Supermassive Black Holes and Their Host Spheroids. I. Disassembling Galaxies

Abstract

Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 µm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K-band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and -for the first time -2D kinematics, we were able to account for spheroids, large-scale, intermediate-scale and nuclear disks, bars, rings, spiral arms, halos, extended or unresolved nuclear sources and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies and identified the optimal decomposition. Moreover, we have independently performed 1D and 2D decompositions, and concluded that, at least when modelling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors.

Galaxy Bulges and Their Massive Black Holes: A Review

“…This agreement with the previously reported mass ratio is not particularly surprising given that the masses used by Kormendy & Ho (2013) for the large number of galaxies in common with differed by more than 0.2 dex for just 8 galaxies, and by more than 0.3 dex for only 5 galaxies. There are of course two quantities that define the M bh -M sph relation, and Savorgnan & Graham (2016a) have recently completed a thorough analysis of the spheroid masses for the galaxies listed in and Rusli et al (2013). Savorgnan & Graham (2016a) not only explain for every galaxy why many published spheroid masses have often disagreed -invariably due to inadequate bulge/disc/etc.…”

“…There are of course two quantities that define the M bh -M sph relation, and Savorgnan & Graham (2016a) have recently completed a thorough analysis of the spheroid masses for the galaxies listed in and Rusli et al (2013). Savorgnan & Graham (2016a) not only explain for every galaxy why many published spheroid masses have often disagreed -invariably due to inadequate bulge/disc/etc. decompositions -but they performed the most careful galaxy decompositions to date, effectively reclassifying many galaxies' morphological type, a process started in -which also included the use of accurate distances to each galaxy.…”

“…From the multicomponent modelling by Savorgnan & Graham (2016a) of galaxies with directly measured black hole masses, it will be possible to populate this diagram and (under certain assumptions) its deprojected cousin.…”

Disky Elliptical Galaxies and the Allegedly Over-Massive Black Hole in the Compact Massive “Es” Galaxy NGC 1271

“…This relationship was established using the careful galaxy decompositions presented in Savorgnan & Graham (2016a), which revealed problems with many past works. Using M sph, * = 9 × 10 10 M , this relation gives log(M bh ) = 8.71 ± 0.49, or M bh = (0.51 +1.07 −0.35 ) × 10 9 M (1-sigma uncertainties).…”

“…However, as done here with NGC 1271, and in Graham et al (2016) with NGC 1277, the spheroid masses first need to be reliably derived. This has now been done for NGC 1332, NGC 3115 and Mrk 1216 (Savorgnan & Graham 2016b) 12 and NGC 821, NGC 3377 and NGC 4697 (Savorgnan & Graham 2016a). …”