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The interaction between supermassive black hole (SMBH) feedback and the circumgalactic medium (CGM) continues to be an open question in galaxy evolution. In our study, we use SPH simulations to explore the impact of SMBH feedback on galactic metal retention and the motion of metals and gas into and through the CGM of L ∗ galaxies. We examine 140 galaxies from the 25 Mpc cosmological volume, Romulus25, with stellar masses between 3 × 10 9 - 3 × 10 11 M ⊙ . We measure the fraction of metals remaining in the ISM and CGM of each galaxy, and calculate the expected mass of its SMBH based on the M−σ relation. The deviation of each SMBH from its expected mass, ΔMBH is compared to the potential of its host via σ . We find that SMBHs with accreted mass above the empirical M−σ relation are about 15\% more effective at removing metals from the ISM than under-massive SMBHs in star forming galaxies. Over-massive SMBHs suppress the overall star formation of their host galaxies and more effectively move metals from the ISM into the CGM. However, we see little evidence for the evacuation of gas from their halos, in contrast with other simulations. Finally, we predict that C IV column densities in the CGM of L ∗ galaxies may depend on host galaxy SMBH mass. Our results show that the scatter in the low mass end of M−σ relation may indicate how effective a SMBH is at the local redistribution of mass in its host galaxy.
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This content will become publicly available on February 4, 2026
A 22 Billion M⊙ Black Hole in Holmberg 15A with Keck KCWI Spectroscopy and Triaxial Orbit Modeling
Holmberg 15A (H15A), the brightest cluster galaxy of A85, has an exceptionally low central surface brightness even among local massive elliptical galaxies with distinct stellar cores, making it exceedingly challenging to obtain high-quality spectroscopy to detect a supermassive black hole (SMBH) at its center. Aided by the superb sensitivity and efficiency of KCWI at the Keck II Telescope, we have obtained spatially resolved stellar kinematics over a ∼100″ x 100″ contiguous field of H15A for this purpose. The velocity field exhibits a low-amplitude (∼20 km/s) rotation along a kinematic axis that is prominently misaligned from the photometric major axis, a strong indicator that H15A is triaxially shaped with unequal lengths for the three principal axes. Using 2500 observed kinematic constraints, we perform extensive calculations of stellar orbits with the triaxial Schwarzschild code, TriOS, and search over ~40,000 galaxy models to simultaneously determine the mass and intrinsic 3D shape parameters of H15A. We determine a ratio of p = 0.89 for the middle-to-long principal axes and q = 0.65 for the short-to-long principal axes. Our best estimate of the SMBH mass, M_BH = (2.16_{−0.18}^{+0.23})x10^{10} M⊙, makes H15A — along with NGC 4889 — the galaxy hosting the most massive SMBHs known in the local Universe. Both SMBHs lie significantly above the mean M_BH–σ scaling relation. Repeating the orbit modeling with the axisymmetrized version of TriOS produces worse fits to the KCWI kinematics and increases M_BH to (2.55 ± 0.20)x10^{10} M⊙, which is still significantly below the M_BH = (4.0 ± 0.8)x10^{10} M⊙ reported in a prior axisymmetric study of H15A.
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- Award ID(s):
- 2206219
- PAR ID:
- 10627909
- Publisher / Repository:
- AAS Journals
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 980
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 58
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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