Infrared Spectral Maps of Star-Forming Regions and Cool-Core Galaxy Clusters

de Messières, Geneviève Escande, Department of Astronomy, University of Virginia
O'Connell, Robert, Department of Astronomy, University of Virginia

In this dissertation, I use infrared spectral maps of star-forming regions to explore the circumstances of star formation in the centers of cool-core galaxy clusters. Using Spitzer's IRS and MIPS instruments, we present a rich spectral map of the nearest super star cluster, 30 Doradus, which acts as as a laboratory for extreme modes of star formation. Photoionization from local hot stars dominates in the region. We present IRS spectra based on sparse spectral maps of BCGs in nine cool-core galaxy clusters. Eight of the nine targets show optical and ultraviolet evidence of star formation. We compare MIR indicators of obscured star formation to evidence of exposed star formation. We find that the BCGs have weaker thermal dust continuum emission than expected for normal star-forming galaxies, relative to several metrics. In six of the targets, we find that star formation is progressing in an unusually exposed environment, consistent with a model of extended filaments with finesubstructure containing star-forming knots. Two other galaxies in the sample evidently have vigorous star formation in a normal disk or nuclear starburst. The efficiency of star formation is high, assuming that the cooling gas is the source of fuel. We find temperatures and masses of the warm H 2 and contrast with other luminous sources of H 2 associated with shocks. We find that star formation powers the PAHanddust emission, but another source of heat (perhaps associated with the surrounding hot ICM) is responsible for the molecular gas emission in the galaxies in at least some targets. We consider shocks and energetic particle heating for theH 2 .Thereare inconsistencies between our data and the type of shocks that power other MOHEGs, and our data are consistent with the particle heating model, but we do not rule out shock heating.

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PHD (Doctor of Philosophy)
star formation, cool-core galaxy
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