Galaxy Mergers Drive Shocks: an Integral Field Study of GOALS galaxies
We present an integral field spectroscopic study of radiative shocks in 27 nearby ultraluminous and luminous infrared galaxies (U/LIRGs) from the Great Observatory All-sky LIRG Survey, a subset of the Revised Bright Galaxy Sample. Our analysis of the resolved spectroscopic data from the Wide Field Spectrograph focuses on determining the detailed properties of the emission-line gas, including a careful treatment of multicomponent emission-line profiles. The resulting information obtained from the spectral fits is used to map the kinematics of the gas, sources of ionizing radiation, and feedback present in each system. The resulting properties are tracked as a function of merger stage. Using emission-line flux ratios and velocity dispersions, we find evidence for widespread, extended shock excitation in many local U/LIRGs. These low-velocity shocks become an increasingly important component of the optical emission lines as a merger progresses. We find that shocks may account for as much as half of the Hα luminosity in the latest-stage mergers in our sample. We discuss some possible implications of our result and consider the presence of active galactic nuclei and their effects on the spectra in our sample.
© 2015 The American Astronomical Society. Received 2015 July 8; accepted 2015 September 22; published 2015 December 7. The authors acknowledge ARC support under Discovery project DP0984657. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has also made use of NASA's Astrophysics Data System and of SAOImage DS9 (Joye & Mandel 2003), developed by the Smithsonian Astrophysical Observatory.
Submitted - 1509.08468v1.pdf
Published - Rich_2015p28.pdf