2019/12/12 by Zhaoming Gan, Brandon S. Hensley, Gan, Zhaoming +9
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #astro-ph.GA
paper · pdf · doi:10.48550/arxiv.1912.06147
20 pages, 15 figures; accepted by ApJ
openalex publication_date 2019/12/12 · arxiv created 2020/08/17 · arxiv updated 2020/08/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
What is the expected infrared output of elliptical galaxies? Here we report the latest findings obtained in this high time resolution (~10 years) and high spatial resolution (2.5 parsec at center) study. We add a set of grain physics to the MACER code, including (a) dust grains made in passive stellar evolution; (b) dust grain growth due to collision and sticking; (c) grain destruction due to thermal sputtering; (d) dust cooling of hot gas via inelastic collisions; and (e) radiation pressure on dust grains. The code improvements enable us to analyze the effects of dust on metal depletion and AGN obscuration, and also to assess the infrared output of the modeled galaxies. We simulate a representative massive elliptical galaxy of a central stellar velocity dispersion ~ 260 km/s and modest rotation. We find that: (1) the circumnuclear disk (of a size <~ 1 kpc) is dusty in its outer region where most of the metals are in dust grains, while in the inner disk most of the dust grains are destroyed by the AGN irradiation; (2) the dusty disk is optically thick to both the starlight within the disk and the radiation from the central AGN. Thus the AGN will be obscured behind the disk, and the latter is of a covering factor ~ 0.2; (3) the dust infrared emission is mainly due to the AGN irradiation. The median infrared luminosity is ~ 2e44 erg/s, and it can reach >~ 1e46 erg/s during outbursts; (4) the duty cycles of the AGN activities, star formation, and the dust infrared luminosity roughly match observations, e.g., in most of its lifetime, the simulated galaxy is a stereotypical "quiescent" elliptical galaxy with LIR ~ 1e11*Lsolar, while the star formation rate can exceed 250 Msolar/yr during central outbursts.