- ID:
- ivo://CDS.VizieR/J/PASJ/53/971
- Title:
- CO catalog of LMC molecular clouds
- Short Name:
- J/PASJ/53/971
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From a ^12^CO (J=1-0) survey with the NANTEN telescope, we present a complete catalog of giant molecular clouds (GMCs) in the Large Magellanic Cloud. In total, 107 CO clouds have been identified, 55 of which were detected at more than 3 observed positions. For the 55 clouds, the physical properties, such as size, line-width, virial mass, and CO luminosity, are cataloged.
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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/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.
- 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/PASJ/73/487
- Title:
- C18O cores in Orion A
- Short Name:
- J/PASJ/73/487
- Date:
- 19 Jan 2022 00:24:20
- Publisher:
- CDS
- Description:
- We have performed an unbiased dense core survey toward the Orion A Giant Molecular Cloud in the C^18^O (J=1-0) emission line taken with the Nobeyama Radio Observatory (NRO) 45 m telescope. The effective angular resolution of the map is 26", which corresponds to ~0.05pc at a distance of 414pc. By using the Herschel-Planck H_2_ column density map, we calculate the C^18^O fractional abundance and find that it is roughly constant over the column density range of <~5x10^22^cm^-3^, although a trend of C^18^O depletion is determined toward higher column density. Therefore, C^18^O intensity can follow the cloud structure reasonably well. The mean C^18^O abundance in Orion A is estimated to be 5.7x10^-7^, which is about three times larger than the fiducial value. We identified 746 C^18^O cores with astrodendro and classified 709 cores as starless cores. We compute the core masses by decomposing the Herschel-Planck dust column density using the relative proportions of the C^18^O integrated intensities of line-of-sight components. Applying this procedure, we attempt to remove the contribution of the background emission, i.e., the ambient gas outside the cores. Then, we derived mass function for starless cores and found that it resembles the stellar initial mass function (IMF). The CMF for starless cores, dN/dM, is fitted with a power-law relation of M^{alpha}^ with a power index of {alpha}=-2.25+/-0.16 at the high-mass slope (>~0.44M_{sun}_). We also found that the ratio of each core mass to the total mass integrated along the line of sight is significantly large. Therefore, in the previous studies, the core masses derived from the dust image are likely to be overestimated by at least a factor of a few. Accordingly, such previous studies may underestimate the star formation efficiency of individual cores.
- ID:
- ivo://CDS.VizieR/J/ApJ/732/101
- Title:
- C^18^O cores in the S140 cloud
- Short Name:
- J/ApJ/732/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of C^18^O(J=1-0) mapping observations of a 20'x18' area in the Lynds 1204 molecular cloud associated with the Sharpless 2-140 (S140) HII region. The C^18^O cube ({alpha}-{delta}-{nu}_LSR_) data show that there are three clumps of sizes ~1pc in the region. Two of these have peculiar redshifted velocity components at their edges, which can be interpreted as the results of the interaction between the cloud and the Cepheus Bubble. From the C^18^O cube data, clumpfind identified 123 C^18^O cores, which have mean radius, velocity width in FWHM, and LTE mass of 0.36+/-0.07pc, 0.37+/-0.09km/s, and 41+/-29M_{sun}_, respectively. Considering the uncertainty in the C^18^O abundance, all the cores in S140 are most likely to be gravitationally bound. We derived a C^18^O core mass function (CMF), which shows a power-law-like behavior above a turnover at 30M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/760/147
- Title:
- ^13^CO cores in the Taurus molecular cloud
- Short Name:
- J/ApJ/760/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young stars form in molecular cores, which are dense condensations within molecular clouds. We have searched for molecular cores traced by ^13^CO J=1-->0 emission in the Taurus molecular cloud and studied their properties. Our data set has a spatial dynamic range (the ratio of linear map size to the pixel size) of about 1000 and spectrally resolved velocity information, which together allow a systematic examination of the distribution and dynamic state of ^13^CO cores in a large contiguous region. We use empirical fit to the CO and CO_2_ ice to correct for depletion of gas-phase CO. The ^13^CO core mass function (^13^CO CMF) can be fitted better with a log-normal function than with a power-law function. We also extract cores and calculate the ^13^CO CMF based on the integrated intensity of ^13^CO and the CMF from Two Micron All Sky Survey. We demonstrate that core blending exists, i.e., combined structures that are incoherent in velocity but continuous in column density. The core velocity dispersion (CVD), which is the variance of the core velocity difference {delta}v, exhibits a power-law behavior as a function of the apparent separation L: CVD(km/s){prop.to}L(pc)^0.7^. This is similar to Larson's law for the velocity dispersion of the gas. The peak velocities of ^13^CO cores do not deviate from the centroid velocities of the ambient ^12^CO gas by more than half of the line width. The low velocity dispersion among cores, the close similarity between CVD and Larson's law, and the small separation between core centroid velocities and the ambient gas all suggest that molecular cores condense out of the diffuse gas without additional energy from star formation or significant impact from converging flows.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A144
- Title:
- 13CO (1-0) data molecular cloud catalogue
- Short Name:
- J/A+A/654/A144
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- New-generation spectroscopic surveys of the Milky Way plane have been revealing the structure of the interstellar medium, allowing the simultaneous study of dense structures from single star-forming objects or systems to entire spiral arms. The good sensitivity of the new surveys and the development of dedicated algorithms now enable building extensive catalogues of molecular clouds and deriving good estimates of their physical properties. This allows studying the behaviour of these properties across the Galaxy. We present the catalogue of molecular clouds extracted from the ^13^CO (1-0) data cubes of the Forgotten Quadrant Survey, which mapped the Galactic plane in the range 220{deg}<l<240{deg}, and -2.5{deg}<b<0{deg} in ^12^CO (1-0) and ^13^CO (1-0). We compared the properties of the clouds of our catalogue with those of other catalogues. The catalogue contains 87 molecular clouds for which the main physical parameters such as area, mass, distance, velocity dispersion, and virial parameter were derived. These structures are overall less extended and less massive than the molecular clouds identified in the ^12^CO (1-0) data-set because they trace the brightest and densest part of the ^12^CO (1-0) clouds. Conversely, the distribution of aspect ratio, equivalent spherical radius, velocity dispersion, and virial parameter in the two catalogues are similar. The mean value of the mass surface density of molecular clouds is 87+/-55M_{sun}_/pc^2^ and is almost constant across the galactocentric radius, indicating that this parameter, which is a proxy of star formation, is mostly affected by local conditions. In data of the Forgotten Quadrant Survey, we find a good agreement between the total mass and velocity dispersion of the clouds derived from ^12^CO (1-0) and ^13^CO (1-0). This is likely because in the surveyed portion of the Galactic plane, the H_2_ column density is not particularly high, leading to a CO emission with a not very high optical depth. This mitigates the effects of the different line opacities between the two tracers on the derived physical parameters. This is a common feature in the outer Galaxy, but our result cannot be readily generalised to the entire Milky Way because regions with higher particle density could show a different behaviour.
