Toward precision supermassive black hole masses using megamaser disks

Journal Article · Tue Mar 01 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/819/1/11· OSTI ID:22886992

Greene, Jenny E. ^[1]; Braatz, James A. ^[2]; Constantin, Anca ^[3]; Kuo, Cheng-Yu ^[4]

---

1. Department of Astrophysics, Princeton University, Princeton, NJ 08544 (United States)
2. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
3. Department of Physics and Astronomy, James Madison University, Harrisonburg, VA 22807 (United States)
4. Physics Department, National Sun Yat-Sen University, No. 70, Lien-Hai Rd, Kaosiung City 80424, Taiwan, R.O.C (China)

Megamaser disks provide the most precise and accurate extragalactic supermassive black hole (BH) masses. Here we describe a search for megamasers in nearby galaxies using the Green Bank Telescope (GBT). We focus on galaxies where we believe that we can resolve the gravitational sphere of influence of the BH and derive a stellar or gas dynamical measurement with optical or NIR observations. Since there are only a handful of super massive BHs that have direct BH mass measurements from more than one method, even a single galaxy with a megamaser disk and a stellar dynamical BH mass would provide necessary checks on the stellar dynamical methods. We targeted 87 objects from the Hobby–Eberly Telescope Massive Galaxy Survey, and detected no new maser disks. Most of the targeted objects are elliptical galaxies with typical stellar velocity dispersions of 250 km s{sup −1} and distances within 130 Mpc. We discuss the implications of our non-detections, whether they imply a threshold X-ray luminosity required for masing, or possibly reflect the difficulty of maintaining a masing disk around much more massive (≳10{sup 8} M{sub ⊙}) BHs at a low Eddington ratio. Given the power of maser disks for probing BH accretion and demographics, we suggest that future maser searches should endeavour to remove remaining sample biases, in order to sort out the importance of these covariant effects.

• OSTI ID: 22886992
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 819; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
DETECTION
DISPERSIONS
DISTANCE
GALAXIES
GALAXY NUCLEI
LUMINOSITY
MASERS
MASS
SUPERMASSIVE STARS
TELESCOPES
VELOCITY
X RADIATION