scholarly journals Early results from a diagnostic 1.3 cm survey of massive young protostars

2012 ◽  
Vol 8 (S287) ◽  
pp. 497-501
Author(s):  
Crystal L. Brogan ◽  
Todd R. Hunter ◽  
Claudia J. Cyganowski ◽  
Remy Indebetouw ◽  
Rachel Friesen ◽  
...  
Keyword(s):  
Massive Star ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Large Array ◽  
Stellar Objects ◽  
Very Large Array ◽  
Early Results ◽  
Wide Range ◽  
First Time ◽  
24 Ghz

AbstractWe have used the recently-upgraded Karl G. Jansky Very Large Array (JVLA) to conduct a K-band (~24 GHz) study of 22 massive young stellar objects in 1.3 cm continuum and a comprehensive set of diagnostic lines. This survey is unique in that it samples a wide range of massive star formation signposts simultaneously for the first time. In this proceeding we present preliminary results for the 11 sources in the 2-4 kpc distance bin. We detect compact NH3 cores in all of the fields, with many showing emission up through the (6,6) transition. Maser emission in the 25 GHz CH3OH ladder is present in 7 of 11 sources. We also detect non-thermal emission in the NH3 (3,3) transition in 7 of 11 sources.

scholarly journals Characterizing the radio continuum nature of sources in the massive star-forming region W75N (B)

2020 ◽  
Vol 496 (3) ◽  
pp. 3128-3141 ◽  
Author(s):  
A Rodríguez-Kamenetzky ◽  
C Carrasco-González ◽  
J M Torrelles ◽  
W H T Vlemmings ◽  
L F Rodríguez ◽  
...  
Keyword(s):  
Massive Star ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Very Large Array ◽  
Star Forming ◽  
Thermal Radio ◽  
Wide Range ◽  
H Ii Region ◽  
Continuum Data

ABSTRACT The massive star-forming region W75N (B) is thought to host a cluster of massive protostars (VLA 1, VLA 2, and VLA 3) undergoing different evolutionary stages. In this work, we present radio continuum data with the highest sensitivity and angular resolution obtained to date in this region, using the VLA-A and covering a wide range of frequencies (4–48 GHz), which allowed us to study the morphology and the nature of the emission of the different radio continuum sources. We also performed complementary studies with multi-epoch Very Large Array (VLA) data and Atacama Large Millimeter Array (ALMA) archive data at 1.3 mm wavelength. We find that VLA 1 is driving a thermal radio jet at scales of ≈0.1 arcsec (≈130 au), but also shows signs of an incipient hypercompact H ii region at scales of ≲1 arcsec (≲1300 au). VLA 3 is also driving a thermal radio jet at scales of a few tenths of arcsec (few hundred of au). We conclude that this jet is shock exciting the radio continuum sources Bc and VLA 4 (obscured Herbig–Haro objects), which show proper motions moving outward from VLA 3 at velocities of ≈112–118 km s−1. We have also detected three new weak radio continuum sources, two of them associated with millimetre continuum cores observed with ALMA, suggesting that these two sources are also embedded young stellar objects in this massive star-forming region.

scholarly journals VLA Observations of Nine Extended Green Objects in the Milky Way: Ubiquitous Weak, Compact Continuum Emission, and Multi-epoch Emission from Methanol, Water, and Ammonia Masers

2021 ◽  
Vol 923 (2) ◽  
pp. 263
Author(s):  
A. P. M. Towner ◽  
C. L. Brogan ◽  
T. R. Hunter ◽  
C. J. Cyganowski
Keyword(s):  
Milky Way ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Large Array ◽  
Spectral Indices ◽  
Physical Processes ◽  
Stellar Objects ◽  
Maser Emission ◽  
Very Large Array

Abstract We have observed a sample of nine Extended Green Objects (EGOs) at 1.3 and 5 cm with the Very Large Array (VLA) with subarcsecond resolution and ∼7–14 μJy beam−1-sensitivities in order to characterize centimeter continuum emission as it first appears in these massive protoclusters. We find an EGO-associated continu um emission—within 1″ of the extended 4.5 μm emission—in every field, which is typically faint (order 101–102 μJy) and compact (unresolved at 0″.3–0″.5). The derived spectral indices of our 36 total detections are consistent with a wide array of physical processes, including both non-thermal (19% of detections) and thermal free–free processes (e.g., ionized jets and compact H ii regions, 78% of sample) and warm dust (1 source). We also find an EGO-associated 6.7 GHz CH3OH and 22 GHz H2O maser emission in 100% of the sample and a NH3 (3,3) masers in ∼45%; we do not detect any NH3 (6,6) masers at ∼5.6 mJy beam−1 sensitivity. We find statistically-significant correlations between L radio and L bol at two physical scales and three frequencies, consistent with thermal emission from ionized jets, but no correlation between L H 2 O and L radio for our sample. From these data, we conclude that EGOs likely host multiple different centimeter continuum-producing processes simultaneously. Additionally, at our ∼1000 au resolution, we find that all EGOs except G18.89−0.47 contain 1 ∼ 2 massive sources based on the presence of CH3OH maser groups, which is consistent with our previous work suggesting that these are typical massive protoclusters, in which only one to a few of the young stellar objects are massive.

Water Maser Survey toward Low‐Mass Young Stellar Objects in the Northern Sky with the Nobeyama 45 Meter Telescope and the Very Large Array

2003 ◽  
Vol 144 (1) ◽  
pp. 71-134 ◽  
Author(s):  
Ray S. Furuya ◽  
Yoshimi Kitamura ◽  
Alwyn Wootten ◽  
Mark J. Claussen ◽  
Ryohei Kawabe
Keyword(s):  
Young Stellar Objects ◽  
Large Array ◽  
Stellar Objects ◽  
Very Large Array ◽  
Low Mass ◽  
Water Maser

scholarly journals EXPLORING THE NATURE OF COMPACT RADIO SOURCES ASSOCIATED TO UCHII REGIONS

2021 ◽  
Vol 57 (1) ◽  
pp. 81-89
Author(s):  
J. M. Masqué ◽  
L. F. Rodríguez ◽  
S. A. Dzib ◽  
S. N. Medina ◽  
L. Loinard ◽  
...  
Keyword(s):  
Massive Star ◽  
Thermal Emission ◽  
Hii Regions ◽  
Radio Sources ◽  
Large Array ◽  
Gravitational Radius ◽  
Very Large Array ◽  
Thermal Sources

We present Very Large Array 7 mm continuum observations of four ultracompact (UC) HII regions, observed previously at 1.3 cm, in order to investigate the nature of the compact radio sources associated with these regions. We detect a total of seven compact radio sources, four of them with thermal emission, and two compact radio sources with clear non- thermal emission. The thermal emission is consistent with the presence of an ionized envelope, either static (i.e., trapped in the gravitational radius of an associated massive star) or flowing away (i.e., a photo-evaporative flow). The nature of the non-thermal sources remains unclear and several possibilities are proposed. The possibility that most of these compact radio sources are photo-evaporating objects, and the remaining ones more evolved objects, is consistent with previous studies on UCHII regions.

scholarly journals Resolving the MYSO binaries PDS 27 and PDS 37 with VLTI/PIONIER

2019 ◽  
Vol 623 ◽  
pp. L5 ◽  
Author(s):  
E. Koumpia ◽  
K. M. Ababakr ◽  
W. J. de Wit ◽  
R. D. Oudmaijer ◽  
A. Caratti o Garatti ◽  
...  
Keyword(s):  
Star Formation ◽  
Binary Systems ◽  
Massive Star ◽  
Young Stellar Objects ◽  
Velocity Analysis ◽  
Stellar Objects ◽  
Massive Binary Systems ◽  
First Time ◽  
Young Binary Systems ◽  
Very High

Context. Binarity and multiplicity appear to be a common outcome in star formation. In particular, the binary fraction of massive (OB-type) stars can be very high. In many cases, the further stellar evolution of these stars is affected by binary interactions at some stage during their lifetime. The origin of this high binarity and the binary parameters are poorly understood because observational constraints are scarce, which is predominantly due to a dearth of known young massive binary systems. Aims. We aim to identify and describe massive young binary systems in order to fill in the gaps of our knowledge of primordial binarity of massive stars, which is crucial for our understanding of massive star formation. Methods. We observed the two massive young stellar objects (MYSOs) PDS 27 and PDS 37 at the highest spatial resolution provided by VLTI/PIONIER in the H-band (1.3 mas). We applied geometrical models to fit the observed squared visibilities and closure phases. In addition, we performed a radial velocity analysis using published VLT/FORS2 spectropolarimetric and VLT/X-shooter spectroscopic observations. Results. Our findings suggest binary companions for both objects at 12 mas (30 au) for PDS 27 and at 22–28 mas (42–54 au) for PDS 37. This means that they are among the closest MYSO binaries resolved to date. Conclusions. Our data spatially resolve PDS 27 and PDS 37 for the first time, revealing two of the closest and most massive (>8 M⊙) YSO binary candidates to date. PDS 27 and PDS 37 are rare but great laboratories to quantitatively inform and test the theories on formation of such systems.

scholarly journals Molecular environs and triggered star formation around the large Galactic infrared bubble N 24

2019 ◽  
Vol 487 (2) ◽  
pp. 1517-1528 ◽  
Author(s):  
Xu Li ◽  
Jarken Esimbek ◽  
Jianjun Zhou ◽  
W A Baan ◽  
Weiguang Ji ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Young Stellar Objects ◽  
Collapse Mechanism ◽  
Kinetic Temperature ◽  
H Ii Regions ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Multi Wavelength ◽  
Mass Size

Abstract A multi-wavelength analysis of the large Galactic infrared bubble N 24 is presented in this paper in order to investigate the molecular and star-formation environment around expanding H ii regions. Using archival data from Herschel and ATLASGAL, the distribution and physical properties of the dust over the entire bubble are studied. Using the Clumpfind2d algorithm, 23 dense clumps are identified, with sizes and masses in the range 0.65–1.73 pc and 600–16 300 M⊙, respectively. To analyse the molecular environment in N 24, observations of NH3 (1,1) and (2,2) were carried out using the Nanshan 26-m radio telescope. Analysis of the kinetic temperature and gravitational stability of these clumps suggests gravitational collapse in several of them. The mass–size distributions of the clumps and the presence of massive young protostars indicate that the shell of N 24 is a region of ongoing massive-star formation. The compatibility of the dynamical and fragmentation timescales and the overabundance of young stellar objects and clumps on the rim suggest that the ‘collect-and-collapse’ mechanism is in play at the boundary of the bubble, but the existence of the infrared dark cloud at the edge of bubble indicates that a ‘radiation-driven implosion’ mechanism may also have played a role there.

scholarly journals YOUNG STELLAR OBJECTS IN THE MASSIVE STAR-FORMING REGION W49

2015 ◽  
Vol 813 (1) ◽  
pp. 25 ◽  
Author(s):  
G. Saral ◽  
J. L. Hora ◽  
S. E. Willis ◽  
X. P. Koenig ◽  
R. A. Gutermuth ◽  
...  
Keyword(s):  
Massive Star ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming

scholarly journals A collimated jet and an infalling-rotating disk in G192 traced by H2O maser emission

2007 ◽  
Vol 3 (S242) ◽  
pp. 340-341
Author(s):  
Hiroshi Imai ◽  
Toshihiro Omodaka ◽  
Tomoya Hirota ◽  
Tomofumi Umemoto ◽  
Kazuo Sorai ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Massive Star ◽  
Rotating Disk ◽  
Stellar Mass ◽  
Young Stellar Objects ◽  
Proper Motions ◽  
Stellar Objects ◽  
Maser Emission ◽  
Star Forming ◽  
Bulk Motion

AbstractWe present H2O masers associated with the massive-star forming region G192 observed with the Japan VLBI network since the year 2005, The spatio-kinematical structure of the maser feature clusters has well persisted since previous observations, in which the masers are associated with two young stellar objects (YSOs) separated by ~1200 AU and expected to be associated with a highly-collimated bipolar jet and an infalling-rotating disk in the northern and southern YSOs, respectively. We estimated a jet speed of ~100 km s−1 and re-estimated a dynamical age of the whole jet to be 5.6×104 years. The spatial distribution of maser Doppler velocities found during the previous and present observations, relative proper motions of H2O maser features in the southern cluster found in the present observations, a relative bulk motion between the two maser clusters are well explained by a model of an infalling-rotating disk with a radius of ~1000 AU and a central stellar mass of ~8 M⊙.

scholarly journals SK 1: A possible case of triggered star formation in perseus

2006 ◽  
Vol 2 (S237) ◽  
pp. 217-221
Author(s):  
Miriam Rengel ◽  
Klaus Hodapp ◽  
Jochen Eislöffel
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Wide Field ◽  
Dust Shell ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Suitable Target

AbstractAccording to a triggered star formation scenario (e.g. Martin-Pintado & Cernicharo 1987) outflows powered by young stellar objects shape the molecular clouds, can dig cavities, and trigger new star formation. NGC 1333 is an active site of low- and intermediate star formation in Perseus and is a suggested site of self-regulated star formation (Norman & Silk 1980). Therefore it is a suitable target for a study of triggered star formation (e.g. Sandell & Knee 2001, SK1). On the other hand, continuum sub-mm observations of star forming regions can detect dust thermal emission of embedded sources (which drive outflows), and further detailed structures.Within the framework of our wide-field mapping of star formation regions in the Perseus and Orion molecular clouds using SCUBA at 850 and 450 μm, we mapped NCG 1333 with an area of around 14′× 21′. The maps show more structure than the previous maps of the region observed in sub-mm. We have unveiled the known embedded SK 1 source (in the dust shell of the SSV 13 ridge) and detailed structure of the region, among some other young protostars.In agreement with the SK 1 observations, our map of the region shows lumpy filaments and shells/cavities that seem to be created by outflows. The measured mass of SK 1 (~0.07 M) is much less than its virial mass (~0.2-1 M). Our observations support the idea of SK 1 as an event triggered by outflow-driven shells in NGC 1333 (induced by an increase in gas pressure and density due to radiation pressure from the stellar winds that have presumably created the dust shell). This kind of evidences provides a more thorough understanding of the star formation regulation processes.

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