- ID:
- ivo://CDS.VizieR/J/ApJ/864/154
- Title:
- Planck cold clump G108.37-01.06 YSO candidates
- Short Name:
- J/ApJ/864/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Planck Galactic Cold Clumps (PGCCs) are possible representations of the initial conditions and very early stages of star formation. With the objective of understanding better the star and star cluster formation, we probe the molecular cloud associated with PGCC G108.37-01.06 (hereafter PG108.3), which can be traced in a velocity range of -57 to -51km/s. The INT Photometric H{alpha} Survey images reveal H{alpha} emission at various locations around PG108.3, and optical spectroscopy of the bright sources in those zones of H{alpha} emission discloses two massive ionizing sources with spectral type O8-O9V and B1V. Using the radio continuum, we estimate ionizing gas parameters and find the dynamical ages of HII regions associated with the massive stars in the range of 0.5-0.75Myr. Based on the stellar surface density map constructed from the deep near-infrared Canada-France-Hawaii Telescope observations, we find two prominent star clusters in PG108.3; of these, the cluster associated with H ii region S148 is moderately massive (~240M_{sun}_). A careful inspection of James Clerk Maxwell telescope ^13^CO (3-2) molecular data exhibits that the massive cluster is associated with a number of filamentary structures. Several embedded young stellar objects (YSOs) are also identified in PG108.3 along the length and junction of filaments. We find evidence of a velocity gradient along the length of the filaments. Along with kinematics of the filaments and the distribution of ionized, molecular gas and YSOs, we suggest that the cluster formation is most likely due to the longitudinal collapse of the most massive filament in PG108.3.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/209/37
- Title:
- Planck cold clumps in ^12^CO, ^13^CO and C^18^O
- Short Name:
- J/ApJS/209/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A mapping study of 71 Planck cold clumps was made with ^12^CO(1-0), ^13^CO(1-0), and C^18^O(1-0) lines at the 13.7m telescope of Purple Mountain Observatory. For all the clumps, ^12^CO(1-0) and ^13^CO(1-0) emissions were detected, while for 55 of them, C^18^O(1-0) emissions were detected. Of the 71 Clumps, 34 are in the Taurus Complex, 24 in the California Complex, and 13 are in the Perseus Complex. In the 76 velocity components, 38 cores are found in 27 clumps; 19 of these cores are in the Taurus Complex, 16 in the California Complex, and 3 in the Perseus Complex. We acquired V_lsr_, T_A_ and FWHM of lines. Physical parameters including T_ex_, N_H2_, {sigma}_Therm_, {sigma}_NT_, and {sigma}_3D_were calculated. Generally, the cores are of T_ex_=2-16K, N_H2_/cm2, and {sigma}_3D_=0.2-1.0km/s. In the Taurus Complex, the cores are less dense on average and have smaller {sigma}_Therm_than the cores in the Perseus and California Complexes. Two of the three cores in the Perseus Complex are revealed to have larger T_ex_, N_H2_, and {sigma}_3D_ than the mean values in the other two regions. Most of the cores have {sigma}_NT_larger than {sigma}_Therm_, suggesting a dominance of turbulence in our cores. The majority of the cores have M_vir_/M_LTE_{Gt} 1, which indicates these cores are not bound and will disperse. By comparing our results with the dust properties revealed by the Planck Early Release Cold Cores Catalog, we investigated the coupling of gas and dust components. We found that most of the cores have dust temperatures higher than their gas temperatures. The stellar objects associated with our sources were checked and 90% of the cores were found to be starless.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/14
- Title:
- Planck Cold Clumps in the lambda Orionis complex. III.
- Short Name:
- J/ApJS/254/14
- Date:
- 17 Jan 2022 00:15:36
- Publisher:
- CDS
- Description:
- Massive stars have a strong impact on their local environments. However, how stellar feedback regulates star formation is still under debate. In this context, we studied the chemical properties of 80 dense cores in the Orion molecular cloud complex composed of the Orion A (39 cores), B (26 cores), and {lambda} Orionis (15 cores) clouds using multiple molecular line data taken with the Korean Very Long Baseline Interferometry Network 21m telescopes. The {lambda} Orionis cloud has an HII bubble surrounding the O-type star {lambda} Ori, and hence it is exposed to the ultraviolet (UV) radiation field of the massive star. The abundances of C_2_H and HCN, which are sensitive to UV radiation, appear to be higher in the cores in the {lambda} Orionis cloud than in those in the Orion A and B clouds, while the HDCO to H_2_CO abundance ratios show the opposite trend, indicating warmer conditions in the {lambda} Orionis cloud. The detection rates of dense gas tracers such as the N_2_H^+^, HCO^+^, and H^13^CO^+^ lines are also lower in the {lambda} Orionis cloud. These chemical properties imply that the cores in the {lambda} Orionis cloud are heated by UV photons from {lambda} Ori. Furthermore, the cores in the {lambda} Orionis cloud do not show any statistically significant excess in the infall signature of HCO^+^ (1-0), unlike those in the Orion A and B clouds. Our results support the idea that feedback from massive stars impacts star formation in a negative way by heating and evaporating dense materials, as in the {lambda} Orionis cloud.
- ID:
- ivo://CDS.VizieR/J/ApJS/202/4
- Title:
- Planck cold clumps survey in the Orion complex
- Short Name:
- J/ApJS/202/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A mapping survey of 51 Planck cold clumps projected on the Orion complex was performed with J=1-0 lines of ^12^CO and ^13^CO with the 13.7m telescope at the Purple Mountain Observatory. The mean column densities of the Planck gas clumps range from 0.5 to 9.5x10^21^cm^-2^, with an average value of (2.9+/-1.9)x10^21^cm^-2^. The mean excitation temperatures of these clumps range from 7.4 to 21.1K, with an average value of 12.1+/-3.0K and the average three-dimensional velocity dispersion {sigma}_3D_ in these molecular clumps is 0.66+/-0.24km/s. The H2 column density of the molecular clumps calculated from molecular lines correlates with the aperture flux at 857GHz of the dust emission. By analyzing the distributions of the physical parameters, we suggest that turbulent flows can shape the clump structure and dominate their density distribution on large scales, but not function on small scales due to local fluctuations. Eighty-two dense cores are identified in the molecular clumps. The dense cores have an average radius and local thermal equilibrium (LTE) mass of 0.34+/-0.14pc and 38^+5^_-30_M_{sun}_, respectively. The structures of low column density cores are more affected by turbulence, while the structures of high column density cores are more affected by other factors, especially by gravity.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/76
- Title:
- Planck cold dust clumps CO survey
- Short Name:
- J/ApJ/756/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey toward 674 Planck cold clumps of the Early Cold Core Catalogue (ECC) in the J=1-0 transitions of ^12^CO, ^13^CO, and C^18^O has been carried out using the Purple Mountain Observatory 13.7m telescope. Six hundred seventy-three clumps were detected with ^12^CO and ^13^CO emission, and 68% of the sample has C^18^O emission. Additional velocity components were also identified. A close consistency of the three line peak velocities was revealed for the first time. Kinematic distances are given for all the velocity components, and half of the clumps are located within 0.5 and 1.5kpc. Excitation temperatures range from 4 to 27K, slightly larger than those of T_d_. Line width analysis shows that the majority of ECC clumps are low-mass clumps. Ten clumps were mapped. Twelve velocity components and 22 cores were obtained. Their morphologies include extended diffuse, dense, isolated, cometary, and filament, of which the last is the majority. Twenty cores are starless, and only seven cores seem to be in a gravitationally bound state. Planck cold clumps are the most quiescent among the samples of weak red IRAS, infrared dark clouds, UC HII candidates, extended green objects, and methanol maser sources, suggesting that Planck cold clumps have expanded the horizon of cold astronomy.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/758
- Title:
- Polarimetry of HH1-2 region
- Short Name:
- J/ApJ/708/758
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HH 1-2 region in the L1641 molecular cloud was observed in the near-infrared (IR) J, H, and Ks bands, and imaging polarimetry was performed. Seventy-six point-like sources were detected in all three bands. The near-IR polarizations of these sources seem to be caused mostly by the dichroic extinction. Using a color-color diagram, reddened sources with little IR excess were selected to trace the magnetic field structure of the molecular cloud. The mean polarization position angle of these sources is about 111{deg}, which is interpreted as the projected direction of the magnetic field in the observed region of the cloud. The distribution of the polarization angle has a dispersion of about 11{deg}, which is smaller than what was measured in previous studies. This small dispersion gives a rough estimate of the strength of the magnetic field to be about 130uG and suggests that the global magnetic field in this region is quite regular and straight. In contrast, the outflows driven by young stellar objects in this region seem to have no preferred orientation. This discrepancy suggests that the magnetic field in the L1641 molecular cloud does not dictate the orientation of the protostars forming inside.
- ID:
- ivo://CDS.VizieR/J/ApJ/603/584
- Title:
- Polarimetry toward Musca dark cloud
- Short Name:
- J/ApJ/603/584
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used CCD imaging polarimetry to obtain linear polarization measurements of background stars toward the filamentary Musca dark cloud. We present a catalog of 2497 objects with polarization signal-to-noise ratio larger than 5. This allows us to build polarization maps to infer the detailed geometry of the local magnetic field. We show composite polarization maps along the cloud and explore general correlations of the polarimetric data with the morphology of the region. We find the overall field to be strikingly aligned with the projected small axis of the filamentary cloud. We detect a lower limit for the polarization across the cloud of ~2%, with an enhanced polarization of 6%-7% in the central region. We find evidence that the polarization pattern is altered in the inner regions, those associated with higher extinction.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1045
- Title:
- Polarimetry toward sightlines through ChaI
- Short Name:
- J/ApJ/720/1045
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained optical multi-band polarimetry toward sightlines through the Chamaeleon I cloud, particularly in the vicinity of the young B9/A0 star HD 97300. We show, in agreement with earlier studies, that the radiation field impinging on the cloud in the projected vicinity of the star is dominated by the flux from the star, as evidenced by a local enhancement in the grain heating. By comparing the differential grain heating with the differential change in the location of the peak of the polarization curve, we show that the grain alignment is enhanced by the increase in the radiation field. We also find a weak, but measurable, variation in the grain alignment with the relative angle between the radiation field anisotropy and the magnetic field direction. Such an anisotropy in the grain alignment is consistent with a unique prediction of modern radiative alignment torque theory and provides direct support for radiatively driven grain alignment.
- ID:
- ivo://CDS.VizieR/J/ApJ/650/945
- Title:
- Polarisation around filamentary dark cloud GF 9
- Short Name:
- J/ApJ/650/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New visible polarization data combined with existing IR and FIR polarization data are used to study how the magnetic field threading the filamentary molecular cloud GF 9 connects to larger structures in its general environment. When visible and NIR polarization data are combined, no evidence is found for a plateau in the polarization above extinction A_V_~1.3, as seen in dark clouds in Taurus. This lack of saturation effect suggests that even in the denser parts of GF 9 magnetic fields can be probed. The visible polarization is smooth and has a well-defined orientation. In the core region, the IR and FIR data are also well defined, but each with a different direction. A multiscale analysis of the magnetic field shows that on the scale of a few times the mean radial dimension of the molecular cloud, it is as if the magnetic field were blind to the spatial distribution of the filaments, while on smaller scales in the core region, multiwavelength polarimetry shows a rotation of the magnetic field lines in these denser phases. Finally, the Chandrasekhar and Fermi method is used to evaluate the magnetic field strength, indicating that the core region is approximately magnetically critical. A global interpretation suggests that in the core region an original poloidal field could have been twisted by a rotating elongated (core+envelope) structure. There is no evidence for turbulence, and ambipolar diffusion does not seem to be effective at the present time.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/893
- Title:
- Polarisation at 850mu{m} in OMC-2 and OMC-3
- Short Name:
- J/ApJ/716/893
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SCUBA polarized 850um thermal emission data of the OMC-2 region in Orion A are added to and homogeneously reduced with data already available in the OMC-3 region. The data set shows that OMC-2 is a region generally less polarized than OMC-3. Where coincident, most of the 850um polarization pattern is similar to that measured in 350um polarization data. Only 850um polarimetry data have been obtained in and around MMS7, FIR1 and FIR2, and in the region south of FIR6. A realignment of the polarization vectors with the filament can be seen near FIR1 in the region south of OMC-3. An analysis shows that the energy injected by CO outflows and H2 jets associated with OMC-2 and OMC-3 does not appear to alter the polarization patterns at a scale of the 14" resolution beam. A second-order structure function analysis of the polarization position angles shows that OMC-2 is a more turbulent region than OMC-3. OMC-3 appears to be a clear case of a magnetically dominated region with respect to the turbulence. However, for OMC-2 it is not clear that this is the case. A more in-depth analysis of five regions displayed along OMC-2/3 indicates a decrease of the mean polarization degree and an increase of the turbulent angular dispersion from north to south. A statistical analysis suggests the presence of two depolarization regimes in our maps: one regime including the effects of the cores, the other one excluding it.
