The characterization of volatiles associated with young stellar objects

In the first portion of this work, we searched for differences in volatiles within a single star forming region, Rho Ophiuchi. We determined the amount, temperature, and composition of two ice features, the bending modes of CO₂ and H₂O at 15 µm and 6 µm, respectively, toward 28 Young Stellar Objects (YSOs). We found that more than 50% of the YSOs studied contained a portion of crystalline CO₂ ice. We also found that some sources with Flat or borderline Class II Spectral Energy Distributions (SEDs) have a larger abundance of CO₂ ice with respect to H₂O ice. In addition to intracloud differences, we compared our results with several other star forming regions, high mass YSOs, and background objects. The average abundance of CO₂ with respect to H2O in Rho Oph is comparable to that in Taurus, Perseus, and the value reported by Oberg et al. (2011) toward high mass YSOs, however, it is less than the average abundance reported toward Corona Australis, Serpens, and the value cited by Oberg et al. (2011) toward low mass YSOs. The second half of this work involved a study of gaseous HCN, C₂H₂, and CO toward a low mass binary system, GV Tau. We report the second detection of these simple molecules toward a low mass YSO. The abundances of these molecules are consistent with that toward the first low mass YSO with a detection, IRS 46 (Lahuis et al., 2006), models from Willacy and Woods (2009), Walsh et al. (2010), and Markwick et al. (2002), and comets. We also found that these molecules have a rotational temperature of ~100 K - 200 K, indicating they may be located in the warm molecular layer of the disk. This work is part of a larger study to characterize volatiles (others include CH₄, NH₃, the 6.8 µm absorption feature, and CH₃OH) in the gas and/or solid phase toward YSOs in different star forming regions. This characterization includes temperature, location, mass, evolutionary state, and abundance. These characteristics will be used as a diagnostic tool to determine the evolution of molecules during the star formation process.

Name thesis:degree_name

Ph. D. in Physics

Grantor

Missouri University of Science and Technology

Year dc:date.available

2016

Author dc:creator

• Wojtkowski, Kari Anne

• Astrochemisty
• Spectroscopy
• Star Formation
• Physics

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/2290

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-3292