scholarly journals High angular resolution observations of the gas phase composition of young stellar objects

1997 ◽  
Vol 178 ◽  
pp. 31-44 ◽  
Author(s):  
Geoffrey A. Blake
Keyword(s):  
Gas Phase ◽  
Angular Resolution ◽  
Young Stellar Objects ◽  
High Angular Resolution ◽  
Stellar Objects ◽  
Star Forming ◽  
Circumstellar Material ◽  
The Past ◽  
Cloud Cores

Recent advances in the observational characterization of young stellar objects (YSOs) with millimeter-wave aperture synthesis arrays and (sub)millimeter single dish telescopes are reviewed. Studies of circumstellar material with ∼arc second resolution, which have only become possible at these frequencies within the past few years and which can potentially probe all stages of the star formation process, are emphasized. Molecules that are sensitive to different routes of formation and modification are outlined, including comments about their utility in distinguishing between a variety of environments and histories in star-forming cloud cores.

scholarly journals High Angular Resolution Observations of Protostellar Disks

1994 ◽  
Vol 158 ◽  
pp. 387-390
Author(s):  
J.-L. Monin ◽  
J. Bouvier ◽  
F. Malbet
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Circumstellar Disks ◽  
Physical Structure ◽  
Young Stellar Objects ◽  
High Angular Resolution ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri ◽  
Chromatic Properties

The existence of circumstellar disks around young stellar objects like T Tauri stars is now well accepted. Such disks would have solar system sizes and, at the distance of the nearest star forming cloud, an angular diameter of 0.01 to 1 arcsecond at most, requiring very high angular resolution to be detected. Due to the nature of the emission process in circumstellar disks and to chromatic properties of ground based observations, disk imaging is expected to be more efficient in the near infrared. Also, multi-aperture interferometry in this wavelength range (1 – 10 μm) is expected to bring considerable insight into the disks properties and evolution in revealing their inner physical structure.In this paper, we present synthetic images of circumstellar accretion disks. The images have been computed from a complete disk vertical structure model.

scholarly journals High Angular Resolution Observations of Maser Kinematics Near Low Mass Young Stellar Objects

2001 ◽  
Vol 205 ◽  
pp. 256-257
Author(s):  
Kevin B. Marvel ◽  
Mark Claussen ◽  
H. Alwyn Wootten ◽  
Bruce Wilking
Keyword(s):  
Angular Resolution ◽  
Surrounding Medium ◽  
Young Stellar Objects ◽  
High Angular Resolution ◽  
Stellar Objects ◽  
Star Forming ◽  
Low Mass ◽  
Water Masers ◽  
Driving Source ◽  
Water Maser

With the advent of new correlators and dedicated arrays, spectral line VLBI is entering its ascendancy as a probe of a variety of interesting astrophysical environments. One of the most interesting environments where spectroscopic VLBI techniques are valuable are the regions directly coincident with forming stars. In these sources, water maser emission is observed when the outflowing jets of material interact with the surrounding medium. Observations of these water masers dramatically reveal the innermost regions of the star formation process at or below the 1-AU scale.We have found that the water masers clearly trace the jets at these scales. The masers show space motions on the order of 60 to 100 kms−1 and form within a few AU of the exciting protostar. By observing the distributions and motions of the water masers associated with these objects, we may be able to address in greater detail the collimation mechanism of the jets seen in these protostars.In this brief poster proceeding, we provide a summary image of the water masers associated with SVS13, the driving source for the HH 7-11 objects. We have also mapped the masers associated with IRAS 16293-2422, IRAS 05413-0104, IRAS 4A and IRAS 4B, both in the NGC 1333 star forming region. For further information on these sources, please contact any of the authors directly.

scholarly journals Water masers and the near-stellar environment in YSOs

2002 ◽  
Vol 206 ◽  
pp. 27-34
Author(s):  
Mark J. Claussen
Keyword(s):  
Main Sequence ◽  
Very Long Baseline Interferometry ◽  
Angular Resolution ◽  
Young Stellar Objects ◽  
High Angular Resolution ◽  
High Luminosity ◽  
Stellar Objects ◽  
Long Baseline ◽  
Water Masers ◽  
Very High

I present a review of observations of water masers, in particular very high angular resolution of water masers using Very Long Baseline Interferometry, with which it is possible to probe the environment of young stellar objects and forming stars within only a few A.U. of the protostar, its accretion disk, and therefore the base of outflowing material. Although reference is made to some high-luminosity sources, the main thrust of the review are the water masers found toward forming objects whose mass and luminosity will be approximately that of the Sun when they reach the main sequence.

scholarly journals A 1.3 mm SMA survey of 29 variable young stellar objects

2018 ◽  
Vol 612 ◽  
pp. A54 ◽  
Author(s):  
Hauyu Baobab Liu ◽  
Michael M. Dunham ◽  
Ilaria Pascucci ◽  
Tyler L. Bourke ◽  
Naomi Hirano ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Accretion Rate ◽  
Dust Emission ◽  
Young Stellar Objects ◽  
Mass Star ◽  
Gas Reservoirs ◽  
Stellar Objects ◽  
Star Forming ◽  
Low Mass ◽  
One Year

Context. Young stellar objects (YSOs) may undergo periods of active accretion (outbursts), during which the protostellar accretion rate is temporarily enhanced by a few orders of magnitude. Whether or not these accretion outburst YSOs possess similar dust and gas reservoirs to each other, and whether or not their dust and gas reservoirs are similar as quiescent YSOs, are issues yet to be clarified. Aims. The aim of this work is to characterize the millimeter thermal dust emission properties of a statistically significant sample of long and short duration accretion outburst YSOs (i.e., FUors and EXors) and the spectroscopically identified candidates of accretion outbursting YSOs (i.e., FUor-like objects). Methods. We have carried out extensive Submillimeter Array (SMA) observations mostly at ~225 GHz (1.33 mm) and ~272 GHz (1.10 mm), from 2008 to 2017. We covered accretion outburst YSOs located at <1 kpc distances from the solar system. Results. We analyze all the existing SMA data of such objects, both published and unpublished, in a coherent way to present a millimeter interferometric database of 29 objects. We obtained 21 detections at >3σ significance. Detected sources except for the two cases of V883 Ori and NGC 2071 MM3 were observed with ~1″ angular resolution. Overall our observed targets show a systematically higher millimeter luminosity distribution than those of the M* > 0.3 M⊙ Class II YSOs in the nearby (≲400 pc) low-mass star-forming molecular clouds (e.g., Taurus, Lupus, Upp Scorpio, and Chameleon I). In addition, at 1 mm our observed confirmed binaries or triple-system sources are systematically fainter than the rest of the sources even though their 1 mm fluxes are broadly distributed. We may have detected ~30−60% millimeter flux variability from V2494 Cyg and V2495 Cyg, from the observations separated by approximately one year.

scholarly journals Dynamical processes in star forming regions: feedback and turbulence generation

2006 ◽  
Vol 2 (S237) ◽  
pp. 165-171
Author(s):  
John Bally
Keyword(s):  
Kinetic Energy ◽  
Massive Stars ◽  
Young Stellar Objects ◽  
Stellar Winds ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Cloud Cores ◽  
Turbulence Generation

AbstractYoung stellar objects (YSOs) inject large amounts of momentum and kinetic energy into their surroundings. Feedback from low mass YSOs is dominated by their outflows. However, as stellar mass increases, UV photo-heating and ionization play increasingly important roles. Massive stars produce powerful stellar winds and explode as supernovae within 3 – 40 Myr after birth. While low-mass protostellar feedback can drive turbulence in cloud cores and even disrupt the star forming environment, feedback from massive stars plays important roles in the generation of cloud structure and motions in the entire ISM.

scholarly journals High Angular Resolution and Young Stellar Objects: Imaging the Surroundings of MWC 158 by Optical Interferometry

2013 ◽  
Vol 59 ◽  
pp. 141-154
Author(s):  
J. Kluska ◽  
F. Malbet ◽  
J.-P. Berger ◽  
M. Benisty ◽  
B. Lazareff ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Optical Interferometry ◽  
Young Stellar Objects ◽  
High Angular Resolution ◽  
Stellar Objects

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

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