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Near-Infrared Synthetic Images of Protostellar Disks and Envelopes

Stark, D. P. and Whitney, B. A. and Stassun, K. and Wood, K. (2006) Near-Infrared Synthetic Images of Protostellar Disks and Envelopes. Astrophysical Journal, 649 (2). pp. 900-913. ISSN 0004-637X.

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We present a grid of near-infrared (IR) synthetic images of pre-main-sequence stars at different stages of evolution, which we simulate by varying envelope mass, disk radius and mass, and outflow cavity shape. Our aim is to determine how variations in physical properties of young stellar objects (e.g., mass infall rate, disk size) affect their observed colors and morphology, and use this information to highlight observable differences between different evolutionary states. We show that the near-IR colors are a function of envelope mass infall rate and inclination; hence both parameters must be constrained if colors are to be used to infer a source's true evolutionary state. Sources with more opaque envelopes have redder diffuse colors, because the scattered light suffers reddening as it propagates through the envelope. Somewhat counterintuitively, colors are reddest at intermediate inclinations (i ~ 45°-70°) and then become bluer edge-on, where light is ~100% scattered. Thus a source with relatively blue colors could be an evolved source or a younger source oriented edge-on. Importantly, we find that at inclinations where scattered light dominates, it is erroneous to derive extinction A_V from observed colors; fully half of all objects will underestimate A_V by at least an order of magnitude. We use our models to interpret six protostellar sources in the Taurus-Auriga molecular cloud observed with HST NICMOS. Of the six young stellar objects modeled in this paper, five require an infalling envelope to match the colors and should thus be classified as young embedded sources. The remaining source, Haro 6-5B, is a disk source, having already dispersed its envelope.

Item Type:Article
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URLURL TypeDescription
Stassun, K.0000-0002-3481-9052
Additional Information:© 2006 American Astronomical Society. Received 2003 July 31; accepted 2006 June 14. This work was supported by the HST Archival Research Program (grant AR-08367.01-97A) and NASA’s Long Term Space Astrophysics Research Program (NAG5-8412). K. S. acknowledges support from the National Science Foundation (grant AST 0349075). K. W. acknowledges support from the UK PPARC Advanced Fellowship. We thank the referee for thoughtful comments that improved the quality of this paper.
Funding AgencyGrant Number
NSFAST 0349075
Particle Physics and Astronomy Research Council (PPARC)UNSPECIFIED
Subject Keywords:circumstellar matter; radiative transfer;scattering; stars: formation; stars: preYmain-sequence
Issue or Number:2
Record Number:CaltechAUTHORS:20110727-113515092
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Official Citation:Near-Infrared Synthetic Images of Protostellar Disks and Envelopes D. P. Stark et al. 2006 ApJ 649 900
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24570
Deposited By: Jason Perez
Deposited On:27 Jul 2011 21:17
Last Modified:03 Oct 2019 02:57

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