Résultats de recherche pour « MBHs »

We present near-infrared (near-IR) surface photometry (2D profiling) for a sample of 29 nearby galaxies for which supermassive black hole (SMBH) masses are constrained. The data are derived from the UKIDSS-LAS representing a significant improvement in image quality and depth over previous studies based on Two Micron All Sky Survey data. We derive the spheroid luminosity and spheroid Sérsic index for each galaxy with galfit3 and use these data to construct SMBH mass–bulge luminosity (Mbh–L) and SMBH–Sérsic index (Mbh–n) relations. The best-fitting K-band relation for elliptical and disc galaxies is log (Mbh/M⊙) =−0.36(±0.03)(MK+ 18) + 6.17(±0.16), with an intrinsic scatter of 0.4+0.09−0.06 dex, whilst for elliptical galaxies we find log (Mbh/M⊙) =−0.42(±0.06)(MK+ 22) + 7.5(±0.15), with an intrinsic scatter of 0.31+0.087−0.047 dex. Our revised Mbh–L relation agrees closely with the previous near-IR constraint by Graham. The lack of improvement in the intrinsic scatter in moving to higher quality near-IR data suggests that the SMBH relations are not currently limited by the quality of the imaging data but is either intrinsic or a result of uncertainty in the precise number of required components required in the profiling process. Contrary to expectation, a relation between SMBH mass and the Sérsic index was not found at near-IR wavelengths. This latter outcome is believed to be explained by the generic inconsistencies between 1D and 2D galaxy profiling which are currently under further investigation.

Abstract To constrain the origin of scaling relations between black hole mass and galaxy properties, i.e., stellar velocity dispersion and bulge luminosity, we investigate the evolution of scaling relations in the past 6 Gyrs. Over the last three years, we have obtained high signal-to-noise ratio Keck spectra of ~ 50 intermediate luminosity broad-line AGNs at z ~ 0.4 and z ~ 0.6, to measure stellar velocity dispersion, and HST (ACS and NICMOS) images of the same objects (~ 40 so far), to measure bulge luminosity from the two-dimensional AGN-galaxy decomposition analysis. In this paper, we will summarize the main results on the MBH–σ and MBH–bulge luminosity relations and their evolution to the present-day universe. The measured scaling relations show that the relations have evolved significantly in the past 6 billion years, and that black hole growth predates the final galaxy assembly.

In this paper, we explore the establishment and evolution of the empirical correlation between black hole mass (MBH) and velocity dispersion (σ) with redshift. We trace the growth and accretion history of massive black holes (MBHs) starting from high-redshift seeds that are planted via physically motivated prescriptions. Two seeding models are explored in this work: ‘light seeds’, derived from Population III remnants, and ‘heavy seeds’, derived from direct gas collapse. Even though the seeds themselves do not satisfy the MBH–σ relation initially, we find that the relation can be established and maintained at all times if self-regulating accretion episodes are associated with major mergers. The massive end of the MBH–σ relation is established early, and lower mass MBHs migrate on to it as hierarchical merging proceeds. How MBHs migrate towards the relation depends critically on the seeding prescription. Light seeds initially lie well below the MBH–σ relation, and MBHs can grow via steady accretion episodes unhindered by self-regulation. In contrast, for the heavy seeding model, MBHs are initially over-massive compared to the empirical correlation, and the host haloes assemble prior to kick-starting the growth of the MBH. We find that the existence of the MBH–σ correlation is purely a reflection of the merging hierarchy of massive dark matter haloes. The slope and scatter of the relation however appear to be a consequence of the seeding mechanism and the self-regulation prescription. We expect flux limited active galactic nucleus surveys to select MBHs that have already migrated on to the MBH–σ relation. Similarly, the Laser Interferometer Space Antenna (LISA) is also likely to be biased towards detecting merging MBHs that preferentially inhabit the MBH–σ. These results are a consequence of major mergers being more common at high redshift for the most massive, biased, galaxies that host MBHs which have already migrated on to the MBH–σ relation. We also predict the existence of a large population of low-mass ‘hidden’ MBHs at high redshift which can easily escape detection. Additionally, we find that if MBH seeds are massive, ∼105 M⊙, the low-mass end of the MBH–σ flattens towards an asymptotic value, creating a characteristic ‘plume’.

We present an updated and improved Mbh–σ diagram containing 64 galaxies for which Mbh measurements (not just upper limits) are available. Because of new and increased black hole masses at the high-mass end, and a better representation of barred galaxies at the low-mass end, the ‘classical’ (all morphological type) Mbh–σ relation for predicting black hole masses is log (Mbh/M⊙) = (8.13 ± 0.05) + (5.13 ± 0.34)log [σ/200 km s−1], with an rms scatter of 0.43 dex. Modifying the regression analysis to correct for a hitherto overlooked sample bias in which black holes with masses <106 M⊙ are not (yet) detectable, the relation steepens further to give log (Mbh/M⊙) = (8.15 ± 0.06) + (5.95 ± 0.44)log [σ/200 km s−1]. We have also updated the ‘barless’ and ‘elliptical-only’Mbh–σ relations introduced by Graham and Hu in 2008 due to the offset nature of barred galaxies. These relations have a total scatter as low as 0.34 dex and currently define the upper envelope of points in the Mbh–σ diagram. They also have a slope consistent with a value 5, in agreement with the prediction by Silk & Rees based on feedback from massive black holes in bulges built by monolithic collapse. Using updated virial products and velocity dispersions from 28 active galactic nuclei, we determine that the optimal scaling factor f– which brings their virial products in line with the 64 directly measured black hole masses – is 2.8+0.7−0.5. This is roughly half the value reported by Onken et al. and Woo et al., and consequently halves the mass estimates of most high-redshift quasars. Given that barred galaxies are, on average, located ∼0.5 dex below the ‘barless’ and ‘elliptical-only’Mbh–σ relations, we have explored the results after separating the samples into barred and non-barred galaxies, and we have also developed a preliminary corrective term to the velocity dispersion based on bar dynamics. In addition, given the recently recognized coexistence of massive black holes and nuclear star clusters, we present the first ever (Mbh+Mnc)–σ diagram and begin to explore how galaxies shift from their former location in the Mbh–σ diagram.

We explore the effects of dissipationless merging on the fundamental plane of elliptical galaxies using an N-body code based on a new, high-performance numerical scheme. We investigate the two extreme cases of galaxy growth by equal-mass merging and accretion of small stellar systems; in a subset of simulations we also consider the presence of dark matter haloes around the merging galaxies. Curiously, we found that the fundamental plane is preserved by major merging, while in the accretion scenario its edge-on thickness is only marginally reproduced, with substantial thickening in the case of merging with low angular momentum. We also found that both the Faber–Jackson and Kormendy relations are not reproduced by the simulations, in accordance with the results of a preliminary analysis based on a simple application of the virial theorem. Finally, we discuss the implications of our results for the origin of the MBH–σ0 and Magorrian relations. We found that dissipationless merging is unable to reproduce the MBH–σ0 relation, if the black hole masses add linearly (while the Magorrian relation is nicely reproduced); in contrast, a black hole merging with substantial emission of gravitational waves reproduces the MBH–σ0 relation but fails to reproduce the Magorrian relation. We argue that our results strongly point towards a major role of dissipation in the formation of early-type galaxies and in the growth of their central supermassive black holes, thus supporting the idea of a link between galaxy formation and quasi-stellar object activity.

Abstract We present a recalibration of the M BH–σ ⋆ relation, based on a sample of 16 reverberation-mapped galaxies with newly determined bulge stellar velocity dispersions (σ ⋆) from integral-field spectroscopy (IFS), and a sample of 32 quiescent galaxies with publicly available IFS. For both samples, σ ⋆ is determined via two different methods that are popular in the literature, and we provide fits for each sample based on both sets of σ ⋆. We find the fit to the active galactic nucleus sample is shallower than the fit to the quiescent galaxy sample, and that the slopes for each sample are in agreement with previous investigations. However, the intercepts to the quiescent galaxy relations are notably higher than those found in previous studies, due to the systematically lower σ ⋆ measurements that we obtain from IFS. We find that this may be driven, in part, by poorly constrained measurements of bulge effective radius (r e ) for the quiescent galaxy sample, which may bias the σ ⋆ measurements low. We use these quiescent galaxy parameterizations, as well as one from the literature, to recalculate the virial scaling factor f. We assess the potential biases in each measurement, and suggest f = 4.82 ± 1.67 as the best currently available estimate. However, we caution that the details of how σ ⋆ is measured can significantly affect f, and there is still much room for improvement.

Abstract Black hole mass (M BH) scaling relations are typically derived using the properties of a galaxy’s bulge and samples dominated by (high-mass) early-type galaxies. Studying late-type galaxies should provide greater insight into the mutual growth of black holes and galaxies in more gas-rich environments. We have used 40 spiral galaxies to establish how M BH scales with both the total stellar mass ( M * , tot ) and the disk’s stellar mass, having measured the spheroid (bulge) stellar mass ( M * , sph ) and presented the M BH– M * , sph relation in Paper I. The relation involving M * , tot may be beneficial for estimating M BH either from pipeline data or at higher redshift, conditions that are not ideal for the accurate isolation of the bulge. A symmetric Bayesian analysis finds log ( M BH / M ⊙ ) = ( 3.05 − 0.49 + 0.57 ) log { M * , tot / [ υ ( 6.37 × 10 10 M ⊙ ) ] } + ( 7.25 − 0.14 + 0.13 ) . The scatter from the regression of M BH on M * , tot

Four new nuclear star cluster masses, Mnc, plus seven upper limits, are provided for galaxies with previously determined black hole masses, Mbh. Together with a sample of 64 galaxies with direct Mbh measurements, 13 of which additionally now have Mnc measurements rather than only upper limits, plus an additional 29 dwarf galaxies with available Mnc measurements and velocity dispersions σ, an diagram is constructed. Given that major dry galaxy merger events preserve the Mbh/L ratio, and given that L∝σ5 for luminous galaxies, it is first noted that the observation Mbh∝σ5 is consistent with expectations. For the fainter elliptical galaxies it is known that L∝σ2, and assuming a constant Mnc/L ratio, the expectation that Mnc∝σ2 is in broad agreement with our new observational result that Mnc∝σ1.57 ± 0.24. This exponent is however in contrast to the value of ∼4 which has been reported previously and interpreted in terms of a regulating feedback mechanism from stellar winds. Finally, it is predicted that host galaxies fainter than MB∼−20.5 mag (i.e. those not formed in dry merger events) which follow the relation Mbh∝σ5, and are thus not ‘pseudo-bulges’, should not have a constant Mbh/Mhost ratio but instead have ⁠. It is argued that the previous near-linear and relations have been biased by the sample selection of luminous galaxies, and as such should not be used to constrain the co-evolution of supermassive black holes in galaxies other than those luminous few built by major dry merger events.