CO{sub 2} ICE TOWARD LOW-LUMINOSITY EMBEDDED PROTOSTARS: EVIDENCE FOR EPISODIC MASS ACCRETION VIA CHEMICAL HISTORY
- Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400 Austin, TX 78712-1205 (United States)
- Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States)
- Department of Astronomy and Space Science, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701 (Korea, Republic of)
We present Spitzer IRS spectroscopy of CO{sub 2} ice bending mode spectra at 15.2 {mu}m toward 19 young stellar objects (YSOs) with luminosity lower than 1 L{sub Sun} (3 with luminosity lower than 0.1 L{sub Sun }). Ice on dust grain surfaces can encode the history of heating because pure CO{sub 2} ice forms only at elevated temperature, T > 20 K, and thus around protostars of higher luminosity. Current internal luminosities of YSOs with L < 1L{sub Sun} do not provide the conditions needed to produce pure CO{sub 2} ice at radii where typical envelopes begin. The presence of detectable amounts of pure CO{sub 2} ice would signify a higher past luminosity. Many of the spectra require a contribution from a pure, crystalline CO{sub 2} component, traced by the presence of a characteristic band splitting in the 15.2 {mu}m bending mode. About half of the sources (9 out of 19) in the low-luminosity sample have evidence for pure CO{sub 2} ice, and 6 of these have significant double-peaked features, which are very strong evidence of pure CO{sub 2} ice. The presence of the pure CO{sub 2} ice component indicates that the dust temperature, and hence luminosity of the central star/accretion disk system, must have been higher in the past. An episodic accretion scenario, in which mixed CO-CO{sub 2} ice is converted to pure CO{sub 2} ice during each high-luminosity phase, explains the presence of pure CO{sub 2} ice, the total amount of CO{sub 2} ice, and the observed residual C{sup 18}O gas.
- OSTI ID:
- 22092096
- Journal Information:
- Astrophysical Journal, Vol. 758, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
MULTIWAVELENGTH OBSERVATIONS OF V2775 Ori, AN OUTBURSTING PROTOSTAR IN L 1641: EXPLORING THE EDGE OF THE FU ORIONIS REGIME
A SYSTEMATIC SEARCH FOR MOLECULAR OUTFLOWS TOWARD CANDIDATE LOW-LUMINOSITY PROTOSTARS AND VERY LOW LUMINOSITY OBJECTS