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Detecting H II Regions in “Pure” Starburst Galaxies with SDSS Data

Published online by Cambridge University Press:  12 September 2016

Anthony Crider
Affiliation:
Department of Physics, Elon University, 2625 Campus Box, Elon NC 27244 Email: [email protected]
Chris Richardson
Affiliation:
Department of Physics, Elon University, 2625 Campus Box, Elon NC 27244
Ben Kaiser
Affiliation:
Department of Physics, Elon University, 2625 Campus Box, Elon NC 27244
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Abstract

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The relationship between active galactic nuclei (AGN) and starburst galaxies is poorly understood, partially due to galaxies exhibiting both AGN and starburst activity. To better understand the connection, we analyze a sample of “pure” AGN or starburst at redshift z = 0.1 selected using mean field independent component analysis (MFICA). Simulations of starburst galaxy emission suggests that the locally optimally-emitting cloud (LOC) model can fit observations and improve our ability to distinguish the impact of differences in metallicity, ionization parameter, and ionizing flux. To test for the existence of such clouds in our galaxy sample, we examine the Sloan Digital Sky Survey (SDSS) images of our pure galaxies. At this distance, even large star-forming H II regions (e.g. 30 Doradus) only fill part of an SDSS pixel. However, we compare the morphology of the distant galaxies to more nearby ones (i.e. NGC 4713, NGC 4038/4039) to estimate the number of larger H II regions. While the clumpiness parameter of a galaxy in theory might indicate the existence of these regions, a straightforward calculation of the clumpiness parameter is ineffective for galaxies at z = 0.1. Typically, one subtracts a smoothed version of a galaxy image from the same image. We instead test a different approach to establish a smooth image and thus better identify the clumps. We subtract the smoother infrared z-band from the sharper ultraviolet u-band. We test this procedure using NGC 4713, a nearby starburst galaxy, artificially degraded to match images of our “pure” starburst galaxies.

Type
Poster Papers
Copyright
Copyright © International Astronomical Union 2015 

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