Is there a black hole in NGC4382?

Abstract

We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of the galaxy NGC4382 (M85) and axisymmetric models of the galaxy to determine mass-to-light ratio (ΥV) and central black hole mass (M BH). We find ΥV = 3.74 0.1 M ⊙/L ⊙ and M BH = 1.3+5.2- 1.2 × 107 M ⊙ at an assumed distance of 17.9Mpc, consistent with no black hole. The upper limit, M BH < 9.6 × 107 M ⊙(2σ) or M BH < 1.4 × 108(3σ), is consistent with the current M-σ relation, which predicts M BH = 8.8 × 107 M ⊙ at σe = 182 km s -1, but low for the current M - L relation, which predicts M BH = 7.8 × 108 M⊙ at LV = 8.9 × 1010 L , V. HST images show the nucleus to be double, suggesting the presence of a nuclear eccentric stellar disk, analogous to the Tremaine disk in M31. This conclusion is supported by the HST velocity dispersion profile. Despite the presence of this non-axisymmetric feature and evidence of a recent merger, we conclude that the reliability of our black hole mass determination is not hindered. The inferred low black hole mass may explain the lack of nuclear activity. © 2011. The American Astronomical Society. All rights reserved.