- ID:
- ivo://CDS.VizieR/J/ApJ/761/37
- Title:
- CO observations in giant molecular clouds of M33
- Short Name:
- J/ApJ/761/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a giant molecular cloud (GMC) catalog of M33 (NGC598), containing 71 GMCs in total, based on wide-field and high-sensitivity CO(J=3-2) observations with a spatial resolution of 100pc using the ASTE 10m telescope. Employing archival optical data, we identify 75 young stellar groups (YSGs) from the excess of the surface stellar density, and estimate their ages by comparing with stellar evolution models. A spatial comparison among the GMCs, YSGs, and H II regions enable us to classify GMCs into four categories: Type A, showing no sign of massive star formation (SF); Type B, being associated only with H II regions; Type C, with both H II regions and <10Myr old YSGs; and Type D, with both H II regions and 10-30Myr YSGs. Out of 65 GMCs (discarding those at the edges of the observed fields), 1 (1%), 13 (20%), 29 (45%), and 22 (34%) are Types A, B, C, and D, respectively. We interpret these categories as stages in a GMC evolutionary sequence. Assuming that the timescale for each evolutionary stage is proportional to the number of GMCs, the lifetime of a GMC with a mass >10^5^M_{sun}_ is estimated to be 20-40Myr. In addition, we find that the dense gas fraction as traced by the CO(J=3-2)/CO(J=1-0) ratio is enhanced around SF regions. This confirms a scenario where dense gas is preferentially formed around previously generated stars, and will be the fuel for the next stellar generation. In this way, massive SF gradually propagates in a GMC until gas is exhausted.
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- ID:
- ivo://CDS.VizieR/J/ApJS/178/56
- Title:
- CO observations of LMC Giant Molecular clouds
- Short Name:
- J/ApJS/178/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second survey of the molecular clouds in the Large Magellanic Cloud in ^12^CO(J=1-0) was carried out by NANTEN. The sensitivity of this survey is twice as high as that of the previous NANTEN survey, leading to a detection of molecular clouds with M_CO_>~2x10^4^solMass. We identified 272 molecular clouds, 230 of which are detected at three or more observed positions. We derived the physical properties, such as size, line width, and virial mass, of the 164 GMCs (Giant Molecular clouds) that have an extent more than the beam size of NANTEN in both the major and minor axes.
- ID:
- ivo://CDS.VizieR/J/ApJS/197/16
- Title:
- CO observations of LMC molecular clouds (MAGMA).
- Short Name:
- J/ApJS/197/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the properties of an extensive sample of molecular clouds in the Large Magellanic Cloud (LMC) mapped at 11pc resolution in the CO(1-0) line. Targets were chosen based on a limiting CO flux and peak brightness as measured by the NANTEN survey. The observations were conducted with the ATNF Mopra Telescope as part of the Magellanic Mopra Assessment. We identify clouds as regions of connected CO emission and find that the distributions of cloud sizes, fluxes, and masses are sensitive to the choice of decomposition parameters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/2121
- Title:
- CO 3-2 observations of outflows in W5
- Short Name:
- J/MNRAS/418/2121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New James Clerk Maxwell Telescope (JCMT) HARP CO 3-2 observations of the W5 star forming complex are presented, totalling an area of ~12000-arcmin^2^ with sensitivity better than 0.1K per 0.4km/s channel. We discovered 55 CO outflow candidates, of which 40 are associated with W5 and 15 are more distant than the Perseus arm.
- ID:
- ivo://CDS.VizieR/J/ApJ/774/22
- Title:
- CO observations of YSOs in NGC 1333
- Short Name:
- J/ApJ/774/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of outflows in the star-forming region NGC 1333 using the Combined Array for Research in Millimeter-Wave Astronomy (CARMA). We combined the ^12^CO and ^13^CO (1-0) CARMA mosaics with data from the 14m Five College Radio Astronomy Observatory to probe the central, most dense, and active region of this protostellar cluster at scales from 5" to 7' (or 1000AU to 0.5pc at a distance of 235pc). We map and identify ^12^CO outflows, and along with ^13^CO data we estimate their mass, momentum, and energy. Within the 7'x7' map, the 5" resolution allows for a detailed study of morphology and kinematics of outflows and outflow candidates, some of which were previously confused with other outflow emission in the region. In total, we identify 22 outflow lobes, as well as 9 dense circumstellar envelopes marked by continuum emission, of which 6 drive outflows. We calculate a total outflow mass, momentum, and energy within the mapped region of 6M_{sun}_, 19M_{sun}_ km/s, and 7x10^44^erg, respectively. Within this same region, we compare outflow kinematics with turbulence and gravitational energy, and we suggest that outflows are likely important agents for the maintenance of turbulence in this region. In the earliest stages of star formation, outflows do not yet contribute enough energy to totally disrupt the clustered region where most star formation is happening, but have the potential to do so as the protostellar sources evolve.
- ID:
- ivo://CDS.VizieR/J/ApJS/230/17
- Title:
- CO obs. of MCs in the Extreme Outer Galaxy region
- Short Name:
- J/ApJS/230/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an unbiased CO survey in the Galactic range of 34.75{deg}<=l<=45.25{deg} and -5.25{deg}<=b<=5.25{deg}, and the velocity range beyond the Outer arm. A total of 168 molecular clouds (MCs) are identified within the Extreme Outer Galaxy (EOG) region, and 31 of these MCs are associated with ^13^CO emission. However, none of them show significant C^18^O emission under the current detection limit. The typical size and mass of these MCs are 5pc and 3x10^3^M_{sun}_, implying a lack of large and massive MCs in the EOG region. Similar to MCs in the outer Galaxy, the velocity dispersions of EOG clouds are also correlated with their sizes; however, they are well displaced below the scaling relationship defined by the inner Galaxy MCs. These MCs with a median Galactocentric radius of 12.6kpc show very different distributions from those of the MCs in the Outer arm published in our previous paper, while roughly following the Outer Scutum-Centaurus arm defined by Dame & Thaddeus (2011ApJ...734L..24D). This result may provide robust evidence for the existence of the Outer Scutum-Centaurus arm. The lower limit of the total mass of this segment is about 2.7x10^5^M_{sun}_, which is about one magnitude lower than that of the Outer arm. The mean thickness of the gaseous disk is about 1.45{deg} or 450pc, and the scale height is about 1.27{deg}, or 400pc above the b=0{deg} plane. The warp traced by CO emission is very obvious in the EOG region and its amplitude is consistent with the predictions by other warp models using different tracers, such as dust, HI, and stellar components of our Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/3
- Title:
- CO obs. of molecular clouds in the MW midplane
- Short Name:
- J/ApJS/254/3
- Date:
- 17 Jan 2022 11:34:49
- Publisher:
- CDS
- Description:
- In this work, we study the properties of molecular clouds in the second quadrant of the Milky Way Midplane, from l=104.75{deg} to l=119.75{deg}, and b=-5.25{deg} to b=5.25{deg}, using the ^12^CO, ^13^CO, and C^18^O J=1-0 emission line data from the Milky Way Imaging Scroll Painting project. We identify 857 and 300 clouds in the ^12^CO and ^13^CO spectral cubes, respectively, using the DENDROGRAM + SCIMES algorithms. The distances of the molecular clouds are estimated, and physical properties such as the mass, size, and surface densities of the clouds are tabulated. The molecular clouds in the Perseus Arm are about 30-50 times more massive, and 4-6 times larger than the clouds in the Local Arm. This result, however, is likely to be biased by distance selection effects. The surface densities of the clouds are enhanced in the Perseus Arm, with an average value of ~100M_{sun}_/pc^2^. Here. we select the 40 most extended (>0.35arcdeg^2^) molecular clouds from the ^12^CO catalog to build the H_2_ column density probability distribution function (N-PDF). Some 78% of the N-PDFs of the selected molecular clouds are well fitted with log-normal functions with only small deviations at high densities, corresponding to star-forming regions with scales of ~1-5pc in the Local Arm, and ~5-10pc in the Perseus Arm. About 18% of the selected molecular clouds have power-law N-PDFs at high densities. In these molecular clouds, the majority of the regions fitted with the power law correspond to molecular clumps at sizes of ~1pc, or filaments at widths of ~1pc.
- ID:
- ivo://CDS.VizieR/J/ApJ/798/L27
- Title:
- CO obs. of molecular clouds in the 2nd quadrant
- Short Name:
- J/ApJ/798/L27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining H I data from the Canadian Galactic Plane Survey and CO data from the Milky Way Imaging Scroll Painting project (MWISP), we have identified a new segment of a spiral arm between Galactocentric radii of 15 and 19kpc that apparently lies beyond the Outer Arm in the second Galactic quadrant. Over most of its length, the arm is 400-600pc thick in z. The new arm appears to be the extension of the distant arm recently discovered by Dame & Thaddeus (2011ApJ...734L..24D) as well as the Scutum-Centaurus Arm into the outer second quadrant. Our current survey identified a total of 72 molecular clouds with masses on the order of 10^2^-10^4^M_{sun}_ that probably lie in the new arm. When all of the available data from the CO molecular clouds are fit, the best-fitting spiral model gives a pitch angle of 9.3{deg}+/-0.7{deg}.
- ID:
- ivo://CDS.VizieR/J/ApJS/248/15
- Title:
- CO obs. of molecular outflows in the Cygnus complex
- Short Name:
- J/ApJS/248/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey of molecular outflows across the dark cloud complex in the Cygnus region, based on a 46.75deg^2^ field of CO isotopologue data from the Milky Way Imaging Scroll Painting (MWISP) survey. A supervised machine-learning algorithm, the support vector machine, is introduced to accelerate our visual assessment of outflow features in the data cube of ^12^CO and ^13^CO J=1-0 emission. A total of 130 outflow candidates are identified, 77 of which show bipolar structures and 118 are new detections. Spatially, these outflows are located inside dense molecular clouds, and some of them are found in clusters or in elongated linear structures tracing the underlying gas filament morphology. Along the line of sight, 97, 31, and 2 candidates reside in the Local, Perseus, and Outer Arms, respectively. Young stellar objects as outflow drivers are found near most outflows, while 36 candidates show no associated source. The clusters of outflows that we detect are inhomogeneous in their properties; nevertheless, we show that the outflows cannot inject turbulent energy on cloud scales. Instead, at best, they are restricted to affecting the so-called "clump" and "core" scales, and only on short (~0.3Myr) estimated timescales. Combined with outflow samples in the literature, our work shows a tight outflow mass-size correlation.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/29
- Title:
- CO obs. of Planck Galactic cold clumps
- Short Name:
- J/ApJS/247/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sixty-five Planck Galactic cold clumps (PGCCs) from the first quadrant (IQuad) and 39 from the anticenter direction region (ACent) were observed in ^12^CO, ^13^CO, and C^18^O J=1-0 lines using the 13.7m telescope of the Purple Mountain Observatory. All the targets were detected in all three lines, except for 12 IQuad and 8 ACent PGCCs without C^18^O detection. Seventy-six and 49 velocity components were obtained in IQuad and ACent respectively; 146 cores were extracted from 76 IQuad clumps and 100 cores from 49 ACent clumps. The average Tex of IQuad cores and ACent cores is 12.4K and 12.1K, respectively. The average line widths of ^13^CO of IQuad cores and ACent cores are 1.55km/s and 1.77km/s, respectively. Among the detected cores, 24 in IQuad and 13 in ACent have asymmetric line profiles. The small blue excesses, ~0.03 in IQuad and 0.01 in ACent, indicate that star formation is not active in these PGCC cores. Power-law fittings of the core mass function to the high-mass end give indices of -0.57 in IQuad and -1.02 in ACent, which are flatter than the slope of the initial mass function given by Salpeter. The large turnover masses of 28M_{sun}_ for IQuad cores and 77M_{sun}_ for ACent cores suggest low star formation efficiencies in PGCCs. The correlation between virial mass and gas mass indicates that most PGCC cores in both regions are not likely pressure-confined.
