Astrophys. J., 724, 1193-1217 (2010/December-1)
Jet-powered molecular hydrogen emission from radio galaxies.
OGLE P., BOULANGER F., GUILLARD P., EVANS D.A., ANTONUCCI R., APPLETON P.N., NESVADBA N. and LEIPSKI C.
Abstract (from CDS):
H2pure-rotational emission lines are detected from warm (100-1500 K) molecular gas in 17/55 (31% of) radio galaxies at redshift z < 0.22 observed with the Spitzer IR Spectrograph. The summed H20-0 S(0)-S(3) line luminosities are L(H2) = 7x1038-2x1042 erg/s, yielding warm H2masses up to 2x1010 M☉. 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 H2 to 7.7 µm polycyclic aromatic hydrocarbon (PAH) emission ratios: L(H2)/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 H2masses, 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 H2 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 H2in 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.
galaxies: active - galaxies: ISM - galaxies: jets - infrared: galaxies - quasars: general
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