title: The Molecular Interstellar Medium of Nearby Star-Forming Galaxies
creator: Schruba, Andreas
subject: ddc-520
subject: 520 Astronomy and allied sciences
description: This thesis presents a comprehensive analysis of the relationship between the star forma- tion rate (SFR) and atomic (HI) and molecular (H2) gas surface densities — known as the 'Star Formation Law'. The investigation capitalizes on the HERACLES survey which mapped molecular gas emission with unprecedented resolution and sensitivity across the star-forming disks of 48 nearby spiral and dwarf galaxies. This data is complemented by recent very high quality radio, infrared, and ultraviolet data to form an unmatched multi-wavelength database. We develop a novel method to average spectral data to derive the most sensitive measurements of CO emission to date. In spiral galaxies, we trace >90% of CO which is located in an exponential disk similar to that of young and old stars. In dwarf galaxies, we derive the first sensitive constraints on the total CO luminosity. With these data we explore the limits of the SF Law in three different regimes: (1) In spiral galaxies, SFR is linearly related with H2, even in regions that are dominated by the atomic gas phase. The highly non-linear relation between SFR and total gas (HI+H2) is thus sensitively controlled by the HI–H2 phase transition. (2) The ratio SFR/CO is approx- imately constant for massive galaxies but increases strongly in low-mass, low-metallicity dwarf galaxies which suggests a significant (factor 10−100) change in the CO-to-H2 conversion factor. (3) The SF Law shows considerable scatter on small (~100 pc) scales, corresponding to the spatial scale of individual star-forming regions and is indicative of their evolution.
date: 2011
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/13526/1/phd_thesis_aschruba.pdf
identifier: DOI:10.11588/heidok.00013526
identifier: urn:nbn:de:bsz:16-opus-135261
identifier:   Schruba, Andreas  (2011) The Molecular Interstellar Medium of Nearby Star-Forming Galaxies.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/13526/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng