DOES THE INTERMEDIATE-MASS BLACK HOLE IN LEDA 87300 (RGG 118) FOLLOW THE NEAR-QUADRATIC M_bh–M_spheroid RELATION?

Abstract

The mass scaling relation between supermassive black holes and their host spheroids has previously been described by a quadratic or steeper relation at low masses (10 5 < M bh /M 10 7 ). How this extends into the realm of intermediate mass black holes (10 2 < M bh /M < 10 5 ) is not yet clear, although for the barred Sm galaxy LEDA 87300, Baldassare et al. have recently reported a nominal virial mass M bh = 5 × 10 4 M residing in a 'spheroid' of stellar mass equal to 6.3 × 10 8 M . We point out, for the first time, that LEDA 87300 therefore appears to reside on the near-quadratic M bh -M sph, * relation. However, Baldassare et al. modelled the bulge and bar as the single spheroidal component of this galaxy. Here we perform a 3-component bulge+bar+disk decomposition and find a bulge luminosity which is 7.7 times fainter than the published 'bulge' luminosity. After correcting for dust, we find that M bulge = 0.9 × 10 8 M and M bulge /M disk = 0.04 -which is now in accord with ratios typically found in Scd-Sm galaxies. We go on to discuss slight revisions to the stellar velocity dispersion (40 ± 11 km s −1 ) and black hole mass (M bh = 2.9 +6.7 −2.3 × 10 4 f 2.3 M ) and show that LEDA 87300 remains consistent with the M bh -σ relation, and also the near-quadratic M bh -M sph, * relation when using the reduced bulge mass. LEDA 87300 therefore offers the first support for the rapid but regulated (near-quadratic) growth of black holes, relative to their host bulge/spheroid, extending into the domain of intermediate mass black holes.

Searching for intermediate-mass black holes in galaxies with low-luminosity AGN: a multiple-method approach

“…The symmetric, near-quadratic relation of Savorgnan et al (2016), though an updated version from GS13, nevertheless agrees very well with the latter (see Graham et al 2016, their Fig. 1).…”

“…4, for the (M BH -M sph ) relation. Y on X-axis regression, dashed lines: symmetric regression), the data that the authors used to obtain them as triangles with error bars (black/gray for ellipticals/spirals), the empty diamonds are two other IMBH candidates (LEDA87300: e.g., Baldassare et al 2015;Graham et al 2016 and Pox52: e.g., Barth et al 2004;Thornton et al 2008;Ciambur 2016), and the colored data points are our results. The green stars come from the Sérsic index, the blue squares from pitch angle and the red circles from the FP-BH.…”

“…Discovering IMBHs and studying their radiative properties will also advance our understanding of the effects of heating and radiation pressure on their surrounding gas, ultimately elucidating the mechanisms of early galaxy formation (Milosavljević et al 2009a,b;Ryu et al 2016). At the same time, discovering active IMBHs in the center of low-mass galaxies, will further our insight into BH feedback and galaxy formation in different mass regimes (Reines et al 2013;Graham et al 2016, and references therein).…”

Blossoms from black hole seeds: properties and early growth regulated by supernova feedback

“…Most BHs have masses ∼ 10 3 M at birth. The lowest mass central BH in a galaxy (ignoring "normal" stellar mass BHs) has a mass estimate of ∼ 50,000 M , and was identified as a low-luminosity AGN in the dwarf galaxy RGG 118 (Reines, Greene & Geha 2013;Graham, Ciambur & Soria 2016;Shankar et al 2016). Our implementation allows for such low-mass BHs to be accounted for.…”

Galaxy Bulges and Their Massive Black Holes: A Review

“…Galaxy reclassification typically occurred when a disk or a bar had been over-looked (e.g. Soria 2016 and, or when the contribution from a disk had been over-estimated in a disky ES type galaxy (as also discussed in Graham 2016b and. The new 2016 spheroid masses, derived from 3.6 µm images which are not affected by dust obscuration, supercede past efforts on many fronts (see Savorgnan & Graham 2016a for details).…”