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Modeling Spitzer Observations of VV Ser. II. An Extended Quantum-heated Nebula and a Disk Shadow

Pontoppidan, Klaus M. and Dullemond, Cornelis P. and Blake, Geoffrey A. and Evans, Neal J., II and Geers, Vincent C. and Harvey, Paul M. and Spiesman, William (2007) Modeling Spitzer Observations of VV Ser. II. An Extended Quantum-heated Nebula and a Disk Shadow. Astrophysical Journal, 656 (2). pp. 991-1000. ISSN 0004-637X. doi:10.1086/510571.

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We present mid-infrared Spitzer IRAC and MIPS images of the UX Orionis star VV Ser and the surrounding cloud. The 5.6-70 μm images show bright, localized, and nebulous emission extended over 4' centered on VV Ser. This nebulosity is due to transiently heated grains excited by UV photons emitted by VV Ser. Imprinted on the nebulosity is a wedge-shaped dark band, centered on the star. We interpret this as the shadow cast by the inner regions of a near-edge-on disk, allowing the PAHs to be excited only outside of this shadow. We extend an axisymmetric radiative transfer model of the VV Ser disk described in a companion paper to include quantum-heated PAH molecules and very small grains (VSGs) in the thermal cooling approximation. The presence of a disk shadow strongly constrains the inclination as well as the position angle of the disk. The nebulosity at 5.6-8.0 μm and the 2175 Å absorption feature seen in an archival spectrum from the IUE can be fit using only PAHs, consistent with the main carrier of the 2175 Å feature being due to the graphite-like structure of the PAHs. The PAH component is found to be relatively smoothly distributed in the cloud, while the population of VSGs emitting at 20-70 μm is strongly concentrated ~50'' to the southeast of VV Ser. Depending on the adopted PAH opacity, the abundance of PAHs in the surrounding cloud is constrained to 5% ± 2% of the total dust mass. Although relatively rare, quantum-heated nebulosities surrounding single, well-defined stars are well-suited for gaining unique insights into the physics of very small particles in molecular clouds.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Pontoppidan, Klaus M.0000-0001-7552-1562
Blake, Geoffrey A.0000-0003-0787-1610
Evans, Neal J., II0000-0001-5175-1777
Additional Information:© 2007 The American Astronomical Society. Received 2005 September 12; accepted 2006 October 13. The authors wish to thank Ruud Visser for use of his code to calculate the PAH opacity and Jean-Charles Augereau for useful discussions. The referee, Kenneth Wood, is thanked for comments that significantly improved the quality of the manuscript. Support for this work was provided by NASA through Hubble Fellowship grant 01201.01, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. Astrochemistry in Leiden is supported by a Spinoza grant of the Netherlands Organization for Scientific Research (NWO). Support for this work, part of the Spitzer Space Telescope Legacy Science Program, was provided by NASA through contracts 1224608 and 1230779, issued by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. This research was supported by the European Research Training Network ‘‘The Origin of Planetary System’’ (PLANETS; contract HPRN-CT- 2002-00308).
Funding AgencyGrant Number
NASA Hubble Fellowship01201.01
NASANAS 5-26555
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
European Research Training NetworkHPRN-CT-2002-00308
Subject Keywords:accretion, accretion disks; circumstellar matter; infrared : stars; stars : pre-main-sequence; stars : formation
Issue or Number:2
Record Number:CaltechAUTHORS:20091203-092846084
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Official Citation:Modeling Spitzer Observations of VV Ser. II. An Extended Quantum-heated Nebula and a Disk Shadow Klaus M. Pontoppidan, Cornelis P. Dullemond, Geoffrey A. Blake, Neal J. Evans II, Vincent C. Geers, Paul M. Harvey, and William Spiesman 2007 ApJ 656 991-1000 doi: 10.1086/510571
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16863
Deposited By: Tony Diaz
Deposited On:04 Jan 2010 23:09
Last Modified:08 Nov 2021 23:30

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