Mapping the Warped H2O Maser Disk in the Dwarf Galaxy IC 750
Abstract
We present the first map of H2O megamasers in the dwarf galaxy IC 750. Very Long Baseline Array (VLBA) K-band images detect maser emission at 22.235 GHz in the central parsec of the galaxy, redshifted 595-835 km s-1. We extracted and mapped maser positions to reveal a nearly edge-on, warped disk structure of diameter 0.20 pc, roughly aligned with the galaxy disk. The disk contains two high-velocity regions, one blueshifted and one redshifted from the optical galaxy recession velocity of 701 km s-1, with masers in Keplerian orbits around the black hole. We iterated a Keplerian fit over possible center locations in a 5 mas x 5 mas region around which the map was nearly symmetric, and for BH recession velocities of 697-705 km s-1. Fitting the red and blue Keplerian regions separately for each point, we accepted masses for which red and blue mass values agreed within 5%. We find a best-fit BH mass range of MBH ≈ (7.1-8.1) x 104 M⊙. Fitting only the highest-velocity points yields an upper limit for the BH mass of MBH ≈ (9.4-11.8) x 104 M⊙. Our image of IC 750 from archival Chandra data shows three hard, compact sources along the galaxy, and soft extended emission along the galaxy and perpendicular to it. The Chandra 0.3-10.0 keV centroid position of the central source is offset from the maser location by 0''.76.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23346002R