- ID:
- ivo://CDS.VizieR/J/A+A/648/A100
- Title:
- Massive G31.41+0.31 protocluster ALMA images
- Short Name:
- J/A+A/648/A100
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- ALMA observations at 1.4mm and ~0.2" (~750au) angular resolution of the Main core in the high-mass star forming region G31.41+0.31 have revealed a puzzling scenario: on the one hand, the continuum emission looks very homogeneous and the core appears to undergo solid-body rotation, suggesting a monolithic core stabilized by the magnetic field; on the other hand, rotation and infall speed up toward the core center, where two massive embedded free-free continuum sources have been detected, pointing to an unstable core having undergone fragmentation. To establish whether the Main core is indeed monolithic or its homogeneous appearance is due to a combination of large dust opacity and low angular resolution, we carried out millimeter observations at higher angular resolution and different wavelengths. We carried out ALMA observations at 1.4mm and 3.5mm that achieved angular resolutions of ~0.1" (~375au) and ~0.075" (~280au), respectively. VLA observations at 7mm and 1.3cm at even higher angular resolution, ~0.05" (~190au) and ~0.07" (~260au), respectively, were also carried out to better study the nature of the free-free continuum sources detected in the core. The millimeter continuum emission of the Main core has been clearly resolved into at least four sources, A, B, C, and D, within 100, indicating that the core is not monolithic. The deconvolved radii of the dust emission of the sources, estimated at 3.5mm, are 400-500au, their masses range from 15 to ~26M_{sun}_, and their number densities are several 10^9^cm^-3^. Sources A and B, located closer to the center of the core and separated by 750au, are clearly associated with two free-free continuum sources, likely thermal radio jets, and are the brightest in the core. The spectral energy distribution of these two sources and their masses and sizes are similar and suggest a common origin. Source C has not been detected at centimeter wavelengths, while source D has been clearly detected at 1.3cm. The fact that source D is likely the driving source of an E-W SiO outflow previously detected in the region suggests that the free-free emission is possibly arising from a radio jet. The observations have confirmed that the Main core in G31.41+0.31 is collapsing, has undergone fragmentation and that its homogeneous appearance previously observed at short wavelengths is a consequence of both large dust opacity and insufficient angular resolution. The low level of fragmentation together with the fact that the core is moderately magnetically supercritical, suggests that G31.41+0.31 could have undergone a phase of magnetically-regulated evolution characterized by a reduced fragmentation efficiency, eventually leading to the formation of a small number of relatively massive dense cores.
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- ID:
- ivo://CDS.VizieR/J/ApJS/235/3
- Title:
- Massive outflows associated with ATLASGAL clumps
- Short Name:
- J/ApJS/235/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken the largest survey for outflows within the Galactic plane using simultaneously observed ^13^CO and C^18^O data. Out of a total of 919 ATLASGAL clumps, 328 have data suitable to identify outflows, and 228 (69%+/-3%) show high-velocity outflows. The clumps with detected outflows show significantly higher clump masses (M_clump_), bolometric luminosities (L_bol_), luminosity-to-mass ratios (L_bol_/M_clump_), and peak H_2_ column densities (N_H2_) compared to those without outflows. Outflow activity has been detected within the youngest quiescent clump (i.e., 70{mu}m weak) in this sample, and we find that the outflow detection rate increases with M_clump_, L_bol_, L_bol_/M_clump_, and N_H2_, approaching 90% in some cases (UC HII regions = 93%+/-3%; masers = 86%+/-4%; HC HII regions = 100%). This high detection rate suggests that outflows are ubiquitous phenomena of massive star formation (MSF). The mean outflow mass entrainment rate implies a mean accretion rate of ~10^-4^M_{sun}_/yr, in full agreement with the accretion rate predicted by theoretical models of MSF. Outflow properties are tightly correlated with M_clump_, L_bol_, and L_bol_/M_clump_ and show the strongest relation with the bolometric clump luminosity. This suggests that outflows might be driven by the most massive and luminous source within the clump. The correlations are similar for both low-mass and high-mass outflows over 7 orders of magnitude, indicating that they may share a similar outflow mechanism. Outflow energy is comparable to the turbulent energy within the clump; however, we find no evidence that outflows increase the level of clump turbulence as the clumps evolve. This implies that the origin of turbulence within clumps is fixed before the onset of star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/432/921
- Title:
- Massive protostellar candidates
- Short Name:
- J/A+A/432/921
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed two rotational transitions of both CS and C^17^O, and the 1.2mm continuum emission towards a sample of 130 high-mass protostellar candidates with DE<-30{deg}. This work represents the first step of the extension to the southern hemisphere of a project started more than a decade ago aimed at the identification of massive protostellar candidates. Following the same approach adopted for sources with DE>=-30{deg}, we have selected from the IRAS Point Source Catalogue 429 sources which potentially are compact molecular clouds on the basis of their IR colours. The sample has then been divided into two groups according to the colour indices [25-12] and [60-12]: the 298 sources with [25-12]>=0.57 and [60-12]>=1.30 have been called High sources, the remaining 131 have been called Low sources. In this paper, we check the association with dense gas and dust in 130 Low sources. We have obtained a detection rate of ~85% in CS, demonstrating a tight association of the sources with dense molecular clumps.
- ID:
- ivo://CDS.VizieR/J/ApJS/243/13
- Title:
- Massive star-forming clump from MALT90
- Short Name:
- J/ApJS/243/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 90 massive star-forming clumps with strong N2H+(1-0), HCO+(1-0), HCN(1-0), and HNC(1-0) emission from the Millimetre Astronomy Legacy Team 90 GHz survey. We obtained Herschel data for all 90 sources and NRAO VLA Sky Survey data for 51 of them. We convolved and regridded all images to the same resolution and pixel size and derived the temperature, H2 column density, molecules' abundances and abundance, and ratios of each pixel. Our analysis yields three main conclusions. First, the abundances of N2H+, HCO+, HCN, and HNC increase when the column density decreases and the temperature increases, with spatial variations in their abundances dominated by changes in the H2 column density. Second, the abundance ratios between N2H+, HCO+, HCN, and HNC also display systemic variations as a function of the column density due to the chemical properties of these molecules. Third, the sources associated with the 20cm continuum emission can be classified into four types based on the behavior of the abundances of the four molecules considered here as a function of this emission. The variations of the first three types could also be attributed to the variation of the H2 column density.
- ID:
- ivo://CDS.VizieR/J/ApJ/719/1104
- Title:
- Massive star forming complexes in GLIMPSE
- Short Name:
- J/ApJ/719/1104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the 13 most luminous sources in the WMAP free-free map using the Spitzer GLIMPSE and Midcourse Space Experiment surveys to identify massive star formation complexes, emitting one-third of the Galactic free-free luminosity. We identify star-forming complexes (SFCs) by a combination of bubble morphology in 8um emission and radio recombination line radial velocities. We find 40 SFCs associated with our WMAP sources and determine unique distances up to 31. We interpret the bubbles as evidence for radial expansion. The radial velocity distribution for each source allows us to measure the intrinsic speed of a complex's expansion. This speed is consistent with the size and age of the bubbles. The high free-free luminosities, combined with negligible synchrotron emission, demonstrate that the bubbles are not driven by supernovae. The kinetic energy of the largest bubbles is a substantial fraction of that measured in the older superbubbles found by Heiles. We find that the energy injected into the interstellar medium by our bubbles is similar to that required to maintain turbulent motion in the gas disk inside 8kpc. We report a number of new SFCs powered by massive (M_*_>10^4^M_{sun}_) star clusters. We measure the scale height of the Galactic O stars to be h_*_=35+/-5pc. We determine an empirical relationship between the 8um and free-free emission of the form F_8um_{propto}F^2^_ff_. Finally, we find that the bubble geometry is more consistent with a spherical shell rather than a flattened disk.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A21
- Title:
- Massive star-forming regions radio lines
- Short Name:
- J/A+A/550/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Australia Telescope Compact Array (ATCA) observations of the H_2_O maser line and radio continuum at 18.0GHz and 22.8GHz toward a sample of 192 massive star-forming regions containing several clumps already imaged at 1.2mm. The main aim of this study is to investigate the water maser and centimeter continuum emission (that likely traces thermal free-free emission) in sources at different evolutionary stages, using evolutionary classifications previously published. We used the recently comissioned Compact Array Broadband Backend (CABB) at ATCA that obtains images with 20arcsec resolution in the 1.3cm continuum and H_2_O maser emission in all targets. For the evolutionary analysis of the sources we used millimeter continuum emission from the literature and the infrared emission from the MSX Point Source Catalog. We detect centimeter continuum emission in 88% of the observed fields with a typical rms noise level of 0.45mJy/beam. Most of the fields show a single radio continuum source, while in 20% of them we identify multiple components. A total of 214 centimeter continuum sources have been identified, that likely trace optically thin HII regions, with physical parameters typical of both extended and compact HII regions. Water maser emission was detected in 41% of the regions, resulting in a total of 85 distinct components. The low angular (20arcsec) and spectral (14km/s) resolutions do not allow a proper analysis of the water maser emission, but suffice to investigate its association with the continuum sources. We have also studied the detection rate of HII regions in the two types of IRAS sources defined in the literature on the basis of the IRAS colors: High and Low. No significant differences are found, with high detection rates (>90%) for both High and Low sources. We classify the millimeter and infrared sources in our fields in three evolutionary stages following the scheme presented previously: (Type 1) millimeter-only sources, (Type 2) millimeter plus infrared sources, (Type 3) infrared-only sources. We find that HII regions are mainly associated with Type 2 and Type 3 objects, confirming that these are more evolved than Type 1 sources. The HII regions associated with Type 3 sources are slightly less dense and larger in size than those associated with Type 2 sources, as expected if the HII region expands as it evolves, and Type 3 objects are older than Type 2 objects. The maser emission is mostly found to be associated with Type 1 and Type 2 sources, with a higher detection rate toward Type 2, consistent with the results of the literature. Finally, our results on HII region and H_2_O maser association with different evolutionary types confirm the evolutionary classification proposed previously.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/70
- Title:
- Massive YSOs in the IR dark cloud G79.3+0.3
- Short Name:
- J/ApJ/876/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- G79.3+0.3 is an infrared dark cloud in the Cygnus-X complex that is home to massive deeply embedded young stellar objects (YSOs). We have produced a Submillimeter Array (SMA) 1.3mm continuum image and ^12^CO line maps of the eastern section of G79.3+0.3 in which we detect five separate YSOs. We have estimated physical parameters for these five YSOs and others in the vicinity of G79.3+0.3 by fitting existing photometry from Spitzer, Herschel, and ground-based telescopes to spectral energy distribution models. Through these model fits we find that the most massive YSOs seen in the SMA 1.3mm continuum emission have masses in the 5-6M_{sun}_ range. One of the SMA sources was observed to power a massive collimated ^12^CO outflow extending at least 0.94pc in both directions from the protostar, with a total mass of 0.83M_{sun}_ and a dynamical timescale of 23kyr.
398. Measured DIB 8620
- ID:
- ivo://CDS.VizieR/J/A+A/654/A116
- Title:
- Measured DIB 8620
- Short Name:
- J/A+A/654/A116
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We made use of the measurements from the Giraffe Inner Bulge Survey (GIBS) and the Gaia-ESO survey (GES) to study the kinematics and distance of the carrier of the DIB at 862nm, as well as other properties. We confirmed a tight relation between EW and E(J-Ks) as well as Av, with similar fitting coefficients as found by previous works. With a more accurate sample and the consideration of the solar motion, the rest-frame wavelength of DIB 8620 was redetermined as 8620.83 angstroms. We studied the kinematics of the DIB carriers by tracing their median radial velocities in each field in the local standard of rest and into the galactocentric frame, respectively, as a function of the Galactic longitudes. Based on the median velocity and two Galactic rotation models, we got valid kinematic distances of the DIB carriers for nine GIBS and ten GES fields. We also found a linear relation between the DIB 8620 measured in this work and the near-infrared DIB in APOGEE spectra at 1.5273 micron.
- ID:
- ivo://CDS.VizieR/J/ApJ/774/72
- Title:
- Measurements of 19 DIBs and 8 other interstellar lines
- Short Name:
- J/ApJ/774/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar bands (DIBs) can trace different conditions of the interstellar medium (ISM) along the sightline toward the observed stars. A small survey was made in optical wavelengths, producing high-resolution and high signal-to-noise spectra. We present measurements of 19 DIBs' properties in 50 sightlines toward hot stars, distributed at a variety of galactic coordinates and interstellar reddening. Equivalent widths were obtained by fitting asymmetric Gaussian and variable continua to DIBs. Conditions of the ISM were calculated from eight atomic and molecular interstellar lines. Two distinctly different types of DIBs were identified by carefully comparing correlation coefficients between DIBs and reddening and by different behavior in UV-shielded ({zeta}) and nonshielded ({sigma}) sightlines. A ratio of DIBs at 5780{AA} and 5797{AA} proved to be reliable enough to distinguish between two different sightline types. Based on the linear relations between DIB equivalent width and reddening for {sigma} and {zeta} sightlines, we divide DIBs into type I (where both linear relations are similar) and type II (where they are significantly different). The linear relation for {zeta} type sightlines always shows a higher slope and larger x-intercept parameter than the relation for {sigma} sightlines. Scatter around the linear relation is reduced after the separation, but it does not vanish completely. This means that UV shielding is the dominant factor of the DIB equivalent width versus reddening relation shape for {zeta} sightlines, but in {sigma} sightlines other physical parameters play a major role. No similar dependency on gas density, electron density, or turbulence was observed. A catalog of all observed interstellar lines is made public.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/151
- Title:
- METAL Hubble program. I. Initial results
- Short Name:
- J/ApJ/871/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud (METAL) is a large cycle 24 program on the Hubble Space Telescope aimed at measuring dust extinction properties and interstellar depletions in the Large Magellanic Cloud (LMC) at half-solar metallicity. The 101-orbit program is composed of Cosmic Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS) spectroscopy toward 33 LMC massive stars between 1150 and 3180{AA} and parallel Wide Field Camera 3 (WFC3) imaging in seven near-UV to near-IR filters. The fraction of silicon in the gas phase (depletion) obtained from the spectroscopy decreases with increasing hydrogen column density. Depletion patterns for silicon differ between the Milky Way, LMC, and Small Magellanic Cloud (SMC), with the silicon depletion level offsetting almost exactly the metallicity differences, leading to constant gas-phase abundances in those galaxies for a given hydrogen column density. The silicon depletion correlates linearly with the absolute-to-selective extinction, RV, indicating a link between gas depletion and dust grain size. Extinction maps are derived from the resolved stellar photometry in the parallel imaging, which can be compared to far-IR images from Herschel and Spitzer to estimate the emissivity of dust at LMC metallicity. The full METAL sample of depletions, UV extinction curves, and extinction maps will inform the abundance, size, composition, and optical properties of dust grains in the LMC, comprehensively improve our understanding of dust properties, and improve the accuracy with which dust-based gas masses, star formation rates, and star formation histories in nearby and high-redshift galaxies are estimated. This overview paper describes the goals, design, data reduction, and initial results of the METAL survey.
