2011/12/19 by Anca Constantin, Anil Seth · 1 citation
Physics and Astronomy · #astro-ph.CO
paper · pdf · doi:10.1155/2012/178060
11 pages, 4 figures, accepted for publication in Advances in Astronomy
arxiv created 2011/12/19 · arxiv updated 2015/06/03
We discuss the peculiar nature of the nucleus of M94 (NGC 4736) in the context of new measurements of the broad Halpha emission from HST-STIS observations. We show that this component is unambiguously associated with the high-resolution X-ray, radio, and variable UV sources detected at the optical nucleus of this galaxy. These multi-wavelength observations suggest that NGC 4736 is one of the least luminous broad-line (type 1) LINERs, with Lbol = 2.5 × 1040 erg/s. This LINER galaxy has also possibly the least luminous broad line region known (LHalpha =2.2×1037 erg/s). We compare black hole mass estimates of this system to the recently measured ~7 × 106 Msun dynamical black hole mass measurement. The fundamental plane and M-sigma relationship roughly agree with the measured black hole mass, while other accretion based estimates (the M-FWHM(Halpha) relation, empirical correlation of BH mass with high-ionization mid IR emission lines, and the X-ray excess variance) provide much lower estimates (~105 Msun). An energy budget test shows that the AGN in this system may be deficient in ionizing radiation relative to the observed emission-line activity. This deficiency may result from source variability or the superposition of multiple sources including supernovae.