Probing the Multiphase Interstellar Medium and Star Formation in Nearby Galaxies through Far-infrared Spectroscopy
dc.contributor.advisor | Bolatto, Alberto | en_US |
dc.contributor.author | Herrera Camus, Rodrigo | en_US |
dc.contributor.department | Astronomy | en_US |
dc.contributor.publisher | Digital Repository at the University of Maryland | en_US |
dc.contributor.publisher | University of Maryland (College Park, Md.) | en_US |
dc.date.accessioned | 2016-02-06T06:37:52Z | |
dc.date.available | 2016-02-06T06:37:52Z | |
dc.date.issued | 2015 | en_US |
dc.description.abstract | We present a study of different aspects of the multi-phase interstellar medium (ISM) of nearby galaxies, including detailed analysis of the low-excitation ionized gas, the thermal pressure (Pth) of the neutral gas, the dust-to-gas mass ratio (DGR) in low-metallicity environments, and the use of far-infrared transitions as tracers of the star formation rate (SFR). We based our work on the largest sample to date of spatially-resolved, infrared observations of nearby galaxies drawn from the KINGFISH and ``Beyond the Peak'' surveys. We use deep infrared observations to study the DGR of the extremely metal-poor galaxy I Zw 18. We measure a DGR upper-limit of 8.1x10^{-5}. This value is a factor of ~8 lower than the expected DGR if a linear correlation between DGR and metallicity, as observed in spirals, were to hold. Based on the line ratio between the [NII] 122 and 205 um transitions, for 140 regions selected from 21 galaxies we measure electron densities of the singly-ionized gas in the ne~1-230 cm^{-3} range, with a median value of ne=30 cm^{-3}. We find that ne increases as a function of SFR and radiation field strength. We study the reliability of the [CII] and [NII] 122 and 205 um transitions as SFR tracers. In general, we find good correlations between the emission from these fine-structure lines and star formation activity. However, a decrease in the photoelectric heating efficiency in the case of the [CII] line, or collisional quenching of the [NII] lines, can cause calibrations based on these transitions to underestimate the SFR. Finally, for a sample of atomic-dominated regions selected from 31 galaxies, we use the [CII] and HI lines to measure the cooling rate per H atom and Pth of the cold, neutral gas. We find a \pt\ distribution that can be well described by a log-normal distribution with median Pth/k~5,500 K cm^{-3}. We find correlations of increasing Pth with radiation field intensity and SFR, which is consistent with the results from two-phase ISM models in pressure equilibrium. | en_US |
dc.identifier | https://doi.org/10.13016/M2071F | |
dc.identifier.uri | http://hdl.handle.net/1903/17261 | |
dc.language.iso | en | en_US |
dc.subject.pqcontrolled | Astronomy | en_US |
dc.subject.pquncontrolled | Dust | en_US |
dc.subject.pquncontrolled | Galaxies | en_US |
dc.subject.pquncontrolled | Gas | en_US |
dc.subject.pquncontrolled | Infrared Astronomy | en_US |
dc.subject.pquncontrolled | Interstellar Medium | en_US |
dc.subject.pquncontrolled | Star Formation | en_US |
dc.title | Probing the Multiphase Interstellar Medium and Star Formation in Nearby Galaxies through Far-infrared Spectroscopy | en_US |
dc.type | Dissertation | en_US |
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