Anca Constantin, Anil Seth
We discuss the peculiar nature of the nucleus of M94 (NGC 4736) in the
context of new measurements of the broad H_alpha 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
\times 10^40 erg/s. This LINER galaxy has also possibly the least luminous
broad line region known (LH_alpha =2.2\times10^37 erg/s). We compare black hole
mass estimates of this system to the recently measured ~7 \times 10^6 M_sun
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(H_alpha) relation, empirical correlation
of BH mass with high-ionization mid IR emission lines, and the X-ray excess
variance) provide much lower estimates (~10^5 M_sun). 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.
View original:
http://arxiv.org/abs/1112.3668
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