High SiO abundance in the HH212 protostellar jet

Previous SiO maps of the innermost regions of HH212 set strong constraints on the structure and origin of this jet. They rule out a fast wide-angle wind, and tentatively favor a magneto-centrifugal disk wind launched out to 0.6 AU. We aim to assess the SiO content at the base of the HH212 jet to set an independent constraint on the location of the jet launch zone with respect to the dust sublimation radius. We present the first sub-arcsecond (0"44x0"96) CO map of the HH212 jet base, obtained with the IRAM Plateau de Bure Interferometer. Combining this with previous SiO(5-4) data, we infer the CO(2-1) opacity and mass-flux in the high-velocity jet and arrive at a much tighter lower limit to the SiO abundance than possible from the (optically thick) SiO emission alone. Gas-phase SiO at high velocity contains at least 10% of the elemental silicon if the jet is dusty, and at least 40% if the jet is dust-free, if CO and SiO have similar excitation temperatures. Such a high SiO content is challenging for current chemical models of both dust-free winds and dusty interstellar shocks. Updated chemical models (equatorial dust-free winds, highly magnetized dusty shocks) and observations of higher J CO lines are required to elucidate the dust content and launch radius of the HH212 high-velocity jet.Comment: 4 pages, 2 figure

Plateau de Bure Interferometer Observations of the Disk and Outflow of HH30

HH30 is a well-known Pre-Main-Sequence star in Taurus. HST observations have revealed a flared, edge-on disk driving a highly-collimated optical jet, making this object a case study for the disk-jet-outflow paradigm. We obtained high angular resolution (about 1") observations of the dust continuum at 2.7 and 1.3 mm, and of the 12CO(2-1), 13CO(2-1) & (1-0), C18O(1-0) emissions around HH30. A standard disk model is used to fit the 13CO(2-1) uv-plane visibilities and derive the disk properties, and the stellar mass. It results that HH30 is a low mass TTauri of spectral type around M1 and age 1 to 4 Myrs, surrounded by a medium size Keplerian disk, of mass around 4e-3 Msun and outer radius 420 AU. The disk rotation vector points toward the North-Eastern jet. Using a distance of 140 pc, we deduce a stellar mass of 0.45 Msun. A highly asymmetric outflow originates from the inner parts of the disk. It presents to first order a conical morphology with a 30 degree half opening angle and a constant (12 km/s) radial velocity field. Outflow rotation was searched for but not found. These observations do not enable to assign the origin of the molecular outflow to entrainment by the optical jet or to a disk wind. In the latter case, the upper limit of the outflow rotation velocity implies an origin in the inner 15 AU of the disk.Comment: 20 pages, 15 PostScript figures. Accepted for publication in Astronomy & Astrophysics. Uses aa LaTeX macro

Small-scale properties of Class 0 protostars from the CALYPSO IRAM-PdBI survey

Because the formation of protostars is believed to be closely tied to the angular momentum problem of star formation, characterizing the properties of the youngest disks around Class 0 objects is crucial. However, not much is known on the structure of the youngest protostellar envelopes, on the small scales at which disks and multiple systems are observed around more evolved YSOs, due to a lack of comprehensive high angular resolution observations (probing 50 au, disk structures are not observed in most Class 0 protostars from our sample, which can be described by various envelope models reproducing satisfactorily the intensity distribution of the dust emission at all scales from 50 au to 5000 au

Ongoing star formation in the proto-cluster IRAS 22134+5834

Aims. Massive stars form in clusters, and their influence on nearby starless cores is still poorly understood. The protocluster associated with IRAS 22134+5834 represents an excellent laboratory for studying the influence of massive YSOs on nearby starless cores and the possible implications in the clustered star formation process. Methods. IRAS 22134+5834 was observed in the cm range with (E)VLA, 3 mm with CARMA, 2 mm with PdBI, and 1.3 mm with SMA, to study both the continuum emission and the molecular lines that trace different physical conditions of the gas. Results. The multiwavelength centimeter continuum observations revealed two radio sources within the cluster, VLA1 and VLA2. VLA1 is considered to be an optically thin UCHII region with a size of 0.01 pc that sits at the edge of the near-infrared (NIR) cluster. The flux of ionizing photons of the VLA1 corresponds to a B1 ZAMS star. VLA2 is associated with an infrared point source and has a negative spectral index. We resolved six millimeter continuum cores at 2 mm, MM2 is associated with the UCHII region VLA1, and other dense cores are distributed around the UCHII region. Two high-mass starless clumps (HMSC), HMSC-E (east) and HMSC-W (west), are detected around the NIR cluster with N2H+(1-0) and NH3 emission, and they show different physical and chemical properties. Two N2D+ cores are detected on an NH3 filament close to the UCHII region with a projected separation of ~8000 AU at the assumed distance of 2.6 kpc. The kinematic properties of the molecular line emission confirm that the UCHII region is expanding and that the molecular cloud around the NIR cluster is also expanding. Conclusions. Our multiwavelength study has revealed different generations of star formation in IRAS 22134+5834. The formed intermediate-to-massive stars show a strong impact on nearby starless clumps. We propose that the starless clumps and HMPOs formed at the edge of the cluster while the stellar wind from the UCHII region and the NIR cluster drives the large scale bubble

First Sagittarius A* Event Horizon Telescope results. II. EHT and multiwavelength observations, data processing, and calibration

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5–11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ∼50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.http://iopscience.iop.org/2041-8205Physic

First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5–11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ∼50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*’s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior

High-sensitivity search for clumps in the Vega Kuiper-belt. New PdBI 1.3mm observations

Previous studies have found that Vega is surrounded by an extended debris disc that is very smooth in the far infrared, but displays possible clumpiness at 850micron and dust emission peaks at 1.3mm. We reobserved Vega at 1.3mm with PdBI to constrain its circumstellar dust distribution. Our observations of a three-field mosaic have a factor of two higher sensitivity than previous observations. We detect Vega photosphere with the expected flux, but none of the previously reported emission peaks that should have been detected at the >6sigma level, with a sensitivity <1mK. This implies that the dust distribution around Vega is principally smooth and circularly symmetric. This also means that no planet is needed to account for dust trapped in mean-motion resonnance

VizieR Online Data Catalog: NGC1333-IRAS2A CALYPSO IRAM-PdBI 1mm and 3mm maps (Maret+, 2014)

VizieR On-line Data Catalog: J/A+A/563/L1. Originally published in: 2014A&A...563L...1MObservations of IRAS2A where carried out with the Plateau de Bure Interferometer (PdBI) between November 2010 and February 2011 using the A can C configuration of the array. Data cubes of the CH3OH (51-42 vt=0 E1) line at 216.945600GHz (1mm), observed using the narrow-band beckend, providing a bandwidth of 512 channels of 39kHz (0.05km/s) each, and of the CH3OH (10-21 vt-1 E1) line at 93.196670GHz (3mm), also observed using the narrow-band backend, but with 256 channels of 312kHz (1.0km/s) each. (2 data files)