Images of star-forming regions. I - Optical and radio morphology of the bipolar outflow source GL 490

Campbell, B.; Persson, S. E.; McGregor, Peter

doi:10.1086/164251

Cited by 24 publications

(26 citation statements)

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“…Above the 3 σ level, a flux of 0.24 Jy was detected which agrees very well with the results obtained by Nakamura et al (1991) and Mundy & Adelman (1988). Based on the flux measurements for wavelengths larger than 1 cm by Campbell et al (1986) and Simon et al (1983), we estimate that the contribution of free-free radiation to the total flux at 97.98 GHz is ≈17(±3) mJy only, which is less than 10% of the total flux.…”

Section: Continuum Measurementssupporting

confidence: 90%

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The young intermediate-mass stellar object AFGL 490 – A disk surrounded by a cold envelope

Schreyer¹,

Henning

Tak

et al. 2002

A&A

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Abstract. AFGL 490 is a key target of the class of deeply embedded intermediate-mass young stellar objects in a transition stage to Herbig Be stars (L = 2.2-4.0 × 10 3 L ). In this paper, we present a comprehensive set of single-dish line data which characterize the envelope of the source. In addition, observations of CS J = 2→1 and the corresponding continuum at 97.98 GHz have been obtained with the Plateau de Bure (PdB) interferometer, which are sensitive to the small-scale structure around the stellar source. The PdB line data show a bar-like elongated gas structure of 22 000 AU × 6000 AU size with a position angle of ≈-45• . This bar represents the flattened inner envelope surrounding a disk-like structure (radius ≤500 AU) for which we find evidence very close to the young B star. Due to strong (self-)absorption in the velocity range v lsr = -12.5 ... -15 km s −1 , only the outer line wings can be used to study the gas motion. Maps of the integrated red and blue line wing emission show two well-separated gas blobs around AFGL 490, which are interpreted as a disk. The 3 mm continuum interferometer map shows a point source at the position of AFGL 490 with a flux of 240 mJy. This flux translates into a total mass of 3-6 M of the disk which is comparable to the stellar mass of about 8 M . This configuration is unstable and will disappear in 10 3 -10 4 years due to gravitational instabilities. Photometric data from ISOPHOT and spectroscopic data from ISO-SWS have been obtained. Together with submillimetre continuum data a very complete spectral energy distribution of the envelope could be compiled. Analysis of the data shows that the central region of AFGL 490 has a steeper density gradient compared with the outer molecular envelope. All data clearly point to a low temperature (25-35 K) of this envelope. To determine the chemical state of the object, we determined the abundances of 13 molecules towards AFGL 490. The molecular line and ISO-SWS data are used to derive the gas-solid abundance ratios for H 2 O, CO, and CO 2 . The chemical results, such as the relatively low gas-to-solid ratios and the low CH 3 OH excitation, emphasize the presence of a cold molecular envelope. We found evidence for other outflow systems in the envelope around AFGL 490. Red-shifted and blue-shifted gas blobs with a separation of about 20 000 AU were detected. Their centre is located roughly 3 to the south of AFGL 490, and their morphology implies that a deeply embedded low-mass object drives a jet which enters the denser envelope material at such a large distance. Two further outflow systems in the close neighbourhood of AFGL 490 could be identified. All these data point to the formation of a group of low-mass stars around AFGL 490. It is very remarkable that these outflows do not influence the global physical and chemical structure of the envelope.

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Section: Continuum Measurementssupporting

confidence: 90%

“…Whereas optical images show only a diffuse nebulosity at this position, AFGL 490 is a luminous source in the near-infrared (e.g., Campbell et al 1986;Minchin et al 1991;Haas et al 1992;Hodapp 1994) surrounded by a couple of low-luminosity objects with projected distances between 5500 and 43 000 AU.…”

Section: General Properties Of Afgl 490mentioning

confidence: 93%

The young intermediate-mass stellar object AFGL 490 – A disk surrounded by a cold envelope

Schreyer¹,

Henning

Tak

et al. 2002

A&A

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“…Interestingly, the extended radio emission observed by Campbell et al (1986) has also not been detected in more recent deep 8 GHz VLA observations by Hoare & Gibb (in preparation). Hence, it is possible that these changes in the morphology of near-IR and radio observations maybe caused by real variability in the source.…”

Section: Gl 490mentioning

confidence: 57%

“…An stellar-like optical counterpart is located at the apex of a conical reflection nebula in the blueshifted outflow lobe (Campbell et al 1986). The light centre of the optical source was found to shift to the SW at bluer wavelengths consistent with a scattered rather than direct source for the optical light (Campbell et al 1986).…”

Section: Gl 490mentioning

confidence: 99%

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Near-IR speckle imaging of massive young stellar objects

Álvarez

Hoare

Glindemann

et al. 2004

A&A

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Abstract. We present near-IR speckle images of 21 massive Young Stellar Objects (YSOs) associated with outflows. The aim of this study is to search for sub-arcsecond reflection nebulae associated with the outflow cavity. We find that 6 of the massive YSOs show a conical nebula which can be interpreted in terms of reflected light from the dusty walls of the outflow cavity. In all cases, the small scale structures seen in our images are compared with outflow indicators found in the literature. No clear correlation is found between the presence of the reflection nebulosity and any property such as degree of embeddedness. We also note that 3 of the sources show close companions, one of them belonging also to the sample with conical nebula.

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Massive Star Formation

Hoare

Franco

Diffuse Matter From Star Forming Regions to Active Galaxies

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This chapter reviews progress in the field of massive star formation. It focuses on evidence for accretion and current models that invoke high accretion rates. In particular it is noted that high accretion rates will cause the massive young stellar object to have a radius much larger than its eventual main sequence radius throughout much of the accretion phase. This results in low effective temperatures which may provide the explanation as to why luminous young stellar objects do not ionized their surroundings to form ultra-compact H II regions. The transition to the ultra-compact H II region phase would then be associated with the termination of the high accretion rate phase. Objects thought to be in a transition phase are discussed and diagnostic diagrams to distinguish between massive young stellar objects and ultra-compact H II regions in terms of line widths and radio luminosity are presented.Comment: 21 pages, 6 figures, chapter in Diffuse Matter from Star Forming Regions to Active Galaxies - A Volume Honouring John Dyson, Edited by T.W. Hartquist, J. M. Pittard, and S. A. E. G. Falle. Series: Astrophysics and Space Science Proceedings. Springer Dordrecht, 2007, p.6

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Images of star-forming regions. I - Optical and radio morphology of the bipolar outflow source GL 490

Cited by 24 publications

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The young intermediate-mass stellar object AFGL 490 – A disk surrounded by a cold envelope

The young intermediate-mass stellar object AFGL 490 – A disk surrounded by a cold envelope

Near-IR speckle imaging of massive young stellar objects

Massive Star Formation

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