Shocked Molecular Hydrogen in the 3C 326 Radio Galaxy System

October 2007 • 2007ApJ...668..699O

Authors • Ogle, Patrick • Antonucci, Robert • Appleton, P. N. • Whysong, David

Abstract • The Spitzer spectrum of the giant FR II radio galaxy 3C 326 is dominated by very strong molecular hydrogen emission lines on a faint IR continuum. The H₂ emission originates in the northern component of a double-galaxy system associated with 3C 326. The integrated luminosity in H₂ pure rotational lines is 8.0×10⁴¹ erg s^-1, which corresponds to 17% of the 8-70 μm luminosity of the galaxy. A wide range of temperatures (125-1000 K) is measured from the H₂ 0-0 S(0)-S(7) transitions, leading to a warm H₂ mass of 1.1×10⁹ M_solar. Low-excitation ionic forbidden emission lines are consistent with an optical LINER classification for the active nucleus, which is not luminous enough to power the observed H₂ emission. The H₂ could be shock heated by the radio jets, but there is no direct indication of this. More likely, the H₂ is shock heated in a tidal accretion flow induced by interaction with the southern companion galaxy. The latter scenario is supported by an irregular morphology, a tidal bridge, and a possible tidal tail imaged with IRAC at 3-9 μm. Unlike ultraluminous infrared galaxies, which in some cases exhibit H₂ line luminosities of comparable strength, 3C 326 shows little star formation activity (~0.1 M_solar yr^-1). This may represent an important stage in galaxy evolution. Starburst activity and efficient accretion onto the central supermassive black hole may be delayed until the shock-heated H₂ can kinematically settle and cool.

Links

• PREPRINT http://arxiv.org/abs/0707.0896
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2007ApJ...668..699O
• ELECTR https://doi.org/10.1086%2F521334
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2007ApJ...668..699O
• PDF https://stacks.iop.org/0004-637X/668/699/pdf
• DATA https://irsa.ipac.caltech.edu/bibdata/2007/O/2007ApJ...668..699O.html