- ID:
- ivo://CDS.VizieR/J/A+A/617/A27
- Title:
- Kinematics of dense gas in L1495 filament
- Short Name:
- J/A+A/617/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nitrogen bearing species, such as NH_3_, N_2_H^+^, and their deuterated isotopolo- gues show enhanced abundances in CO-depleted gas, and thus are perfect tracers of dense and cold gas in star-forming regions. The Taurus molecular cloud contains the long L1495 filament providing an excellent opportunity to study the process of star formation in filamentary environments. We study the kinematics of the dense gas of starless and protostellar cores traced by the N_2_D^+^(2-1), N_2_H^+^(1-0), DCO^+^(2-1), and H^13^CO^+^(1-0) transitions along the L1495 filament and the kinematic links between the cores and surrounding molecular cloud. We measured velocity dispersions, local and total velocity gradients, and estimate the specific angular momenta of 13 dense cores in the four transitions using on-the-fly observations with the IRAM 30-m antenna. To study a possible connection to the filament gas, we used the C^18^O(1-0) observations.
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- ID:
- ivo://CDS.VizieR/J/A+A/644/A10
- Title:
- LARS XI. Turbulence Driven Lyman Alpha Escape
- Short Name:
- J/A+A/644/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the global dust and (molecular) gas content in the Lyman Alpha Reference Sample (LARS), i.e. 14 local star-forming galaxies. We characterize their interstellar medium and relate newly derived properties to quantities relevant for Ly{alpha} escape. We observed LARS galaxies with Herschel/PACS, SOFIA/FIFI-LS, the IRAM 30m telescope and APEX, targeting far-infrared (FIR) continuum and emission lines of [CII]158um, [OI]63um, [OIII]88um and low-J CO lines. Using Bayesian methods we derive dust model parameters and estimate total gas masses for all LARS galaxies, taking into account a metallicity-dependent gas-to-dust ratio. Star formation rates were estimated from FIR, [CII]158um and [OI]63um luminosities. LARS covers a wide dynamic range in the derived properties, with FIR-based star formation rates from ~0.5-100M_{sun}/yr, gas fractions between ~15-80% and gas depletion times ranging from a few hundred Myr up to more than 10Gyr. The distribution of LARS galaxies in the {SIGMA}_gas_ vs. {SIGMA}_SFR_ (Kennicutt-Schmidt plane) is thus quite heterogeneous. However, we find that LARS galaxies with the longest gas depletion times, i.e. relatively high gas surface densities ({SIGMA}_gas_) and low star formation rate densities ({SIGMA}_SFR_ have by far the highest Ly{alpha} escape fraction. A strong [Math Processing Error]linear relation is found between Ly{alpha} escape fraction and the total gas (HI+H_2_) depletion time. We argue that the Ly{alpha} escape in those galaxies is driven by turbulence in the star-forming gas that shifts the Ly{alpha} photons out of resonance close to the places where they originate. We further report on an extreme [CII]158um excess in LARS 5, corresponding to ~14+/-3% of the FIR luminosity, i.e. the most extreme [CII]-to-FIR ratio observed in a non-AGN galaxy to date.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A20
- Title:
- L1157-B1 DCN (2-1) and H^13^CN (2-1) datacubes
- Short Name:
- J/A+A/604/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed high-angular-resolution observations toward L1157-B1 with the IRAM NOEMA interferometer of the DCN (2-1) and H^13^CN (2-1) lines to compute the deuterated fraction, D_frac_(HCN), and compare it with previously reported D_frac_ of other molecular species. Our aim is to observationally investigate the role of the different chemical processes at work that lead to formation of the DCN and compare it with HDCO, the two deuterated molecules imaged with an interferometer, and test the predictions of the chemical models for their formation.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A115
- Title:
- Millimetric and far-IR maps of IRDC 18310-4
- Short Name:
- J/A+A/553/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Because of their short evolutionary time-scales, the earliest stages of high-mass star formation prior to the existence of any embedded heating source have barely been characterized until today. We study the fragmentation and dynamical properties of a massive starless gas clump at the onset of high-mass star formation. Based on Herschel continuum data we identify a massive gas clump that remains far-infrared dark up to 100um wavelengths. The fragmentation and dynamical properties are investigated by means of Plateau de Bure Interferometer and Nobeyama 45m single-dish spectral line and continuum observations.
- ID:
- ivo://CDS.VizieR/J/ApJS/202/1
- Title:
- 1mm spectral line survey toward GLIMPSE EGOs
- Short Name:
- J/ApJS/202/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A northern subsample of 89 Spitzer GLIMPSE extended green objects (EGOs), the candidate massive young stellar objects, are surveyed for molecular lines in two 1GHz ranges: 251.5-252.5 and 260.188-261.188GHz. A comprehensive catalog of observed molecular line data and spectral plots are presented. Eight molecular species are undoubtedly detected: H^13^CO^+^, SiO, SO, CH_3_OH, CH_3_OCH_3_, CH_3_CH_2_CN, HCOOCH_3_, and HN^13^C. The H^13^CO^+^ 3-2 line is detected in 70 EGOs, among which 37 also show the SiO 6-5 line, demonstrating their association with dense gas and supporting the outflow interpretation of the extended 4.5um excess emission. Our major dense gas and outflow tracers (H^13^CO^+^, SiO, SO, and CH_3_OH) are combined with our previous survey of ^13^CO, ^12^CO, and C^18^O 1-0 toward the same sample of EGOs for a multi-line, multi-cloud analysis of linewidth and luminosity correlations.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A148
- Title:
- 12 molecular clouds of M31 spectra
- Short Name:
- J/A+A/625/A148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse molecular observations performed at IRAM interferometer in CO(1-0) of the circum-nuclear region (within 250pc) of Andromeda, with 2. arcsec=11pc resolution. We detect 12 molecular clumps in this region, corresponding to a total molecular mass of (8.4+/ 0.4)x10^4^M_{sun}_. They follow the Larson's mass-size relation, but lie well above the velocity-size relation. We discuss that these clumps are probably not virialised, but transient agglomerations of smaller entities that might be virialised. Three of these clumps have been detected in CO(2-1) in a previous work, and we find temperature line ratio below 0.5. With a RADEX analysis, we show that this gas is in non local thermal equilibrium with a low excitation temperature (Tex=5-9K). We find a surface beam filling factor of order 5 percent and a gas density in the range 60-650cm^-3^, well below the critical density. With a gas-to-stellar mass fraction of 4x10^-4^ and dust-to-gas ratio of 0.01, this quiescent region has exhausted his gas budget. Its spectral energy distribution is compatible with passive templates assembled from elliptical galaxies. While weak dust emission is present in the region, we show that no star formation is present and support the previous results that the dust is heated by the old and intermediate stellar population. We study that this region lies formally in the low-density part of the Kennicutt-Schmidt law, in a regime where the SFR estimators are not completely reliable. We confirm the quiescence of the inner part of this galaxy known to lie on the green valley.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A95
- Title:
- Molecular DNM in Chamaeleon CO spectra
- Short Name:
- J/A+A/627/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To determine carbon monoxide column densities along sightlines through the Chamaeleon cloud complex where molecular absorption had been observed but CO emission had not been detected. We took ^12^CO J=1-0 absorption profiles toward 6 of 8 members of a group of sightlines in Chamaeleon having abundant dark neutral matter and molecular hydrogen but no detectable CO emission. CO absorption was detected along five of the six sightlines at column densities 4x10^+13^cm^-2^<~N(CO)<~10^15^cm^-2^ that are below typical survey detection limits of 1-2K-km/s. Dark gas absent in CO emission along sightlines in the outskirts of the Chamaeleon complex where molecular gas is readily detected in HCO^+^ absorption results from small CO column densities around the onset of CO formation at the HI/H_2_ transition. Relative abundances N(CO)/H_2_<3x10^-6^ in Chamaeleon are comparable to those seen in UV absorption toward early-type stars and in a CO absorption/emission line survey toward local quasar background targets away from the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A26
- Title:
- Molecular ion abundances in diffuse ISM
- Short Name:
- J/A+A/622/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The transition between atomic and molecular hydrogen is associated with important changes in the structure of interstellar clouds, and marks the beginning of interstellar chemistry. Most molecular ions are rapidly formed (in ion-molecule reactions) and destroyed (by dissociative recombination) in the diffuse ISM. Because of the relatively simple networks controlling their abundances, molecular ions are usually good probes of the underlying physical conditions including for instance the fraction of gas in molecular form or the fractional ionization. In this paper we focus on three possible probes of the molecular hydrogen column density, HCO^+^, HOC^+^, and CF^+^. We presented high sensitivity ALMA absorption data toward a sample of compact HII regions and bright QSOs with prominent foreground absorption, in the ground state transitions of the molecular ions HCO^+^, HOC^+^, and CF^+^ and the neutral species HCN and HNC, and from the excited state transitions of C_3_H^+^(4-3) and ^13^CS(2-1). These data are compared with Herschel absorption spectra of the ground state transition of HF and p-H_2_O. We show that the HCO^+^, HOC^+^, and CF^+^ column densities are well correlated with each other. HCO^+^ and HOC^+^ are tightly correlated with p-H_2_O, while they exhibit a different correlation pattern with HF depending on whether the absorbing matter is located in the Galactic disk or in the central molecular zone. We report new detections of C_3_H^+^ confirming that this ion is ubiquitous in the diffuse matter, with an abundance relative to H_2_ of ~7x10^-11^. We confirm that the CF^+^ abundance is lower than predicted by simple chemical models and propose that the rate of the main formation reaction is lower by a factor of about 3 than usually assumed. In the absence of CH or HF data, we recommend to use the ground state transitions of HCO^+^, CCH, and HOC^+^ to trace diffuse molecular hydrogen, with mean abundances relative to H_2_ of 3x10^-9^, 4x10^-8^ and 4x10^-11^ respectively, leading to sensitivity N(H_2_)/{int}{tau}dv of 4x10^20^, 1.5x10^21^, and 6x10^22^cm^-2^/km/s, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A40
- Title:
- MSX high-contrast IRDCs with NH_3_
- Short Name:
- J/A+A/552/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite increasing research in massive star formation, little is known about its earliest stages. Infrared Dark Clouds (IRDCs) are cold, dense and massive enough to harbour the sites of future high-mass star formation. But up to now, mainly small samples have been observed and analysed. To understand the physical conditions during the early stages of high-mass star formation, it is necessary to learn more about the physical conditions and stability in relatively unevolved IRDCs. Thus, for characterising IRDCs studies of large samples are needed. We investigate a complete sample of 220 northern hemisphere high-contrast IRDCs using the ammonia (1,1)- and (2,2)-inversion transitions. We detected ammonia (1,1)-inversion transition lines in 109 of our IRDC candidates. Using the data we were able to study the physical conditions within the star-forming regions statistically. We compared them with the conditions in more evolved regions which have been observed in the same fashion as our sample sources. Our results show that IRDCs have, on average, rotation temperatures of 15K, are turbulent (with line width FWHMs around 2km/s), have ammonia column densities on the order of 10^14^cm^-2^ and molecular hydrogen column densities on the order of 10^22^cm^-2^. Their virial masses are between 100 and a few 1000M_{sun}_. The comparison of bulk kinetic and potential energies indicate that the sources are close to virial equilibrium. IRDCs are on average cooler and less turbulent than a comparison sample of high-mass protostellar objects, and have lower ammonia column densities. Virial parameters indicate that the majority of IRDCs are currently stable, but are expected to collapse in the future.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A133
- Title:
- New APEX-SEPIA660 observations in OMC-1
- Short Name:
- J/A+A/644/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The star-formation rates and stellar densities found in young massive clusters suggest that these stellar systems originate from gas at densities of n(H_2_)>10^6^cm^-3^. Until today, however, the physical characterization of this ultra high density material remains largely unconstrained in observations. We investigate the density properties of the star-forming gas in the OMC-1 region located in the vicinity of the Orion Nebula Cluster (ONC). Methods. We mapped the molecular emission at 652GHz in OMC-1 as part of the APEX-SEPIA660 Early Science. We detect bright and extended N_2_H^+^ (J=7-6) line emission along the entire OMC-1 region. Comparisons with previous ALMA data of the (J=1-0) transition and radiative transfer models indicate that the line intensities observed in this N_2_H^+^ (7-6) line are produced by large mass reservoirs of gas at densities n(H_2_)>10^7^cm^-3^. The first detection of this N_2_H^+^ (7-6) line at parsec-scales demonstrates the extreme density conditions of the star-forming gas in young massive clusters such as the ONC. Our results highlight the unique combination of sensitivity and mapping capabilities of the new SEPIA660 receiver for the study of the ISM properties at high frequencies.
