- ID:
- ivo://CDS.VizieR/J/ApJ/819/143
- Title:
- HCO+ and N2D+ dense cores in Perseus
- Short Name:
- J/ApJ/819/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of an HCO^+^ (3-2) and N_2_D^+^ (3-2) molecular line survey performed toward 91 dense cores in the Perseus molecular cloud using the James Clerk Maxwell Telescope, to identify the fraction of starless and protostellar cores with systematic radial motions. We quantify the HCO^+^ asymmetry using a dimensionless asymmetry parameter {delta}_v_, and identify 20 cores with significant blue or red line asymmetries in optically thick emission indicative of collapsing or expanding motions, respectively. We separately fit the HCO^+^ profiles with an analytic collapse model and determine contraction (expansion) speeds toward 22 cores. Comparing the {delta}_v_ and collapse model results, we find that {delta}_v_ is a good tracer of core contraction if the optically thin emission is aligned with the model-derived systemic velocity. The contraction speeds range from subsonic (0.03km/s) to supersonic (0.40km/s), where the supersonic contraction speeds may trace global rather than local core contraction. Most cores have contraction speeds significantly less than their free-fall speeds. Only 7 of 28 starless cores have spectra well-fit by the collapse model, which more than doubles (15 of 28) for protostellar cores. Starless cores with masses greater than the Jeans mass (M/M_J_>1) are somewhat more likely to show contraction motions. We find no trend of optically thin non-thermal line width with M/M_J_, suggesting that any undetected contraction motions are small and subsonic. Most starless cores in Perseus are either not in a state of collapse or expansion, or are in a very early stage of collapse.
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- ID:
- ivo://CDS.VizieR/J/ApJ/874/172
- Title:
- H_2_CO & H110{alpha} obs. toward Aquila
- Short Name:
- J/ApJ/874/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formaldehyde H_2_CO(1_10_-1_11_) absorption line and H110{alpha} radio recombination line have been observed toward the Aquila Molecular Cloud using the Nanshan 25m telescope operated by the Xinjiang Astronomical Observatory CAS. These first observations of the H_2_CO (1_10_-1_11_) absorption line determine the extent of the molecular regions that are affected by the ongoing star formation in the Aquila molecular complex and show some of the dynamic properties. The distribution of the excitation temperature Tex for H_2_CO identifies the two known star formation regions W40 and Serpens South as well as a smaller new region Serpens 3. The intensity and velocity distributions of H_2_CO and ^13^CO(1-0) do not agree well with each other, which confirms that the H_2_CO absorption structure is mostly determined by the excitation of the molecules resulting from the star formation rather than by the availability of molecular material as represented by the distribution. Some velocity-coherent linear ^13^CO(1-0) structures have been identified in velocity channel maps of H2CO and it is found that the three star formation regions lie on the intersect points of filaments. The H110{alpha} emission is found only at the location of the W40 HII region and spectral profile indicates a redshifted spherical outflow structure in the outskirts of the HII region. Sensitive mapping of H_2_CO absorption of the Aquila Complex has correctly identified the locations of star formation activity in complex molecular clouds and the spectral profiles reveal the dominant velocity components and may identify the presence of outflows.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/154
- Title:
- H_2_CO TMRT obs. of Galactic molecular clouds
- Short Name:
- J/ApJ/877/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of the C-band 1_10_-1_11_ (4.8GHz) and Ku-band 2_11_-2_12_ (14.5GHz) K-doublet lines of H_2_CO and the C-band 1_10_-1_11_ (4.6GHz) line of H_2_^13^CO toward a large sample of Galactic molecular clouds, through the Shanghai Tianma 65m radio telescope (TMRT). Our sample with 112 sources includes strong H_2_CO sources from the TMRT molecular line survey at C-band and other known H_2_CO sources. All three lines are detected toward 38 objects (43 radial velocity components) yielding a detection rate of 34%. Complementary observations of their continuum emission at both C- and Ku-bands were performed. Combining spectral line parameters and continuum data, we calculate the column densities, the optical depths and the isotope ratio H_2_^12^CO/H_2_^13^CO for each source. To evaluate photon trapping caused by sometimes significant opacities in the main isotopologue's rotational mm-wave lines connecting our measured K-doublets, and to obtain ^12^C/^13^C abundance ratios, we used the RADEX non-LTE model accounting for radiative transfer effects. This implied the use of the new collision rates from Wiesenfeld & Faure. Also implementing distance values from trigonometric parallax measurements for our sources, we obtain a linear fit of ^12^C/^13^C=(5.08+/-1.10)D_GC_+(11.86+/-6.60), with a correlation coefficient of 0.58. D_GC_ refers to Galactocentric distances. Our ^12^C/^13^C ratios agree very well with the ones deduced from CN and C^18^O but are lower than those previously reported on the basis of H_2_CO, tending to suggest that the bulk of the H_2_CO in our sources was formed on dust grain mantles and not in the gas phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/798/58
- Title:
- HELGA VI. Giant molecular cloud associations in M31
- Short Name:
- J/ApJ/798/58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present a catalog of giant molecular clouds (GMCs) in the Andromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy Andromeda (HELGA) data set. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterize the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al. (Paper II, 2012ApJ...756...40S). A total of 326 GMCs in the mass range 10^4^-10^7^M_{sun}_ are identified; their cumulative mass distribution is found to be proportional to M^-2.34^, in agreement with earlier studies. The GMCs appear to follow the same correlation of cloud mass to L_CO_ observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit, suggesting that we are observing associations of GMCs. Following Gordon et al. (2006ApJ...638L..87G), we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8.9{deg} to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A102
- Title:
- Herschel cold clumps CO survey
- Short Name:
- J/A+A/606/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical state of cold cloud clumps has a great impact on the process and efficiency of star formation and the masses of the forming stars inside these objects. The sub-millimetre survey of the Planck space observatory and the far-infrared follow-up mapping of the Herschel space telescope provide an unbiased, large sample of these cold objects. We have observed ^12^CO(1-0) and ^13^CO(1-0) emission in 35 high-density clumps in 26 Herschel fields sampling different environments in the Galaxy. We derive the physical properties of the objects and estimate their gravitational stability. The densities and temperatures of the clumps were calculated from both the dust continuum and the molecular line data. Kinematic distances were derived using ^13^CO(1-0) line velocities to verify previous distance estimates and the sizes and masses of the objects were calculated by fitting 2D Gaussian functions to their optical depth distribution maps on 250um. The masses and virial masses were estimated assuming an upper and lower limit on the kinetic temperatures and considering uncertainties due to distance limitations.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A72
- Title:
- Herschel counterparts of SDC
- Short Name:
- J/A+A/590/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The goal of this paper is to identify which of the clouds from the Spitzer Dark Cloud catalogue (Peretto & Fuller, 2009, Cat. J/A+A/505/405) are real, which are artefacts. For this we used Herschel Hi-GAL (Molinari et al., 2010PASP..122..314M) column density maps and search for spatial associations between Spitzer Dark Cloud and Herschel column density peaks. Description: This table provides some of the key properties of the Spitzer Dark Clouds that we estimated using the Herschel data and used to disentangle between real and spurious clouds. For each cloud of the Peretto & Fuller (2009, Cat. J/A+A/505/405) catalogue we give the cloud name, the cloud equivalent radius, the average Herschel column density within the boundaries of the SDCs, the average Herschel column density immediately outside the boundary of the SDCs, the Herschel column density noise at the position of the SDC, the Herschel column density peak within the boundaries of the SDCs, the value for criterion c1, the value for criterion c2, the value for criterion c3, and a tag that indicates if the cloud has been identified as real by our automated detection scheme based on the values of c1 and c2. This tag can take a number of values. These are: 'y' for yes; n for no; 'sat' for a SDC entirely located in a saturated portion of the Herschel images; 'ysat' for a cloud that is considered real despite being partially saturated; 'out' for a SDC that is not covered by Herschel images; 'yout' for a cloud that is considered real despite being partially covered by Herschel images; 'nout' for a cloud considered spurious despite being partially covered by Herschel images. Also, note that the column referring to the equivalent radius Req is the same quantity as the one quoted in Table 1 column 11 of Peretto & Fuller (2009, Cat. J/A+A/505/405). However, these latter values should be discarded since a mistake has been found in the calculation of the equivalent radius. Only the new values, the ones provided in Table 1 column 2 of this paper should be considered.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A91
- Title:
- Herschel/HIFI and IRAM 30m images of OMC1
- Short Name:
- J/A+A/622/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young massive stars regulate the physical conditions, ionization, and fate of their natal molecular cloud. It is important to find tracers that help quantifying the stellar feedback processes that take place at different scales. We present ~85arcmin^2^ velocity-resolved maps of several submm molecular lines toward the closest high-mass star-forming region, OMC-1. The observed rotational lines include probes of warm and dense molecular gas that are difficult to detect from ground-based telescopes: CH^+^ (1-0), CO (10-9), HCO^+^ (6-5), and HCN (6-5). These lines trace an extended but thin layer of molecular gas at high thermal pressure, P_th_~10^7^-10^9^K/cm^3^, associated with the FUV-irradiated surface of OMC-1. The intense FUV field, emerging from massive stars in the Trapezium cluster, heats, compresses and photoevaporates the cloud edge. It also triggers the formation of reactive molecules such as CH^+^. The CH^+^ (1-0) emission spatially correlates with the flux of FUV photons impinging the cloud: G_0 from 1e3 to 1e5. This correlation is supported by isobaric PDR models in the parameter space P_th_/G_0_~[5*10^3^-8*10^4^]K/cm^3^ where many PDRs seem to lie. The CH^+^ (1-0) emission correlates with the extended emission from vibrationally excited H_2_, and with that of [CII]158um and CO 10-9, all emerging from FUV-irradiated gas. These correlations link the presence of CH^+^ to the availability of C^+^ ions and of FUV-pumped H_2_(v>0) molecules. The parsec-scale CH^+^ emission and narrow-line (dv~3 km/s) mid-J CO emission arises from extended PDRs and not from fast shocks. PDR line tracers are the smoking gun of the stellar feedback from young massive stars. The PDR component in OMC-1 represents 5 to 10 % of the total gas mass, however, it dominates the emitted line luminosity. These results provide insights into the source of submm CH+ and mid-J CO emission from distant star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A30
- Title:
- Herschel maps of {rho} Oph
- Short Name:
- J/A+A/581/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of nearby star-forming regions with the Herschel Space Observatory complement our view of the protoplanetary disks in Ophiuchus with information about the outer disks. The main goal of this project is to provide new far-infrared fluxes for the known disks in the core region of Ophiuchus and to identify potential transitional disks using data from Herschel. We obtained PACS and SPIRE photometry of previously spectroscopically confirmed young stellar objects (YSO) in the region and analysed their spectral energy distributions.
- ID:
- ivo://CDS.VizieR/J/ApJ/852/102
- Title:
- Herschel nearby isolated low-mass clouds maps
- Short Name:
- J/ApJ/852/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present intensity-corrected Herschel maps at 100, 160, 250, 350, and 500{mu}m for 56 isolated low-mass clouds. We determine the zero-point corrections for Herschel Photodetector Array Camera and Spectrometer (PACS) and Spectral Photometric Imaging Receiver (SPIRE) maps from the Herschel Science Archive (HSA) using Planck data. Since these HSA maps are small, we cannot correct them using typical methods. Here we introduce a technique to measure the zero-point corrections for small Herschel maps. We use radial profiles to identify offsets between the observed HSA intensities and the expected intensities from Planck. Most clouds have reliable offset measurements with this technique. In addition, we find that roughly half of the clouds have underestimated HSA-SPIRE intensities in their outer envelopes relative to Planck, even though the HSA-SPIRE maps were previously zero-point corrected. Using our technique, we produce corrected Herschel intensity maps for all 56 clouds and determine their line-of-sight average dust temperatures and optical depths from modified blackbody fits. The clouds have typical temperatures of ~14-20K and optical depths of ~10^-5^-10^-3^. Across the whole sample, we find an anticorrelation between temperature and optical depth. We also find lower temperatures than what was measured in previous Herschel studies, which subtracted out a background level from their intensity maps to circumvent the zero-point correction. Accurate Herschel observations of clouds are key to obtaining accurate density and temperature profiles. To make such future analyses possible, intensity-corrected maps for all 56 clouds are publicly available in the electronic version.
- ID:
- ivo://CDS.VizieR/J/A+A/426/171
- Title:
- H_2_ flows in rho Ophiuchi A
- Short Name:
- J/A+A/426/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an unbiased search for molecular hydrogen emission in the L1688 cloud within the rho Ophiuchi molecular cloud complex. Our near-infrared survey covers a connected region of extent 35'x35'. We detect several new H_2_ flows but the total number of detected outflows is low and is consistent with the paucity of Class 0 and Class 1 sources in the molecular cloud. From the spatial distribution, their collimation and the individual shapes of the bow shocks, we suggest possible candidates for the outflow sources. Most of the candidate driving sources are deeply embedded in dense cores of the molecular cloud. A very young outflow arises from the newly discovered Class 0 source MMS 126. Two major outflows in the NE-SW direction arise from the YLW 15 and YLW 16 Class I sources. Three additional outflows, which both extend over several arcminutes, arise from the Class I sources YLW 31 and YLW 52. Flow directions are generally NE-SW, perpendicular to the elongation directions of the cloud filaments. The apparent extents of molecular flows are related to either the widths of cloud filaments or to the separation between filaments. The estimated jet power needed to continuously drive and excite the detected portions of the shocked H_2_ outflows lies in the range 0.02-0.2L_{sun}_. Given the critical dependence on the environment, however, the total sizes and powers of the outflows may be considerably larger.
