JET-POWERED MOLECULAR HYDROGEN EMISSION FROM RADIO GALAXIES

• Main Authors: Ogle, Patrick M. (Author), Boulanger, Francois (Author), Guillard, Pierre (Author), Evans, Daniel A. (Contributor), Antonucci, Robert (Author), Appleton, P. N. (Author), Nesvadba, Nicole (Author), Leipski, Christian (Author)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor)
• Format: Article
• Language: English
• Published: IOP Publishing, 2015-02-26T21:00:13Z.
• Subjects: Article
• Online Access: Get fulltext

H[subscript 2] pure-rotational emission lines are detected from warm (100-1500 K) molecular gas in [17 over 55] (31% of) radio galaxies at redshift z < 0.22 observed with the Spitzer IR Spectrograph. The summed H[subscript 2] 0-0 S(0)-S(3) line luminosities are L(H[subscript 2]) = 7 × 10[superscript 38]-2 × 10[superscript 42] erg s[superscript -1], yielding warm H[subscript 2] masses up to 2 × 10[superscript 10] M [subscript ☉]. These radio galaxies, of both FR radio morphological types, help to firmly establish the new class of radio-selected molecular hydrogen emission galaxies (radio MOHEGs). MOHEGs have extremely large H[subscript 2] to 7.7 μm polycyclic aromatic hydrocarbon (PAH) emission ratios: L(H[subscript 2]) [over L(PAH7.7)] = 0.04-4, up to a factor 300 greater than the median value for normal star-forming galaxies. In spite of large H[subscript 2] masses, MOHEGs appear to be inefficient at forming stars, perhaps because the molecular gas is kinematically unsettled and turbulent. Low-luminosity mid-IR continuum emission together with low-ionization emission line spectra indicates low-luminosity active galactic nuclei (AGNs) in all but three radio MOHEGs. The AGN X-ray emission measured with Chandra is not luminous enough to power the H[subscript 2] emission from MOHEGs. Nearly all radio MOHEGs belong to clusters or close pairs, including four cool-core clusters (Perseus, Hydra, A2052, and A2199). We suggest that the H[subscript 2] in radio MOHEGs is delivered in galaxy collisions or cooling flows, then heated by radio-jet feedback in the form of kinetic energy dissipation by shocks or cosmic rays.
United States. National Aeronautics and Space Administration (Jet Propulsion Laboratory (U.S.). Contract 1407)
United States. National Aeronautics and Space Administration (Smithsonian Astrophysical Observatory. Chandra X-ray Observatory (U.S.))