The circumstellar disc, envelope and bipolar outflow of the massive young stellar object W33A

Davies, Ben; Lumsden, S. L.; Hoare, M. G.; Oudmaijer, R. D.; Wit, W. J. de

doi:10.1111/j.1365-2966.2009.16077.x

Cited by 96 publications

(122 citation statements)

References 24 publications

Supporting

Mentioning

109

Contrasting

Unclassified

Order By: Relevance

“…The CO bandheads in emission are usually believed to originate in the inner gaseous disc (see e.g. Carr et al 1993;Antoniucci et al 2008), and have been observed in YSOs that display strong jets and Herbig-Haro (HH) objects (see, e.g., Davis et al 2011), whereas the CO bandheads in absorption may originate in cooler regions, like the YSO envelope (Davies et al 2010) or the photosphere of cool YSOs (see e.g. Rayner et al 2009).…”

Section: Optical and Nir Spectramentioning

confidence: 99%

POISSON project

Garatti

Lopez

Antoniucci

et al. 2012

A&A

View full text Add to dashboard Cite

Context. Characterising stellar and circumstellar properties of embedded young stellar objects (YSOs) is mandatory for understanding the early stages of the stellar evolution. This task requires the combination of both spectroscopy and photometry, covering the widest possible wavelength range, to disentangle the various protostellar components and activities. Aims. As part of the POISSON project (Protostellar Optical-Infrared Spectral Survey On NTT), we present a multi-wavelength spectroscopic and photometric investigation of embedded YSOs in L 1641, aimed to derive the stellar parameters and evolutionary stages and to infer their accretion properties. Methods. Our multi-wavelength database includes low-resolution optical-IR spectra from the NTT and Spitzer (0.6−40 μm) and photometric data covering a spectral range from 0.4 to 1100 μm, which allow us to construct the YSOs spectral energy distributions (SEDs) and to infer the main stellar parameters (visual extinction, spectral type, accretion, stellar, bolometric luminosity, mass accretion, and ejection rates). Results. The NTT optical-NIR spectra are rich in emission lines, which are mostly associated with YSO accretion, ejection, and chromospheric activities. A few emission lines, prominent ice (H 2 O and CO 2 ), and amorphous silicate absorption features have also been detected in the Spitzer spectra. The SED analysis allows us to group our 27 YSOs into nine Class I, eleven Flat, and seven Class II objects. However, on the basis of the derived stellar properties, only six Class I YSOs have an age of ∼10 5 yr, while the others are older (5 × 10 5 −10 6 yr), and, among the Flat sources, three out of eleven are more evolved objects (5 × 10 6 −10 7 yr), indicating that geometrical effects can significantly modify the SED shapes. Inferred mass accretion rates (Ṁ acc ) show a wide range of values (3.6 × 10 −9 to 1.2 × 10 −5 M yr −1 ), which reflects the age spread observed in our sample well. Average values of mass accretion rates, extinction, and spectral indices decrease with the YSO class. The youngest YSOs have the highestṀ acc , whereas the oldest YSOs do not show any detectable jet activity in either images and spectra. Apart from the outbursting source #25 and, marginally, #20, none of the remaining YSOs is accretion-dominated (L acc > L * ). We also observe a clear correlation among the YSOṀ acc , M * , and age. For YSOs with t > 10 5 yr and 0.4 M ≤ M * ≤ 1.2 M , a relationship betweenṀ acc and t (Ṁ acc ∝ t −1.2 ) has been inferred, consistent with mass accretion evolution in viscous disc models and indicating that the mass accretion decay is slower than previously assumed. Finally, our results suggest that episodic outbursts are required for Class I YSOs to reach typical classical T Tauri stars stellar masses.

show abstract

Section: Optical and Nir Spectramentioning

confidence: 99%

POISSON project

Garatti

Lopez

Antoniucci

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…This lends support to 145 • position angle to be the actual orientation of the system. The high-angular resolution IFU images presented in Davies et al (2010) have contributions from shocked H 2 emission as traced by extended 4.5 μm emission in Spitzer IRAC images (Cyganowski et al 2008). …”

Section: The Molecular Outflow and Near-ir Reflection Nebulamentioning

confidence: 99%

“…In Davies et al (2010), spectro-astrometry of the Brγ transition is also used to show that the near-IR source is at the base of the bipolar outflow on scales of 200 μ-arcseconds. The near-IR source most likely corresponds to the central object in W33A, as was assumed during the execution of the MIDI observations.…”

Section: The Molecular Outflow and Near-ir Reflection Nebulamentioning

confidence: 99%

The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A

Wit

Hoare

Oudmaijer

et al. 2010

A&A

View full text Add to dashboard Cite

Aims. In this paper we aim to determine the structure on 100 AU scales of the massive young stellar object W33A, using interferometric observations in the mid-infrared. This emission could be caused by a variety of elements, for example, the inner protostellar envelope, outflow cavity walls, or a dusty or gaseous accretion disk. Methods. We used the Unit Telescopes of the VLT Interferometer in conjunction with the MIDI instrument to obtain spectrally dispersed visibilities in the N-band on 4 baselines with an angular resolution between 25 and 60 milli-arcsec (equivalent to 95 and 228 AU at 3.8 kpc). The visibility spectra and spectral energy distribution were compared to 2D-axi-symmetric dust radiative transfer models with a geometry that includes a rotationally flattened envelope and outflow cavities. We assumed an O 7.5 ZAMS star as the central source, consistent with the observed bolometric luminosity. The observations were compared to models with and without (dusty and gaseous) accretion disks. Results. The visibilities are between 5% and 15%, and the non-spherically symmetric emitting structure has a typical size of 100 AU. A satisfactory model is constructed to reproduce the visibility spectra for each (u, v) point. It fits the N-band flux spectrum, the midinfrared slope, the far-infrared peak, and the (sub)mm regime of the SED. It produces a 350 μm morphology consistent with the observations. Conclusions. The mid-infrared emission of W33A on 100 AU scales is dominated by the irradiated walls of the cavity sculpted by the outflow. The protostellar envelope has an equivalent mass infall rate of 7.5 × 10 −4 M yr −1 , and an outflow opening angle of 2θ = 20 • . The visibilities rule out the presence of any dust disk with total (gas and dust) mass more than 0.01 M . Within the model, this implies a diskṀ acc of less than 1.1 × 10 −7 (α/0.01) M yr −1 , where α is the viscosity of the Shakura-Sunyaev prescription. However, optically thick accretion disks, which are inside the dust sublimation radius, are allowed to accrete at rates equalling the envelope's mass infall rate (up to 10 −3 M yr −1 ) without substantially affecting the visibilities due to the extinction by the extremely massive envelope of W33A.

show abstract

“…Spectroscopic observations have also provided important kinematical evidence of accretion disks (see, e.g., Chandler et al 1995;Bik & Thi 2004;Wheelwright et al 2010;Davies et al 2010). These studies have greatly advanced our understanding of the physics of young stellar objects (YSOs), how the young stars gain their final mass, how the circumstellar matter, in which…”

Section: Introductionmentioning

confidence: 99%

Detection of a large massive circumstellar disk around a high-mass young stellar object in the Carina Nebula

Preibisch

Ratzka

Gehring

et al. 2011

A&A

View full text Add to dashboard Cite

Context. The characterization of circumstellar disks around young stellar objects can provide important information about the process of star formation and the possible formation of planetary systems. Aims. We investigate the spatial structure and the spectral energy distribution of a newly discovered edge-on circumstellar disk around an optically invisible young stellar object that is embedded in a dark cloud in the Carina Nebula. Methods. The disk object was serendipitously discovered in our deep near-IR imaging survey of the Carina Nebula obtained with HAWK-I at the ESO VLT. Whereas the object was detected as an apparently point-like source in earlier infrared observations, only the superb image quality (FWHM ≈ 0.5 ) of the HAWK-I data could reveal, for the first time, the peculiar morphology of the object. It consists of a very red point-like central source that is surrounded by a roughly spherical nebula, which is intersected by a remarkable dark lane through the center. We construct the spectral energy distribution of the object from 1 μm to 870 μm and perform a detailed radiative transfer modeling of the spectral energy distribution and the source morphology. Results. The observed object morphology in the near-IR images clearly suggests a young stellar object that is embedded in an extended, roughly spherical envelope and surrounded by a large circumstellar disk with a diameter of ≈5500 AU that is seen nearly edge-on. The radiative transfer modeling shows that the central object is highly luminous and thus must be a massive young stellar object, most likely in the range 10−15 M . The circumstellar disk has a mass of about 2 M . Conclusions. The disk object in Carina is one of the most massive young stellar objects for which a circumstellar disk has been detected so far. The size and mass of the disk are very large compared to the corresponding values found for most other similar objects. These results support the assumption that 10−15 M stars can form via accretion from a circumstellar disk.

show abstract

The circumstellar disc, envelope and bipolar outflow of the massive young stellar object W33A

Cited by 96 publications

References 24 publications

POISSON project

POISSON project

The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A

Detection of a large massive circumstellar disk around a high-mass young stellar object in the Carina Nebula

Contact Info

Product

Resources

About