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Looney, Leslie W. Looney, Leslie W. Kemball, Athol J. Gammie, Charles F. Mouschovias, T. Ch. Chiang, Hsin-Fang 2012-02-01T00:56:16Z 2014-02-01T11:00:35Z 2012-02-01T00:56:16Z 2011-12 This thesis presents observations and modeling of nearby embedded sources in the earliest stage of protostellar evolution, i.e., Class 0 young stellar objects, using interferometric data of the Berkeley-Illinois-Maryland Association array and the Combined Array for Research in Millimeter-wave Astronomy. Protostars form through gravitational collapse inside their natal envelopes, and these circumstellar envelopes contain valuable information about the physical processes of star formation. In this thesis, both molecular lines and dust continuum are utilized to investigate the nature of the collapsing envelopes. In particular, I focus on the isolated edge-on low-mass protostar L1157. While a large-scale (~20,000 AU) flattened envelope is detected in both the N2H+ line and the 8 micron extinction perpendicular to the outflow orientation, the dust continuum shows spherical structures at scales between ~10^2 and ~10^3 AU. The N2H+ observations not only reveal the outer envelope that is too dim to be detected in dust continuum, but they also unveil the kinematic structures of the flattened envelope. The dust continuum is compared with theoretical collapse models using radiative transfer calculation and Bayesian inference. The modeling techniques, as well as the associated uncertainties, are detailed. The results show that a power-law envelope model with a density index p ~ 2 provides a better fit to the observations than the simple Shu model or the commonly-used Terebey-Shu-Cassen model. Furthermore, I discuss the implications of the modeling results on the dust grain properties and the constraints they place on the youngest circumstellar disk embedded inside the envelope. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-10-12T13:51:19Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Chiang_Hsin-Fang.pdf: 3671537 bytes, checksum: 023ee11b83a5522f3c57c2e8d1429c37 (MD5) Made available in DSpace on 2012-02-01T00:56:16Z (GMT). No. of bitstreams: 2 Chiang_Hsin-Fang.pdf: 3671537 bytes, checksum: 023ee11b83a5522f3c57c2e8d1429c37 (MD5) license.txt: 4061 bytes, checksum: 1263ea79581f9c57047bdeffadd1a91b (MD5) Item marked as restricted to the 'Administrator' Group (id=1) by William Ingram (wingram2@illinois.edu) on 2012-02-01T00:57:22Z Item is restricted until 2014-02-01T00:56:58Z Item reinstated by Sarah Shreeves (sshreeve@illinois.edu) on 2014-02-01T11:00:35Z Item was in collections: Dissertations and Theses - Astronomy (ID: 684) Graduate Theses and Dissertations at Illinois (ID: 204) No. of bitstreams: 3 Chiang_Hsin-Fang.pdf.txt: 270250 bytes, checksum: 2169b6898e4436b5b1f7e6606107d310 (MD5) Chiang_Hsin-Fang.pdf: 3671537 bytes, checksum: 023ee11b83a5522f3c57c2e8d1429c37 (MD5) license.txt: 4061 bytes, checksum: 1263ea79581f9c57047bdeffadd1a91b (MD5) Item released from any restrictions by Sarah Shreeves (sshreeve@illinois.edu) on 2014-02-01T11:00:35Z http://hdl.handle.net/2142/29575 en Copyright 2011 Hsin-Fang Chiang star formation Circumstellar environments around the youngest protostars: interferometric observations and modeling Astronomy 1430 Astronomy 0333 University of Illinois at Urbana-Champaign Dissertation Ph.D. PHD:Astronomy -UIUC 10KS0333PHD