Search

This thesis presents a comprehensive analysis of galaxies spanning a wide range in mass and environment, using deep optical/infrared spectroscopy and high-resolution imaging to understand the physical mechanisms deriving their formation and evolution. The research is structured around three primary studies. 1) I studied the metal enrichment of galaxies in protoclusters and the effect of the environment on the mass-metallicity relation (MZR). I found that massive galaxies residing in protoclusters are metal-deficient compared to galaxies in the field. This implies that primordial cold gas, channeled through cosmic filaments, dilutes the metal content of the protocluster; 2) I investigated the fraction of clumpy galaxies at 0.5< z< 3, using UVCANDELS and CANDELS imaging data to examine clump properties in star-forming galaxies. The results reveal a peak in clumpiness around cosmic noon, with a decline towards the present and a lack of environmental dependence, suggesting that internal processes predominantly drive clump formation; 3) I extended the analyses to dwarf galaxies at z ~ 0.15, establishing a robust mass-metallicity relation and confirming the fundamental metallicity relation at low masses, highlighting the nuanced interplay between star formation rate and gas-phase metallicity. I find that the intrinsic scatter in the MZR is larger for dwarf galaxies compared to normal galaxies, indicating more diverse star formation histories and/or stronger environmental effects in these systems. This work advances our understanding of galaxy evolution across cosmic time, offering new insights into the mechanisms influencing star formation and chemical enrichment and finding the complex interplay between internal dynamics and environmental factors in shaping galaxy evolution.

Está depositada la versión preprint del artículo, We report a detailed study of an unidentified gamma-ray source located in the region of the compact stellar cluster NGC 3603. This is a star-forming region (SFR) powered by a massive cluster of OB stars. A dedicated analysis of about 10 yr of data from 10 GeV to 1 TeV, provided by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, yields the detection of a pointlike source at a significance of 9 sigma. The source photon spectrum can be described by a power-law model with a best-fit spectral index of 2.35 0.03. In addition, the analysis of a deep Chandra image in the 0.5-7 keV band reliably rules out an extragalactic origin for the gamma-rays. We also conclude that the broadband spectral energy distribution of the point source can be explained well with both leptonic and hadronic models. No firm evidence of association with any other classes of known gamma-ray emitters is found; therefore, we speculate that 4FGL J1115.1-6118 is a gamma-ray-emitting SFR., Ministerio de Economía y Competitividad (España), ERDF under the Spanish MINECO, Ramon and Cajal program, Istituto Nazionale Astrofisica (INAF), Agenzia Spaziale Italiana (ASI), United States Department of Energy (DOE), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2023 The Authors. We are grateful to the referee for a very thorough report that helped us improve the quality of the paper. DFA work is funded by a Consejo Nacional de Ciencia y Tecnología (CONACyT, México) grant through project A1-S22784. This publication is based on data obtained with the MEGARA instrument at the GTC, installed in the Spanish Observatorio del Roque de los Muchachos, in the island of La Palma. MEGARA has been built by a Consortium led by the Universidad Complutense de Madrid (Spain) and that also includes the Instituto de Astrofísica, Óptica y Electrónica (INAOE, México), Instituto de Astrofísica de Andalucía (CSIC, Spain), and the Universidad Politécnica de Madrid (Spain). MEGARA is funded by the Consortium institutions, GRANTECAN S.A. and European Regional Development Funds (ERDF), through Programa Operativo Canarias FEDER 2014-2020. YDM thanks CONACYT for the research grant CB-A1-S-25070 and DRG for the research grant CB-A1-S-22784 from which the postdoctoral grant that supported DFA was obtained. RC also thanks CONACyT for the research grant CF-320152. RA acknowledges support from ANID Fondecyt Regular 1202007. ALGM acknowledges support from the Spanish Ministry of Science and Innovation, project PID2019-107408GB-C43 (ESTALLIDOS), and from Gobierno de Canarias through EU FEDER funding, project PID2020010050. JMA acknowledges the support of the Viera y Clavijo Senior program funded by ACIISI and ULL. JIP acknowledges finantial support from projects Estallidos6 AYA2016-79724-C4 (Spanish Ministerio de Economía y Competitividad), Estallidos7 PID2019-107408GB-C44 (Spanish Ministerio de Ciencia e Innovación), grant P18-FR-2664 (Junta de Andalucía), and grant SEV-2017-0709 “Center of Excellence Severo Ochoa Program” (State Agency for Research of the Spanish MCIU)., We present a spatially resolved spectroscopic study for the metal poor H_(II) galaxy J084220+115000 using MEGARA Integral Field Unit observations at the Gran Telescopio Canarias. We estimated the gas metallicity using the direct method for oxygen, nitrogen and helium and found a mean value of 12+log(O/H)=8.03±0.06, and integrated electron density and temperature of ∼ 161 cm^(−3) and ∼ 15400 K, respectively. The metallicity distribution shows a large range of ∆(O/H) = 0.72 dex between the minimum and maximum (7.69±0.06 and 8.42±0.05) values, unusual in a dwarf starforming galaxy. We derived an integrated log(N/O) ratio of −1.51 ± 0.05 and found that both N/O and O/H correspond to a primary production of metals. Spatially resolved maps indicate that the gas appears to be photoionized by massive stars according to the diagnostic line ratios. Between the possible mechanisms to explain the starburst activity and the large variation of oxygen abundance in this galaxy, our data support a possible scenario where we are witnessing an ongoing interaction triggering multiple star-forming regions localized in two dominant clumps., Consejo Nacional de Ciencia y Tecnología (CONACyT, México), Universidad Complutense de Madrid, Instituto de Astrofísica, Óptica y Electrónica (INAOE, México), Instituto de Astrofísica de Andalucía, Universidad Politécnica de Madrid, GRANTECAN S.A, European Regional Development Funds (ERDF), through Programa Operativo Canarias FEDER 2014-2020, ANID Fondecyt Regular, Ministerio de Ciencia e Innovación, Gobierno de Canarias through EU FEDER funding, Viera y Clavijo Senior program funded by ACIISI and ULL, Ministerio de Economía y Competitividad Project Estallidos6, Ministerio de Economía y Competitividad Project Estallidos7, Junta de Andalucía, “Center of Excellence Severo Ochoa Program”, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2014. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant 127740 of the Academy of Finland, by the DFG Cluster of Excellence “Origin and Structure of the Universe”, by the Croatian Science Foundation Project 09/176, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESSMAGIC/2010/0., Aims. HESS J1857+026 is an extended TeV gamma-ray source that was discovered by H. E. S. S. as part of its Galactic plane survey. Given its broadband spectral energy distribution and its spatial coincidence with the young energetic pulsar PSR J1856+0245, the source has been put forward as a pulsar wind nebula (PWN) candidate. MAGIC has performed follow-up observations aimed at mapping the source down to energies approaching 100 GeV in order to better understand its complex morphology. Methods. HESS J1857+026 was observed by MAGIC in 2010, yielding 29 h of good quality stereoscopic data that allowed us to map the source region in two separate ranges of energy. Results. We detected very-high-energy gamma-ray emission from HESS J1857+026 with a significance of 12 sigma above 150 GeV. The differential energy spectrum between 100 GeV and 13 TeV is described well by a power law function dN/dE = N-0(E/1TeV)(-Gamma) with N-0 = (5.37 +/- 0.44(stat) +/- 1.5(sys)) X 10(-12) (TeV-1 cm(-2) s(-1)) and Gamma = 2.16 +/- 0.07(stat) +/- 0.15(sys), which bridges the gap between the GeV emission measured by Fermi-LAT and the multi-TeV emission measured by H.E.S.S.. In addition, we present a detailed analysis of the energy-dependent morphology of this region. We couple these results with archival multiwavelength data and outline evidence in favor of a two-source scenario, whereby one source is associated with a PWN, while the other could be linked with a molecular cloud complex containing an HII region and a possible gas cavity., German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

We present a python software repository implementing the PyGMMis (Melchior & Goudling 2018) method to astronomical data cubes of velocity resolved line observations. This implementation is described extensively in Tiwari et al. 2023, ApJ. An example is included in /example/ containing the SOFIA data of RCW120 used in Tiwari et al. 2023, ApJ, along with example scripts describing the full implementation of our code. The majority of parameter tweaking can be performed within 'rcw120-params.txt' which is continuously called during the procedure. A full description of the code and how to use it is in README.md (markdown file).

We present a python software repository implementing the PyGMMis (Melchior & Goudling 2018) method to astronomical data cubes of velocity resolved line observations. This implementation is described extensively in Tiwari et al. 2023, ApJ. An example is included in /example/ containing the SOFIA data of RCW120 used in Tiwari et al. 2023, ApJ, along with example scripts describing the full implementation of our code. The majority of parameter tweaking can be performed within 'rcw120-params.txt' which is continuously called during the procedure. A full description of the code and how to use it is in README.md (markdown file).

We report the first detection of deuterated water (HDO) toward an extragalactic hot core. The HDO 2(11)-2(12) line has been detected toward hot cores N 105-2 A and 2 B in the N 105 star-forming region in the low-metallicity Large Magellanic Cloud (LMC) dwarf galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). We have compared the HDO line luminosity (L (HDO)) measured toward the LMC hot cores to those observed toward a sample of 17 Galactic hot cores covering three orders of magnitude in L (HDO), four orders of magnitude in bolometric luminosity (L (bol)), and a wide range of Galactocentric distances (thus metallicities). The observed values of L (HDO) for the LMC hot cores fit very well into the L (HDO) trends with L (bol) and metallicity observed toward the Galactic hot cores. We have found that L (HDO) seems to be largely dependent on the source luminosity, but metallicity also plays a role. We provide a rough estimate of the H2O column density and abundance ranges toward the LMC hot cores by assuming that HDO/H2O toward the LMC hot cores is the same as that observed in the Milky Way; the estimated ranges are systematically lower than Galactic values. The spatial distribution and velocity structure of the HDO emission in N 105-2 A is consistent with HDO being the product of the low-temperature dust grain chemistry. Our results are in agreement with the astrochemical model predictions that HDO is abundant regardless of the extragalactic environment and should be detectable with ALMA in external galaxies.

We present high-resolution Karl G. Jansky Very Large Array (VLA) observations of the protostar L1527 IRS at 7 mm, 1.3 cm, and 2 cm wavelengths. We detect the edge-on dust disk at all three wavelengths and find that it is asymmetric, with the southern side of the disk brighter than the northern side. We confirm this asymmetry through analytic modeling and also find that the disk is flared at 7 mm. We test the data against models including gap features in the intensity profile, and though we cannot rule such models out, they do not provide a statistically significant improvement in the quality of fit to the data. From these fits, we can, however, place constraints on allowed properties of any gaps that could be present in the true, underlying intensity profile. The physical nature of the asymmetry is difficult to associate with physical features owing to the edge-on nature of the disk, but it could be related to spiral arms or asymmetries seen in other imaging of more face-on disks.

We present high-resolution Karl G. Jansky Very Large Array (VLA) observations of the protostar L1527 IRS at 7 mm, 1.3 cm, and 2 cm wavelengths. We detect the edge-on dust disk at all three wavelengths and find that it is asymmetric, with the southern side of the disk brighter than the northern side. We confirm this asymmetry through analytic modeling and also find that the disk is flared at 7 mm. We test the data against models including gap features in the intensity profile, and though we cannot rule such models out, they do not provide a statistically significant improvement in the quality of fit to the data. From these fits, we can, however, place constraints on allowed properties of any gaps that could be present in the true, underlying intensity profile. The physical nature of the asymmetry is difficult to associate with physical features owing to the edge-on nature of the disk, but it could be related to spiral arms or asymmetries seen in other imaging of more face-on disks.

We report the first detection of deuterated water (HDO) toward an extragalactic hot core. The HDO 2(11)-2(12) line has been detected toward hot cores N 105-2 A and 2 B in the N 105 star-forming region in the low-metallicity Large Magellanic Cloud (LMC) dwarf galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). We have compared the HDO line luminosity (L (HDO)) measured toward the LMC hot cores to those observed toward a sample of 17 Galactic hot cores covering three orders of magnitude in L (HDO), four orders of magnitude in bolometric luminosity (L (bol)), and a wide range of Galactocentric distances (thus metallicities). The observed values of L (HDO) for the LMC hot cores fit very well into the L (HDO) trends with L (bol) and metallicity observed toward the Galactic hot cores. We have found that L (HDO) seems to be largely dependent on the source luminosity, but metallicity also plays a role. We provide a rough estimate of the H2O column density and abundance ranges toward the LMC hot cores by assuming that HDO/H2O toward the LMC hot cores is the same as that observed in the Milky Way; the estimated ranges are systematically lower than Galactic values. The spatial distribution and velocity structure of the HDO emission in N 105-2 A is consistent with HDO being the product of the low-temperature dust grain chemistry. Our results are in agreement with the astrochemical model predictions that HDO is abundant regardless of the extragalactic environment and should be detectable with ALMA in external galaxies.

Context. The chemistry of sulphur-bearing species in the interstellar medium remains poorly understood, but might play a key role in the chemical evolution of star-forming regions. Aims. Coupling laboratory experiments to observations of sulphur-bearing species in different parts of star-forming regions, we aim to understand the chemical behavior of the sulphur species in cold and warm regions of protostars, and we ultimately hope to connect them. Methods. We performed laboratory experiments in which we tested the reactivity of hydrogen sulfide (H2S) on a cold substrate with hydrogen and/or carbon monoxide (CO) under different physical conditions that allowed us to determine the products from sulphur reactions using a quadrupole mass spectrometer. The laboratory experiments were complemented by observations. We observed two luminous binary sources in the Cygnus-X star-forming complex, Cygnus X-N30 and N12, covering a frequency range of 329-361 GHz at a spatial resolution of 1 '' 5 with the SubMillimeter Array (SMA). This study was complemented by a 3 mm line survey of Cygnus X-N12 covering specific frequency windows in the frequency ranges 72.0-79.8 GHz at a spatial resolution of 34 '' 0-30 '' 0 and 84.2-115.5 GHz at a spatial resolution of 29 '' 0-21 '' 0, with the IRAM-30 m single-dish telescope. Column densities and excitation temperatures were derived under the local thermodynamic equilibrium approximation. Results. We find that OCS is a direct product from H2S reacting with CO and H under cold temperatures (T < 100 K) from laboratory experiments. OCS is therefore found to be an important solid-state S-reservoir. We identify several S-species in the cold envelope of Cyg X-N12, principally organo-sulphurs (H2CS, CS, OCS, CCS, C3S, CH3SH, and HSCN). For the hot cores of Cyg X-N12 and N30, only OCS, CS and H2CS were detected. We found a difference in the S-diversity between the hot core and the cold envelope of N12, which is likely due to the sensitivity of t

Chemistry along the star- and planet-formation sequence regulates how prebiotic building blocks-carriers of the elements CHNOPS-are incorporated into nascent planetesimals and planets. Spectral line observations across the electromagnetic spectrum are needed to fully characterize interstellar CHNOPS chemistry, yet to date there are only limited astrochemical constraints at THz frequencies. Here, we highlight advances to the study of CHNOPS astrochemistry that will be possible with the Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS). OASIS is a NASA mission concept for a space-based observatory that will utilize an inflatable 14-m reflector along with a heterodyne receiver system to observe at THz frequencies with unprecedented sensitivity and angular resolution. As part of a survey of H2O and HD toward similar to 100 protostellar and protoplanetary disk systems, OASIS will also obtain statistical constraints on the emission of complex organics from protostellar hot corinos and envelopes as well as light hydrides including NH3 and H2S toward protoplanetary disks. Line surveys of high-mass hot cores, protostellar outflow shocks, and prestellar cores will also leverage the unique capabilities of OASIS to probe high-excitation organics and small hydrides, as is needed to fully understand the chemistry of these objects.

We present velocity-resolved Stratospheric Observatory for Infrared Astronomy (SOFIA)/upgrade German REceiver for Astronomy at Terahertz Frequencies observations of [O I] and [C II] lines toward a Class I protostar, L1551 IRS 5, and its outflows. The SOFIA observations detect [O I] emission toward only the protostar and [C II] emission toward the protostar and the redshifted outflow. The [O I] emission has a width of similar to 100 km s(-1) only in the blueshifted velocity, suggesting an origin in shocked gas. The [C ii] lines are narrow, consistent with an origin in a photodissociation region. Differential dust extinction from the envelope due to the inclination of the outflows is the most likely cause of the missing redshifted [O I] emission. Fitting the [O I] line profile with two Gaussian components, we find one component at the source velocity with a width of similar to 20 km s(-1) and another extremely broad component at -30 km s(-1) with a width of 87.5 km s(-1), the latter of which has not been seen in L1551 IRS 5. The kinematics of these two components resemble cavity shocks in molecular outflows and spot shocks in jets. Radiative transfer calculations of the [O I], high-J CO, and H2O lines in the cavity shocks indicate that [O I] dominates the oxygen budget, making up more than 70% of the total gaseous oxygen abundance and suggesting [O]/[H] of similar to 1.5 x 10(-4). Attributing the extremely broad [O I] component to atomic winds, we estimate an intrinsic mass-loss rate of (1.3 +/- 0.8) x 10(-6) M-circle dot yr(-1). The intrinsic mass-loss rates derived from low-J CO, [O i], and H i are similar, supporting the model of momentum-conserving outflows, where the atomic wind carries most momentum and drives the molecular outflows.

Chemistry along the star- and planet-formation sequence regulates how prebiotic building blocks-carriers of the elements CHNOPS-are incorporated into nascent planetesimals and planets. Spectral line observations across the electromagnetic spectrum are needed to fully characterize interstellar CHNOPS chemistry, yet to date there are only limited astrochemical constraints at THz frequencies. Here, we highlight advances to the study of CHNOPS astrochemistry that will be possible with the Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS). OASIS is a NASA mission concept for a space-based observatory that will utilize an inflatable 14-m reflector along with a heterodyne receiver system to observe at THz frequencies with unprecedented sensitivity and angular resolution. As part of a survey of H2O and HD toward similar to 100 protostellar and protoplanetary disk systems, OASIS will also obtain statistical constraints on the emission of complex organics from protostellar hot corinos and envelopes as well as light hydrides including NH3 and H2S toward protoplanetary disks. Line surveys of high-mass hot cores, protostellar outflow shocks, and prestellar cores will also leverage the unique capabilities of OASIS to probe high-excitation organics and small hydrides, as is needed to fully understand the chemistry of these objects.

Context. The chemistry of sulphur-bearing species in the interstellar medium remains poorly understood, but might play a key role in the chemical evolution of star-forming regions. Aims. Coupling laboratory experiments to observations of sulphur-bearing species in different parts of star-forming regions, we aim to understand the chemical behavior of the sulphur species in cold and warm regions of protostars, and we ultimately hope to connect them. Methods. We performed laboratory experiments in which we tested the reactivity of hydrogen sulfide (H2S) on a cold substrate with hydrogen and/or carbon monoxide (CO) under different physical conditions that allowed us to determine the products from sulphur reactions using a quadrupole mass spectrometer. The laboratory experiments were complemented by observations. We observed two luminous binary sources in the Cygnus-X star-forming complex, Cygnus X-N30 and N12, covering a frequency range of 329-361 GHz at a spatial resolution of 1 '' 5 with the SubMillimeter Array (SMA). This study was complemented by a 3 mm line survey of Cygnus X-N12 covering specific frequency windows in the frequency ranges 72.0-79.8 GHz at a spatial resolution of 34 '' 0-30 '' 0 and 84.2-115.5 GHz at a spatial resolution of 29 '' 0-21 '' 0, with the IRAM-30 m single-dish telescope. Column densities and excitation temperatures were derived under the local thermodynamic equilibrium approximation. Results. We find that OCS is a direct product from H2S reacting with CO and H under cold temperatures (T < 100 K) from laboratory experiments. OCS is therefore found to be an important solid-state S-reservoir. We identify several S-species in the cold envelope of Cyg X-N12, principally organo-sulphurs (H2CS, CS, OCS, CCS, C3S, CH3SH, and HSCN). For the hot cores of Cyg X-N12 and N30, only OCS, CS and H2CS were detected. We found a difference in the S-diversity between the hot core and the cold envelope of N12, which is likely due to the sensitivity of t

We present velocity-resolved Stratospheric Observatory for Infrared Astronomy (SOFIA)/upgrade German REceiver for Astronomy at Terahertz Frequencies observations of [O I] and [C II] lines toward a Class I protostar, L1551 IRS 5, and its outflows. The SOFIA observations detect [O I] emission toward only the protostar and [C II] emission toward the protostar and the redshifted outflow. The [O I] emission has a width of similar to 100 km s(-1) only in the blueshifted velocity, suggesting an origin in shocked gas. The [C ii] lines are narrow, consistent with an origin in a photodissociation region. Differential dust extinction from the envelope due to the inclination of the outflows is the most likely cause of the missing redshifted [O I] emission. Fitting the [O I] line profile with two Gaussian components, we find one component at the source velocity with a width of similar to 20 km s(-1) and another extremely broad component at -30 km s(-1) with a width of 87.5 km s(-1), the latter of which has not been seen in L1551 IRS 5. The kinematics of these two components resemble cavity shocks in molecular outflows and spot shocks in jets. Radiative transfer calculations of the [O I], high-J CO, and H2O lines in the cavity shocks indicate that [O I] dominates the oxygen budget, making up more than 70% of the total gaseous oxygen abundance and suggesting [O]/[H] of similar to 1.5 x 10(-4). Attributing the extremely broad [O I] component to atomic winds, we estimate an intrinsic mass-loss rate of (1.3 +/- 0.8) x 10(-6) M-circle dot yr(-1). The intrinsic mass-loss rates derived from low-J CO, [O i], and H i are similar, supporting the model of momentum-conserving outflows, where the atomic wind carries most momentum and drives the molecular outflows.

Context. Ultraviolet radiation (UV) influences the physics and chemistry of star-forming regions, but its properties and significance in the immediate surroundings of low-mass protostars are still poorly understood.Aims. Our aim is to extend the use of the CN/HCN ratio, already established for high-mass protostars, to the low-mass regime to trace and characterize the UV field around low-mass protostars on similar to 0.6 x 0.6 pc scales.Methods. We present 5' x 5' maps of the Serpens Main Cloud encompassing ten protostars observed with the EMIR receiver at the IRAM 30 m telescope in CN 1-0, HCN 1-0, CS 3-2, and some of their isotopologs. The radiative-transfer code RADEX and the chemical model Nahoon were used to determine column densities of molecules, gas temperature and density, and the UV field strength, G(0).Results. The spatial distribution of HCN and CS are closely correlated with CO 6-5 emission, that traces outflows. The CN emission is extended from the central protostars to their immediate surroundings also tracing outflows, likely as a product of HCN photodissociation. The ratio of CN to HCN total column densities ranges from similar to 1 to 12 corresponding to G(0) approximate to 10(1) -10(3) for gas densities and temperatures typical for outflows of low-mass protostars.Conclusions. UV radiation associated with protostars and their outflows is indirectly identified in a significant part of the Serpens Main low-mass star-forming region. Its strength is consistent with the values obtained from the OH and H2O ratios observed with Herschel and compared with models of UV-illuminated shocks. From a chemical viewpoint, the CN to HCN ratio is an excellent tracer of UV fields around low- and intermediate-mass star-forming regions.

Stellar feedback is needed to produce realistic giant molecular clouds and galaxies in simulations, but due to limited numerical resolution, feedback must be implemented using sub-grid models. Observational work is an important means to test and anchor these models, but limited studies have assessed the relative dynamical role of multiple feedback modes, particularly at the earliest stages of expansion when H ii regions are still deeply embedded. In this paper, we use multiwavelength (radio, infrared, and X-ray) data to measure the pressures associated with direct radiation (P-dir), dust-processed radiation (P-IR), photoionization heating (P-H II), and shock-heating from stellar winds (P-X) in a sample of 106 young, resolved H ii regions with radii less than or similar to 0.5 pc to determine how stellar feedback drives their expansion. We find that the P-IR dominates in 84% of the regions and that the median P-dir and P-H II are smaller than the median P-IR by factors of 6 and 9, respectively. Based on the radial dependences of the pressure terms, we show that H ii regions transition from P-IR-dominated to P-H II-dominated at radii of similar to 3 pc. We find a median trapping factor of f(trap) similar to 8 without any radial dependence for the sample, suggesting this value can be adopted in sub-grid feedback models. Moreover, we show that the total pressure is greater than the gravitational pressure in the majority of our sample, indicating that the feedback is sufficient to expel gas from the regions.

Context. Ultraviolet radiation (UV) influences the physics and chemistry of star-forming regions, but its properties and significance in the immediate surroundings of low-mass protostars are still poorly understood.Aims. Our aim is to extend the use of the CN/HCN ratio, already established for high-mass protostars, to the low-mass regime to trace and characterize the UV field around low-mass protostars on similar to 0.6 x 0.6 pc scales.Methods. We present 5' x 5' maps of the Serpens Main Cloud encompassing ten protostars observed with the EMIR receiver at the IRAM 30 m telescope in CN 1-0, HCN 1-0, CS 3-2, and some of their isotopologs. The radiative-transfer code RADEX and the chemical model Nahoon were used to determine column densities of molecules, gas temperature and density, and the UV field strength, G(0).Results. The spatial distribution of HCN and CS are closely correlated with CO 6-5 emission, that traces outflows. The CN emission is extended from the central protostars to their immediate surroundings also tracing outflows, likely as a product of HCN photodissociation. The ratio of CN to HCN total column densities ranges from similar to 1 to 12 corresponding to G(0) approximate to 10(1) -10(3) for gas densities and temperatures typical for outflows of low-mass protostars.Conclusions. UV radiation associated with protostars and their outflows is indirectly identified in a significant part of the Serpens Main low-mass star-forming region. Its strength is consistent with the values obtained from the OH and H2O ratios observed with Herschel and compared with models of UV-illuminated shocks. From a chemical viewpoint, the CN to HCN ratio is an excellent tracer of UV fields around low- and intermediate-mass star-forming regions.

We present results of continuum and spectral line observations with Atacama Large Millimeter/submillimeter Array (ALMA) and 22 GHz water (H2O) maser observations using the KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry) array (KaVA) toward a high-mass star-forming region, G25.82–0.17. Multiple 1.3 mm continuum sources are revealed, indicating the presence of young stellar objects (YSOs) at different evolutionary stages, namely an ultracompact H ii region, G25.82–E, a high-mass young stellar object (HM-YSO), G25.82–W1, and starless cores, G25.82–W2 and G25.82–W3. Two SiO outflows, at N–S and SE–NW orientations, are identified. The CH3OH 8−1–70 E line, known to be a Class I CH3OH maser at 229 GHz, is also detected, showing a mixture of thermal and maser emission. Moreover, the H2O masers are distributed in a region ~0farcs25 shifted from G25.82–W1. The CH3OH 224–215 E line shows a compact ringlike structure at the position of G25.82–W1 with a velocity gradient, indicating a rotating disk or envelope. Assuming Keplerian rotation, the dynamical mass of G25.82–W1 is estimated to be >25 M ⊙ and the total mass of 20–84 M ⊙ is derived from the 1.3 mm continuum emission. The driving source of the N–S SiO outflow is G25.82–W1 while that of the SE–NW SiO outflow is uncertain. Detection of multiple high-mass starless/protostellar cores and candidates without low-mass cores implies that HM-YSOs could form in individual high-mass cores as predicted by the turbulent core accretion model. If this is the case, the high-mass star formation process in G25.82 would be consistent with a scaled-up version of low-mass star formation

H2O maser emission associated with the massive star formation region W49N were observed with the Space-VLBI mission RadioAstron. The procedure for processing of the maser spectral line data obtained in the RadioAstron observations is described. Ultra-fine spatial structures in the maser emission were detected on space-ground baselines of up to 9.6 Earth diameters. The correlated flux densities of these features range from 0.1% to 0.6% of the total flux density. These low values of correlated flux density are probably due to turbulence either in the maser itself or in the interstellar medium. © 2019 COSPAR

We present results of continuum and spectral line observations with Atacama Large Millimeter/submillimeter Array (ALMA) and 22 GHz water (H2O) maser observations using the KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry) array (KaVA) toward a high-mass star-forming region, G25.82–0.17. Multiple 1.3 mm continuum sources are revealed, indicating the presence of young stellar objects (YSOs) at different evolutionary stages, namely an ultracompact H ii region, G25.82–E, a high-mass young stellar object (HM-YSO), G25.82–W1, and starless cores, G25.82–W2 and G25.82–W3. Two SiO outflows, at N–S and SE–NW orientations, are identified. The CH3OH 8−1–70 E line, known to be a Class I CH3OH maser at 229 GHz, is also detected, showing a mixture of thermal and maser emission. Moreover, the H2O masers are distributed in a region ~0farcs25 shifted from G25.82–W1. The CH3OH 224–215 E line shows a compact ringlike structure at the position of G25.82–W1 with a velocity gradient, indicating a rotating disk or envelope. Assuming Keplerian rotation, the dynamical mass of G25.82–W1 is estimated to be >25 M ⊙ and the total mass of 20–84 M ⊙ is derived from the 1.3 mm continuum emission. The driving source of the N–S SiO outflow is G25.82–W1 while that of the SE–NW SiO outflow is uncertain. Detection of multiple high-mass starless/protostellar cores and candidates without low-mass cores implies that HM-YSOs could form in individual high-mass cores as predicted by the turbulent core accretion model. If this is the case, the high-mass star formation process in G25.82 would be consistent with a scaled-up version of low-mass star formation

The physical evolution of young stellar objects (YSOs) is accompanied by an enrichment of the molecular complexity, mainly triggered by the heating and energetic processing of astrophysical ices. In this paper, a study of how the ice column density varies across the protostellar evolution has been performed. Tabulated data of H2O, CO2, CH3OH, and HCOOH observed by ground- and space-based telescopes toward 27 early-stage YSOs were taken from the literature. The observational data show that ice column density and spectral index (alpha), used to classify the evolutionary stage, are well correlated. A 2D continuum radiative transfer simulation containing bare and ice-covered grains at different levels of cosmic-ray processing were used to calculate the spectral energy distributions in different angle inclinations between face-on and edge-on configurations. The H2O:CO(2)ice mixture was used to address the H2O and CO(2)column density variation, whereas CH3OH and HCOOH are by-products of the virgin ice after energetic processing. The simulated spectra were used to calculate the ice column densities of YSOs in an evolutionary sequence. As a result, the models show that the ice column density variation of HCOOH with alpha can be justified by envelope dissipation and energetic processing of ice. On the other hand, the ice column densities are mostly overestimated in the cases of H2O, CO(2)and CH3OH, even though the physical and cosmic-ray processing effects are taken into account.

Recent high angular resolution (≃40 mas) ALMA observations at 1.14 mm resolve a compact (R ≃ 200 au), flattened dust structure perpendicular to the HH 80-81 jet emanating from the GGD 27-MM1 high-mass protostar, making it a robust candidate for a true accretion disk. The jet-disk system (HH 80-81/GGD 27-MM1) resembles those found in association with low- A nd intermediate-mass protostars. We present radiative transfer models that fit the 1.14 mm ALMA dust image of this disk, which allow us to obtain its physical parameters and predict its density and temperature structure. Our results indicate that this accretion disk is compact (R disk ≃ 170 au) and massive (≃5 M o), at about 20% of the stellar mass of ≃20 M o. We estimate the total dynamical mass of the star-disk system from the molecular line emission, finding a range between 21 and 30 M o, which is consistent with our model. We fit the density and temperature structures found by our model with power-law functions. These results suggest that accretion disks around massive stars are more massive and hotter than their low-mass siblings, but they still are quite stable. We also compare the temperature distribution in the GGD 27-MM1 disk with that found in low- A nd intermediate-mass stars and discuss possible implications for the water snow line. We have also carried out a study of the distance based on Gaia DR2 data and the population of young stellar objects in this region and from the extinction maps. We conclude that the source distance is within 1.2 and 1.4 kpc, closer than what was derived in previous studies (1.7 kpc). © 2020. The American Astronomical Society. All rights reserved.

The physical evolution of young stellar objects (YSOs) is accompanied by an enrichment of the molecular complexity, mainly triggered by the heating and energetic processing of astrophysical ices. In this paper, a study of how the ice column density varies across the protostellar evolution has been performed. Tabulated data of H2O, CO2, CH3OH, and HCOOH observed by ground- and space-based telescopes toward 27 early-stage YSOs were taken from the literature. The observational data show that ice column density and spectral index (alpha), used to classify the evolutionary stage, are well correlated. A 2D continuum radiative transfer simulation containing bare and ice-covered grains at different levels of cosmic-ray processing were used to calculate the spectral energy distributions in different angle inclinations between face-on and edge-on configurations. The H2O:CO(2)ice mixture was used to address the H2O and CO(2)column density variation, whereas CH3OH and HCOOH are by-products of the virgin ice after energetic processing. The simulated spectra were used to calculate the ice column densities of YSOs in an evolutionary sequence. As a result, the models show that the ice column density variation of HCOOH with alpha can be justified by envelope dissipation and energetic processing of ice. On the other hand, the ice column densities are mostly overestimated in the cases of H2O, CO(2)and CH3OH, even though the physical and cosmic-ray processing effects are taken into account.

We present Atacama Large Millimeter/submillimeter Array (0.87 mm) and Very Large Array (9 mm) observations toward OMC-2 FIR4 and OMC-2 FIR3 within the Orion integral-shaped filament, thought to be two of the nearest regions of intermediate-mass star formation. We characterize the continuum sources within these regions on ∼40 au (0.″1) scales and associated molecular line emission at a factor of ∼30 better resolution than previous observations at similar wavelengths. We identify six compact continuum sources within OMC-2 FIR4, four in OMC-2 FIR3, and one additional source just outside OMC-2 FIR4. This continuum emission is tracing the inner envelope and/or disk emission on less than 100 au scales. HOPS-108 is the only protostar in OMC-2 FIR4 that exhibits emission from high-excitation transitions of complex organic molecules (e.g., methanol and other lines) coincident with the continuum emission. HOPS-370 in OMC-2 FIR3, with L ∼ 360 L o˙, also exhibits emission from high-excitation methanol and other lines. The methanol emission toward these two protostars is indicative of temperatures high enough to thermally evaporate it from icy dust grains; overall, these protostars have characteristics similar to hot corinos. We do not identify a clear outflow from HOPS-108 in 12CO, but we find evidence of interaction between the outflow/jet from HOPS-370 and the OMC-2 FIR4 region. A multitude of observational constraints indicate that HOPS-108 is likely a low- to intermediate-mass protostar in its main mass accretion phase and is the most luminous protostar in OMC-2 FIR4. The high-resolution data presented here are essential for disentangling the embedded protostars from their surrounding dusty environments and characterizing them. © 2019. The American Astronomical Society. All rights reserved.

We observed 13 Planck cold clumps with the James Clerk Maxwell Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N2H+ distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2 dust distribution. The 82 GHz HC3N, 82 GHz CCS, and 94 GHz CCS emission are often distributed differently with respect to the N2H+ emission. The CCS emission, which is known to be abundant in starless molecular cloud cores, is often very clumpy in the observed targets. We made deep single-pointing observations in DNC, (HNC)-C-13, N2D+, and cyclic-C3H2 toward nine clumps. The detection rate of N2D+ is 50%. Furthermore, we observed the NH3 emission toward 15 Planck cold clumps to estimate the kinetic temperature, and confirmed that most targets are cold (less than or similar to 20 K). In two of the starless clumps we observed, the CCS emission is distributed as it surrounds the N2H+ core (chemically evolved gas), which resembles the case of L1544, a prestellar core showing collapse. In addition, we detected both DNC and N2D+. These two clumps are most likely on the verge of star formation. We introduce the chemical evolution factor (CEF) for starless cores to describe the chemical evolutionary stage, and analyze the observed Planck cold clumps.

The Heterodyne Instrument for the Far Infrared (HIFI) onboard the Herschel Space Observatory allows the first observations of light diatomic molecules at high spectral resolution and in multiple transitions. Here, we report deep integrations using HIFI in different lines of hydrides towards the high-mass star forming region AFGL 2591. Detected are CH, CH+, NH, OH+, H2O+, while NH+ and SH+ have not been detected. All molecules except for CH and CH+ are seen in absorption with low excitation temperatures and at velocities different from the systemic velocity of the protostellar envelope. Surprisingly, the CH(J(F,P) = 3/2(2),(-) - 1/2(1,+)) and CH+(J = 1-0, J = 2-1) lines are detected in emission at the systemic velocity. We can assign the absorption features to a foreground cloud and an outflow lobe, while the CH and CH+ emission stems from the envelope. The observed abundance and excitation of CH and CH+ can be explained in the scenario of FUV irradiated outflow walls, where a cavity etched out by the outflow allows protostellar FUV photons to irradiate and heat the envelope at larger distances driving the chemical reactions that produce these molecules.

We monitored the 22 GHz H2O maser emission toward W49N from December 1989 through May 1990. During this period we observed an outburst in a component at -66.25 km s(-1). The flux density of the flaring component increased by a factor of greater than or similar to 10 to a maximum of 4020 Jy over a period of 24 days and decreased over the following 34 days to 1400 Jy on the last day of monitoring. During the flux increase the line narrowed from about 1.1 to 0.8 k s(-1); it subsequently rebroadened to 1.0 km s(-1) Most interestingly, during the flaring behavior the line center shifted by approximately 0.5 km s(-1) over the 58 day period. To explain the flare, particularly its shifting line center, we present a model of two interacting maser clouds. In the model, saturated maser radiation produced in a background cloud is amplified by an unsaturated, masing foreground cloud. Motion of the foreground cloud across the line of sight produces a flaring line, accompanied by line narrowing. We demonstrate that the observed flare in W49N may be explained by such a model where a rotating foreground cloud passes in front of a non-rotating background cloud. The differential amplification of the background cloud's radiation produces the observed increase in flux density, line narrowing, and systematic shift in center velocity.

We monitored the 22 GHz H2O maser emission toward W49N from December 1989 through May 1990. During this period we observed an outburst in a component at -66.25 km s(-1). The flux density of the flaring component increased by a factor of greater than or similar to 10 to a maximum of 4020 Jy over a period of 24 days and decreased over the following 34 days to 1400 Jy on the last day of monitoring. During the flux increase the line narrowed from about 1.1 to 0.8 k s(-1); it subsequently rebroadened to 1.0 km s(-1) Most interestingly, during the flaring behavior the line center shifted by approximately 0.5 km s(-1) over the 58 day period. To explain the flare, particularly its shifting line center, we present a model of two interacting maser clouds. In the model, saturated maser radiation produced in a background cloud is amplified by an unsaturated, masing foreground cloud. Motion of the foreground cloud across the line of sight produces a flaring line, accompanied by line narrowing. We demonstrate that the observed flare in W49N may be explained by such a model where a rotating foreground cloud passes in front of a non-rotating background cloud. The differential amplification of the background cloud's radiation produces the observed increase in flux density, line narrowing, and systematic shift in center velocity.