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Register a new userThe supermassive black hole mass - Sersic index relations for bulges and elliptical galaxies
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Scaling relations between supermassive black hole mass, M_BH, and host galaxy properties are a powerful instrument for studying their coevolution. A complete picture involving all of the black hole scaling relations, in which each relation is consistent with the others, is necessary to fully understand the black hole-galaxy connection. The relation between M_BH and the central light concentration of the surrounding bulge, quantified by the Sersic index n, may be one of the simplest and strongest such relations, requiring only uncalibrated galaxy images. We have conducted a census of literature Sersic index measurements for a sample of 54 local galaxies with directly measured M_BH values. We find a clear M_BH - n relation, despite an appreciable level of scatter due to the heterogeneity of the data. Given the current M_BH - L_sph and the L_sph - n relations, we have additionally derived the expected M_BH - n relations, which are marginally consistent at the 2 sigma level with the observed relations. Elliptical galaxies and the bulges of disc galaxies are each expected to follow two distinct bent M_BH - n relations due to the Sersic/core-Sersic divide. For the same central light concentration, we predict that M_BH in the Sersic bulges of disc galaxies are an order magnitude higher than in Sersic elliptical galaxies if they follow the same M_BH - L_sph relation.
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We use data from the Galaxy And Mass Assembly (GAMA) survey in the redshift range 0.01$<$z$<$0.1 (8399 galaxies in $g$ to $K_s$ bands) to derive the stellar mass $-$ half-light radius relations for various divisions of early and late-type samples. We find the choice of division between early and late (i.e., colour, shape, morphology) is not particularly critical, however, the adopted mass limits and sample selections (i.e., the careful rejection of outliers and use of robust fitting methods) are important. In particular we note that for samples extending to low stellar mass limits ($<10^{10}mathcal{M_{odot}}$) the Sersic index bimodality, evident for high mass systems, becomes less distinct and no-longer acts as a reliable separator of early- and late-type systems. The final set of stellar mass $-$ half-light radius relations are reported for a variety of galaxy population subsets in 10 bands ($ugrizZYJHK_s$) and are intended to provide a comprehensive low-z benchmark for the many ongoing high-z studies. Exploring the variation of the stellar mass $-$ half-light radius relations with wavelength we confirm earlier findings that galaxies appear more compact at longer wavelengths albeit at a smaller level than previously noted: at $10^{10}mathcal{M_{odot}}$ both spiral systems and ellipticals show a decrease in size of 13% from $g$ to $K_s$ (which is near linear in log wavelength). Finally we note that the sizes used in this work are derived from 2D Sersic light profile fitting (using GALFIT3), i.e., elliptical semi-major half light radii, improving on earlier low-z benchmarks based on circular apertures.
(Abridged) The repeated discovery of supermassive black holes (SMBHs) at the centers of galactic bulges, and the discovery of relations between the SMBH mass (M) and the properties of these bulges, has been fundamental in directing our understanding of both galaxy and SMBH formation and evolution. However, there are still many questions surrounding the SMBH - galaxy relations. For example, are the scaling relations linear and constant throughout cosmic history, and do all SMBHs lie on the scaling relations? These questions can only be answered by further high quality direct M estimates from a wide range in redshift. In this paper we determine the observational requirements necessary to directly determine SMBH masses, across cosmological distances, using current M modeling techniques. We also discuss the SMBH detection abilities of future facilities. We find that if different M modeling techniques, using different spectral features, can be shown to be consistent, then both 30 m ground- and 16 m space-based telescopes will be able to sample M 1e9Msol across ~95% of cosmic history. However, we find that the abilities of ground-based telescopes critically depend on future advancements in adaptive optics systems; more limited AO systems will result in limited effective spatial resolutions, and forces observations towards the near-infrared where spectral features are weaker and more susceptible to sky features. Ground-based AO systems will always be constrained by relatively bright sky backgrounds and atmospheric transmission. The latter forces the use of multiple spectral features and dramatically impacts the SMBH detection efficiency. The most efficient way to advance our database of direct SMBH masses is therefore through the use of a large (16 m) space-based UVOIR telescope.
We use a large sample of upper limits and accurate estimates of supermassive black holes masses coupled with libraries of host galaxy velocity dispersions, rotational velocities and photometric parameters extracted from Sloan Digital Sky Survey i-band images to establish correlations between the SMBH and host galaxy parameters. We test whether the mass of the black hole, MBH, is fundamentally driven by either local or global galaxy properties. We explore correlations between MBH and stellar velocity dispersion sigma, bulge luminosity, bulge mass Sersic index, bulge mean effective surface brightness, luminosity of the galaxy, galaxy stellar mass, maximum circular velocity Vc, galaxy dynamical and effective masses. We verify the tightness of the MBH-sigma relation and find that correlations with other galaxy parameters do not yield tighter trends. We do not find differences in the MBH-sigma relation of barred and unbarred galaxies. The MBH-sigma relation of pseudo-bulges is also coarser and has a different slope than that involving classical bulges. The MBH-bulge mass is not as tight as the MBH-sigma relation, despite the bulge mass proving to be a better proxy of MBH than bulge luminosity. We find a rather poor correlation between MBH and Sersic index suggesting that MBH is not related to the bulge light concentration. The correlations between MBH and galaxy luminosity or mass are not a marked improvement over the MBH sigma relation. If Vc is a proxy for the dark matter halo mass, the large scatter of the MBH-Vc relation then suggests that MBH is more coupled to the baryonic rather than the dark matter. We have tested the need for a third parameter in the MBH scaling relations, through various linear correlations with bulge and galaxy parameters, only to confirm that the fundamental plane of the SMBH is mainly driven by sigma, with a small tilt due to the effective radius. (Abridged)
The mass estimator used to calculate black hole (BH) masses in broad-line active galactic nuclei (AGNs) relies on a virial coefficient (the $f$ factor) that is determined by comparing reverberation-mapped (RM) AGNs with measured bulge stellar velocity dispersions against the $M_{rm BH}-sigma_*$ relation of inactive galaxies. It has recently been recognized that only classical bulges and ellipticals obey a tight $M_{rm BH}-sigma_*$ relation; pseudobulges have a different zero point and much larger scatter. Motivated by these developments, we reevaluate the $f$ factor for RM AGNs with available $sigma_*$ measurements, updated H$beta$ RM lags, and new bulge classifications based on detailed decomposition of high-resolution ground-based and space-based images. Separate calibrations are provided for the two bulge types, whose virial coefficients differ by a factor of $sim 2$: $f=6.3pm1.5$ for classical bulges and ellipticals and $f = 3.2pm0.7$ for pseudobulges. The structure and kinematics of the broad-line region, at least as crudely encoded in the $f$ factor, seems to related to the large-scale properties or formation history of the bulge. Lastly, we investigate the bulge stellar masses of the RM AGNs, show evidence for recent star formation in the AGN hosts that correlates with Eddington ratio, and discuss the potential utility of the $M_{rm BH}-M_{rm bulge}$ relation as a more promising alternative to the conventionally used $M_{rm BH}-sigma_*$ relation for future refinement of the virial mass estimator for AGNs.
We obtained adaptive-optics assisted SINFONI observations of the central regions of the giant elliptical galaxy NGC5419 with a spatial resolution of 0.2 arcsec ($approx 55$ pc). NGC5419 has a large depleted stellar core with a radius of 1.58 arcsec (430 pc). HST and SINFONI images show a point source located at the galaxys photocentre, which is likely associated with the low-luminosity AGN previously detected in NGC5419. Both the HST and SINFONI images also show a second nucleus, off-centred by 0.25 arcsec ($approx 70$ pc). Outside of the central double nucleus, we measure an almost constant velocity dispersion of $sigma sim 350$ km/s. In the region where the double nucleus is located, the dispersion rises steeply to a peak value of $sim 420$ km/s. In addition to the SINFONI data, we also obtained stellar kinematics at larger radii from the South African Large Telescope. While NGC5419 shows low rotation ($v < 50$ km/s), the central regions (inside $sim 4 , r_b$) clearly rotate in the opposite direction to the galaxys outer parts. We use orbit-based dynamical models to measure the black hole mass of NGC5419 from the kinematical data outside of the double nuclear structure. The models imply M$_{rm BH}=7.2^{+2.7}_{-1.9} times 10^9$ M$_{odot}$. The enhanced velocity dispersion in the region of the double nucleus suggests that NGC5419 possibly hosts two supermassive black holes at its centre, separated by only $approx 70$ pc. Yet our measured M$_{rm BH}$ is consistent with the black hole mass expected from the size of the galaxys depleted stellar core. This suggests, that systematic uncertainties in M$_{rm BH}$ related to the secondary nucleus are small.
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