Does the Lockstep Growth between Black Holes and Bulges Create Their Mass Relation?

Yang, Guang; Brandt, W. N.; Alexander, David M.; Boquien, Médéric; Ni, Qingling; Papovich, Casey; Spilker, Justin S.; Vito, Fabio; Walsh, Jonelle L.; Zhang, Chengpeng

Abstract

Recent studies have revealed a strong relation between the sample-averaged black hole (BH) accretion rate (BHAR) and star formation rate (SFR) among bulge-dominated galaxies—i.e., "lockstep" BH–bulge growth—in the distant universe. This relation might be closely connected to the BH–bulge mass correlation observed in the local universe. To further understand BH–bulge coevolution, we present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) or CO(3–2) observations of seven star-forming bulge-dominated galaxies at z = 0.5–2.5. Using the ALMA data, we detect significant (>3σ) CO emission from four objects. For our sample of seven galaxies, we measure (or constrain with upper limits) their CO line fluxes and estimate their molecular gas masses (Mgas). We also estimate their stellar masses (Mstar) and SFRs, by modeling their spectral energy distributions. Using these physical properties, we derive the gas depletion timescales (τdep ≡ Mgas/SFR) and compare them with the bulge/BH growth timescales (τgrow ≡ Mstar/SFR ∼ MBH/BHAR). Our sample generally has τdep shorter than τgrow by a median factor of ≳4, indicating that the cold gas will be depleted before significant bulge/BH growth takes place. This result suggests that BH–bulge lockstep growth is mainly responsible for maintaining the mass relation, not creating it. We note that our sample is small and limited to z < 2.5; JWST and ALMA will be able to probe to higher redshifts in the near future.

Citation

Yang, G., Brandt, W. N., Alexander, D. M., Boquien, M., Ni, Q., Papovich, C., …Zhang, C. (2022). Does the Lockstep Growth between Black Holes and Bulges Create Their Mass Relation?. Astrophysical Journal, 940(2), Article 146. https://doi.org/10.3847/1538-4357/ac9c68

• Journal Article Type: Article
• Acceptance Date: Oct 17, 2022
• Online Publication Date: Nov 30, 2022
• Publication Date: Dec 1, 2022
• Deposit Date: Oct 31, 2023
• Publicly Available Date: Oct 31, 2023
• Journal: The Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 940
• Issue: 2
• Article Number: 146
• DOI: https://doi.org/10.3847/1538-4357/ac9c68
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://durham-repository.worktribe.com/output/1872832