Is there a black hole in NGC 4382?

TL;DR

This study uses HST observations and axisymmetric models to estimate the black hole mass in NGC 4382, finding it consistent with no black hole and discussing implications for galaxy relations and nuclear activity.

Contribution

First detailed black hole mass estimate in NGC 4382 using HST data and axisymmetric modeling, highlighting potential deviations from established galaxy-black hole relations.

Findings

Black hole mass consistent with zero within uncertainties

Upper limit aligns with M-σ relation predictions

Nucleus shows a double structure suggesting a stellar disk

Abstract

We present HST STIS observations of the galaxy NGC 4382 (M85) and axisymmetric models of the galaxy to determine mass-to-light ration (M/L, V-band) and central black hole mass (M_BH). We find M/L = 3.74 +/- 0.1 (solar units) and M_BH = 1.3 (+5.2, -1.2) \times 10^7 M_sun at an assumed distance of 17.9 Mpc, consistent with no black hole. The upper limit, M_BH < 9.6 \times 10^7 M_sun (2{\sigma}) or M_BH < 1.4 \times 10^8 M_sun (3{\sigma}) is consistent with the current M-{\sigma} relation, which predicts M_BH = 8.8 \times 10^7 M_sun at {\sigma}_e = 182 km/s, but low for the current M-L relation, which predicts M_BH = 7.8 \times 10^8 M_sun at L_V = 8.9 \times 10^10 L_sun,V. HST images show the nucleus to be double, suggesting the presence of a nuclear eccentric stellar disk, in analogy 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.