COMPOSITE SPECTRA IN MERGING U/LIRGs CAUSED BY SHOCKS

Journal Article · Mon Jan 20 00:00:00 EST 2014 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/781/1/L12· OSTI ID:22364024

Rich, J. A. ^[1]; Kewley, L. J.

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1. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

We present a key result from our optical integral field spectroscopic survey of 27 nearby ultraluminous and luminous infrared galaxies (U/LIRGs) from the Great Observatory All-Sky LIRG Survey. Using spatially resolved multi-component emission line fitting to trace the emission line ratios and velocity dispersion of the ionized gas, we quantify for the first time the widespread shock ionization in gas-rich merging U/LIRGs. Our results show a fractional contribution to the total observed Hα flux from radiative shocks increasing from a few percent during early merger stages to upward of 60% of the observed optical emission line flux in late-stage mergers. We compare our resolved spectroscopy to nuclear spectra and find that 3/4 of the galaxies in our sample that would be classified as ''composite'' based on optical spectroscopy are primarily characterized by a combination of star formation and merger-driven shocks. Our results have important implications for the interpretation of ''composite'' rest-frame optical spectra of U/LIRGs as starburst+active galactic nucleus (AGN), as the shock emission combined with star formation can mimic ''composite'' optical spectra in the absence of any contribution from an AGN.

• OSTI ID: 22364024
• Journal Information: Astrophysical Journal Letters, Vol. 781, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
EMISSION SPECTRA
GALAXIES
GALAXY NUCLEI
SKY
STAR EVOLUTION
STARS
VELOCITY