Hubble Space Telescope Captures UGC 12591: bulge/disc properties, star formation and ‘missing baryons’ census in a very massive and fast-spinning hybrid galaxy

Journal Article · Wed Sep 28 00:00:00 EDT 2022 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stac2683· OSTI ID:2425056

Ray, Shankar ^[1]; Bagchi, Joydeep ^[2]; Dhiwar, Suraj ^[3]; Pandge, M. B. ^[4]; Mirakhor, Mohammad ^[5]; Walker, Stephen A. ^[5]; Mukherjee, Dipanjan ^[6]

---

1. Dayanand Science College, Latur (India); CHRIST University, Bengaluru (India)
2. CHRIST University, Bengaluru (India)
3. Dayanand Science College, Latur (India); Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune (India); Savitribai Phule Pune University (India)
4. Dayanand Science College, Latur (India)
5. University of Alabama, Huntsville, AL (United States)
6. Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune (India)

We present Hubble Space Telescope (HST) observations of the nearby, massive, highly rotating hybrid galaxy UGC 12591, along with observations in the UV to FIRbands. HST data in V, I, and H bands is used to disentangle the structural components. Surface photometry shows a dominance of the bulge over the disc with an H-band B/D ratio of $$69{{\,\rm per\,cent}}$$. The spectral energy distribution (SED) fitting reveals an extremely low global star formation rate (SFR) of $$\rm \sim 0.1\!-\!0.2\, M_\odot \, yr^{-1}$$, exceptionally low for the galaxy’s huge stellar mass of $$\rm 1.6\times 10^{11}M_\odot$$, implying a strong quenching of its SFR with a star formation efficiency of 3–5 per cent. For at least the past $$\rm 10^{8}$$ yr, the galaxy has remained in a quiescent state as a sterile, ‘red and dead’ galaxy. UGC 12591 hosts a supermassive black hole (SMBH) of $$\rm 6.18\times 10^{8} \, M_\odot$$, which is possibly quiescent at present, i.e. we neither see large ($$\rm \gt 1 kpc$$) radio jets nor the SMBH contributing significantly to the mid-IR SED, ruling out strong radiative feedback of AGN. We obtained a detailed census of all observable baryons with a total mass of $$\rm 6.46\times 10^{11} \, M_\odot$$ within the virial radius, amounting to a baryonic deficiency of $${\sim }85{{\,\rm per\,cent}}$$ relative to the cosmological mean. Only a small fraction of these baryons reside in a warm/hot circumgalactic X-ray halo, while the majority are still unobservable. We discussed various astrophysical scenarios to explain its unusual properties. Our work is a major step forward in understanding the assembly history of such extremely massive, isolated galaxies.

• Research Organization: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); USDOE Office of Science (SC)
• OSTI ID: 2425056
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 1 Vol. 517; ISSN 0035-8711; ISSN 1365-2966
• Publisher: Oxford University Press
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
Astronomy & Astrophysics
Galaxy: formation
Galaxy: fundamental parameters
galaxies: ISM
galaxies: individual: UGC12591
galaxies: spiral