Doctoral Dissertations


"The ρ Ophiuchi and Serpens molecular clouds are sites of low mass star formation. The goals of this study were to identify young stellar objects (YSOs) and estimate ages and masses in order to infer an initial mass function (IMF), investigate disk evolution, and determine the star-forming history. Optical spectroscopic surveys of an unbiased sample of candidate young stars have been completed. Optical images taken in different photometric bands were used to create color-magnitude diagrams from which sources were selected for spectroscopic observation. In combination with published data, 135 association members in ρ Ophiuchi and 63 association members plus 16 possible members in Serpens have been identified based on the presence of Hα in emission, lithium absorption, X-ray emission, a mid-infrared excess, and/or reflection nebulosity. Effective temperatures and bolometric luminosities were compared with theoretical tracks and isochrones for pre-main-sequence stars to estimate ages and masses.

Both regions have similar median ages, supporting the idea that star formation is a relatively fast process. In ρ Ophiuchi, no age spread was found. In Serpens, an age spread of 1-5 Myrs was found; it could not be determined if this age spread was intrinsic or a result of contamination from foreground young stars. Consistent with these ages similar circumstellar disk frequencies were found. In ρ Ophiuchi, an IMF consistent with the field star IMF for YSOs with masses >0.2 M⊙ was inferred. In Serpens, the IMF was in agreement with the field star IMF for M>1 M⊙. Previous studies of these regions have been biased towards particular stages in the star formation process. This study has provided an unbiased sample of pre-main sequence objects, necessary to obtain a complete picture of star formation"--Abstract, page iv.


Wilking, Bruce A.

Committee Member(s)

Schmitt, John L.
Gibb, Erika
Meyer, Michael
Yamilov, Alexey



Degree Name

Ph. D. in Physics


Sigma Xi, the Scientific Research Society. Grants in Aid of Research
Missouri Space Grant Consortium
National Optical Astronomy Observatory (U.S.)
Missouri University of Science and Technology. Chancellor's Graduate Scholars Dissertation Program
Missouri Research Board


Dissertation completed as part of a cooperative degree program with Missouri University of Science and Technology and the University of Missouri--St. Louis.


Missouri University of Science and Technology

Publication Date

Fall 2013

Journal article titles appearing in thesis/dissertation

  • The initial mass function and disk frequency of the ρ Ophiuchi Cloud: An extinction-limited sample
  • A spectroscopic survey of the Serpens Main Cluster


xi, 139 pages

Note about bibliography

Includes bibliographical references.


© 2013 Kristen Leilani Erickson, All rights reserved.

Document Type

Dissertation - Open Access

File Type




Subject Headings

Stars -- Formation
Stars -- Clusters
Stars, New
Optical spectroscopy

Thesis Number

T 10388

Electronic OCLC #


Included in

Physics Commons