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Variations of the ISM Compactness Across the Main Sequence of Star Forming Galaxies: Observations and Simulations

Martínez-Galarza, J. R. and Smith, H. A. and Lanz, L. and Hayward, Christopher C. and Zezas, A. and Rosenthal, L. and Weiner, A. and Hung, C. and Ashby, M. L. N. and Groves, B. (2016) Variations of the ISM Compactness Across the Main Sequence of Star Forming Galaxies: Observations and Simulations. Astrophysical Journal, 817 (1). Art. No. 76. ISSN 0004-637X.

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The majority of star-forming galaxies follow a simple empirical correlation in the star formation rate (SFR) versus stellar mass (M*) plane, of the form SFR ∝ M^α_*, usually referred to as the star formation main sequence (MS). The physics that sets the properties of the MS is currently a subject of debate, and no consensus has been reached regarding the fundamental difference between members of the sequence and its outliers. Here we combine a set of hydro-dynamical simulations of interacting galactic disks with state-of-the-art radiative transfer codes to analyze how the evolution of mergers is reflected upon the properties of the MS. We present Chiburst, a Markov Chain Monte Carlo spectral energy distribution (SED) code that fits the multi-wavelength, broad-band photometry of galaxies and derives stellar masses, SFRs, and geometrical properties of the dust distribution. We apply this tool to the SEDs of simulated mergers and compare the derived results with the reference output from the simulations. Our results indicate that changes in the SEDs of mergers as they approach coalescence and depart from the MS are related to an evolution of dust geometry in scales larger than a few hundred parsecs. This is reflected in a correlation between the specific star formation rate, and the compactness parameter C, that parametrizes this geometry and hence the evolution of dust temperature (T_(dust)) with time. As mergers approach coalescence, they depart from the MS and increase their compactness, which implies that moderate outliers of the MS are consistent with late-type mergers. By further applying our method to real observations of luminous infrared galaxies (LIRGs), we show that the merger scenario is unable to explain these extreme outliers of the MS. Only by significantly increasing the gas fraction in the simulations are we able to reproduce the SEDs of LIRGs.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Martínez-Galarza, J. R.0000-0002-5069-0324
Lanz, L.0000-0002-3249-8224
Hayward, Christopher C.0000-0003-4073-3236
Zezas, A.0000-0001-8952-676X
Rosenthal, L.0000-0001-8391-5182
Weiner, A.0000-0001-8835-1355
Hung, C.0000-0002-6879-3639
Ashby, M. L. N.0000-0002-3993-0745
Groves, B.0000-0002-9768-0246
Alternate Title:Variations of the ISM Conditions Across the Main Sequence of Star-Forming Galaxies: Observations and Simulations
Additional Information:© 2016 The American Astronomical Society. Received 2014 December 5; accepted 2015 December 7; published 2016 January 22. We thank the anonymous referee for very useful remarks on the paper. The authors would also like to thank Dimitra Rigopoulou and Georgios Magdis for providing the photometry for the ULIRGs. J. R. M. G., H. A. S. and L. L. acknowledge partial support from NASA grants NNX10AD68G and NNX14AJ61G, and JPL RSA contracts 1369565 and 1369566. This research has made use of NASAs Astrophysics Data System Bibliographic Services. The simulations in this paper were performed on the Odyssey cluster supported by the FAS Research Computing Group at Harvard University.
Group:Infrared Processing and Analysis Center (IPAC), TAPIR
Funding AgencyGrant Number
Harvard UniversityUNSPECIFIED
Subject Keywords:evolution – galaxies: evolution – galaxies: interactions – galaxies: starburst – galaxies: star formation
Issue or Number:1
Record Number:CaltechAUTHORS:20150428-152931332
Persistent URL:
Official Citation:J. R. Martínez-Galarza et al 2016 ApJ 817 76
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57070
Deposited By: Christopher Hayward
Deposited On:28 Apr 2015 23:44
Last Modified:29 Jan 2021 20:39

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