The Complex Chemistry and Evolution of Low-mass Starless and Prestellar Cores in the Taurus Molecular Cloud
Publisher
The University of Arizona.Rights
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.Abstract
Before low-mass (M < few Msun) stars like our Sun form, they are conceived inside cold (10 K) and dense (> 10^5 cm^-3) regions of gas and dust known as starless cores or dynamically collapsing prestellar cores. It is essential to study the chemical complexity and evolution of starless and prestellar cores because they set the initial conditions of star and planet formation. Interstellar complex organic molecules (COMs), defined as any molecule with at least one carbon atom and six total atoms, are of particular interest because they are precursors of the prebiotic molecules important to life on Earth. In the L1495 filamentary region of the Taurus Molecular Cloud, I searched for COMs in 31 starless and prestellar cores spanning a wide range of evolutionary stages. I detected methanol (CH3OH) in 100% of the cores targeted and acetaldehyde CH3CHO in 70%. In the dynamically and chemically young starless core L1521E, also in Taurus, I observed for the first time dimethyl ether (CH3OCH3), methyl formate (HCOOCH3) and vinyl cyanide (CH2CHCN). The prevalence of COMs in the starless and prestellar cores in Taurus suggests that these molecules are forming at least one million years earlier than previously thought and are thus likely seeded early on before the formation of protostars and planets. To better understand the physical conditions needed to form COMs in prestellar core environments, I also performed 3D radiative transfer dust modeling with the code RADMC-3D, which was aided by high resolution (12 and 19 arcsecond) dust continuum maps (at 1.2mm and 2.0mm) of the B10 region within the L1495 filament. Constraints were placed on the central densities, density slopes, aspect ratios, dust opacities, and external radiation field strengths for 14 cores embedded within B10. The models were used to assess the stability and evolutionary state of each COM-rich core, which in turn has shed light on the conditions needed for COM chemistry to thrive.Type
Electronic Dissertationtext
Degree Name
Ph.D.Degree Level
doctoralDegree Program
Graduate CollegeAstronomy