title: The Fragmentation of Massive Star-Forming Regions
creator: Rodón, Javier Adrián
subject: 520
subject: 520 Astronomy and allied sciences
description: Since its discovery by E. Salpeter in 1955, the high-mass end of the Initial Mass Function (IMF) has been continuously tested, and its slope has not changed from the value -2.35 originally calculated by Salpeter, the "Salpeter value". Furthermore, it is found that this value is universal. It not only describes the mass distribution of stellar masses in the Milky Way but also in other galaxies. Stars form individually or in systems within molecular clouds, from local condensations of sizes on the order of ~0.01 pc, the so-called "dense cores". In the case of low-mass star-forming regions, it is found that the Core Mass Function (CMF) resembles the Salpeter IMF. However, in the case of massive star-forming (MSF) regions, the answer is not that clear. The first CMF for a MSF region was derived in 2004 by H. Beuther and P. Schilke for the MSF region IRAS19410+2336. They found that this CMF also resembled the  Salpeter IMF. Since then, a few more CMFs for MSF regions have been derived, always with exponents comparable to Salpeter. This suggested that the CMF and the IMF are related in a one-to-one or nearly one-to-one relationship, and that the fragmentation processes within a molecular cloud would set the shape of the IMF at an early evolutionary stage. Attempting to test that scenario, in this thesis I present and analyze high angular resolution interferometric observations of several MSF regions at millimeter wavelengths, describing their protostellar content and deriving their CMF whenever is possible. We confirm the result of Beuther & Schilke (2004) and obtain a CMF with a power-law slope similar to the Salpeter IMF, however for other MSF regions we obtain a CMF with a power-law slope flatter than Salpeter. This difference suggests that the IMF might not be set at the moment of the fragmentation of the cloud, but insted would be a result of the evolution of the cloud, starting with a flatter mass distribution that becomes steeper at later evolutionary stages. This result is not conclusive yet, and we suggest a series of observations that would be needed to fully test it.
date: 2009
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/10037/1/thesis.pdf
identifier: DOI:10.11588/heidok.00010037
identifier: urn:nbn:de:bsz:16-opus-100379
identifier:   Rodón, Javier Adrián  (2009) The Fragmentation of Massive Star-Forming Regions.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/10037/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng