- ID:
- ivo://CDS.VizieR/J/ApJ/872/121
- Title:
- Molecular cloud cores in the GC 50km/s cloud
- Short Name:
- J/ApJ/872/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic center 50km/s molecular cloud (50MC) is the most remarkable molecular cloud in the Sagittarius A region. This cloud is a candidate for the massive star formation induced by cloud-cloud collision (CCC) with a collision velocity of ~30km/s that is estimated from the velocity dispersion. We observed the whole of the 50MC with a high angular resolution (~2.0"x1.4") in Atacama Large Millimeter/submillimeter Array cycle 1 in the H^13^CO^+^ J=1-0 and C^34^S J=2-1 emission lines. We identified 241 and 129 bound cores with a virial parameter of less than 2, which are thought to be gravitationally bound, in the H^13^CO^+^ and C^34^S maps using the clumpfind algorithm, respectively. In the CCC region, the bound H^13^CO^+^ and C^34^S cores are 119 and 82, whose masses are 68% and 76% of those in the whole 50MC, respectively. The distribution of the core number and column densities in the CCC are biased to larger densities than those in the non-CCC region. The distributions indicate that the CCC compresses the molecular gas and increases the number of the dense bound cores. Additionally, the massive bound cores with masses of >3000M_{sun}_ exist only in the CCC region, although the slope of the core mass function (CMF) in the CCC region is not different from that in the non-CCC region. We conclude that the compression by the CCC efficiently formed massive bound cores even if the slope of the CMF is not changed so much by the CCC.
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- ID:
- ivo://CDS.VizieR/J/ApJS/110/21
- Title:
- Molecular clouds in Cepheus and Cassiopeia
- Short Name:
- J/ApJS/110/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A large-scale ^13CO(J=1-0) survey for nearby molecular clouds was performed toward the Cepheus and Cassiopeia regions (100{deg}<l<130{deg} and -10{deg}<b<20{deg}) with the velocity coverage of -40<V_LSR_<+20km/s by using the two 4m millimeter-wave telescopes at Nagoya University. An area of 866 square degrees was covered at an 8' grid spacing with a 2.7' beam, and 48750 positions were observed. Significant ^13^CO emission (>=1.8K.km/s=3{sigma}) is detected at 1015 positions. On the basis of the ^13^CO data, 188 distinct ^13^CO clouds are identified whose total mass is 1.0x10^5^M_{sun}_. Physical properties of the ^13^CO clouds such as molecular column densities, sizes, and masses are derived for each cloud. Astronomical objects associated with the ^13^CO clouds were searched for in the literature: 10 H II regions, eight reflection nebulae, 23 T Tauri type stars, 28 molecular outflows, and 125 IRAS point sources selected as candidates for protostars are likely to be associated with the ^13^CO clouds.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/136
- Title:
- Molecular clouds in the Antennae from CO(2-1)
- Short Name:
- J/ApJ/750/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Super star clusters--extremely massive clusters found predominately in starburst environments--are essential building blocks in the formation of galaxies and thought to dominate star formation in the high-redshift universe. However, the transformation from molecular gas into these ultracompact star clusters is not well understood. To study this process, we used the Submillimeter Array and the Plateau de Bure Interferometer to obtain high angular resolution (~1.5" or 160pc) images of the Antennae overlap region in CO(2-1) to search for the molecular progenitors of the super star clusters. We resolve the molecular gas distribution into a large number of clouds, extending the differential cloud mass function down to a 5{sigma} completeness limit of 3.8x10^5^M_{sun}_. We identify a distinct break in the mass function around log M_mol_/M_{sun}_{approx}6.5, which separates the molecular clouds into two distinct populations. The smaller, less massive clouds reside in more quiescent areas in the region, while the larger, more massive clouds cluster around regions of intense star formation. A broken power-law fit to the mass function yields slopes of {alpha}=-1.39+/-0.10 and {alpha}=-1.44+/-0.14 for the low- and high-mass cloud population, well matched to the mass function found for super star clusters in the Antennae galaxies. We find large velocity gradients and velocity dispersions at the locations of intense star formation, suggestive of compressive shocks. It is likely that these environmental factors contribute to the formation of the observed massive molecular clouds and super star clusters in the Antennae galaxies.
- ID:
- ivo://CDS.VizieR/J/A+AS/144/441
- Title:
- Molecular clouds SO and CS obs. I.
- Short Name:
- J/A+AS/144/441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the article we present a rather extensive mapping survey of 19 molecular clouds in the SO(3_2_-2_1_) and CS(2-1) molecular lines and, at certain positions, also the corresponding 34S isotope lines. Here we present the maps of the survey.
- ID:
- ivo://CDS.VizieR/J/A+A/358/257
- Title:
- Molecular clouds SO and CS obs. II.
- Short Name:
- J/A+A/358/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We here analyse the observational SO and CS data presented in Nilsson et al. (2000A&AS..144..441N). The SO/CS integrated intensity ratio maps are presented for 19 molecular clouds, together with tables of relevant ratios at strategic positions, where w e have also observed ^34^SO and/or C^34^S.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/113
- Title:
- Molecular clouds with GLIMPSE/MIPSGAL data
- Short Name:
- J/ApJ/839/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the star-formation (SF) law in 12 Galactic molecular clouds with ongoing high-mass star-formation (HMSF) activity, as traced by the presence of a bright IRAS source and other HMSF tracers. We define the molecular cloud (MC) associated with each IRAS source using ^13^CO line emission, and count the young stellar objects (YSOs) within these clouds using GLIMPSE and MIPSGAL 24{mu}m Spitzer databases. The masses for high-luminosity YSOs (L_bol_>10L_{sun}_) are determined individually using pre-main-sequence evolutionary tracks and the evolutionary stages of the sources, whereas a mean mass of 0.5M_{sun}_ was adopted to determine the masses in the low-luminosity YSO population. The star-formation rate surface density ({Sigma}SFR) corresponding to a gas surface density ({Sigma}gas) in each MC is obtained by counting the number of the YSOs within successive contours of ^13^CO line emission. We find a break in the relation between {Sigma}SFR and {Sigma}gas, with the relation being a power law ({Sigma}SFR{propto}{Sigma}gas^N^) with the index N varying between 1.4 and 3.6 above the break. The {Sigma}gas at the break is between 150-360M_{sun}_/pc^2^ for the sample clouds, which compares well with the threshold gas density found in recent studies of Galactic star-forming regions. Our clouds treated as a whole lie between the Kennicutt relation and the linear relation for Galactic and extra-galactic dense star-forming regions. We find a tendency for the high- mass YSOs to be found preferentially in dense regions at densities higher than 1200M_{sun}_/pc^2^ (~0.25g/cm^2^).
- ID:
- ivo://CDS.VizieR/J/other/RAA/20.115
- Title:
- Molecular clumps CO, HCO and HCN data
- Short Name:
- J/other/RAA/20.1
- Date:
- 19 Jan 2022 00:26:13
- Publisher:
- CDS
- Description:
- Gravitational accretion accumulates the original mass. This process is crucial for us to understand the initial phases of star formation. Using the specific infall profiles in optically thick and thin lines, we searched the clumps with infall motion from the Milky Way Imaging Scroll Painting (MWISP) CO data in previous work. In this study, we selected 133 sources as a sub-sample for further research and identification. The excitation temperatures of these sources are between 7.0 and 38.5K, while the H_2_ column densities are between 10^21^ and 10^23^cm^-2^. We have observed optically thick lines HCO+(1-0) and HCN(1-0) using the DLH 13.7-m telescope, and found 56 sources with a blue profile and no red profile in these two lines, which are likely to have infall motions, with a detection rate of 42%. This suggests that using CO data to restrict the sample can effectively improve the infall detection rate. Among these confirmed infall sources are 43 associated with Class 0/I young stellar objects (YSOs), and 13 which are not. These 13 sources are probably associated with the sources in the earlier evolutionary stage. In comparison, the confirmed sources that are associated with Class 0/I YSOs have higher excitation temperatures and column densities, while the other sources are colder and have lower column densities. Most infall velocities of the sources that we confirmed are between 10^-1^ to 100km/s, which is consistent with previous studies.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A95
- Title:
- Molecular DNM in Chamaeleon CO spectra
- Short Name:
- J/A+A/627/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To determine carbon monoxide column densities along sightlines through the Chamaeleon cloud complex where molecular absorption had been observed but CO emission had not been detected. We took ^12^CO J=1-0 absorption profiles toward 6 of 8 members of a group of sightlines in Chamaeleon having abundant dark neutral matter and molecular hydrogen but no detectable CO emission. CO absorption was detected along five of the six sightlines at column densities 4x10^+13^cm^-2^<~N(CO)<~10^15^cm^-2^ that are below typical survey detection limits of 1-2K-km/s. Dark gas absent in CO emission along sightlines in the outskirts of the Chamaeleon complex where molecular gas is readily detected in HCO^+^ absorption results from small CO column densities around the onset of CO formation at the HI/H_2_ transition. Relative abundances N(CO)/H_2_<3x10^-6^ in Chamaeleon are comparable to those seen in UV absorption toward early-type stars and in a CO absorption/emission line survey toward local quasar background targets away from the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A109
- Title:
- Molecular gas associated with IRAS 10361-5830
- Short Name:
- J/A+A/570/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the distribution of the molecular gas and dust in the molecular clump linked to IRAS 10361-5830, located in the environs of the bubble-shaped HII region Gum 31 in the Carina region, with the aim of determining the main parameters of the associated material and of investigating the evolutionary state of the young stellar objects identified there.
- ID:
- ivo://CDS.VizieR/J/ApJS/163/282
- Title:
- Molecular hydrogen column densities
- Short Name:
- J/ApJS/163/282
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurements of molecular hydrogen (H_2_) column densities are presented for the first six rotational levels (J=0-5) for 73 extragalactic targets observed with the Far Ultraviolet Spectroscopic Explorer (FUSE). All of these have a final signal-to-noise ratio larger than 10 and are located at Galactic latitude |b|>20{deg}. The individual observations were calibrated with the FUSE calibration pipeline CalFUSE version 2.1 or higher and then carefully aligned in velocity. The final velocity shifts for all the FUSE segments are listed. H_2_ column densities or limits are determined for the six lowest rotational (J) levels for each HI component in the line of sight, using a curve-of-growth approach at low column densities (<16.5) and Voigt-profile fitting at higher column densities. Detections include 65 measurements of low-velocity H_2_ in the Galactic disk and lower halo. Eight sight lines yield nondetections for Galactic H_2_.
