Optical images of star-formation regions

1986 ◽  
Vol 64 (4) ◽  
pp. 387-391
Author(s):  
Bel Campbell ◽  
S. E. Persson
Keyword(s):  
Optical Imaging ◽  
Near Infrared ◽  
Scattered Light ◽  
Position Angle ◽  
Small Sample ◽  
Young Stellar Objects ◽  
Image Size ◽  
Radio Image ◽  
Stellar Objects ◽  
Molecular Outflow

New and sensitive optical imaging of a small sample of young stellar objects is presented. The observations are part of a continuing program of deep, red optical imaging of star-forming regions performed with the 4Shooter charge-coupled-device (CCD) system on the Palomar 5-m telescope. Each of the sources presented is of moderately high luminosity [Formula: see text] and is associated with a bipolar outflow of molecular gas. The results on the source GL490 are discussed in some detail. We find the source core to be well resolved and elongated orthogonal to the outflow direction despite an unresolved image size (< 0.3″) in the near infrared; in addition, there is an extended (> 0.8 pc) cone of diffuse emission out from the core source in the direction of the blue-shifted portion of the molecular outflow. From astrometry of the CCD frame, we find that the center of the optical position is displaced from the radio-image centroid by approximately 1.5″ to the southwest, also in the direction of the blue-shifted outflow. It is proposed that the optical image is totally due to scattered light from a source that is entirely obscured from direct view. Owing to inconsistencies in the orientations of the radio image and polarization position angle with the other source orientations, we conclude that a simple disk plus an orthogonal-outflow scenario is no longer supportable for this object and that continued observations may reveal many equally complex cases.

scholarly journals Short- and long-term near-infrared spectroscopic variability of eruptive protostars from VVV

2019 ◽  
Vol 492 (1) ◽  
pp. 294-314 ◽  
Author(s):  
Zhen Guo (郭震) ◽  
P W Lucas ◽  
C Contreras Peña ◽  
R G Kurtev ◽  
L C Smith ◽  
...  
Keyword(s):  
Time Scales ◽  
Near Infrared ◽  
Accretion Rate ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Molecular Outflow ◽  
Infrared Spectroscopic ◽  
Long Time ◽  
The One ◽  
H2 Flux

ABSTRACT Numerous eruptive variable young stellar objects (YSOs), mostly Class I systems, were recently detected by the near-infrared Vista Variables in the Via Lactea (VVV) survey. We present an exploratory near-infrared spectroscopic variability study of 14 eruptive YSOs. The variations were sampled over one-day and one-to-two-year intervals and analysed in combination with VVV light curves. CO overtone absorption features are observed on three objects with FUor-like spectra: all show deeper absorption when they are brighter. This implies stronger emission from the circumstellar disc with a steeper vertical temperature gradient when the accretion rate is higher. This confirms the nature of fast VVV FUor-like events, in line with the accepted picture for classical FUors. The absence of Brγ emission in a FUor-like object declining to pre-outburst brightness suggests that reconstruction of the stellar magnetic field is a slow process. Within the one-day time-scale, 60 per cent of H2-emitting YSOs show significant but modest variation, and 2/6 sources have large variations in Brγ. Over year-long time-scales, H2 flux variations remain modest despite up to 1.8 mag variation in Ks. This indicates that emission from the molecular outflow usually arises further from the protostar and is unaffected by relatively large changes in accretion rate on year-long time-scales. Two objects show signs of on/off magnetospheric accretion traced by Brγ emission. In addition, a 60 per cent inter-night brightening of the H2 outflow is detected in one YSO.

scholarly journals Parsec-scale jets driven by high-mass young stellar objects

2018 ◽  
Vol 616 ◽  
pp. A126 ◽  
Author(s):  
R. Fedriani ◽  
A. Caratti o Garatti ◽  
D. Coffey ◽  
R. Garcia Lopez ◽  
S. Kraus ◽  
...  
Keyword(s):  
Mass Loss ◽  
Near Infrared ◽  
Dynamic Properties ◽  
Mass Loss Rate ◽  
Position Angle ◽  
Young Star ◽  
Young Stellar Objects ◽  
High Mass ◽  
Stellar Objects ◽  
Protostellar Jets

Context. Protostellar jets in high-mass young stellar objects (HMYSOs) play a key role in the understanding of star formation and provide us with an excellent tool to study fundamental properties of HMYSOs. Aims. We aim at studying the physical and kinematic properties of the near-infrared (NIR) jet of IRAS 13481-6124 from au to parsec scales. Methods. Our study includes NIR data from the Very Large Telescope instruments SINFONI, CRIRES, and ISAAC. Information about the source and its immediate environment is retrieved with SINFONI. The technique of spectro-astrometry is performed with CRIRES to study the jet on au scales. The parsec-scale jet and its kinematic and dynamic properties are investigated using ISAAC. Results. The SINFONI spectra in H and K bands are rich in emission lines that are mainly associated with ejection and accretion processes. Spectro-astrometry is applied to the Brγ line, and for the first time, to the Brα line, revealing their jet origin with milliarcsecond-scale photocentre displacements (11−15 au). This allows us to constrain the kinematics of the au-scale jet and to derive its position angle (~216°). ISAAC spectroscopy reveals H2 emission along the parsec-scale jet, which allows us to infer kinematic and dynamic properties of the NIR parsec-scale jet. The mass-loss rate inferred for the NIR jet is Ṁejec ~ 10−4 M⊙ yr−1 and the thrust is Ṗ ~ 10−2 M⊙ yr−1 km s−1, which is roughly constant for the formation history of the young star. A tentative estimate of the ionisation fraction is derived for the massive jet by comparing the radio and NIR mass-loss rates. An ionisation fraction ≲8% is obtained, which means that the bulk of the ejecta is traced by the NIR jet and that the radio jet only delineates a small portion of it.

scholarly journals The GRAVITY young stellar object survey

2020 ◽  
Vol 635 ◽  
pp. L12 ◽  
Author(s):  
◽  
A. Caratti o Garatti ◽  
R. Fedriani ◽  
R. Garcia Lopez ◽  
M. Koutoulaki ◽  
...  
Keyword(s):  
Near Infrared ◽  
Major Axis ◽  
Position Angle ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Stellar Objects ◽  
Axis Position ◽  
The Continuum ◽  
Gaseous Disc

Context. The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. Aims. We deploy near-infrared spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3–2.4 μm). Methods. We present the first GRAVITY/VLTI observations at high spectral (ℛ = 4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS 2. Results. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases (≤8°). Our best ellipsoid model provides a disc inclination of 34° ±1°, a disc major axis position angle (PA) of 166° ± 1°, and a disc diameter of 3.99 ± 0.09 mas (or 1.69  ±  0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74±0.070.08 mas (1.16  ±  0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and PA matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of M* ∼ 14.7−3.6+2 M⊙ by combining our interferometric and spectral modelling results.

A Near-Infrared Search for Companions around Very Low Luminosity Young Stellar Objects in Taurus

1999 ◽  
Vol 117 (3) ◽  
pp. 1471-1484 ◽  
Author(s):  
Yoichi Itoh ◽  
Motohide Tamura ◽  
Tadashi Nakajima
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
Stellar Objects

scholarly journals Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

2021 ◽  
Vol 503 (1) ◽  
pp. 270-291
Author(s):  
F Navarete ◽  
A Damineli ◽  
J E Steiner ◽  
R D Blum
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Rotation Axis ◽  
Principal Component ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Rotating Disc ◽  
Stellar Objects ◽  
K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

First Near-infrared Imaging Polarimetry of Young Stellar Objects in the Circinus Molecular Cloud

2018 ◽  
Vol 234 (2) ◽  
pp. 42 ◽  
Author(s):  
Jungmi Kwon ◽  
Takao Nakagawa ◽  
Motohide Tamura ◽  
James H. Hough ◽  
Minho Choi ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Young Stellar Objects ◽  
Near Infrared Imaging ◽  
Stellar Objects ◽  
Imaging Polarimetry

scholarly journals Preliminary observations of water masers associated with IRAS4A and IRAS4B

2002 ◽  
Vol 206 ◽  
pp. 63-67 ◽  
Author(s):  
Kevin B. Marvel ◽  
Mark Claussen ◽  
Alwyn Wootten
Keyword(s):  
Proper Motion ◽  
Position Angle ◽  
Young Stellar Objects ◽  
Linear Features ◽  
Stellar Objects ◽  
Star Forming ◽  
Water Masers

We present preliminary observations of water masers associated with IRAS4, a pair of young stellar objects in the NGC 1333 star forming region. The masers are quite strong and spatially distinct. Proper motion observations have been obtained from various epochs of observation typically separated by about three weeks. IRAS4A consists of two regions of maser activity separated by about 114 AU along a position angle of 138 degrees. Expansion of about 68 km/s is detected. IRAS4B consists of two linear emission regions separated by about 175 AU on a 150 degree position angle. The linear features are about 15 AU in length and about 2 AU thick. They are expanding away from each other at about 70 km/s.

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