Shock Excited Molecules in NGC 1266: ULIRG Conditions at the Center of a Bulge-dominated Galaxy

摘要

We investigate the far infrared (IR) spectrum of NGC 1266, a S0 galaxy that contains a massive reservoir of highly excited molecular gas. Using the Herschel Fourier Transform Spectrometer, we detect the ^(12)CO ladder up to J = (13-12), [C I] and [N II] lines, and also strong water lines more characteristic of UltraLuminous IR Galaxies (ULIRGs). The ^(12)CO line emission is modeled with a combination of a low-velocity C-shock and a photodissociation region. Shocks are required to produce the H_2O and most of the high-J CO emission. Despite having an IR luminosity 30 times less than a typical ULIRG, the spectral characteristics and physical conditions of the interstellar medium of NGC 1266 closely resemble those of ULIRGs, which often harbor strong shocks and large-scale outflows.