Falcke et al., Molecular Hydrogen ... in Cooling Flow Galaxies

Molecular Hydrogen and Paschen-alpha Emission in Cooling Flow Galaxies

Heino Falcke(1), Marcia J. Rieke(2), George H. Rieke(2), Chris Simpson(3), Andrew S. Wilson(1,4)

(1) Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (hfalcke@astro.umd.edu)
(2) Steward Observatory, University of Arizona, Tucson, AZ 85721 (mrieke, grieke@as.arizona.edu)
(3) Jet Propulsion Laboratory, MS 169-327, 4800 Oak Grove Drive, Pasadena, CA 91109 (bart@fornax.jpl.nasa.gov)
(4) Adjunct Astronomer, Space Telescope Science Institute (wilson@astro.umd.edu)

Astrophysical Journal Letters (1998), Vol. 494, February 20, in press


We present near-infrared spectra obtained to search for Paalpha and molecular hydrogen lines in edge-darkened (FR I-type) radio galaxies with bright Halpha emission in the redshift range 0.06<z<0.15. We find that all three galaxies in our sample which are associated with strong cooling flows (PKS 0745-191, Abell 1795, & Abell 2597) also have strong Paalpha and H2 1-0 S(1) through S(5) emission, while other radio galaxies do not. Together with earlier observations this confirms claims that cooling flow galaxies are copious emitters of molecular hydrogen with large H2 1-0 S(3)/Paalpha ratios in the range 0.5 to 2. The emission is centrally concentrated within the inner few kiloparsec and could come from warm (T ~ 1000-1500 K) molecular material which is being deposited by the cooling flow. We speculate that the H2 emission could be related to the interaction between the jets and the inflowing molecular gas.

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Questions: Heino Falcke, hfalcke@mpifr-bonn.mpg.de