- ID:
- ivo://CDS.VizieR/J/A+A/631/A110
- Title:
- N131 bubble CO (3-2), (2-1) and (1-0) observations
- Short Name:
- J/A+A/631/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- N131 is a typical infrared dust bubble showing an expanding ringlike shell. We study what kinds of CO line ratios can be used to trace the interaction in the expanding bubble. We carry out new CO (3-2) observations towards bubble N131 using JCMT 15-m telescope, and derive line ratios by combining with our previous CO (2-1) and CO (1-0) data from IRAM 30-m observations. To trace the interaction between the molecular gas and the ionized gas in the HII region, we use RADEX to model the dependence of CO line ratios on kinetic temperature and H_2_ volume density, and examine the abnormal line ratios based on other simulations. We present CO (3-2), CO (2-1), and CO (1-0) integrated intensity maps convolved to the same angular resolution (22.5"). The three different CO transition maps show apparently similar morphology. The line ratios of W_CO_(3-2)/W_CO_(2-1) mostly range from 0.2 to 1.2 with a median of 0.54+/-0.12, while the line ratios of W_CO_(2-1)/W_CO_(1-0) range from 0.5 to 1.6 with a median of 0.84+/-0.15. The high CO line ratios W_CO_(3-2)/W_CO_(2-1)>0.8 and W_CO_(2-1)/W_CO_(1-0)>1.2 are beyond the threshold predicted by numerical simulations based on the assumed density-temperature structure for the inner rims of ringlike shell, where are the compressed areas in bubble N131. These high CO integrated intensity ratios, such as W_CO_(3-2)/W_CO_(2-1)>0.8 and W_CO_(2-1)/W_CO_(1-0)>1.2, can be used as a tracer of gas compressed regions with a relatively high temperature and density. This further suggests that the non-Gaussian part of the line-ratio distribution can be used to trace the interaction between the molecular gas and the hot gas in the bubble.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/585/A117
- Title:
- N131 bubble CO integrated intensity maps
- Short Name:
- J/A+A/585/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- OB-type stars have strong ionizing radiation and drive energetic winds. The ultraviolet radiation from ionizing stars may heat dust and ionize gas to sweep up an expanding bubble shell. This shell may be the result of feedback leading to a new generation of stars. N131 is an infrared dust bubble residing in a molecular filament. We study the formation and fragmentation of this bubble with multiwavelength dust and gas observations. Towards the bubble N131, we analysed archival multiwavelength observations including 3.6, 4.5, 5.8, 8.0, 24, 70, 160, 250, 350, 500um, 1.1mm, and 21cm. In addition, we performed new observations of CO (2-1), CO (1-0), and ^13^CO (1-0) with the IRAM 30m telescope.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/154
- Title:
- N159 ^12^CO and ^13^CO (2-1) clumps
- Short Name:
- J/ApJ/854/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The N159 star-forming region is one of the most massive giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC). We show the ^12^CO, ^13^CO, CS molecular gas lines observed with ALMA in N159 west (N159W) and N159 east (N159E). We relate the structure of the gas clumps to the properties of 24 massive young stellar objects (YSOs) that include 10 newly identified YSOs based on our search. We use dendrogram analysis to identify properties of the molecular clumps, such as flux, mass, linewidth, size, and virial parameter. We relate the YSO properties to the molecular gas properties. We find that the CS gas clumps have a steeper size-linewidth relation than the ^12^CO or ^13^CO gas clumps. This larger slope could potentially occur if the CS gas is tracing shocks. The virial parameters of the ^13^CO gas clumps in N159W and N159E are low (<1). The threshold for massive star formation in N159W is 501M_{sun}_/pc^2^, and the threshold for massive star formation in N159E is 794M_{sun}_/pc^2^. We find that ^13^CO is more photodissociated in N159E than N159W. The most massive YSO in N159E has cleared out a molecular gas hole in its vicinity. All the massive YSO candidates in N159E have a more evolved spectral energy distribution type in comparison to the YSO candidates in N159W. These differences lead us to conclude that the giant molecular cloud complex in N159E is more evolved than the giant molecular cloud complex in N159W.
- ID:
- ivo://CDS.VizieR/J/ApJ/824/95
- Title:
- Near-infrared imaging polarimetry of GGD 27
- Short Name:
- J/ApJ/824/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared imaging polarimetry in the J, H, and K_ s_ bands was carried out for GGD 27 in the dark cloud Lynds 291. Details of an infrared reflection nebula associated with the optical nebulosity GGD27 and the infrared nebula GGD 27 IRS are presented. Aperture photometry of 1263 point-like sources, detected in all three bands, was used to classify them based on a color-color diagram, and the linear polarization of several hundred sources was determined, with the latter used to map the magnetic field structure around GGD 27. This field, around GGD 27 IRS, appears to be associated with the extended CO outflow of IRAS 18162-2048; however, there are partly distorted or bent components in the field. The Chandrasekhar-Fermi method gives an estimate of the magnetic field strength as ~90{mu}G. A region associated with GGD 27 IRS is discovered to have a circular polarization in the range of ~2%-11% in the K_s_ band. The circular polarization has an asymmetric positive/negative pattern and extends out to ~120" or 1.0pc. The circular and linear polarization patterns are explained as resulting from a combination of dense inner and fainter outer lobes, suggesting episodic outflow.
- ID:
- ivo://CDS.VizieR/J/PASJ/64/96
- Title:
- Near-infrared survey of bright rimmed clouds
- Short Name:
- J/PASJ/64/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted wide-field near-infrared imaging observations of 32 bright rimmed clouds (BRCs). Given a detection limit of 17.7mag at the K-band, we identified 2099 objects as young stellar object (YSO) candidates that displayed near-infrared excesses. Their masses, estimated from luminosities, range from 0.006M_{sun}_ to 2.7M_{sun}_. The candidates are not uniformly distributed. For 21 BRCs, more than half of the associated YSO candidates are located inside the cloud. We found clear evidence of triggered star formation. The number of YSO candidates is not correlated with the core mass of the molecular clouds. Instead, the YSO number increases with increasing UV photon flux from the exciting star illuminating the cloud surface. UV radiation activates star formation in the BRCs.
- ID:
- ivo://CDS.VizieR/J/A+A/579/A130
- Title:
- Near-IR BN/KL outflow images
- Short Name:
- J/A+A/579/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Adaptive optics images are used to test the hypothesis that the explosive BN/KL outflow from the Orion OMC1 cloud core was powered by the dynamical decay of a non-hierarchical system of massive stars. Narrow-band H_2_, [FeII], and broad-band Ks obtained with the Gemini South multi-conjugate adaptive optics (AO) system GeMS and near-infrared imager GSAOI are presented. The images reach resolutions of 0.08 to 0.10" to the 0.07" diffraction limit of the 8-meter telescope at 2.12um. Comparison with previous AO-assisted observations of sub-fields and other ground-based observations enable measurements of proper motions and the investigation of morphological changes in H_2_ and [FeII] features with unprecedented precision. The images are compared with numerical simulations of compact, high-density clumps moving ~10^3^ times their own diameter through a lower density medium at Mach 10^3^.
- ID:
- ivo://CDS.VizieR/J/ApJS/196/4
- Title:
- New young star candidates in Taurus-Auriga
- Short Name:
- J/ApJS/196/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Taurus Molecular Cloud subtends a large solid angle on the sky, in excess of 250deg^2^. The search for legitimate Taurus members to date has been limited by sky coverage as well as the challenge of distinguishing members from field interlopers. The Wide-field Infrared Survey Explorer has recently observed the entire sky, and we take advantage of the opportunity to search for young stellar object (YSO) candidate Taurus members from a ~260deg^2^ region designed to encompass previously identified Taurus members. We use near- and mid-infrared colors to select objects with apparent infrared excesses and incorporate other catalogs of ancillary data to present a list of rediscovered Taurus YSOs with infrared excesses (taken to be due to circumstellar disks), a list of rejected YSO candidates (largely galaxies), and a list of 94 surviving candidate new YSO-like Taurus members. There is likely to be contamination lingering in this candidate list, and follow-up spectra are warranted.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A94
- Title:
- NGC 2264 clumps column densities
- Short Name:
- J/A+A/645/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass segregation of stellar clusters could be primordial rather than dynamical. Despite the abundance of studies of mass segregation for stellar clusters, those for stellar progenitors are still scarce, so the question on the origin and evolution of mass segregation is still open. Our goal is to characterize the structure of the NGC 2264 molecular cloud and compare the populations of clumps and young stellar objects (YSOs) in this region whose rich YSO population has shown evidence of sequential star formation. We separated the Herschel column density map of NGC 2264 in three subregions and compared their cloud power spectra using a multiscale segmentation technique. We identified in the whole NGC 2264 cloud a population of 256 clumps with typical sizes of ~0.1pc and masses ranging from 0.08M_{sun}_ to 53M_{sun}_. Although clumps have been detected all over the cloud, the central subregion of NGC 2264 concentrates most of the massive, bound clumps. The local surface density and the mass segregation ratio indeed indicate a strong degree of mass segregation for the 15 most massive clumps, with a median Sigma_6 _three time that of the whole clumps population and Lambda_MSR_ about 8. We showed that this cluster of massive clumps is forming within a high-density cloud ridge, itself formed and probably still fed by the high concentration of gas observed on larger scales in the central subregion. The time sequence obtained from the combined study of the clump and YSO populations in NGC 2264 suggests that the star formation started in the northern subregion, that it is now actively developing at the center and will soon start in the southern subregion. Taken together, the cloud structure and the clump and YSO populations in NGC 2264 argue for a dynamical scenario of star formation.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1131
- Title:
- NGC 1333 low-mass stars infrared photometry
- Short Name:
- J/AJ/127/1131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of near-infrared imaging and low-resolution near-infrared spectroscopy of low-mass objects in the NGC 1333 molecular cloud. A JHK survey of an 11.4'x11.7' area of the northern cluster was conducted to a sensitivity of K<=16mag. Using near-infrared magnitudes and colors from this and previously published surveys, 25 brown dwarf candidates were selected toward the high-extinction cloud core. Spectra in the K band were obtained and comparisons of the depths of water vapor absorption bands in our candidate objects with a grid of dwarf, subgiant, and giant standards were made to derive spectral types. These data were then used to derive effective temperatures and stellar luminosities that, when combined with theoretical tracks and isochrones for pre-main-sequence objects, resulted in estimates for their masses and ages.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A154
- Title:
- NGC6357 686 molecular cores physical properties
- Short Name:
- J/A+A/647/A154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We mapped the NGC6357 star forming region at 450 and 850 micron with SCUBA-2 and in the CO(3-2) line with HARP at the JCMT. We also retrieved Herschel Hi-GAL data at 70 and 160 micron. The submm continuum emission was decomposed into cores with the algorithm Gaussclumps (Stutzki & Guesten, 1990ApJ...356..513S). By fitting greybodies to the core 4-point SEDs we derived their temperature and mass. Core mass functions were derived in the region more exposed to the FUV flux from massive stars (associated with the HII regions G353.2+0.9, G353.1+0.6, and G353.2+0.7) and in the region less exposed. Table 2 lists the physical properties of the cores in NGC6357.
