HERSCHEL OH SPECTROSCOPY OF SEYFERT, LINER, AND STARBURST GALAXIES

Runco, Jordan; Malkan, Matthew; Fernández-Ontiveros, J. A.; Spinoglio, Luigi
Bibliographical reference

American Astronomical Society, AAS Meeting #233, id.#434.07

Advertised on:
1
2019
Number of authors
4
IAC number of authors
1
Citations
0
Refereed citations
0
Description
We select a sample of 179 local (0 ≤ z < 0.35) galaxies from the Hershel Science Archive to investigate possible relationships between the 65μm, 71μm, 79μm, 84μm, 119μm, and 163μm OH lines and the central region of the galaxy. The sample was observed using the PACS instrument, and contains a wide range of Seyfert galaxies, LINERs, and non-active star-forming galaxies. We fit the profiles of the six OH lines when available in each galaxy to obtain the equivalent width (EW). We find 24 galaxies with some P-Cygni or reverse P-Cygni line profiles, which indicate outflows and inflows. We find a significant correlation between the EW of the 79μm and 119μm OH lines and both the optical spectral type, and the dust temperature measured by 25μm/60μm slope. The more powerful the AGN, the more likely the OH lines are in emission. OH emission is more common in Seyfert-1's than in Seyfert-2's. The other four OH lines have fewer observations; they do not show these correlations. This could be related to the process by which the OH lines go into emission. For the 79μm and 119μm lines, this is thought to be from collisional excitation in the dense AGN environment. Emission in the other four lines is probably generated by radiative pumping, since they arise from much higher energy levels (E/k = 300-600K). Bivariate linear regressions reveal that the correlations are strongest with optical spectral type, and that the correlation with dust temperature is secondary, due to the warmer dust in Seyfert nuclei. Lastly, we use the [NUV – H] color to estimate the amount of dust obscuration. We find that more dust obscuration makes the 119μm line more likely to be in absorption, but not the other five OH lines. This additional correlation with EW(OH119) is driven by P-Cygni features in outflows which are particularly prominent in ULIRGs, where the absorption component often dominates the emission component.