- ID:
- ivo://CDS.VizieR/J/A+A/552/A123
- Title:
- Far-IR study of G29.96-0.02
- Short Name:
- J/A+A/552/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- G29.96-0.02 is a high-mass star-forming cloud observed at 70, 160, 250, 350, and 500{mu}m as part of the Herschel survey of the Galactic plane (Hi-GAL) during the science demonstration phase. We wish to conduct a far-infrared study of the sources associated with this star-forming region by estimating their physical properties and evolutionary stage, and investigating the clump mass function, the star formation efficiency and rate in the cloud. We have identified the Hi-GAL sources associated with the cloud, searched for possible counterparts at centimeter and infrared wavelengths, fitted their spectral energy distribution and estimated their physical parameters.
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- ID:
- ivo://CDS.VizieR/J/ApJ/849/63
- Title:
- FIR-mm data of YSOs in star-forming regions
- Short Name:
- J/ApJ/849/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Far-infrared and (sub)millimeter fluxes can be used to study dust in protoplanetary disks, the building blocks of planets. Here, we combine observations from the Herschel Space Observatory with ancillary data of 284 protoplanetary disks in the Taurus, Chamaeleon I, and Ophiuchus star-forming regions, covering from the optical to mm/cm wavelengths. We analyze their spectral indices as a function of wavelength and determine their (sub)millimeter slopes when possible. Most disks display observational evidence of grain growth, in agreement with previous studies. No correlation is found between other tracers of disk evolution and the millimeter spectral indices. A simple disk model is used to fit these sources, and we derive posterior distributions for the optical depth at 1.3mm and 10au, the disk temperature at this same radius, and the dust opacity spectral index {beta}. We find the fluxes at 70{mu}m to correlate strongly with disk temperatures at 10au, as derived from these simple models. We find tentative evidence for spectral indices in Chamaeleon I being steeper than those of disks in Taurus/Ophiuchus, although more millimeter observations are needed to confirm this trend and identify its possible origin. Additionally, we determine the median spectral energy distribution of each region and find them to be similar across the entire wavelength range studied, possibly due to the large scatter in disk properties and morphologies.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/4
- Title:
- First-look analysis of {rho} Oph-A at 850um
- Short Name:
- J/ApJ/859/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 850{mu}m imaging polarimetry data of the {rho} Oph-A core taken with the Submillimeter Common-User Bolometer Array-2 (SCUBA-2) and its polarimeter (POL-2) as part of our ongoing survey project, B-fields In STar forming RegiOns (BISTRO). The polarization vectors are used to identify the orientation of the magnetic field projected on the plane of the sky at a resolution of 0.01pc. We identify 10 subregions with distinct polarization fractions and angles in the 0.2pc {rho} Oph-A core; some of them can be part of a coherent magnetic field structure in the {rho} Oph region. The results are consistent with previous observations of the brightest regions of {rho} Oph-A, where the degrees of polarization are at a level of a few percent, but our data reveal for the first time the magnetic field structures in the fainter regions surrounding the core where the degree of polarization is much higher (>5%). A comparison with previous near-infrared polarimetric data shows that there are several magnetic field components that are consistent at near-infrared and submillimeter wavelengths. Using the Davis-Chandrasekhar-Fermi method, we also derive magnetic field strengths in several subcore regions, which range from approximately 0.2 to 5mG. We also find a correlation between the magnetic field orientations projected on the sky and the core centroid velocity components.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A147
- Title:
- FQS. Galactic Plane CO survey
- Short Name:
- J/A+A/633/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Forgotten Quadrant Survey (FQS), an ESO large project that used the 12m antenna of the Arizona Radio Observatory to map the Galactic Plane in the range 220{deg}<l<240{deg}, and -2.5{deg}<b<0{deg}, both in ^12^CO(1-0), and ^13^CO(1-0), at a spectral resolution of 0.65km/s and 0.26km/s. We used the (1-0) transition of carbon monoxide to trace the molecular component of the interstellar medium. Our data set allows us to easily identify how the molecular dense gas is organised at different spatial scales: from the giant clouds with their denser filamentary networks, down to the clumps and cores that host the new-born stars and to obtain reliable estimates of their key physical parameters such as size and mass. We present the first release of the data of the FQS survey and discuss their quality. Spectra with 0.65km/s velocity channels have noise ranging from 0.8K to 1.3K for ^12^CO (1-0) and from 0.3K to 0.6K for ^13^CO (1-0). In this first paper, we used the ^12^CO (1-0) spectral cubes to produce a catalogue of 263 molecular clouds. The clouds are grouped in three main structures corresponding to the Local, Perseus, and Outer arms up to a distance of ~8.6kpc from the Sun. This is the first self-consistent statistical catalogue of molecular clouds of the outer Galaxy obtained with a subarcminute spatial resolution and therefore able to detect not only the classical giant molecular clouds, but also the small clouds and to resolve the cloud structure at the sub-parsec scale up to a distance of a few kiloparsec. We found two classes of objects: structures with sizes above a few parsecs that are typical molecular clouds and may be self-gravitating, and subparsec structures that cannot be in gravitational equilibrium and are likely transient or confined by external pressure. We used the ratio between the Herschel H2 column density and the integrated intensity of the CO lines to calculate the CO conversion factor and we found mean values of (3.3+/-1.4)x10^20^cm^-2^/(K.km/s) and (1.2+/-0.4)x10^21^cm^-2^/(K.km/s), for ^12^CO (1-0) and ^13^CO (1-0), respectively. FQS contributes to the general effort in producing a new generation of high-quality spectroscopic data for the Galactic Plane in the less studied third Galactic Quadrant, toward the outer Galaxy. FQS has produced a data-set of great legacy value, largely improving the data quality both in terms of sensitivity and spatial resolution over previous data sets.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A142
- Title:
- G24.78+0.08 A1 ALMA images and datacubes
- Short Name:
- J/A+A/650/A142
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Hyper-compact (HC) or ultra-compact HII regions are the first manifestations of the radiation feedback from a newly born massive star. Therefore, their study is fundamental to understanding the process of massive (>=8M_{sun}_) star formation. We employed Atacama Large Millimeter/submillimeter Array (ALMA) 1.4mm Cycle 6 observations to investigate at high angular resolution (~0.050, corresponding to 330au) the HC HII region inside molecular core A1 of the high-mass star-forming cluster G24.78+0.08. We used the H30{alpha} emission and different molecular lines of CH_3_CN and ^13^CH_3_CN to study the kinematics of the ionized and molecular gas, respectively. At the center of the HC HII region, at radii <~500au, we observe two mutually perpendicular velocity gradients, which are directed along the axes at PA=39{deg} and PA=133{deg}, respectively. The velocity gradient directed along the axis at PA=39{deg} has an amplitude of 22km/s/mpc, which is much larger than the other;s, 3km/s/mpc. We interpret these velocity gradients as rotation around, and expansion along, the axis at PA=39{deg}. We propose a scenario where the H30{alpha} line traces the ionized heart of a disk-jet system that drives the formation of the massive star (~20M_{sun}_) responsible for the HC HII region. Such a scenario is also supported by the position-velocity plots of the CH_3_CN and ^13^CH_3_CN lines along the axis at PA=133{deg}, which are consistent with Keplerian rotation around a 20M_{sun}_ star. Toward the HC HII region in G24.78+0.08, the coexistence of mass infall (at radii of ~5000au), an outer molecular disk (from <~4000 au to >~500au), and an inner ionized disk (<~500au) indicates that the massive ionizing star is still actively accreting from its parental molecular core. To our knowledge, this is the first example of a molecular disk around a high-mass forming star that, while becoming internally ionized after the onset of the HII region, continues to accrete mass onto the ionizing star.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/79
- Title:
- Galactic CHaMP. II. Dense gas clumps.
- Short Name:
- J/ApJ/779/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Census of High- and Medium-mass Protostars (CHaMP) is the first large-scale (280{deg}<l<300{deg}, -4{deg}<b<2{deg}), unbiased, subparsec resolution survey of Galactic molecular clumps and their embedded stars. Barnes et al. (Paper I, 2011, J/ApJS/196/12) presented the source catalog of ~300 clumps based on HCO^+^(1-0) emission, used to estimate masses M. Here we use archival midinfrared-to-millimeter continuum data to construct spectral energy distributions. Fitting two-temperature gray-body models, we derive bolometric luminosities, L. We find that the clumps have 10<~L/L_{sun}_<~10^6.5^ and 0.1<~L/M/[L_{sun}_/M_{sun}_]<~10^3^, consistent with a clump population spanning a range of instantaneous star-formation efficiencies from 0 to ~50%. We thus expect L/M to be a useful, strongly varying indicator of clump evolution during the star cluster formation process.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/67
- Title:
- Galactic CHaMP. III. ^12^CO dense clump properties
- Short Name:
- J/ApJ/831/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the second complete molecular line data release from the Census of High- and Medium-mass Protostars (CHaMP), a large-scale, unbiased, uniform mapping survey at sub-parsec resolution, of millimeter-wave line emission from 303 massive, dense molecular clumps in the Milky Way. This release is for all ^12^CO J=1->0 emission associated with the dense gas, the first from Phase II of the survey, which includes ^12^CO, ^13^CO, and C^18^O. The observed clump emission traced by both ^12^CO and HCO^+^ (from Phase I) shows very similar morphology, indicating that, for dense molecular clouds and complexes of all sizes, parsec-scale clumps contain {Xi}~75% of the mass, while only 25% of the mass lies in extended (>~10pc) or "low density" components in these same areas. The mass fraction of all gas above a density of 10^9^m^-3^ is {xi}_9_>~50%. This suggests that parsec-scale clumps may be the basic building blocks of the molecular interstellar medium, rather than the standard giant molecular cloud (GMC) concept. Using ^12^CO emission, we derive physical properties of these clumps in their entirety, and compare them to properties from HCO^+^, tracing their denser interiors. We compare the standard X-factor converting I_^12^CO_ to N_H2_ with alternative conversions, and show that only the latter give whole-clump properties that are physically consistent with those of their interiors. We infer that the clump population is systematically closer to virial equilibrium than when considering only their interiors, with perhaps half being long-lived (10s of Myr), pressure-confined entities that only terminally engage in vigorous massive star formation, supporting other evidence along these lines that was previously published.
- ID:
- ivo://CDS.VizieR/J/A+A/584/A92
- Title:
- Galactic Cold Cores. IV. Cold sub-mm sources
- Short Name:
- J/A+A/584/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the project Galactic cold cores, Herschel photometric observations were carried out as a follow-up of cold regions of interstellar clouds previously identified with the Planck satellite. The aim of the project is to derive the physical properties of the population of cold sources and to study its connection to ongoing and future star formation. We build a catalogue of cold sources within the clouds in 116 fields observed with the Herschel PACS and SPIRE instruments. We wish to determine the general physical characteristics of the cold sources and to examine the correlations with their host cloud properties. From Herschel data, we compute colour temperature and column density maps of the fields. We estimate the distance to the target clouds and provide both uncertainties and reliability flags for the distances. The getsources multi-wavelength source extraction algorithm is employed to build a catalogue of several thousands of cold sources. Mid-infrared data are used along with a colour and position criteria to separate starless and protostellar sources. We also propose another classification method based on sub-millimetre temperature profiles. We analyse the statistical distributions of the physical properties of the source samples. We provide a catalogue of ~4000 cold sources within or near star forming clouds, most of which are located either in nearby molecular complexes (<1kpc) or in star forming regions of the nearby galactic arms (~2kpc). About 70% of the sources have a size compatible with an individual core, and 35% of those sources are likely gravitationally bound. Significant statistical differences in physical properties are found between starless and protostellar sources, in column density - dust temperature, mass - size, and mass - dust temperature diagrams. The core mass functions are very similar to those previously reported for other regions. On statistical grounds we find that gravitationally bound sources have higher background column densities (median N_bg_(H_2_)~5x10^21^cm-2) than unbound sources (median N_bg_(H_2_)~3x10^21^cm-2). These values of N_bg_(H_2_) are higher for larger dust temperature of the external layers of the parent cloud. However, only in few cases do we find clear N_bg_(H_2_) thresholds for the presence of cores. The dust temperature of cloud external layers shows clear variations with galactic location, as possibly do the source temperatures. Our data support a more complex view of star formation than in the simple idea of a column density threshold. They show a clear influence of the surrounding UV-visible radiation on how cores distribute in their host clouds, with possible variations on the Galactic scale.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/73
- Title:
- Galactic MCs associated with HII regions
- Short Name:
- J/ApJ/831/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relations between star formation and properties of molecular clouds (MCs) are studied based on a sample of star-forming regions in the Galactic Plane. Sources were selected by having radio recombination lines to provide identification of associated MCs and dense clumps. Radio continuum emission and mid-infrared emission were used to determine star formation rates (SFRs), while ^13^CO and submillimeter dust continuum emission were used to obtain the masses of molecular and dense gas, respectively. We test whether total molecular gas or dense gas provides the best predictor of SFR. We also test two specific theoretical models, one relying on the molecular mass divided by the free-fall time, the other using the free-fall time divided by the crossing time. Neither is supported by the data. The data are also compared to those from nearby star-forming regions and extragalactic data. The star formation "efficiency," defined as SFR divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all of the molecular gas.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A111
- Title:
- Galactic plane dust temperature maps with Herschel
- Short Name:
- J/A+A/564/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust grains absorb the interstellar far ultra-violet and visible photons and re-emit them in far-infrared (FIR) wavebands. The dust FIR continuum can be predicted by a grid of models using various values of the interstellar radiation field. We analyze the dust continuum emission in two Hi-GAL science-demonstration phase (SDP) fields using both the radiative transfer code, Cloudy, and the DustEM dust model, to explore the effect of radiative transfer on dust temperature. The 500um sub-millimeter excess emission and the very small grain (VSG) contribution to the 70um intensity are investigated by spectral energy distribution (SED) fitting using the Cloudy model.