Molecular Gas Heating and Modified Dust Properties in Active Galaxies: Growing Black Holes or Tidal Shocks?
Abstract
We investigate if and how growing supermassive black holes and gravitational interactions affect the warm molecular gas and dust of galaxies. Our analysis focuses on the morphologies and warm interstellar medium (ISM) properties of 630 galaxies at z < 0.1. We use grizy images from the Pan-STARRS survey to classify the galaxies into mergers, early mergers, and non-mergers. We look at the effect of merger status on the molecular hydrogen (H2) temperature and dust properties of the ISM inferred from mid-infrared (MIR) spectroscopic measurements, including the active galactic nucleus (AGN) contribution to the total IR emission, the H2 rotational transitions, PAH emission lines, and the strength of the silicate absorption lines. We find that in AGN hosts, the ISM is warmer, the PAHs are more ionized, and the silicate strengths have a wider range of values than in non-AGN hosts. We find some statistical differences between the H2 properties of mergers and non-mergers, but those differences are less statistically significant than those between AGN and non-AGN hosts. We also infer that the warm gas and dust of non-AGN hosts spans a smaller range of properties than that of AGN-dominated sources. A growing supermassive black hole increases the temperature of at least one component of the warm molecular ISM, the relative importance of H2 to PAH cooling, and the ionization of PAHs, while mergers are associated with higher 11.3 PAH luminosities and deeper silicate absorption features. These statistical findings may reflect a wide range of triggering mechanisms, AGN orientations, and the evolutionary stages of the hosts galaxies.
- Publication:
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American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23530409M