Draft version November 7, 2018 Preprint typeset using LATEX style emulateapj v. 12/16/11 HERSCHEL SPECTROSCOPY OF EARLY TYPE GALAXIES Ryen Carl Lapham and Lisa M. Young Physics Department, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801;
[email protected],
[email protected] and Alison Crocker Physics Department, Reed College, Portland, OR 97202;
[email protected] Draft version November 7, 2018 ABSTRACT We present Herschel spectroscopy of atomic lines arising in photodissociation regions as well as ion- ization regions of nearby early-type galaxies (ETGs), focusing on the volume-limited Atlas3D sample. Our data include the [C II], [O I], and [N II] 122 and 205 µm lines, along with ancillary data includ- ing CO and H I maps. We find ETGs have [C II]/FIR ratios slightly lower than spiral galaxies in the KINGFISH sample, and several ETGs have unusually large [N II] 122/[C II] ratios. The [N II] 122/[C II] ratio is correlated with UV colors and there is a strong anti-correlation of [C II]/FIR with NUV-K seen in both spirals and ETGs, likely due to a softer radiation field with fewer photons avail- able to ionize carbon and heat the gas. The correlation thus makes a [C II] deficit in galaxies with redder stellar populations. The high [N II] 122/[C II] (and low [C II]/FIR) line ratios could also be affected by the removal of much of the diffuse, low density gas, which is consistent with the low H I/H2 ratios.