YOUNG STELLAR OBJECTS IN THE MASSIVE STAR-FORMING REGION W49

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.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307013324 ◽

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⊙.

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Young Stellar Objects in the Massive Star-forming Regions W51 and W43

The Astrophysical Journal ◽

10.3847/1538-4357/aa6575 ◽

2017 ◽

Vol 839 (2) ◽

pp. 108 ◽

Cited By ~ 15

Author(s):

G. Saral ◽

J. L. Hora ◽

M. Audard ◽

X. P. Koenig ◽

J. R. Martínez-Galarza ◽

...

Keyword(s):

Massive Star ◽

Young Stellar Objects ◽

Stellar Objects ◽

Star Forming ◽

Star Forming Regions

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Distance and Maser Outflows of the Galactic Star-forming Region W51 Main/South

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312007454 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 423-424 ◽

Cited By ~ 1

Author(s):

Mayumi Sato ◽

Mark J. Reid ◽

Andreas Brunthaler ◽

Karl M. Menten

Keyword(s):

Massive Star ◽

Young Stellar Objects ◽

Small Range ◽

Stellar Objects ◽

Maser Emission ◽

Star Forming ◽

Star Forming Regions ◽

Long Baseline ◽

Trigonometric Parallax ◽

Very Long Baseline Array

AbstractWe report on high-resolution astrometry of 22 GHz H2O maser emission in the Galactic massive star-forming region W51 Main/South using the Very Long Baseline Array. We measured the trigonometric parallax of W51 Main/South to be 0.185 ± 0.010 mas, corresponding to a distance of 5.41+0.31−0.28 kpc. The H2O maser emission in W51 Main/South traces four powerful bipolar outflows within a 0.4 pc size region, three of which are associated with dusty molecular hot cores and/or hyper- or ultra-compact Hii regions. The maser outflows in W51 Main/South have a relatively small range of internal 3D speeds, suggesting that multiple speed maser outflows in other Galactic massive star-forming regions may come from separate young stellar objects closely spaced on the sky.

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ERRATUM: “YOUNG STELLAR OBJECTS IN THE MASSIVE STAR FORMING REGION W49” (2015, ApJ, 813, 25)

The Astrophysical Journal ◽

10.3847/0004-637x/816/1/47 ◽

2015 ◽

Vol 816 (1) ◽

pp. 47 ◽

Cited By ~ 1

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

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Photometric and spectroscopic studies of very low mass YSOs and young Brown Dwarfs in S106

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307002451 ◽

2006 ◽

Vol 2 (S237) ◽

pp. 457-457

Author(s):

Yumiko Oasa

Keyword(s):

Massive Star ◽

Near Infrared ◽

Brown Dwarfs ◽

Spectroscopic Studies ◽

Young Stellar Objects ◽

Stellar Objects ◽

Hii Region ◽

Star Forming ◽

Star Forming Regions ◽

Low Mass

Young brown dwarfs have been identified in a significant population in various star forming regions. Some deep surveys have yielded less massive objects with planetary-mass (e.g., Oasa et al. 1999; Lucas & Roche 2000). Nevertheless, it is not yet clear how abundant these very low-mass objects are formed. S106 is one of the nearest massive star-forming regions associated with prominent bipolar nebulae and an HII region. We have conducted near-infrared photometric and spectroscopic observations of very low-mass young stellar objects (YSOs) in the S106 region.

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Hα emission-line stars in molecular clouds

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731578 ◽

2019 ◽

Vol 630 ◽

pp. A90 ◽

Cited By ~ 2

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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Variability of young stellar objects in the star-forming region Pelican Nebula

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935418 ◽

2019 ◽

Vol 627 ◽

pp. A135 ◽

Cited By ~ 3

Author(s):

A. Bhardwaj ◽

N. Panwar ◽

G. J. Herczeg ◽

W. P. Chen ◽

H. P. Singh

Keyword(s):

Main Sequence ◽

T Tauri Stars ◽

Young Stellar Objects ◽

Spectral Energy ◽

Physical Parameters ◽

Main Sequence Stars ◽

Stellar Objects ◽

Star Forming ◽

T Tauri ◽

Optical Wavelengths

Context. Pre-main-sequence variability characteristics can be used to probe the physical processes leading to the formation and initial evolution of both stars and planets. Aims. The photometric variability of pre-main-sequence stars is studied at optical wavelengths to explore star–disk interactions, accretion, spots, and other physical mechanisms associated with young stellar objects. Methods. We observed a field of 16′ × 16′ in the star-forming region Pelican Nebula (IC 5070) at BVRI wavelengths for 90 nights spread over one year in 2012−2013. More than 250 epochs in the VRI bands are used to identify and classify variables up to V ∼ 21 mag. Their physical association with the cluster IC 5070 is established based on the parallaxes and proper motions from the Gaia second data release (DR2). Multiwavelength photometric data are used to estimate physical parameters based on the isochrone fitting and spectral energy distributions. Results. We present a catalog of optical time-series photometry with periods, mean magnitudes, and classifications for 95 variable stars including 67 pre-main-sequence variables towards star-forming region IC 5070. The pre-main-sequence variables are further classified as candidate classical T Tauri and weak-line T Tauri stars based on their light curve variations and the locations on the color-color and color-magnitude diagrams using optical and infrared data together with Gaia DR2 astrometry. Classical T Tauri stars display variability amplitudes up to three times the maximum fluctuation in disk-free weak-line T Tauri stars, which show strong periodic variations. Short-term variability is missed in our photometry within single nights. Several classical T Tauri stars display long-lasting (≥10 days) single or multiple fading and brightening events of up to two magnitudes at optical wavelengths. The typical mass and age of the pre-main-sequence variables from the isochrone fitting and spectral energy distributions are estimated to be ≤1 M⊙ and ∼2 Myr, respectively. We do not find any correlation between the optical amplitudes or periods with the physical parameters (mass and age) of pre-main-sequence stars. Conclusions. The low-mass pre-main-sequence stars in the Pelican Nebula region display distinct variability and color trends and nearly 30% of the variables exhibit strong periodic signatures attributed to cold spot modulations. In the case of accretion bursts and extinction events, the average amplitudes are larger than one magnitude at optical wavelengths. These optical magnitude fluctuations are stable on a timescale of one year.

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Far-IR Spectrophotometry of HH Flows with the ISO Long-Wavelength Spectrometer

Symposium - International Astronomical Union ◽

10.1017/s0074180900061593 ◽

1997 ◽

Vol 182 ◽

pp. 111-120

Author(s):

R. Liseau ◽

T. Giannini ◽

B. Nisini ◽

P. Saraceno ◽

L. Spinoglio ◽

...

Keyword(s):

Mass Loss ◽

Line Emission ◽

Young Stellar Objects ◽

Stellar Objects ◽

Star Forming ◽

Star Forming Regions ◽

Shock Models ◽

Ir Spectrophotometry ◽

Hh Objects ◽

Loss Rates

Full Iso-Lws spectral scans between about 45 to 190 μm of 17 individual HH objects in 7 star forming regions have revealed essentially only [O I] 63 μm line emission, implying that the Fircooling of these objects is totally dominated by this line alone. In this case, J-shock models can be used to determine the mass loss rates of the HH exciting sources. These mass loss rates are in reasonably good agreement with those estimated for the accompanying CO flows, providing first observational evidence that HH and molecular flows are driven by the same agent. The Lmech – Lbol relation, based on our results with the Lws, implies that young stellar objects of lower mass are loosing mass at relatively higher rates than their more massive counterparts.

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Identification of Young Stellar Object candidates in the Gaia DR2 x AllWISE catalogue with machine learning methods

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1301 ◽

2019 ◽

Vol 487 (2) ◽

pp. 2522-2537 ◽

Cited By ~ 12

Author(s):

G Marton ◽

P Ábrahám ◽

E Szegedi-Elek ◽

J Varga ◽

M Kun ◽

...

Keyword(s):

Machine Learning ◽

3D Structure ◽

Physical Nature ◽

Machine Learning Techniques ◽

Young Stellar Objects ◽

Support Vector ◽

Wide Field ◽

Stellar Objects ◽

Star Forming ◽

Gaia Dr2

ABSTRACT The second Gaia Data Release (DR2) contains astrometric and photometric data for more than 1.6 billion objects with mean Gaia G magnitude <20.7, including many Young Stellar Objects (YSOs) in different evolutionary stages. In order to explore the YSO population of the Milky Way, we combined the Gaia DR2 data base with Wide-field Infrared Survey Explorer (WISE) and Planck measurements and made an all-sky probabilistic catalogue of YSOs using machine learning techniques, such as Support Vector Machines, Random Forests, or Neural Networks. Our input catalogue contains 103 million objects from the DR2xAllWISE cross-match table. We classified each object into four main classes: YSOs, extragalactic objects, main-sequence stars, and evolved stars. At a 90 per cent probability threshold, we identified 1 129 295 YSO candidates. To demonstrate the quality and potential of our YSO catalogue, here we present two applications of it. (1) We explore the 3D structure of the Orion A star-forming complex and show that the spatial distribution of the YSOs classified by our procedure is in agreement with recent results from the literature. (2) We use our catalogue to classify published Gaia Science Alerts. As Gaia measures the sources at multiple epochs, it can efficiently discover transient events, including sudden brightness changes of YSOs caused by dynamic processes of their circumstellar disc. However, in many cases the physical nature of the published alert sources are not known. A cross-check with our new catalogue shows that about 30 per cent more of the published Gaia alerts can most likely be attributed to YSO activity. The catalogue can be also useful to identify YSOs among future Gaia alerts.

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