- ID:
- ivo://CDS.VizieR/J/A+A/632/A101
- Title:
- Extremely high-velocity jets in Serpens
- Short Name:
- J/A+A/632/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- ALMA observations of four molecular transitions, CO 2-1, SiO 5-4, H_2_CO 3_03_-2_02_ in Band 6 (ALMA project 2013.1.00726.S; PI: C. Hull) and HCN 1-0 observed in Band 3 (ALMA project 2016.1.00710.S; PI: C. Hull) are presented. The synthesized beam of the observations is between 0.3 and 0.6 arcsec, corresponding to 130-260au at the distance to Serpens Main. The largest recoverable scale in the data is 5 arcsec and 12 arcsec (2150 and 4960au) for Band 3 and Band 6, respectively. The spectral resolution of the observations differs between the spectral windows, ranging from 0.04 to 0.3km/s. For both bands, only 12-m array data were used. The Band 6 data were obtained in two configurations (C43-1 and C43-4 with resolutions of 1.1 and 0.3 arcsec, respectively, and the final images are produced from the combined datasets.
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- ID:
- ivo://CDS.VizieR/J/A+A/593/A49
- Title:
- G35.20-0.74N VLA continuum images
- Short Name:
- J/A+A/593/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Atacama Large Millimeter/submillimeter Array (ALMA) observations of the high-mass star-forming region G35.20-0.74N have revealed the presence of a Keplerian disk in core B rotating about a massive object of 18M_{sun}_, as computed from the velocity field. The luminosity of such a massive star would be comparable to (or higher than) the luminosity of the whole star-forming region. To solve this problem it has been proposed that core B could harbor a binary system. This could also explain the possible precession of the radio jet associated with this core, which has been suggested by its S-shaped morphology. We establish the origin of the free-free emission from core B and investigate the existence of a binary system at the center of this massive core and the possible precession of the radio jet. We carried out VLA continuum observations of G35.20-0.74N at 2cm in the B configuration and at 1.3cm and 7mm in the A and B configurations. The bandwidth at 7mm covers the CH3OH maser line at 44.069GHz. Continuum images at 6 and 3.6cm in the A configuration were obtained from the VLA archive. We also carried out VERA observations of the H_2_O maser line at 22.235GHz.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A31
- Title:
- HCO+, CN, and 13CO maps of R Mon
- Short Name:
- J/A+A/617/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To our knowledge, R Mon is the only B0 star in which a gaseous Keplerian disk has been detected. However, there is some controversy about the spectral type of R Mon. Some authors propose that it could be a later B8e star, where disks are more common. Our goal is to re-evaluate the R Mon spectral type and characterize its protoplanetary disk. The spectral type of R Mon has been re-evaluated using the available continuum data and UVES emission lines. We used a power-law disk model to fit previous ^12^CO 1-0 and 2-1 interferometric observations and the PACS CO data to investigate the disk structure. Interferometric detections of ^13^CO J=1-0, HCO^+^ 1-0, and CN 1-0 lines using the IRAM Plateau de Bure Interferometer (PdBI) are presented. The HCN 1-0 line was not detected. Our analysis confirms that R Mon is a B0 star. The disk model compatible with the ^12^CO 1-0 and 2-1 interferometric observations falls short of predicting the observed fluxes of the 14<Ju<31 PACS lines; this is consistent with the scenario in which some contribution to these lines is coming from a warm envelope and/or UV-illuminated outflow walls. More interestingly, the upper limits to the fluxes of the Ju>31 CO lines suggest the existence of a region empty of CO at R<=20au in the proto-planetary disk. The intense emission of the HCO^+^ and CN lines shows the strong influence of UV photons on gas chemistry. The observations gathered in this paper are consistent with the presence of a transition disk with a cavity of Rin>=20 au around R Mon. This size is similar to the photoevaporation radius that supports the interpretation that UV photoevaporation is main disk dispersal mechanism in massive stars
- ID:
- ivo://CDS.VizieR/J/A+A/605/A21
- Title:
- H_2_CO production in HD 163296
- Short Name:
- J/A+A/605/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the radial distribution of H_2_CO and C^18^O in the protoplanetary disk around HD 163296, a Herbig Ae type protostar, with the aim of determining possible formation scenarios of H_2_CO. By comparing the two molecules and the millimeter continuum, we investigate the relationship between the presence of H_2_CO and CO depletion in the disk.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A49
- Title:
- Herschel EPoS: high-mass overview
- Short Name:
- J/A+A/547/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars are born deeply embedded in molecular clouds. In the earliest embedded phases, protostars emit the bulk of their radiation in the far-infrared wavelength range, where Herschel is perfectly suited to probe at high angular resolution and dynamic range. In the high-mass regime, the birthplaces of protostars are thought to be in the high-density structures known as infrared-dark clouds (IRDCs). While massive IRDCs are believed to have the right conditions to give rise to massive stars and clusters, the evolutionary sequence of this process is not well-characterized. As part of the Earliest Phases of Star formation (EPoS) Herschel guaranteed time key program, we isolate the embedded structures within IRDCs and other cold, massive molecular clouds. We present the full sample of 45 high-mass regions which were mapped at PACS 70, 100, and 160um and SPIRE 250, 350, and 500um. In the present paper, we characterize a population of cores which appear in the PACS bands and place them into context with their host molecular cloud and investigate their evolutionary stage.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A19
- Title:
- IRAM intensity maps of 3 low-mass protostars
- Short Name:
- J/A+A/632/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methanol is a key species in astrochemistry since it is the most abundant organic molecule in the interstellar medium and is thought to be the mother molecule of many complex organic species. Estimating the deuteration of methanol around young protostars is of crucial importance because it highly depends on its formation mechanisms and the physical conditions during its moment of formation. We analyse several dozens of transitions from deuterated methanol isotopologues coming from various existing observational datasets obtained with the IRAM-PdBI and ALMA sub-mm interferometers to estimate the methanol deuteration surrounding three low-mass protostars on Solar System scales. A population diagram analysis allows us to derive a [CH_2_DOH]/[CH_3_OH] abundance ratio of 3-6% and a [CH_3_OD]/[CH_3_OH] ratio of 0.4-1.6% in the warm inner (<100-200AU) protostellar regions. These values are typically ten times lower than those derived with previous single-dish observations towards these sources but they are one to two orders of magnitude higher than the methanol deuteration measured in massive hot cores. Dust temperature maps obtained from Herschel and Planck observations show that massive hot cores are located in warmer molecular clouds than low-mass sources, with temperature differences of about 10K. The comparison of our measured values with the predictions of the gas-grain astrochemical model GRAINOBLE shows that such a temperature difference is sufficient to explain the different deuteration observed in low- to high-mass sources. This suggests that the physical conditions of the molecular cloud at the origin of the protostars mostly govern the present observed deuteration of methanol and, therefore, of more complex organic molecules. Finally, the methanol deuteration measured towards young solar-type protostars on Solar System scales seems to be higher by a factor of about 5 than the upper limit in methanol deuteration estimated in comet Hale-Bopp. If this result is confirmed by subsequent observations of other comets, this would imply that an important reprocessing of the organic material likely occurred in the solar nebula during the formation of the Solar System.
- ID:
- ivo://CDS.VizieR/J/A+A/544/L7
- Title:
- IRAS 16293-2422 ALMA maps
- Short Name:
- J/A+A/544/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We focus on the kinematical properties of a proto-binary to study the infall and rotation of gas toward its two protostellar components. We present ALMA Science Verification observations with high-spectral resolution of IRAS 16293-2422 at 220.2GHz. The wealth of molecular lines in this source and the very high spectral resolution offered by ALMA allow us to study the gas kinematics with unprecedented detail.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A70
- Title:
- Linking high- and low-mass star formation
- Short Name:
- J/A+A/657/A70
- Date:
- 21 Mar 2022 09:28:51
- Publisher:
- CDS
- Description:
- Astronomers have yet to establish whether high-mass protostars form from high-mass prestellar cores, similar to their lower-mass counterparts, or from lower-mass fragments at the heart of a pre-protostellar cluster undergoing large-scale collapse. Part of the uncertainty is due to a shortage of envelope structure data on protostars of a few tens of solar masses, where we expect to see a transition from intermediate-mass star formation to the high-mass process. We sought to derive the masses, luminosities, and envelope density profiles for eight sources in Cygnus-X, whose mass estimates in the literature placed them in the sampling gap. Combining these sources with similarly evolved sources in the literature enabled us to perform a meta-analysis of protostellar envelope parameters over six decades in source luminosity. We performed spectral energy distribution (SED) fitting on archival broadband photometric continuum data from 1.2 to 850 microns, to derive bolometric luminosities for our eight sources plus initial mass and radius estimates for modelling density and temperature profiles with the radiative transfer package Transphere. The envelope masses, densities at 1000AU, outer envelope radii, and density power law indices as functions of bolometric luminosity all follow established trends in the literature spanning six decades in luminosity. Most of our sources occupy an intermediate to moderately high range of masses and luminosities, which helps more firmly establish the continuity between low- and high-mass star formation mechanisms. Our density power law indices are consistent with observed values in literature, which show no discernible trends with luminosity. Finally, we show that the trends in all of the envelope parameters for high-mass protostars are statistically indistinguishable from trends in the same variables for low- and intermediate-mass protostars.
- ID:
- ivo://CDS.VizieR/J/A+A/567/A116
- Title:
- Maps and datacubes of NGC 7538 IRS 1
- Short Name:
- J/A+A/567/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 7538 IRS 1-3 is a high-mass star-forming cluster with several detected dust cores, infrared sources, (ultra)compact HII regions, molecular outflows, and masers. In such a complex environment, interactions and feedback among the embedded objects are expected to play a major role in the evolution of the region. We study the dust, kinematic, and polarimetric properties of the NGC 7538 IRS 1-3 region to investigate the role of the different forces in the formation and evolution of high-mass star-forming clusters. Methods: We performed SMA high angular resolution observations at 880um with the compact configuration. We developed the RATPACKS code to generate synthetic velocity cubes from models of choice to be compared to the observational data. To quantify the stability against gravitational collapse we developed the "mass balance" analysis that accounts for all the energetics on core scales. We detect 14 dust cores from 3.5M_{sun}_ to 37M_{sun}_ arranged in two larger scale structures: a central bar and a filamentary spiral arm. The spiral arm presents large-scale velocity gradients in H^13^CO^+^ 4-3 and C^17^O 3-2, and magnetic field segments aligned well to the dust main axis. The velocity gradient is reproduced well by a spiral arm expanding at 9km/s with respect to the central core MM1, which is known to power a large precessing outflow. The energy of the outflow is comparable to the spiral-arm kinetic energy, which dominates gravitational and magnetic energies. In addition, the dynamical ages of the outflow and spiral arm are comparable. On core scales, those embedded in the central bar seem to be unstable against gravitational collapse and prone to forming high-mass stars, while those in the spiral arm have lower masses that seem to be supported by non-thermal motions and magnetic fields. The NGC 7538 IRS 1-3 cluster seems to be dominated by protostellar feedback. The dusty spiral arm appears to be formed in a snowplow fashion owing to the outflow from the MM1 core. We speculate that the external pressure from the redshifted lobe of the outflow could trigger star formation in the spiral arm cores. This scenario would form a small cluster with a few central high-mass stars, surrounded by a number of low-mass stars formed through protostellar feedback.
- 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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