南方基地知识库

We present the analysis of the physical properties of the interstellar medium in the nearby early-type galaxy NGC 3665, based on the far-infrared photometric and spectroscopic data as observed by the Herschel Space Observatory. The fit to the spectral energy distribution reveals a high dust content in the galaxy, with a dust-to-stellar mass ratio of M-dust/M-* similar to 1.1 x 10(-4) that is nearly three times larger than the mean value of local S0+S0a galaxies. For the ionized regions (H II regions), the electron density (ne) is around 49.5 +/- 11.9 cm(-3) based on the [N II] 122 mu m/[N II] 205 mu m ratio. For the photodissociation regions, the heating efficiency ranges from 1.26. x. 10(-3) to 1.37 x 10-3 based on the ([C II]+[O I] 63 mu m)/L-TIR, which is slightly lower than other local galaxies; the hydrogen nucleus density and the strength of the far-UV radiation field are n similar to 10(4) cm(-3) and G0 similar to 10(-0.25), respectively. The above results are consistent with the presence of weak active galactic nuclei and a low level of star-forming activity in NGC 3665. Our results give strong support to the "morphological quenching" scenario, where a compact, massive bulge can stabilize the amount of cool gas against star formation.