- ID:
- ivo://CDS.VizieR/J/A+A/554/A55
- Title:
- C^18^O(1-0) and N_2_H^+^(1-0) in L1495/B213
- Short Name:
- J/A+A/554/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Core condensation is a critical step in the star-formation process, but it is still poorly characterized observationally. We have studied the 10pc-long L1495/B213 complex in Taurus to investigate how dense cores have condensed out of the lower density cloud material. We observed L1495/B213 in C^18^O(1-0), N_2_H^+^(1-0), and SO(J_N_=3_2_-2_1_) with the 14m FCRAO telescope, and complemented the data with dust continuum observations using APEX (870um) and IRAM 30m (1200um).
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Search Results
- ID:
- ivo://CDS.VizieR/J/PASJ/62/557
- Title:
- CO clouds in the Galactic Center from NANTEN
- Short Name:
- J/PASJ/62/557
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to better understand molecular clouds and their properties toward the Galactic center region, we have analyzed the NANTEN database of ^12^CO (J=1-0) and ^13^CO (J=1-0) to search for associations with candidates for young high-mass star-forming regions, such as IRAS point sources, radio continuum sources, recombination line sources, maser line sources, and other molecular line sources. We have also compared the data with TeV gamma-ray sources. The analyzed region covers -12{deg}<=l<=12{deg} and -1.5{deg}<=b<=1.5{deg} for ^12^CO, and -6{deg}<=l<=8{deg} and -1{deg}<=b<=1{deg} for ^13^CO. As a result, we identified 167 IRAS point sources, 73 recombination line sources, 58 maser sources, 107 radio continuum sources, and 77 molecular line sources associated with 169 positions with the CO emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/686/384
- Title:
- ^12^CO, ^13^CO, C^18^O survey of IRDCs
- Short Name:
- J/ApJ/686/384
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared dark clouds (IRDCs) are extinction features against the Galactic infrared background, mainly in the mid-infrared band. Recently they were proposed to be potential sites of massive star formation. In this work we have made a ^12^CO, ^13^CO, and C^18^O (J=1->0) survey of 61 IRDCs, 52 of which are in the first Galactic quadrant, selected from a catalog given by Simon and coworkers (2006, Cat. J/ApJ/639/227), while the others are in the outer Galaxy, selected by visually inspecting the Midcourse Space Experiment (MSX) images. Detection rates in the three CO lines are 90%, 71%, and 62%, respectively. The distribution of IRDCs in the first Galactic quadrant is consistent with the 5kpc molecular ring picture, while a slight trace of a spiral pattern is also noticeable, and needs to be further examined. The IRDCs have a typical excitation temperature of 10K and typical column density of several 10^22^cm^-2^. Their typical physical size is estimated to be several parsecs using angular sizes from the Simon catalog.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/259
- Title:
- CO column densities in dark clouds
- Short Name:
- J/ApJ/720/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data from the Five College Radio Astronomy Observatory CO Mapping Survey of the Taurus molecular cloud are combined with extinction data for a sample of 292 background field stars to investigate the uptake of CO from the gas to icy grain mantles on dust within the cloud. On the assumption that the reservoir of CO in the ices is represented well by the combined abundances of solid CO and solid CO_2_ (which forms by oxidation of CO on the dust), we find that the total column density (gas+solid) correlates tightly with visual extinction (A_V_) over the range 5mag<A_V_<30mag, i.e., up to the highest extinctions covered by our sample. The mean depletion of gas-phase CO, expressed as {delta}(CO)=N(CO)_ice_/N(CO)_total_, increases monotonically from negligible levels for A_V_<~5 to ~0.3 at A_V_=10 and ~0.6 at A_V_=30. As these results refer to line-of-sight averages, they must be considered lower limits to the actual depletion at loci deep within the cloud, which may approach unity. We show that it is plausible for such high levels of depletion to be reached in dense cores on timescales ~0.6Myr, comparable with their expected lifetimes. Dispersal of cores during star formation may be effective in maintaining observable levels of gaseous CO on the longer timescales estimated for the age of the cloud.
- ID:
- ivo://CDS.VizieR/J/A+A/430/549
- Title:
- C^18^O/C^17^O near rho Oph
- Short Name:
- J/A+A/430/549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of up to ten carbon monoxide (CO and isotopomers) transitions are presented to study the interstellar C^18^O/C^17^O ratio towards 21 positions in the nearby (d~140pc) low-mass star forming cloud {rho} Oph. A map of the C^18^O J=1-0 distribution of parts of the cloud is also shown.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/28
- Title:
- C^18^O/C^17^O ratios in the Galactic center
- Short Name:
- J/ApJS/219/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ^18^O/^17^O isotopic ratio of oxygen is a crucial measure of the secular enrichment of the interstellar medium by ejecta from high-mass versus intermediate-mass stars. So far, however, there is a lack of data, particularly from the Galactic center (GC) region. Therefore, we have mapped typical molecular clouds in this region in the J=1-0 lines of C^18^O and C^17^O with the Delingha 13.7m telescope (DLH). Complementary pointed observations toward selected positions throughout the GC region were obtained with the IRAM 30m and Mopra 22m telescopes. C^18^O/C^17^O abundance ratios reflecting the ^18^O/^17^O isotope ratios were obtained from integrated intensity ratios of C^18^O and C^17^O. For the first time, C^18^O/C^17^O abundance ratios are determined for Sgr C (V~-58km/s), Sgr D (V~80km/s), and the 1.3{deg} complex (V~80km/s). Through our mapping observations, abundance ratios are also obtained for Sgr A (~0 and ~50km/s component) and Sgr B2 (~60km/s), which are consistent with the results from previous single-point observations. Our frequency-corrected abundance ratios of the GC clouds range from 2.58+/-0.07 (Sgr D, V~80km/s, DLH) to 3.54+/-0.12 (Sgr A, ~50km/s). In addition, strong narrow components (line width less than 5km/s) from the foreground clouds are detected toward Sgr D (-18km/s), the 1.3{deg} complex (-18km/s), and M+5.3-0.3 (22km/s), with a larger abundance ratio around 4.0. Our results show a clear trend of lower C^18^O/C^17^O abundance ratios toward the GC region relative to molecular clouds in the Galactic disk. Furthermore, even inside the GC region, ratios appear not to be uniform. The low GC values are consistent with an inside-out formation scenario for our Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/686/948
- Title:
- CO in extragalactic giant molecular clouds
- Short Name:
- J/ApJ/686/948
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use high spatial resolution observations of CO to systematically measure the resolved size-line width, luminosity-line width, luminosity-size, and mass-luminosity relations of GMCs in a variety of extragalactic systems. Although the data are heterogeneous, we analyze them in a consistent manner to remove the biases introduced by limited sensitivity and resolution, thus obtaining reliable sizes, velocity dispersions, and luminosities. We compare the results obtained in dwarf galaxies with those from the Local Group spiral galaxies. We find that extragalactic GMC properties measured across a wide range of environments are very much compatible with those in the Galaxy. The property that shows the largest variability is their resolved brightness temperature, although even that is similar to the average Galactic value in most sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/181/255
- Title:
- CO in Galactic HII regions
- Short Name:
- J/ApJS/181/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the molecular properties for a sample of 301 Galactic HII regions including 123 ultra compact (UC), 105 compact, and 73 diffuse nebulae. We analyze all sources within the BU-FCRAO Galactic Ring Survey (GRS) of ^13^CO emission known to be HII regions based upon the presence of radio continuum and cm-wavelength radio recombination line emission. Unlike all previous large area coverage ^13^CO surveys, the GRS is fully sampled in angle and yet covers ~75deg^2^ of the Inner Galaxy. The angular resolution of the GRS (46") allows us to associate molecular gas with HII regions without ambiguity and to investigate the physical properties of this molecular gas. We find clear CO/HII morphological associations in position and velocity for ~80% of the nebular sample. Compact HII region molecular gas clouds are on average larger than UC clouds: 2.2' compared to 1.7'.
- ID:
- ivo://CDS.VizieR/J/ApJS/141/157
- Title:
- CO (J=1-0) data of cold IRAS sources
- Short Name:
- J/ApJS/141/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a large-scale survey for the cold infrared sources along the northern Galactic plane in the CO (J=1-0) line. There are 1912 IRAS sources selected on the basis of their color indices over the 12, 25, and 60{mu}m wave bands and their association with regions of recent star formation. A quick single-point survey was made toward all of the sources, which results in a detection of 1331 sources with significant CO emission above the detection limit of 0.7K, inferring a CO detection rate of 70%. Located over a wide range of the Galactocentric distances, the CO sources show high concentration toward the spiral arms. Among the detected sources, there are 351 sources found to have high-velocity CO wing emission. A search for the latest catalog of high-velocity CO flows (HVFs) from young stellar objects indicates that 289 sources are beyond the present lists of HVFs. These high-velocity wing sources provide us with a comprehensive database for the study of HVFs from young stellar objects. Using the known outflow sources as an effective indicator, we found that the detection rate for high-velocity wings during the quick survey is 62%, moderately sensitive in searching for new outflow sources. The CO detection rate of the IRAS sources, combined with the ratio of high-velocity wing, suggests that 41% of the CO sources are undergoing the HVF phase. In this paper, the CO spectra are presented along with the preliminary statistics of the data.
- ID:
- ivo://CDS.VizieR/J/MNRAS/485/2417
- Title:
- CO J=2-1 NOEMA observations of mu Cep
- Short Name:
- J/MNRAS/485/2417
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red supergiant stars are surrounded by a gaseous and dusty circumstellar environment created by their mass loss which spreads heavy elements into the interstellar medium. The structure and the dynamics of this envelope are crucial to understand the processes driving the red supergiant mass loss and the shaping of the pre-supernova ejecta. We have observed the emission from the CO J=2-1 line from the red supergiant star {mu} Cep with the NOEMA interferometer. In the line the synthesized beam was 0.92x0.72-arcsec (590x462au at 641pc). The continuum map shows only the unresolved contribution of the free-free emission of the star chromosphere. The continuum-subtracted channel maps reveal a very inhomogeneous and clumpy circumstellar environment. In particular, we detected a bright CO clump, as bright as the central source in the line, at 1.80-arcsec south-west from the star, in the blue channel maps. After a deprojection of the radial velocity assuming two different constant wind velocities, the observations were modelled using the 3D radiative transfer code LIME to derive the characteristics of the different structures. We determine that the gaseous clumps observed around {mu} Cep are responsible for a mass loss rate of (4.9+/-1.0)x10^-7^M_[sun}_/yr, in addition to a spatially unresolved wind component with an estimated mass-loss rate of 2.0x10^-6^M_[sun}_/yr. Therefore, the clumps have a significant role in {mu} Cep's mass loss (>=25%). We cannot exclude that the unresolved central outflow may be made of smaller unresolved clumps.