intensity features fitting them with Gaussian functions; the emission measures, central velocities and velocity dispersions for the red and blue features take similar values. We interpret the features as signatures of expanding shells inside the HII regions. Up to a shell radius of R(shell)~0.2R(reg), the stellar winds from the central ionizing stars appear to satisfy the energy and momentum requirements for the formation and driving the shell. Several examples of the most luminous HII regions show that the shells appear to have larger radii; in these cases additional mechanisms may well be needed to explain the kinetic energies and momenta of the shells., Comment: 16 pages, 9 figures, accepted for publication in A&A