VLA ammonia observations of L1287

Aims. In this paper, we study the dense gas of the molecular cloud LDN 1287 (L1287), which harbors a double FU Ori system, an energetic molecular outflow, and a still-forming cluster of deeply embedded low-mass young stellar objects that show a high level of fragmentation. Methods. We present optical Hα and [SII], and VLA NH3 (1, 1) and (2, 2) observations with an angular resolution of ~3′′.5. The observed NH3 spectra have been analyzed with the Hyperfine Structure tool, fitting simultaneously three different velocity components. Results. The NH3 emission from L1287 comes from four different structures: a core associated with RNO 1, a guitar-shaped core (the Guitar) and two interlaced filaments (the blue and red filaments) roughly centered toward the binary FU Ori system RNO 1B/1C and its associated cluster. Regarding the Guitar core, there are clear signatures of gas infall onto a central mass that has been estimated to be ~2.1M⊙. Regarding the two filaments, they have radii of ~0.03 pc, masses per unit length of ~50M⊙ pc−1, and are in near isothermal equilibrium. A central cavity is identified, probably related with the outflow and also revealed by the Hα and [SII] emission, with several young stellar objects near its inner walls. Both filaments show clear signs of perturbation by the high-velocity gas of the outflows driven by one or several young stellar objects of the cluster. The blue and red filaments are coherent in velocity and have nearly subsonic gas motions, except at the position of the embedded sources. Velocity gradients across the blue filament can be interpreted either as infalling material onto the filament or rotation. Velocity gradients along the filaments are interpreted as infall motions toward a gravitational well at the intersection of the two filaments.

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Sequential star formation in the filamentary structures of the Planck Galactic cold clump G181.84+0.31

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1266 ◽

2019 ◽

Vol 487 (1) ◽

pp. 1315-1334 ◽

Cited By ~ 2

Author(s):

Lixia Yuan ◽

Ming Zhu ◽

Tie Liu ◽

Jinghua Yuan ◽

Yuefang Wu ◽

...

Keyword(s):

Star Formation ◽

Unit Length ◽

Line Emission ◽

Young Stellar Objects ◽

Wide Field ◽

Stellar Objects ◽

Filamentary Structure ◽

Dense Cores ◽

Velocity Gradients ◽

Sky Survey

Abstract We present a multiwavelength study of the Planck Galactic cold clump G181.84+0.31, which is located at the northern end of the extended filamentary structure S242. We have extracted nine compact dense cores from the SCUBA-2 850-$\hbox{$\mu $m}$ map, and we have identified 18 young stellar objects (YSOs; four Class I and 14 Class II) based on their Spitzer, Wide-field Infrared Survey Explorer(WISE) and Two-Micron All-Sky Survey (2MASS) near- and mid-infrared colours. The dense cores and YSOs are mainly distributed along the filamentary structures of G181.84 and are well traced by HCO+(1–0) and N2H+(1–0) spectral-line emission. We find signatures of sequential star formation activities in G181.84: dense cores and YSOs located in the northern and southern substructures are younger than those in the central region. We also detect global velocity gradients of about 0.8 ± 0.05 and 1.0 ± 0.05 km s−1 pc−1 along the northern and southern substructures, respectively, and local velocity gradients of 1.2 ± 0.1 km s−1 pc−1 in the central substructure. These results might be due to the fact that the global collapse of the extended filamentary structure S242 is driven by an edge effect, for which the filament edges collapse first and then further trigger star formation activities inward. We identify three substructures in G181.84 and estimate their critical masses per unit length, which are ∼101 ± 15, 56 ± 8 and 28 ± 4 M⊙ pc−1, respectively. These values are all lower than the observed values (∼200 M⊙ pc−1), suggesting that these substructures are gravitationally unstable.

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The Observational Evidence for Accretion

Symposium - International Astronomical Union ◽

10.1017/s0074180900061805 ◽

1997 ◽

Vol 182 ◽

pp. 391-405 ◽

Cited By ~ 2

Author(s):

Lee Hartmann

Keyword(s):

Large Range ◽

Observational Evidence ◽

Young Stars ◽

Young Stellar Objects ◽

Stellar Objects ◽

T Tauri ◽

Accretion Rates ◽

Low Mass ◽

Stellar Magnetospheres ◽

Mass Ejection

Outflows from low-mass young stellar objects are thought to draw upon the energy released by accretion onto T Tauri stars. I briefly summarize the evidence for this accretion and outline present estimates of mass accretion rates. Young stars show a very large range of accretion rates, and this has important implications for both mass ejection and for the structure of stellar magnetospheres which may truncate T Tauri disks.

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Erratum: “Water Maser Survey toward Low‐Mass Young Stellar Objects in the Northern Sky with the Nobeyama 45 Meter Telescope and the Very Large Array” (ApJS, 144, 71 [2003])

The Astrophysical Journal Supplement Series ◽

10.1086/516825 ◽

2007 ◽

Vol 171 (1) ◽

pp. 349-351 ◽

Cited By ~ 3

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

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Submillimeter CO Spectroscopy of Low Mass Young Stellar Objects

Circumstellar Matter 1994 ◽

10.1007/978-94-011-0147-9_22 ◽

1995 ◽

pp. 117-120

Author(s):

K. F. Schuster ◽

A. P. G. Russell ◽

A. I. Harris

Keyword(s):

Young Stellar Objects ◽

Stellar Objects ◽

Low Mass

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Physical Properties of Molecular Envelopes in Low-Mass Star-Forming Regions

Symposium - International Astronomical Union ◽

10.1017/s007418090016468x ◽

2000 ◽

Vol 197 ◽

pp. 61-70

Author(s):

Nagayoshi Ohashi

Keyword(s):

Physical Properties ◽

Young Stellar Objects ◽

Mass Star ◽

Narrow Line ◽

Stellar Objects ◽

Velocity Pattern ◽

Star Forming ◽

Star Forming Regions ◽

Low Mass ◽

Line Widths

We have carried out interferometric observations of pre-protostellar and protostellar envelopes in Taurus. Protostellar envelopes are dense gaseous condensations with young stellar objects or protostars, while pre-protostellar envelopes are those without any known young stellar objects. Five pre-protostellar envelopes have been observed in CCS JN=32–21, showing flattened and clumpy structures of the envelopes. The observed CCS spectra show moderately narrow line widths, ~0.1 to ~0.35 km s–1. One pre-protostellar envelope, L1544, shows a remarkable velocity pattern, which can be explained in terms of infall and rotation. Our C18O J=1–0 observations of 8 protostellar envelopes show that they have also flattened structures like pre-protostellar envelopes but no clumpy structures. Four out the eight envelopes show velocity patterns that can be explained by motions of infall (and rotation). Physical properties of pre-protostellar and protostellar envelopes are discussed in detail.

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Magnetic Fields and Disks in Star-forming Regions

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000025777 ◽

1993 ◽

Vol 10 (3) ◽

pp. 247-249 ◽

Cited By ~ 5

Author(s):

C.M. Wright ◽

D.K. Aitken ◽

C.H. Smith ◽

P.F. Roche

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Transverse Component ◽

Young Stellar Objects ◽

Stellar Objects ◽

Star Forming ◽

Star Forming Regions ◽

Molecular Outflow ◽

The Magnetic Field

AbstractThe star-formation process is an outstanding and largely unsolved problem in astrophysics. The role of magnetic fields is unclear but is widely considered to be important at all stages of protostellar evolution, from cloud collapse to ZAMS. For example, in some hydromagnetic models, the field may assist in removing angular momentum, thereby driving accretion and perhaps bipolar outflows.Spectropolarimetry between 8 and 13μm provides information on the direction of the transverse component of a magnetic field through the alignment of dust grains. We present results of 8–13μm spectropolarimetric observations of a number of bipolar molecular outflow sources, and compare the field directions observed with the axes of the outflows and putative disk-like structures observed to be associated with some of the objects. There is a strong correlation, though so far with limited statistics, between the magnetic field and disk orientations. We compare our results with magnetic field configurations predicted by current models for hydromagnetically driven winds from the disks around Young Stellar Objects (YSOs). Our results appear to argue against the Pudritz and Norman model and instead seem to support the Uchida and Shibata model.

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Observational signatures of outbursting protostars - I: From hydrodynamic simulations to observations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1512 ◽

2019 ◽

Vol 487 (4) ◽

pp. 5106-5117 ◽

Cited By ~ 3

Author(s):

Benjamin MacFarlane ◽

Dimitris Stamatellos ◽

Doug Johnstone ◽

Gregory Herczeg ◽

Giseon Baek ◽

...

Keyword(s):

Radiative Transfer ◽

Radiation Field ◽

Young Stellar Objects ◽

Stellar Objects ◽

Hydrodynamic Simulations ◽

Long Wavelength ◽

Fu Ori ◽

Flux Increase

Abstract Accretion onto protostars may occur in sharp bursts. Accretion bursts during the embedded phase of young protostars are probably most intense, but can only be inferred indirectly through long-wavelength observations. We perform radiative transfer calculations for young stellar objects (YSOs) formed in hydrodynamic simulations to predict the long wavelength, sub-mm and mm, flux responses to episodic accretion events, taking into account heating from the young protostar and from the interstellar radiation field. We find that the flux increase due to episodic accretion events is more prominent at sub-mm wavelengths than at mm wavelengths; e.g. a factor of ∼570 increase in the luminosity of the young protostar leads to a flux increase of a factor of 47 at 250 $\mu$m but only a factor of 10 at 1.3 mm. Heating from the interstellar radiation field may reduce further the flux increase observed at longer wavelengths. We find that during FU Ori-type outbursts the bolometric temperature and luminosity may incorrectly classify a source as a more evolved YSO due to a larger fraction of the radiation of the object being emitted at shorter wavelengths.

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Envelope Structure on 700 AU Scales and the Molecular Outflows of Low‐Mass Young Stellar Objects

The Astrophysical Journal ◽

10.1086/305885 ◽

1998 ◽

Vol 502 (1) ◽

pp. 315-336 ◽

Cited By ~ 142

Author(s):

Michiel R. Hogerheijde ◽

Ewine F. van Dishoeck ◽

Geoffrey A. Blake ◽

Huib Jan van Langevelde

Keyword(s):

Young Stellar Objects ◽

Stellar Objects ◽

Molecular Outflows ◽

Low Mass

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3374 ◽

2019 ◽

Vol 492 (1) ◽

pp. 294-314 ◽

Cited By ~ 3

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.

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