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3041. CO, [CI] and [NII] lines from Herschel spectra
ID:
ivo://CDS.VizieR/J/ApJ/829/93
Title:
CO, [CI] and [NII] lines from Herschel spectra
Short Name:
J/ApJ/829/93
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of all CO (J=4-3 through J=13-12), [CI], and [NII] lines available from extragalactic spectra from the Herschel SPIRE Fourier Transform Spectrometer (FTS) archive combined with observations of the low-J CO lines from the literature and from the Arizona Radio Observatory. This work examines the relationships between L_FIR_, L'_CO_, and L_CO_/L_CO,1-0_. We also present a new method for estimating probability distribution functions from marginal signal-to-noise ratio Herschel FTS spectra, which takes into account the instrumental "ringing" and the resulting highly correlated nature of the spectra. The slopes of log(L_FIR_) versus log(L'_CO_) are linear for all mid- to high-J CO lines and slightly sublinear if restricted to (ultra)luminous infrared galaxies ((U)LIRGs). The mid- to high-J CO luminosity relative to CO J=1-0 increases with increasing L_FIR_, indicating higher excitement of the molecular gas, although these ratios do not exceed ~180. For a given bin in L_FIR_, the luminosities relative to CO J=1-0 remain relatively flat from J=6-5 through J=13-12, across three orders of magnitude of L_FIR_. A single component theoretical photodissociation region (PDR) model cannot match these flat SLED shapes, although combinations of PDR models with mechanical heating added qualitatively match the shapes, indicating the need for further comprehensive modeling of the excitation processes of warm molecular gas in nearby galaxies.
3042. CO+[CI] emission in distant galaxies
ID:
ivo://CDS.VizieR/J/A+A/641/A155
Title:
CO+[CI] emission in distant galaxies
Short Name:
J/A+A/641/A155
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the detection of multiple carbon monoxide CO line transitions with ALMA in a few tens of infrared-selected galaxies on and above the main sequence at z=1.1-1.7. We reliably detected the emission of CO(5-4), CO(2-1), and CO(7-6)+[CI](2-1) in 50, 33, and 13 galaxies, respectively, and we complemented this information with available CO(4-3) and [CI](1-0) fluxes for part of the sample, and by modeling of the optical-to-millimeter spectral energy distribution. We retrieve a quasi-linear relation between LIR and CO(5-4) or CO(7-6) for main-sequence galaxies and starbursts, corroborating the hypothesis that these transitions can be used as star formation rate (SFR) tracers. We find the CO excitation to steadily increase as a function of the star formation efficiency (SFE), the mean intensity of the radiation field warming the dust (<U>), the surface density of SFR (SigmaSFR), and, less distinctly, with the distance from the main sequence. This adds to the tentative evidence for higher excitation of the CO+[CI] spectral line energy distribution (SLED) of starburst galaxies relative to that for main-sequence objects, where the dust opacities play a minor role in shaping the high-J CO transitions in our sample. However, the distinction between the average SLED of upper main-sequence and starburst galaxies is blurred, driven by a wide variety of intrinsic shapes. Large velocity gradient radiative transfer modeling demonstrates the existence of a highly excited component that elevates the CO SLED of high-redshift main-sequence and starbursting galaxies above the typical values observed in the disk of the Milky Way. This excited component is dense and it encloses ~50% of the total molecular gas mass in main-sequence objects. We interpret the observed trends involving the CO excitation as to be mainly determined by a combination of large SFRs and compact sizes, as a large SigmaSFR is naturally connected with enhanced dense molecular gas fractions and higher dust and gas temperatures, due to increasing ultraviolet radiation fields, cosmic ray rates, as well as dust and gas coupling. We release the full data compilation and the ancillary information to the community.
3043. CO clouds in the Galactic Center from NANTEN
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.
3044. ^13^CO clumps toward the Cassiopeia A supernova remnant
ID:
ivo://CDS.VizieR/J/ApJ/878/44
Title:
^13^CO clumps toward the Cassiopeia A supernova remnant
Short Name:
J/ApJ/878/44
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have conducted a large-field simultaneous survey of ^12^CO, ^13^CO, and C^18^O J=1-0 emission toward the Cassiopeia A (Cas A) supernova remnant (SNR), which covers a sky area of 3.5{deg}x3.1{deg}. The Cas giant molecular cloud (GMC) mainly consists of three individual clouds with masses on the order of 10^4^-10^5^M_{sun}_. The total mass derived from the ^13^CO emission of the GMC is 2.1x10^5^M_{sun}_ and is 9.5x10^5^M_{sun}_ from the ^12^CO emission. Two regions with broadened (6-7km/s) or asymmetric ^12^CO line profiles are found in the vicinity (within a 10'x10' region) of the Cas A SNR, indicating possible interactions between the SNR and the GMC. Using the GAUSSCLUMPS algorithm, 547 ^13^CO clumps are identified in the GMC, 54% of which are supercritical (i.e., {alpha}_vir_<2). The mass spectrum of the molecular clumps follows a power-law distribution with an exponent of -2.20. The pixel-by-pixel column density of the GMC can be fitted with a log-normal probability distribution function (N-PDF). The median column density of molecular hydrogen in the GMC is 1.6x10^21^cm^-2^ and half the mass of the GMC is contained in regions with H_2_ column density lower than 3x10^21^cm^-2^, which is well below the threshold of star formation. The distribution of the YSO candidates in the region shows no agglomeration.
3045. ^12^CO, ^13^CO, C^18^O survey of IRDCs
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.
3046. CO, C & O gas content of debris discs predictions
ID:
ivo://CDS.VizieR/J/MNRAS/469/521
Title:
CO, C & O gas content of debris discs predictions
Short Name:
J/MNRAS/469/521
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper uses observations of dusty debris discs, including a growing number of gas detections in these systems, to test our understanding of the origin and evolution of this gaseous component. It is assumed that all debris discs with icy planetesimals create second generation CO, C and O gas at some level, and the aim of this paper is to predict that level and assess its observability. We present a new semi-analytical equivalent of the numerical model of Kral et al. (2016MNRAS.461.1614K) allowing application to large numbers of systems. That model assumes CO is produced from volatile-rich solid bodies at a rate that can be predicted from the debris discs fractional luminosity. CO photodissociates rapidly into C and O that then evolve by viscous spreading. This model provides a good qualitative explanation of all current observations, with a few exceptional systems that likely have primordial gas. The radial location of the debris and stellar luminosity explain some non-detections, e.g. close-in debris (like HD 172555) is too warm to retain CO, while high stellar luminosities (like {eta} Tel) result in short CO lifetimes. We list the most promising targets for gas detections, predicting >15 CO detections and >30 CI detections with ALMA, and tens of CII and O I detections with future far-IR missions. We find that CO, CI, CII and OI gas should be modelled in non-LTE for most stars, and that CO, CI and OI lines will be optically thick for the most gas-rich systems. Finally, we find that radiation pressure, which can blow out CI around early-type stars, can be suppressed by self-shielding.
3047. CO column densities in dark clouds
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.
3048. C^18^O/C^17^O near rho Oph
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.
3049. 12CO/13CO ratio in 126 nearby galaxy centers
ID:
ivo://CDS.VizieR/J/A+A/635/A131
Title:
12CO/13CO ratio in 126 nearby galaxy centers
Short Name:
J/A+A/635/A131
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present ground-based measurements of 126 nearby galaxy centers in ^12^CO and 92 in ^13^CO in various low-J transitions. More than 60 galaxies were measured in at least four lines. The average relative intensities of the first four J ^12^CO transitions are 1.00:0.92:0.70:0.57. In the first three J transitions, the average ^12^CO-to-^13^CO intensity ratios are 13.0, 11.6, and 12.8, with individual values in any transition ranging from 5 to 25. The sizes of central CO concentrations are well defined in maps, but poorly determined by multi-aperture photometry. On average, the J=1-0 ^12^CO fluxes increase linearly with the size of the observing beam. CO emission covers only a quarter of the HI galaxy disks. Using radiative transfer models (RADEX), we derived model gas parameters. The assumed carbon elemental abundances and carbon gas depletion onto dust are the main causes of uncertainty. The new CO data and published [CI] and [CII] data imply that CO, C, and C^+^ each represent about one-third of the gas-phase carbon in the molecular interstellar medium. The mean beam-averaged molecular hydrogen column density is N(H_2_)=(1.5+/-0.2)10^21^cm^-2^. Galaxy center CO-to- H2 conversion factors are typically ten times lower than the 'standard' Milky Way X disk value, with a mean X(CO)=(1.9+/-0.2)10^19^cm^-2^/(K.km/s) and a dispersion 1.7. The corresponding [CI]-H_2_ factor is five times higher than X(CO), with X[CI]=(9+/-2)10^19^cm^-2^/(K.km/s). No unique conversion factor can be determined for [CII]. The low molecular gas content of galaxy centers relative to their CO intensities is explained in roughly equal parts by high central gas-phase carbon abundances, elevated gas temperatures, and large gas velocity dispersions relative to the corresponding values in galaxy disks.
3050. C^18^O/C^17^O ratios in the Galactic center
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.

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