The Megamaser Cosmology Project: precise black hole mass measurement and the implication for the M BH-σ* relation

We made dynamical black hole mass measurements from nineteen Seyfert 2 galaxies which host sub-parsec H₂O maser disks using the H₂O megamaser technique. The nearly perfect Keplerian rotation curves in many of these maser systems guarantee the high accuracy and precision of the black hole mass measurements. With the stellar velocity dispersion (σ*) of the galaxy bulges measured with the Dupont 2.5 m telescope at Las Campanas Observatory in the South and the Apache Point Observatory (APO) 3.5m telescope in the North, we found that H₂O maser galaxies, most of which host pseudo bulges rather than classical bulges, do not all follow the M _BH -σ* relation shown in the literature. This result is well consistent with the latest findings by Kormendy & Ho (2013) that only early type galaxies and galaxies with classical bulges follow a tight M_BH-σ* relation. Such a tight correlation may not exist in pseudo bulge galaxies.