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- ID:
- ivo://CDS.VizieR/J/ApJS/252/20
- Title:
- CO survey of the CMa OB1 complex
- Short Name:
- J/ApJS/252/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Purple Mountain Observatory 13.7m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous survey of ^12^CO, ^13^CO, and C^18^O (J=1-0) toward the CMa OB1 complex with a sky coverage of 16.5deg^2^ (221.5{deg}<=l<=227{deg}, -2.5{deg}<=b<=0.5{deg}). Emission from the CMa OB1 complex is found in the range 7km/s<=V_LSR_<=25km/s. The large-scale structure, physical properties, and chemical abundances of the molecular clouds are presented. A total of 83 C^18^O molecular clumps are identified with the GaussClumps algorithm within the mapped region. We find that 94% of these C18O molecular clumps are gravitationally bound. The relationship between their size and mass indicates that none of the C^18^O clumps has the potential to form high-mass stars. Using a semiautomatic IDL algorithm, we newly discover 85 CO outflow candidates in the mapped area, including 23 bipolar outflow candidates. Additionally, a comparative study reveals evidence for a significant variety of physical properties, evolutionary stages, and levels of star formation activity in different subregions of the CMa OB1 complex.
- ID:
- ivo://CDS.VizieR/J/ApJS/152/81
- Title:
- CO survey toward starless cores
- Short Name:
- J/ApJS/152/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A CO survey is undertaken toward about 80% of the starless cores in the Lee & Myers catalog that can be observed in the northern hemisphere to investigate their general observational properties such as line width and intensity, from which one can deduce their environmental physical conditions. The peak ^12^CO intensity implies a kinetic temperature close to 10K, as is already known, but for some of the cores the kinetic temperature is much higher than 10K, suggesting either that they are not really starless or that they are externally heated. We derive the ratios of peak intensities and line widths for the pairs of ^12^CO and ^13^CO lines and find a value of ~1.7 for both. The linear correlations between them are most likely to be due to clumpy structure. These data are also compared with data sets of CS 2-1 and N_2_H^+^ 1-0 lines tracing high-density regions. It is found that the peak intensity and line width of ^13^CO are roughly correlated with those of CS, suggesting that the outer envelope is kinematically related to the inner dense core. Confirming that the ^12^CO lines seldom exhibit deep self-reversal features, whereas this is not unusual for the CS lines, we propose a heuristic model where the outer part is clumpy, but the inner part has a rather smooth density profile, with a uniform temperature and mean density decreasing outward. We apply three-dimensional radiative transfer calculations to this simple model, demonstrating that the essential observational features of the starless cores are successfully reproduced.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/319
- Title:
- COUP: observations and source lists
- Short Name:
- J/ApJS/160/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a description of the data reduction methods and the derived catalog of more than 1600 X-ray point sources from the exceptionally deep 2003 January Chandra X-Ray Observatory (Chandra) observation of the Orion Nebula Cluster and embedded populations around OMC-1. The observation was obtained with Chandra's Advanced CCD Imaging Spectrometer (ACIS) and has been nicknamed the Chandra Orion Ultradeep Project (COUP). With an 838ks exposure made over a continuous period of 13.2 days, the COUP observation provides the most uniform and comprehensive data set on the X-ray emission of normal stars ever obtained in the history of X-ray astronomy.
- ID:
- ivo://CDS.VizieR/J/A+A/417/107
- Title:
- CO velocities in southern HII regions
- Short Name:
- J/A+A/417/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ^12^CO(1-0), ^12^CO(2-1) and/or ^13^CO(1-0) observations in the direction of HII regions located in the southern Galactic plane. The CO lines have been fitted with gaussian lines. For each direction (indicated by the galactic coordinates put in the source identification) we detect several components. The parameter, central position, line width and intensity of every component are listed in tables 2 and 3. In addition, we indicate, in the last two columns the velocity from radio and H{alpha} data of the pointed HII region.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A222
- Title:
- CS isotopes towards Galactic centre clouds
- Short Name:
- J/A+A/642/A222
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measuring isotopic ratios is a sensitive technique to obtain information on stellar nucleosynthesis and chemical evolution. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50km/s Cloud and several line-of-sight clouds towards Sgr B2(N). Towards the +50km/s Cloud, we observed the J=2-1 rotational transitions of ^12^C^32^S, ^12^C^34^S, ^13^C^32^S, ^12^C^33^S, and ^13^C^34^S, and the J=3-2 transitions of ^12^C^32^S and ^12^C^34^S with the IRAM-30m telescope, as well as the J=6-5 transitions of ^12^C^34^S and ^13^C^32^S with the APEX 12m telescope, all in emission. The J=2-1 rotational transitions of ^12^C^32^S, ^12^C^34^S, ^13^C^32^S, and ^13^C^34^S were observed with ALMA in Sgr B2(N)'s envelope, with those of ^12^C^32^S and ^12^C^34^S also observed in the line-of-sight clouds towards Sgr B2(N), all in absorption. In the +50km/s Cloud, we derive a ^12^C/^13^C isotopic ratio of 22.1^+3.3^_-2.4_, that leads, with the measured ^13^C^32^S/^12^C^34^S line intensity ratio, to a ^32^S/^34^S ratio of 16.3^+3.0^_-2.4_. We have also derived the ^32^S/^34^S isotopic ratio more directly from the two isotopologues ^13^C^32^S and ^13^C^34^S, which leads to an independent ^32^S/^34^S estimation of 16.3^+2.1^_-1.7_ and 17.9+/-5.0 for the +50km/s Cloud and Sgr B2(N), respectively. We also obtain a ^34^S/^33^S ratio of 4.3+/-0.2 in the +50km/s Cloud. Previous studies observed a decreasing trend in the ^32^S/^34^S isotopic ratios when approaching the Galactic centre. Our result indicates a termination of this tendency at least at a galactocentric distance of 130^+60^_-30_pc. This is at variance with findings based on ^12^C/^13^C, ^14^N/^15^N and ^18^O/^17^O isotope ratios, where the above-mentioned trend is observed to continue right to the central molecular zone. This can indicate a drop in the production of massive stars at the Galactic centre, in the same line as recent metallicity gradient ([Fe/H]) studies, and opens the work towards a comparison with Galactic and stellar evolution models.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/994
- Title:
- Cyano- to methanol and ammonia observations
- Short Name:
- J/ApJ/724/994
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of an effort to study gas-grain chemical models in star-forming regions as they relate to molecules containing cyanide (-C{\equiv}N) groups, we present here a search for the molecules 2-cyanoethanol (OHCH_2_CH_2_CN) and methoxyacetonitrile (CH_3_OCH_2_CN) in the galactic center region SgrB2. These species are structural isomers of each other and are targeted to investigate the cross-coupling of pathways emanating from the photolysis products of methanol and ammonia with pathways involving cyano-containing molecules. Methanol and ammonia ices are two of the main repositories of the elements C, O, and N in cold clouds and understanding their link to cyanide chemistry could give important insights into prebiotic molecular evolution. Neither species was positively detected, but the upper limits we determined allow comparison to the general patterns gleaned from chemical models. Our results indicate the need for an expansion of the model networks to better deal with cyano-chemistry, in particular with respect to pathways including products of methanol photolysis. In addition to these results, the two main observational routes for detecting new interstellar molecules are discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A1
- Title:
- Cygnus-X CO and SiO outflows datacubes
- Short Name:
- J/A+A/570/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a PdBI study of six massive dense cores in Cygnus-X, with CO (2-1) and SiO (2-1) emission. We studied the outflows of the individual protostars with CO (Duarte-Cabral et al., 2013A&A...558A.125D), and investigated the interstellar shocks responsible for the SiO emission (in Duarte-Cabral et al. 2014A&A...570A...1D).
- ID:
- ivo://CDS.VizieR/J/A+A/641/A35
- Title:
- Dark dust and single-cloud sightlines in ISM
- Short Name:
- J/A+A/641/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The precise characteristics of clouds and the nature of dust in the diffuse interstellar medium can only be extracted by inspecting the rare cases of single-cloud sightlines. In our nomenclature such objects are identified by interstellar lines, such as KI, that show at a resolving power of {lambda}{Delta}{lambda}~75000 one dominating Doppler component that accounts for more than half of the observed column density. We searched for such sightlines using high-resolution spectroscopy towards reddened OB stars for which far-UV extinction curves are known. We compiled a sample of 186 spectra, 100 of which were obtained specifically for this project with UVES. In our sample we identified 65 single-cloud sightlines, about half of which were previously unknown. We used the CH/CH^+^ line ratio of our targets to establish whether the sightlines are dominated by warm or cold clouds. We found that CN is detected in all cold (CH/CH^+^>1) clouds, but {is frequently absent} in warm clouds. We inspected the WISE (3-22um) observed emission morphology around our sightlines and excluded a circumstellar nature for the observed dust extinction. We found that most sightlines are dominated by cold clouds that are located far away from the heating source. For 132 stars, we derived the spectral type and the associated spectral type-luminosity distance. We also applied the interstellar CaII distance scale, and compared these two distance estimates with GAIA parallaxes. These distance estimates scatter by ~40%. By comparing spectral type-luminosity distances with those of GAIA, we detected a hidden dust component that amounts to a few mag of extinction for eight sightlines. This dark dust is populated by >~ 1um large grains and predominately appears in the field of the cold interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/158
- Title:
- Dark molecular gas in the Galaxy II. Perseus arm
- Short Name:
- J/ApJ/883/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results from a new, highly sensitive ({Delta}T_mb_~3mK) survey for thermal OH emission at 1665 and 1667MHz over a dense, 9x9pix grid covering a 1{deg}x1{deg} patch of sky in the direction of l=105.00{deg}, b=+2.50{deg} toward the Perseus spiral arm of our Galaxy. We compare our Green Bank Telescope 1667MHz OH results with archival ^12^CO(1-0) observations from the Five College Radio Astronomy Observatory Outer Galaxy Survey within the velocity range of the Perseus Arm at these galactic coordinates. Out of the 81 statistically independent pointings in our survey area, 86% show detectable OH emission at 1667MHz, and 19% of them show detectable CO emission. We explore the possible physical conditions of the observed features using a set of diffuse molecular cloud models. In the context of these models, both OH and CO disappear at current sensitivity limits below an A_v_ of 0.2, but the CO emission does not appear until the volume density exceeds 100-200cm^-3^. These results demonstrate that a combination of low column density A_v_ and low volume density n_H_ can explain the lack of CO emission along sight lines exhibiting OH emission. The 18cm OH main lines, with their low critical density of n*~1cm^-3^, are collisionally excited over a large fraction of the quiescent galactic environment and, for observations of sufficient sensitivity, provide an optically thin radio tracer for diffuse H_2_.
