Abstract

Nearby Young Moving Groups (NYMGs), i.e., loose groups of stars of agevicinity, present ideal, accessible observational laboratories for studies on star and planet formation. Studying individual members of NYMGs, especially those hosting protoplanetary disks, in the infrared and millimeter regimes gives astronomers key information on disk evolution and the planet formation process. In this dissertation, I present an analysis of newly available data for members of one of the youngest known NYMGs, the Epsilon Chameleonitis Association (ECA), including detailed studies of two ECA members that host protoplanetary disks viewed at high inclinations (i.e. within ~30 degrees of edge-on). Through analysis of Gaia Space Astrometry Mission data for the ECA, I present updated constraints on the Galactic positions and kinematics and color-magnitude diagram positions of ECA members and candidates. I reassess their membership status and refine estimates of the multiplicity and disk fraction of the group. I determine a mean distance to ECA of 101.0±4.6 pc and confirm that, at an age of 5±3 Myr, it represents the youngest stellar group within ~100 pc of Earth. The two nearly edge-on star-disk systems studied here are representative of the diversity of planet-forming environments around young stars. The first, 2M1155-79B, was discovered during the aforementioned Gaia study of the ECA. Near-infrared spectra of 2M1155-79B, along with analysis of photometry from Gaia EDR3, 2MASS, VHS, and WISE, reveal that 2M1155-79B is most likely a young, late-M, star near the hydrogen-burning limit that is partially obscured by, and actively accreting from, a nearly edge-on circumstellar disk. The second planet-forming disk studied here orbits T Cha, a near solar-mass ECA member. I present archival Atacama Large Millimeter Array images of the millimeter continuum and 12CO (3-2) and 13CO (3-2) emission from the highly inclined (i~73°) T Cha disk. Radial brightness profiles show a limb-brightened ring of CO gas orbiting inside of the large dust grains generating the millimeter continuum, surrounded by a radially and vertically extended region of CO gas out to radii of ~200 AU that modelling reveals is likely probing the vertical freeze-out. These analyses illustrate the future potential of the ECA for providing new insights into star and planet formation processes.

Library of Congress Subject Headings

Protoplanetary disks--Evolution; Stars--Age; Space astronomy

Publication Date

6-2022

Document Type

Dissertation

Student Type

Graduate

Degree Name

Astrophysical Sciences and Technology (Ph.D.)

Department, Program, or Center

School of Physics and Astronomy (COS)

Advisor

Gabriel J. Diaz

Advisor/Committee Member

Joshua Faber

Advisor/Committee Member

Jacqueline Faherty

Campus

RIT – Main Campus

Plan Codes

ASTP-PHD

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