- 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.
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- 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/ApJ/789/L38
- Title:
- LRLL54361 protostar Herschel/PACS fluxes
- Short Name:
- J/ApJ/789/L38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report Herschel/Photodetector Array Camera and Spectrometer (PACS) photometric observations at 70 {mu}m and 160 {mu}m of LRLL54361, a suspected binary protostar that exhibits periodic (P = 25.34 days) flux variations at shorter wavelengths (3.6 {mu}m and 4.5 {mu}m) thought to be due to pulsed accretion caused by binary motion. The PACS observations show unprecedented flux variation at these far-infrared wavelengths that are well correlated with the variations at shorter wavelengths. At 70 {mu}m the object increases its flux by a factor of six while at 160 {mu}m the change is about a factor of two, consistent with the wavelength dependence seen in the far-infrared spectra. The source is marginally resolved at 70 {mu}m with varying FWHM. Deconvolved images of the sources show elongations exactly matching the outflow cavities traced by the scattered light observations. The spatial variations are anti-correlated with the flux variation, indicating that a light echo is responsible for the changes in FWHM. The observed far-infrared flux variability indicates that the disk and envelope of this source is periodically heated by the accretion pulses of the central source, and suggests that such long wavelength variability in general may provide a reasonable proxy for accretion variations in 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.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A121
- Title:
- Missing low-mass stars in S254-S258
- Short Name:
- J/A+A/533/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this study was to find an explanation for the remarkable morphology of the central part of the S254-S258 star forming complex. We performed a deep Chandra X-ray observation of the S254-S258 region in order to efficiently discriminate young stars (with and without circumstellar matter) from the numerous older field stars in the area. We detected 364 X-ray point sources in a 17'x17' field. This X-ray catalog provides, for the first time, a complete sample of all young stars in the region down to about 0.5M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A22
- Title:
- Monoceros R2 filament hub FIR observations
- Short Name:
- J/A+A/607/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present far-infrared observations of Monoceros R2 (a giant molecular cloud at approximately 830pc distance, containing several sites of active star formation), as observed at 70um, 160um, 250um, 350um, and 500um by the PACS and SPIRE instruments on the Herschel Space Observatory as part of the HOBYS Key programme. The Herschel data are complemented by SCUBA-2 data in the submillimetre range, and WISE and Spitzer data in the mid-infrared. In addition, C^18^O data from the IRAM 30-m Telescope are presented, and used for kinematic information. Sources were extracted from the maps with getsources, and from the fluxes measured, spectral energy distributions were constructed, allowing measurements of source mass and dust temperature. Of 177 Herschel sources robustly detected in the region (a detection with high signal-to-noise and low axis ratio at multiple wavelengths), including protostars and starless cores, 29 are found in a filamentary hub at the centre of the region (a little over 1% of the observed area). These objects are on average smaller, more massive, and more luminous than those in the surrounding regions (which together suggest that they are at a later stage of evolution), a result that cannot be explained entirely by selection effects. These results suggest a picture in which the hub may have begun star formation at a point significantly earlier than the outer regions, possibly forming as a result of feedback from earlier star formation. Furthermore, the hub may be sustaining its star formation by accreting material from the surrounding filaments.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A58
- Title:
- Oph A mosaic image
- Short Name:
- J/A+A/631/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of young stellar objects (YSOs) in centimeter bands can probe the continuum emission from growing dust grains, ionized winds, and magnetospheric activity, which are intimately connected to the evolution of protoplanetary disks and the formation of planets. We have carried out sensitive continuum observations toward the Ophiuchus A star-forming region using the Karl G. Jansky Very Large Array (VLA) at 10GHz over a field-of-view of 6' with a spatial resolution of {theta}_maj_x{theta}_min_~0.4"x0.2". We achieved a 5{mu}Jy/beam root-mean-square noise level at the center of our mosaic field of view. Among the eighteen sources we detected, sixteen are YSOs (three Class 0, five Class I, six Class II, and two Class III) and two are extragalactic candidates.We find that thermal dust emission generally contributes less that 30% of the emission at 10GHz. The radio emission is dominated by other types of emission such as gyro-synchrotron radiation from active magnetospheres, free-free emission from thermal jets, free-free emission from the outflowing photo-evaporated disk material, and/or synchrotron emission from accelerated cosmic-rays in jet or protostellar surface shocks. These different types of emission could not be clearly disentangled. Our non-detections towards Class II/III disks suggest that extreme UV-driven photoevaporation is insufficient to explain the disk dispersal, assuming that the contribution of UV photoevaporating stellar winds to radio flux does not evolve with time. The sensitivity of our data cannot exclude photoevaporation due to X-ray photons as an efficient mechanism for disk dispersal. Deeper surveys with the Square Kilometre Array will be able to provide strong constraints on disk photoevaporation.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A106
- Title:
- Probing midplane structure with DCO+ in HD169142
- Short Name:
- J/A+A/614/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the radial distribution of DCO^+^ in the protoplanetary disk around HD 169142, a Herbig Ae type star, with the aim of determining possible formation scenarios of DCO^+^. Using a simple chemical model, we investigate the effect of gas-phase CO abundance and gas temperature on the production of DCO^+^ near the disk midplane. Model fits to the DCO^+^ radial profile suggest a much colder disk midplane than the disk physical structure obtained from the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/291/943
- Title:
- Protostellar cores
- Short Name:
- J/A+A/291/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Basing on the coagulation model of Ossenkopf (1993A&A...280..617O), we systematically computed and tabulated the opacity of dust in dense protostellar cores between 1 micrometers and 1.3 mm. The possible physical conditions were varied especially considering the influence of different gas densities and molecular depletion ratios. In comparison to the dust opacity in the diffuse interstellar medium, we found nowhere changes by more than the factor 5 for ice-covered dust grains. Possible uncertainties and deviations in environments with different physical conditions are discussed. Although one may imagine very special situations in which the dust opacity is changed by more than a factor 10, for physically reasonable conditions in dense protostellar cores, all possible deviations from the tabulated values may not sum up to more than a factor of 2. Using these tables of dust opacities, the submm continuum radiation of cold dust in protostellar cores is a good tracer of their total mass.
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