AN EVOLUTIONARY PARADIGM FOR DUSTY ACTIVE GALAXIES AT LOW REDSHIFT

Journal Article · Mon Jul 20 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/700/1/395; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21313868

Farrah, D; Oliver, S; Liddle, A R ^[1]; Connolly, B ^[2]; Connolly, N ^[3]; Spoon, H W. W.; Houck, J R ^[4]; Prosper, H B ^[5]; Armus, L

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1. Astronomy Centre, University of Sussex, Brighton (United Kingdom)
2. Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104-6396 (United States)
3. Physics Department, Hamilton College, Clinton, NY 13323 (United States)
4. Astronomy Department, Cornell University, Ithaca, NY 14853 (United States)
5. Department of Physics, Florida State University, Tallahassee, FL 32306 (United States)

We apply methods from Bayesian inferencing and graph theory to a data set of 102 mid-infrared spectra, and archival data from the optical to the millimeter, to construct an evolutionary paradigm for z < 0.4 infrared-luminous galaxies. We propose that the ultraluminous infrared galaxies (ULIRG) lifecycle consists of three phases. The first phase lasts from the initial encounter until approximately coalescence. It is characterized by homogeneous mid-IR spectral shapes, and IR emission mainly from star formation, with a contribution from an active galactic nucleus (AGN) in some cases. At the end of this phase, a ULIRG enters one of two evolutionary paths depending on the dynamics of the merger, the available quantities of gas, and the masses of the black holes in the progenitors. On one branch, the contributions from the starburst and the AGN to the total IR luminosity decline and increase, respectively. The IR spectral shapes are heterogeneous, likely due to feedback from AGN-driven winds. Some objects go through a brief QSO phase at the end. On the other branch, the decline of the starburst relative to the AGN is less pronounced, and few or no objects go through a QSO phase. We show that the 11.2 {mu}m polycyclic aromatic hydrocarbon feature is a remarkably good diagnostic of evolutionary phase, and identify six ULIRGs that may be archetypes of key stages in this lifecycle.

• OSTI ID: 21313868
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 700; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
BLACK HOLES
COALESCENCE
DATA ANALYSIS
EMISSION
GALACTIC EVOLUTION
GALAXIES
GRAPH THEORY
INFRARED SPECTRA
LUMINOSITY
MASS
POLYCYCLIC AROMATIC HYDROCARBONS
RED SHIFT
STARS