Abstract
Abstract We present a study of the relationship between black hole accretion rate (BHAR) and star formation rate (SFR) in a sample of giant elliptical galaxies. These galaxies, which live at the centers of galaxy groups and clusters, have star formation and black hole activity that is primarily fueled by gas condensing out of the hot intracluster medium. For a sample of 46 galaxies spanning five orders of magnitude in BHAR and SFR, we find a mean ratio of , independent of the methodology used to constrain both SFR and BHAR. This ratio is significantly higher than most previously published values for field galaxies. We investigate whether these high BHAR/SFR ratios are driven by high BHAR, low SFR, or a different accretion efficiency in radio galaxies. The data suggest that the high BHAR/SFR ratios are primarily driven by boosted black hole accretion in spheroidal galaxies compared to their disk counterparts. We propose that the angular momentum of the cool gas is the primary driver in suppressing BHAR in lower-mass galaxies, with massive galaxies accreting gas that has condensed out of the hot phase on nearly radial trajectories. Additionally, we demonstrate that the relationship between specific BHAR and SFR (sBHAR and sSFR) has much less scatter over six orders of magnitude in both parameters, due to competing dependence on morphology between the M BH–M * and BHAR–SFR relations. In general, active galaxies selected by typical techniques have sBHAR/sSFR ∼ 10, while galactic nuclei with no clear AGN signatures have sBHAR/sSFR ∼ 1, consistent with a universal M BH–M spheroid relation.
Highlights
Giant elliptical galaxies, which typically occupy the centers of galaxy groups and clusters, are the most massive galaxies in the Universe
We have considered the ratio of the black hole accretion rate (BHAR) to the star formation rate (SFR) for a sample of giant elliptical galaxies
We consider the relationship between BHAR and SFR where the BHAR is derived based on the jet power of the central active galactic nuclei (AGN)
Summary
Giant elliptical galaxies, which typically occupy the centers of galaxy groups and clusters, are the most massive galaxies in the Universe. While the majority of previous studies have used X-ray luminosity, optical emission lines, or mid-IR luminosity as a proxy for the power output of an AGN, we can instead measure the mechanical power output of radio-loud AGN by calculating the work required to inflate the observed bubbles in the intracluster or intragroup medium (e.g., Bırzan et al 2004; Dunn et al 2005; Rafferty et al 2006; Hlavacek-Larrondo et al 2012) Such measurements of the jet power are sensitive to accretion rates as low as
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