- ID:
- ivo://CDS.VizieR/J/ApJ/775/63
- Title:
- Gould's Belt VLA Survey. I. Ophiuchus complex
- Short Name:
- J/ApJ/775/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present large-scale (~2000arcmin^2^), deep (~20{mu}Jy), high-resolution (~1") radio observations of the Ophiuchus star-forming complex obtained with the Karl G. Jansky Very Large Array at {lambda}=4 and 6cm. In total, 189 sources were detected, 56 of them associated with known young stellar sources, and 4 with known extragalactic objects; the other 129 remain unclassified, but most of them are most probably background quasars. The vast majority of the young stars detected at radio wavelengths have spectral types K or M, although we also detect four objects of A/F/B types and two brown dwarf candidates. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronas characterized by high levels of variability, negative spectral indices, and (in some cases) significant circular polarization. As expected, there is a clear tendency for the fraction of non-thermal sources to increase from the younger (Class 0/I or flat spectrum) to the more evolved (Class III or weak line T Tauri) stars. The young stars detected both in X-rays and at radio wavelengths broadly follow a Gudel-Benz relation, but with a different normalization than the most radioactive types of stars. Finally, we detect a ~70mJy compact extragalactic source near the center of the Ophiuchus core, which should be used as gain calibrator for any future radio observations of this region.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/818/116
- Title:
- Gould's Belt VLA survey. V. Perseus region
- Short Name:
- J/ApJ/818/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multiepoch, large-scale (~2000 arcmin^2^), fairly deep (~16 {mu}Jy), high-resolution (~1") radio observations of the Perseus star-forming complex obtained with the Karl G. Jansky Very Large Array at frequencies of 4.5 and 7.5 GHz. These observations were mainly focused on the clouds NGC 1333 and IC 348, although we also observed several fields in other parts of the Perseus complex. We detect a total of 206 sources, 42 of which are associated with young stellar objects (YSOs). The radio properties of about 60% of the YSOs are compatible with a nonthermal radio emission origin. Based on our sample, we find a fairly clear relation between the prevalence of nonthermal radio emission and evolutionary status of the YSOs. By comparing our results with previously reported X-ray observations, we show that YSOs in Perseus follow a Gudel-Benz relation with {kappa}=0.03, consistent with other regions of star formation. We argue that most of the sources detected in our observations but not associated with known YSOs are extragalactic, but provide a list of 20 unidentified radio sources whose radio properties are consistent with being YSO candidates. Finally, we also detect five sources with extended emission features that can clearly be associated with radio galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A57
- Title:
- G328.2551-0.5321 spectra
- Short Name:
- J/A+A/632/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical hot cores are rich in molecular emission, and they show a high abundance of complex organic molecules (COMs). The emergence of molecular complexity that is represented by COMs, in particular, is poorly constrained in the early evolution of hot cores. We put observational constraints on the physical location of COMs in a resolved high-mass protostellar envelope associated with the G328.2551-0.5321 clump. The protostar is single down to 400au scales and we resolved the envelope structure down to this scale. High angular resolution observations using the Atacama Large Millimeter Array allowed us to resolve the structure of the inner envelope and pin down the emission region of COMs. We use local thermodynamic equilibrium modelling of the available 7.5GHz bandwidth around 345GHz to identify the COMs towards two accretion shocks and a selected position representing the bulk emission of the inner envelope. We quantitatively discuss the derived molecular column densities and abundances towards these positions, and use our line identification to qualitatively compare this to the emission of COMs seen towards the central position, corresponding to the protostar and its accretion disk. We detect emission from 10 COMs, and identify a line of deuterated water (HDO). In addition to methanol (CH_3_OH), methyl formate (CH_3_OCHO) and formamide (HC(O)NH_2_) have the most extended emission. Together with HDO, these molecules are found to be associated with both the accretion shocks and the inner envelope, which has a moderate temperature of Tkin~110K. We find a significant difference in the distribution of COMs. O-bearing COMs, such as ethanol, acetone, and ethylene glycol are almost exclusively found and show a higher abundance towards the accretion shocks with Tkin~180K. Whereas N-bearing COMs with a CN group, such as vinyl and ethyl cyanide peak on the central position, thus the protostar and the accretion disk. The molecular composition is similar towards the two shock positions, while it is significantly different towards the inner envelope, suggesting an increase in abundance of O-bearing COMs towards the accretion shocks. We present the first observational evidence for a large column density of COMs seen towards accretion shocks at the centrifugal barrier at the inner envelope. The overall molecular emission shows increased molecular abundances of COMs towards the accretion shocks compared to the inner envelope. The bulk of the gas from the inner envelope is still at a moderate temperature of Tkin~110K, and we find that the radiatively heated inner region is very compact (<1000au). Since the molecular composition is dominated by that of the accretion shocks and the radiatively heated hot inner region is very compact, we propose this source to be a precursor to a classical, radiatively heated hot core. By imaging the physical location of HDO, we find that it is consistent with an origin within the moderately heated inner envelope, suggesting that it originates from sublimation of ice from the grain surface and its destruction in the vicinity of the heating source has not been efficient yet.
- ID:
- ivo://CDS.VizieR/J/ApJS/208/28
- Title:
- H{alpha} survey in the ONC
- Short Name:
- J/ApJS/208/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from an H{alpha} emission line survey in a 1 deg^2^ area centered on the Orion Nebula Cluster, obtained with the Wide Field Grism Spectrograph 2 on the 2.2 m telescope of the University of Hawaii. We identified 587 stars with H{alpha} emission, 99 of which, located mainly in the outer regions of the observed area, have not appeared in previous H{alpha} surveys. We determined the equivalent width (EW) of the line and, based on this, classified 372 stars as classical T Tauri stars (CTTSs) and 187 as weak-line T Tauri stars (WTTSs). Simultaneous r', i' photometry indicates a limiting magnitude of r' ~ 20 mag, but the sample is incomplete at r' > 17 mag. The surface distribution of the H{alpha} emission stars reveals a clustered population and a dispersed population, the former consisting of younger and more massive young stars than the latter. Comparison of the derived EWs with those found in the literature indicates variability of the H{alpha} line. We found that the typical amplitudes of the variability are not greater than a factor of two to three in most cases. We identified a subgroup of low-EW stars with infrared signatures indicative of optically thick accretion disks. We studied the correlations between the EW and other properties of the stars. Based on literature data, we examined several properties of our CTTS and WTTS subsamples and found significant differences in mid-infrared color indices, average rotational periods, and spectral energy distribution characteristics of the subsamples.
- 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/626/A95
- Title:
- HD160305 images with SPHERE
- Short Name:
- J/A+A/626/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Direct imaging of debris disks gives important information about their nature, their global morphology and allows to identify specific structures possibly in connection with the presence of gravitational perturbers. It is the most straightforward technique to observe planetary systems as a whole. We present the first resolved images of the debris disk around the young F-type star HD 160305, detected in scattered light using the VLT/SPHERE instrument in the near infrared. We used a post-processing method based on Angular Differential Imaging and synthetic images of debris disks produced with a disk modeling code (GRaTer) to constrain the main characteristics of the disk around HD160305. All of the point sources in the field of the IRDIS camera were analyzed with an astrometric tool to determine whether they are bound objects or background stars. We detect a very inclined (~82{deg}) ring-like debris disk located at a stellocentric distance of about 86au (deprojected width ~27au). The disk displays a brightness asymmetry between the two sides of the major axis, as can be expected from scattering properties of dust grains. We derive an anisotropic scattering factor g>0.5. A second right-left asymmetry is also observed with respect to the minor axis. We measure a surface brightness ratio of 0.73+/-0.18 between the bright and the faint sides. Because of the low signal-to-noise ratio (S/N) of the images we cannot easily discriminate between several possible explanations for this left-right asymmetry, such as perturbations by an unseen planet, the aftermath of the breakup of a massive planetesimal, or the pericenter glow effect due to an eccentric ring. Two epochs of observations allow us to reject the companionship hypothesis for the 15 point sources present in the field.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A108
- Title:
- HD61005 SPHERE H and Ks images
- Short Name:
- J/A+A/591/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Debris disks offer valuable insights into the latest stages of circumstellar disk evolution, and can possibly help us to trace the outcomes of planetary formation processes. In the age range 10 to 100Myr, most of the gas is expected to have been removed from the system, giant planets (if any) must have already been formed, and the formation of terrestrial planets may be on-going. Pluto-sized planetesimals, and their debris released in a collisional cascade, are under their mutual gravitational influence, which may result into non-axisymmetric structures in the debris disk. Here we present new VLT/SPHERE and ALMA observations of the debris disk around the 40Myr-old solar-type star HD61005. We resolve the disk at unprecedented resolution both in the near-infrared (in scattered and polarized light) and at millimeter wavelengths. We perform a detailed modeling of these observations, including the spectral energy distribution. Thanks to the new observations, we propose a solution for both the radial and azimuthal distribution of the dust grains in the debris disk. We find that the disk has a moderate eccentricity and that the dust density is two times larger at the pericenter compared to the apocenter. With no giant planets detected in our observations, we investigate alternative explanations besides planet-disk interactions to interpret the inferred disk morphology. We postulate that the morphology of the disk could be the consequence of a massive collision between 1000km-sized bodies at 61 au. If this interpretation holds, it would put stringent constraints on the formation of massive planetesimals at large distances from the star.
- 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/ApJ/799/100
- Title:
- Herschel FIR observations of NGC3603
- Short Name:
- J/ApJ/799/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the giant H II region around the NGC 3603 young stellar cluster (YC) with the five broad bands (70, 160, 250, 350, 500{mu}m) of the SPIRE and PACS instruments, on board the Herschel Space Observatory. Together with what is currently known of the stellar, atomic, molecular, and warm dust components, this additional and crucial information should allow us to better understand the details of the star-formation history in this region. The main objective of the investigation is to study, at high spatial resolution, the distribution and main physical characteristics of the cold dust. By reconstructing the temperature and density maps, we found, respectively, a mean value of 36K and log_10_N_H_=22.0+/-0.1/cm2. We carried out a photometric analysis detecting 107 point-like sources, mostly confined to the north and south of the cluster. By comparing our data with spectral energy distribution models, we found that 35 sources are well represented by young stellar objects in early evolutionary phases, from Class 0 to Class I. The Herschel detections also provided far-IR counterparts for 4 H_2_O masers and 11 objects previously known from mid-IR observations. The existence of so many embedded sources confirms the hypothesis of intense and ongoing star-formation activity in the region around NGC 3603 YC.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/13
- Title:
- Herschel obs. of protoplanetary disks in L1641
- Short Name:
- J/ApJ/863/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze Herschel Space Observatory observations of 104 young stellar objects with protoplanetary disks in the ~1.5Myr star-forming region Lynds 1641 (L1641) within the Orion A Molecular Cloud. We present spectral energy distributions from the optical to the far-infrared including new photometry from the Herschel Photodetector Array Camera and Spectrometer at 70{mu}m. Our sample, taken as part of the Herschel Orion Protostar Survey, contains 24 transitional disks, 8 of which we identify for the first time in this work. We analyze the full disks (FDs) with irradiated accretion disk models to infer dust settling properties. Using forward modeling to reproduce the observed n_Ks-[70]_ index for the FD sample, we find the observed disk indices are consistent with models that have depletion of dust in the upper layers of the disk relative to the midplane, indicating significant dust settling. We perform the same analysis on FDs in Taurus with Herschel data and find that Taurus is slightly more evolved, although both samples show signs of dust settling. These results add to the growing literature that significant dust evolution can occur in disks by ~1.5Myr.
