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

2015 ◽  
Vol 11 (S315) ◽  
pp. 114-117
Author(s):  
Anaëlle Maury ◽  
Philippe André ◽  
Sébastien Maret ◽  
Arnaud Belloche ◽  
Claudio Codella ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Angular Resolution ◽  
Dust Emission ◽  
Continuum Emission ◽  
Small Scale ◽  
High Angular Resolution ◽  
Multiple Systems ◽  
Small Scales ◽  
Molecular Lines ◽  
Scale Properties

AbstractBecause 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 <100 AU). In order to tackle this issue, we conducted a large observing program with the IRAM Plateau de Bure interferometer (PdBI): the CALYPSO survey, providing us with detailed maps of molecular lines and millimeter continuum emission, probing scales down to ~30–50 au towards a sample of 17 Class 0 protostars. Here we present our analysis of the CALYPSO dust continuum emission maps, constraining disk properties of the Class 0 protostars in our sample. We show that large, r > 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.

scholarly journals SMA observations of polarized dust emission in solar-type Class 0 protostars: Magnetic field properties at envelope scales

2018 ◽  
Vol 616 ◽  
pp. A139 ◽  
Author(s):  
Maud Galametz ◽  
Anaëlle Maury ◽  
Josep M. Girart ◽  
Ramprasad Rao ◽  
Qizhou Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Dust Emission ◽  
Point Of View ◽  
Continuum Emission ◽  
Small Scale ◽  
Theoretical Point ◽  
Multiple Systems ◽  
Linearly Polarized ◽  
Solar Type ◽  
The Magnetic Field

Aims. Although from a theoretical point of view magnetic fields are believed to play a significant role during the early stages of star formation, especially during the main accretion phase, the magnetic field strength and topology is poorly constrained in the youngest accreting Class 0 protostars that lead to the formation of solar-type stars. Methods. We carried out observations of the polarized dust continuum emission with the SMA interferometer at 0.87 mm to probe the structure of the magnetic field in a sample of 12 low-mass Class 0 envelopes in nearby clouds, including both single protostars and multiple systems. Our SMA observations probed the envelope emission at scales ~600 − 5000 au with a spatial resolution ranging from 600 to 1500 au depending on the source distance. Results. We report the detection of linearly polarized dust continuum emission in all of our targets with average polarization fractions ranging from 2% to 10% in these protostellar envelopes. The polarization fraction decreases with the continuum flux density, which translates into a decrease with the H2 column density within an individual envelope. Our analysis show that the envelope-scale magnetic field is preferentially observed either aligned or perpendicular to the outflow direction. Interestingly, our results suggest for the first time a relation between the orientation of the magnetic field and the rotational energy of envelopes, with a larger occurrence of misalignment in sources in which strong rotational motions are detected at hundreds to thousands of au scales. We also show that the best agreement between the magnetic field and outflow orientation is found in sources showing no small-scale multiplicity and no large disks at ~100 au scales.

scholarly journals High gas-to-dust size ratio indicating efficient radial drift in the mm-faint CX Tauri disk

2019 ◽  
Vol 626 ◽  
pp. L2 ◽  
Author(s):  
S. Facchini ◽  
E. F. van Dishoeck ◽  
C. F. Manara ◽  
M. Tazzari ◽  
L. Maud ◽  
...  
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Spectral Energy Distribution ◽  
Theoretical Models ◽  
Intensity Profile ◽  
Continuum Emission ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Sharp Drop ◽  
Large Program

The large majority of protoplanetary disks have very compact continuum emission (≲15 AU) at millimeter wavelengths. However, high angular resolution observations that resolve these small disks are still lacking, due to their intrinsically fainter emission compared with large bright disks. In this Letter we present 1.3 mm ALMA data of the faint disk (∼10 mJy) orbiting the TTauri star CX Tau at a resolution of ∼40 mas, ∼5 AU in diameter. The millimeter dust disk is compact, with a 68% enclosing flux radius of 14 AU, and the intensity profile exhibits a sharp drop between 10 and 20 AU, and a shallow tail between 20 and 40 AU. No clear signatures of substructure in the dust continuum are observed, down to the same sensitivity level of the DSHARP large program. However, the angular resolution does not allow us to detect substructures on the scale of the disk aspect ratio in the inner regions. The radial intensity profile closely resembles the inner regions of more extended disks imaged at the same resolution in DSHARP, but with no rings present in the outer disk. No inner cavity is detected, even though the disk has been classified as a transition disk from the spectral energy distribution in the near-infrared. The emission of 12CO is much more extended, with a 68% enclosing flux radius of 75 AU. The large difference of the millimeter dust and gas extents (> 5) strongly points to radial drift, and closely matches the predictions of theoretical models.

scholarly journals High Angular Resolution Stokes V Spectra in Penumbrae

1993 ◽  
Vol 141 ◽  
pp. 192-195
Author(s):  
J. Sánchez Almeida ◽  
V. Martínez Pillet ◽  
J. Trujillo Bueno ◽  
B.W. Lites
Keyword(s):  
Angular Resolution ◽  
Small Scale ◽  
High Angular Resolution ◽  
Quiet Sun ◽  
Continuum Intensity

AbstractStokes I and V profiles of Fel 630.1 nm and Fel 630.2 nm observed in a sunspot with an angular resolution ≥0.5” are analyzed. We find asymmetric V-profiles whose shapes are in agreement with previous determinations having lower angular resolution (~5”). We also find a correlation between penumbral small scale variations of continuum intensity and velocity. Although it involves smaller velocities, such correlation resembles that existing in the quiet sun as a consequence of convection.

scholarly journals Fragmentation of a Protostellar Core: The Case of CB 230

2001 ◽  
Vol 200 ◽  
pp. 117-121 ◽  
Author(s):  
Ralf Launhardt
Keyword(s):  
Main Sequence ◽  
Angular Resolution ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Mass Star ◽  
Star Forming ◽  
Binary Separation ◽  
Molecular Outflow ◽  
Low Mass ◽  
Core Fragmentation

The Bok globule CB230 (L1177) contains an active, low-mass star-forming core which is associated with a double NIR reflection nebula, a collimated bipolar molecular outflow, and strong mm continuum emission. The morphology of the NIR nebula suggests the presence of a deeply embedded, wide binary protostellar system. High-angular resolution observations now reveal the presence of two sub-cores, two distinct outflow centers, and an embedded accretion disk associated with the western bipolar NIR nebula. Judging from the separation and specific angular momentum, the CB230 double protostar system probably results from core fragmentation and will end up at the upper end of the pre-main sequence binary separation distribution.

scholarly journals Characterizing young protostellar disks with the CALYPSO IRAM-PdBI survey: large Class 0 disks are rare

2019 ◽  
Vol 621 ◽  
pp. A76 ◽  
Author(s):  
A. J. Maury ◽  
Ph. André ◽  
L. Testi ◽  
S. Maret ◽  
A. Belloche ◽  
...  
Keyword(s):  
Size Distribution ◽  
Protoplanetary Disks ◽  
Continuum Emission ◽  
Formation Mechanisms ◽  
Multiple Systems ◽  
Protostellar Disks ◽  
Disk Size ◽  
Small Scales ◽  
Prestellar Cores ◽  
Protostellar Collapse

Context. Understanding the formation mechanisms of protoplanetary disks and multiple systems and also their pristine properties are key questions for modern astrophysics. The properties of the youngest disks, embedded in rotating infalling protostellar envelopes, have largely remained unconstrained up to now. Aims. We aim to observe the youngest protostars with a spatial resolution that is high enough to resolve and characterize the progenitors of protoplanetary disks. This can only be achieved using submillimeter and millimeter interferometric facilities. In the framework of the IRAM Plateau de Bure Interferometer survey CALYPSO, we have obtained subarcsecond observations of the dust continuum emission at 231 and 94 GHz for a sample of 16 solar-type Class 0 protostars. Methods. In an attempt to identify disk-like structures embedded at small scales in the protostellar envelopes, we modeled the dust continuum emission visibility profiles using Plummer-like envelope models and envelope models that include additional Gaussian disk-like components. Results. Our analysis shows that in the CALYPSO sample, 11 of the 16 Class 0 protostars are better reproduced by models including a disk-like dust continuum component contributing to the flux at small scales, but less than 25% of these candidate protostellar disks are resolved at radii >60 au. Including all available literature constraints on Class 0 disks at subarcsecond scales, we show that our results are representative: most (>72% in a sample of 26 protostars) Class 0 protostellar disks are small and emerge only at radii <60 au. We find a multiplicity fraction of the CALYPSO protostars ≲57% ± 10% at the scales 100–5000 au, which generally agrees with the multiplicity properties of Class I protostars at similar scales. Conclusions. We compare our observational constraints on the disk size distribution in Class 0 protostars to the typical disk properties from protostellar formation models. If Class 0 protostars contain similar rotational energy as is currently estimated for prestellar cores, then hydrodynamical models of protostellar collapse systematically predict a high occurrence of large disks. Our observations suggest that these are rarely observed, however. Because they reduce the centrifugal radius and produce a disk size distribution that peaks at radii <100 au during the main accretion phase, magnetized models of rotating protostellar collapse are favored by our observations.

scholarly journals Large Radio Telescopes for Anomalous Microwave Emission Observations

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
E. S. Battistelli ◽  
E. Carretti ◽  
P. de Bernardis ◽  
S. Masi
Keyword(s):  
Angular Resolution ◽  
Signal To Noise Ratio ◽  
Dust Emission ◽  
Merit Function ◽  
Microwave Emission ◽  
High Angular Resolution ◽  
Merit Functions ◽  
Current State ◽  
The World ◽  
Continuum Observation

We discuss in this paper the problem of the Anomalous Microwave Emission (AME) in the light of ongoing or future observations to be performed with the largest fully steerable radio telescope in the world. High angular resolution observations of the AME will enable astronomers to drastically improve the knowledge of the AME mechanisms as well as the interplay between the different constituents of the interstellar medium in our galaxy. Extragalactic observations of the AME have started as well, and high resolution is even more important in this kind of observations. When cross-correlating with IR-dust emission, high angular resolution is also of fundamental importance in order to obtain unbiased results. The choice of the observational frequency is also of key importance in continuum observation. We calculate a merit function that accounts for the signal-to-noise ratio (SNR) in AME observation given the current state-of-the-art knowledge and technology. We also include in our merit functions the frequency dependence in the case of multifrequency observations. We briefly mention and compare the performance of four of the largest radiotelescopes in the world and hope the observational programs in each of them will be as intense as possible.

scholarly journals Probing the initial conditions of high-mass star formation

2019 ◽  
Vol 627 ◽  
pp. A85 ◽  
Author(s):  
Chuan-Peng Zhang ◽  
Timea Csengeri ◽  
Friedrich Wyrowski ◽  
Guang-Xing Li ◽  
Thushara Pillai ◽  
...  
Keyword(s):  
Star Formation ◽  
Multiple Scales ◽  
Initial Conditions ◽  
Dust Emission ◽  
Radio Continuum ◽  
High Mass ◽  
Small Scale ◽  
High Angular Resolution ◽  
H Ii Regions ◽  
Mass Star

Context. Fragmentation and feedback are two important processes during the early phases of star formation. Aims. Massive clumps tend to fragment into clusters of cores and condensations, some of which form high-mass stars. In this work, we study the structure of massive clumps at different scales, analyze the fragmentation process, and investigate the possibility that star formation is triggered by nearby H ii regions. Methods. We present a high angular resolution study of a sample of massive proto-cluster clumps G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71. Combining infrared data at 4.5, 8.0, 24, and 70 μm, we use a few arcsecond resolution, radiometer and millimeter inteferometric data taken at 1.3 cm, 3.5 mm, 1.3 mm, and 870 μm to study their fragmentation and evolution. Our sample is unique in the sense that all the clumps have neighboring H ii regions. Taking advantage of that, we tested triggered star formation using a novel method where we study the alignment of the center of mass traced by dust emission at multiple scales. Results. The eight massive clumps, identified based on single-dish observations, have masses ranging from 228 to 2279 M⊙ within an effective radius of Reff ~ 0.5 pc. We detect compact structures towards six out of the eight clumps. The brightest compact structures within infrared bright clumps are typically associated with embedded compact radio continuum sources. The smaller scale structures of Reff ~ 0.02 pc observed within each clump are mostly gravitationally bound and massive enough to form at least a B3-B0 type star. Many condensations have masses larger than 8 M⊙ at a small scale of Reff ~ 0.02 pc. We find that the two infrared quiet clumps with the lowest mass and lowest surface density with <300 M⊙ do not host any compact sources, calling into question their ability to form high-mass stars. Although the clumps are mostly infrared quiet, the dynamical movements are active at clump scale (~1 pc). Conclusions. We studied the spatial distribution of the gas conditions detected at different scales. For some sources we find hints of external triggering, whereas for others we find no significant pattern that indicates triggering is dynamically unimportant. This probably indicates that the different clumps go through different evolutionary paths. In this respect, studies with larger samples are highly desired.

scholarly journals Small-scale physical and chemical structure of diffuse and translucent molecular clouds along the line of sight to Sgr B2

2019 ◽  
Vol 623 ◽  
pp. A68 ◽  
Author(s):  
V. Thiel ◽  
A. Belloche ◽  
K. M. Menten ◽  
A. Giannetti ◽  
H. Wiesemeyer ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Velocity Structure ◽  
Angular Resolution ◽  
Principal Component ◽  
High Sensitivity ◽  
Field Of View ◽  
Continuum Emission ◽  
Line Of Sight ◽  
Small Scale ◽  
Galactic Centre

Context. The diffuse and translucent molecular clouds traced in absorption along the line of sight to strong background sources have so far been investigated mainly in the spectral domain because of limited angular resolution or small sizes of the background sources. Aims. We aim to resolve and investigate the spatial structure of molecular clouds traced by several molecules detected in absorption along the line of sight to Sgr B2(N). Methods. We have used spectral line data from the EMoCA survey performed with the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of its high sensitivity and angular resolution. The velocity structure across the field of view is investigated by automatically fitting synthetic spectra to the detected absorption features, which allows us to decompose them into individual clouds located in the Galactic centre (GC) region and in spiral arms along the line of sight. We compute opacity maps for all detected molecules. We investigated the spatial and kinematical structure of the individual clouds with statistical methods and perform a principal component analysis to search for correlations between the detected molecules. To investigate the nature of the molecular clouds along the line of sight to Sgr B2, we also used archival Mopra data. Results. We identify, on the basis of c-C3H2, 15 main velocity components along the line of sight to Sgr B2(N) and several components associated with the envelope of Sgr B2 itself. The c-C3H2 column densities reveal two categories of clouds. Clouds in Category I (3 kpc arm, 4 kpc arm, and some GC clouds) have smaller c-C3H2 column densities, smaller linewidths, and smaller widths of their column density PDFs than clouds in Category II (Scutum arm, Sgr arm, and other GC clouds). We derive opacity maps for the following molecules: c-C3H2, H13CO+, 13CO, HNC and its isotopologue HN13C, HC15N, CS and its isotopologues C34S and 13CS, SiO, SO, and CH3OH. These maps reveal that most molecules trace relatively homogeneous structures that are more extended than the field of view defined by the background continuum emission (about 15′′, that is 0.08–0.6 pc depending on the distance). SO and SiO show more complex structures with smaller clumps of size ~5–8′′. Our analysis suggests that the driving of the turbulence is mainly solenoidal in the investigated clouds. Conclusions. On the basis of HCO+, we conclude that most line-of-sight clouds towards Sgr B2 are translucent, including all clouds where complex organic molecules were recently detected. We also conclude that CCH and CH are good probes of H2 in both diffuse and translucent clouds, while HCO+ and c-C3H2 in translucent clouds depart from the correlations with H2 found in diffuse clouds.

scholarly journals First Results from ATCA at Millimetre Wavelengths

2004 ◽  
Vol 221 ◽  
pp. 275-282
Author(s):  
Vincent Minier
Keyword(s):  
Star Formation ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Dust Emission ◽  
Protoplanetary Disks ◽  
High Angular Resolution ◽  
Star Forming ◽  
Star Forming Regions ◽  
First Results ◽  
Excellent Tool

The newly upgraded Australia Telescope Compact Array (ATCA) at millimetre wavelengths is the first millimetre interferometer to be built in the Southern Hemisphere. The full array will be operational in 2004-2005 and will provide arcsec angular resolution at 3 mm and 12 mm. This will be a unique instrument to study at high angular resolution the interstellar chemistry and more generally the star formation process, especially in the bulk of the galactic plane and in the Magellanic Clouds. The upgraded ATCA will also be an excellent tool to detect dust emission from nearby protoplanetary disks. In this paper I will present the first results from the upgraded ATCA at 3 mm and 12 mm. The result review will cover the topics of massive star formation and hot molecular cores dust emission from star-forming regions and detection of protoplanetary disks.

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