Kayhan Gültekin

THE M-σ AND M-L RELATIONS IN GALACTIC BULGES, AND DETERMINATIONS OF THEIR INTRINSIC SCATTER

We derive improved versions of the relations between supermassive black hole mass (M BH) and host-galaxy bulge velocity dispersion (σ) and luminosity (L; the M-σ and M-L relations), based on 49 M BH measurements and 19 upper limits. Particular attention is paid to recovery of the intrinsic scatter (e0) in both relations. We find log(M BH/M) = α + βlog(σ/200 km s-1) with (α, β, e0) = (8.12 0.08, 4.24 0.41, 0.44 0.06) for all galaxies and (α, β, e0) = (8.23 0.08, 3.96 0.42, 0.31 0.06) for ellipticals. The results for ellipticals are consistent with previous studies, but the intrinsic scatter recovered for spirals is significantly larger. The scatter inferred reinforces the need for its consideration when calculating local black hole mass function based on the M-σ relation, and further implies that there may be substantial selection bias in studies of the evolution of the M-σ relation. We estimate the M-L relationship as log(M BH/M) = α + βlog(LV /1011 L V) of (α, β, e0) = (8.95 0.11, 1.11 0.18, 0.38 0.09); using only early-type galaxies. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We show that culling the sample according to the resolution of the black holes sphere of influence biases the relations to larger mean masses, larger slopes, and incorrect intrinsic residuals.

The fundamental plane of accretion onto black holes with dynamical masses

Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray luminosity, and black hole mass. With the assumption that radio and X-ray luminosities are suitable proxies for jet power and accretion power, respectively, a broad fundamental connection between accretion and jet production is implied. In an effort to refine these links and enhance their power, we have explored the above relations exclusively among black holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors incurred through the use of secondary mass measurements, but also effectively restricts the range of distances considered to a volume-limited sample. Further, we have exclusively used archival data from the Chandra X-ray Observatory to best isolate nuclear sources. We find log LR = (4.80 ? 0.24) + (0.78 ? 0.27)log M BH + (0.67 ? 0.12)log LX , in broad agreement with prior efforts. Owing to the nature of our sample, the plane can be turned into an effective mass predictor. When the full sample is considered, masses are predicted less accurately than with the well-known M-? relation. If obscured active galactic nuclei are excluded, the plane is potentially a better predictor than other scaling measures.

An over-massive black hole in the compact lenticular galaxy NGC 1277

Most massive galaxies have supermassive black holes at their centres, and the masses of the black holes are believed to correlate with properties of the host-galaxy bulge component. Several explanations have been proposed for the existence of these locally established empirical relationships, including the non-causal, statistical process of galaxy–galaxy merging, direct feedback between the black hole and its host galaxy, and galaxy–galaxy merging and the subsequent violent relaxation and dissipation. The empirical scaling relations are therefore important for distinguishing between various theoretical models of galaxy evolution, and they furthermore form the basis for all black-hole mass measurements at large distances. Observations have shown that the mass of the black hole is typically 0.1 per cent of the mass of the stellar bulge of the galaxy. Until now, the galaxy with the largest known fraction of its mass in its central black hole (11 per cent) was the small galaxy NGC 4486B. Here we report observations of the stellar kinematics of NGC 1277, which is a compact, lenticular galaxy with a mass of 1.2 × 1011 solar masses. From the data, we determine that the mass of the central black hole is 1.7 × 1010 solar masses, or 59 per cent of its bulge mass. We also show observations of five other compact galaxies that have properties similar to NGC 1277 and therefore may also contain over-massive black holes. It is not yet known if these galaxies represent a tail of a distribution, or if disk-dominated galaxies fail to follow the usual black-hole mass scaling relations.

A quintet of black hole mass determinations

We report five new measurements of central black hole masses based on Space Telescope Imaging Spectrograph and Wide Field Planetary Camera 2 observations with the Hubble Space Telescope (HST) and on axisymmetric, three-integral, Schwarzschild orbit-library kinematic models. We selected a sample of galaxies within a narrow range in velocity dispersion that cover a range of galaxy parameters (including Hubble type and core/power-law surface density profile) where we expected to be able to resolve the galaxys sphere of influence based on the predicted value of the black hole mass from the M-σ relation. We find masses for the following galaxies: NGC 3585, M BH = 3.4+1.5 –0.6 × 108 M ☉; NGC 3607, M BH = 1.2+0.4 –0.4 × 108 M ☉; NGC 4026, M BH = 2.1+0.7 –0.4 × 108 M ☉; and NGC 5576, M BH = 1.8+0.3 –0.4 × 108 M ☉, all significantly excluding M BH = 0. For NGC 3945, M BH = 9+17 –21 × 106 M ☉, which is significantly below predictions from M-σ and M-L relations and consistent with M BH = 0, though the presence of a double bar in this galaxy may present problems for our axisymmetric code.

Growth of Intermediate-Mass Black Holes in Globular Clusters

We present results of numerical simulations of sequences of binary-single scattering events of black holes in dense stellar environments. The simulations cover a wide range of mass ratios from equal mass objects to 1000:10:10 Mand compare purely Newtonian simulations to simulations in which Newtonian encounters are interspersed with gravitational wave emission from the binary. In both cases, the sequence is terminated when the binarys merger time due to gravitational radiation is less than the arrival time of the next interloper. We find that black hole binaries typically merge with a very high eccentricity (0:93 � e � 0:95 pure Newtonian; 0:85 � e � 0:90 with gravitational wave emission) and that adding gravitational wave emission decreases the time to harden a binary until merger by � 30%-40%. We discuss the implications of this work for the formation of intermediate- mass black holes and gravitational wave detection. Subject headingg black hole physics — galaxies: star clusters — globular clusters: general — stellar dynamics

Flows of X-ray gas reveal the disruption of a star by a massive black hole

Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/ultraviolet flares in galactic centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC 043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.

REGULATION OF BLACK HOLE WINDS AND JETS ACROSS THE MASS SCALE

We present a study of the mechanical power generated by both winds and jets across the black hole mass scale. We begin with the study of ionized X-ray winds and present a uniform analysis using Chandra grating spectra. The high-quality grating spectra facilitate the characterization of the outflow velocity, ionization, and column density of the absorbing gas. We find that the kinetic power of the winds, derived from these observed quantities, scales with increasing bolometric luminosity as log(Lwind,42/Cv) = (1.58 ±0.07)log(LBol,42) − (3.19 ±0.19). This suggests that supermassive black holes may be more efficient than stellar-mass black holes in launching winds, per unit filling factor, Cv. If the black hole binary (BHB) and active galactic nucleus (AGN) samples are fit individually, the slopes flatten to α BHB = 0.91 ±0.31 and α AGN = 0.63 ±0.30 (formally consistent within errors). The broad fit and individual fits both characterize the data fairly well, and the possibility of common slopes may point to common driving mechanisms across the mass scale. For comparison, we examine jet production, estimating jet power based on the energy required to inflate local bubbles. The jet relation is log(LJet,42) = (1.18 ±0.24)log(LBondi,42) − (0.96 ±0.43). The energetics of the bubble associated with Cygnus X-1 are particularly difficult to determine, and the bubble could be a background supernova remnant. If we exclude Cygnus X-1 from our fits, then the jets follow a relation consistent with the winds, but with a higher intercept, log(LJet,42) = (1.34 ±0.50)log(LBondi,42) − (0.80 ±0.82). The formal consistency in the wind and jet scaling relations, when assuming that LBol and LBondi are both proxies for mass accretion rate, suggests that a common launching mechanism may drive both flows; magnetic processes, such as magnetohydrodynamics and magnetocentrifugal forces, are viable possibilities. We also examine winds that are moving at especially high velocities, v> 0.01c. These ultra-fast outflows tend to resemble the jets more than the winds in terms of outflow power, indicating that we may be observing a regime in which winds become jets. A transition at approximately LBol ≈ 10 −2 LEdd is apparent when outflow power is plotted versus Eddington fraction. At low Eddington fractions, the jet power is dominant, and at high Eddington fractions, the wind power is dominant. This study allows for the total power from black hole accretion, both mechanical and radiative, to be characterized in a simple manner and suggests possible connections between winds and jets. X-ray wind data and jet cavity data will enable stronger tests.

THREE-BODY DYNAMICS WITH GRAVITATIONAL WAVE EMISSION

We present numerical three-body experiments that include the effects of gravitational radiation reaction by using equations of motion that include the 2.5-order post-Newtonian force terms, which are the leading-order terms of energy loss from gravitational waves. We simulate binary-single interactions and show that close-approach cross sections for three 1 M☉ objects are unchanged from the purely Newtonian dynamics except for close approaches smaller than 10-5 times the initial semimajor axis of the binary. We also present cross sections for mergers resulting from gravitational radiation during three-body encounters for a range of binary semimajor axes and mass ratios including those of interest for intermediate-mass black holes (IMBHs). Building on previous work, we simulate sequences of high-mass-ratio three-body encounters that include the effects of gravitational radiation. The simulations show that the binaries merge with extremely high eccentricity such that when the gravitational waves are detectable by LISA, most of the binaries will have eccentricities e > 0.9, although all will have circularized by the time they are detectable by LIGO. We also investigate the implications for the formation and growth of IMBHs and find that the inclusion of gravitational waves during the encounter results in roughly half as many black holes ejected from the host cluster for each black hole accreted onto the growing IMBH.

HOW IMPORTANT IS THE DARK MATTER HALO FOR BLACK HOLE GROWTH

In this paper, we examine whether the properties of central black holes in galactic nuclei correlate with their host dark matter halos. We analyze the entire sample of galaxies where black hole mass, velocity dispersion σ, and asymptotic circular velocity Vc have all been measured. We fit M BH-σ and M BH-Vc to a power law, and find that in both relationships the scatter and slope are similar. This model-independent analysis suggests that although the black hole masses are not uniquely determined by dark matter halo mass, when considered for the current sample as a whole, the M BH-Vc correlation may be as strong (or as weak) as M BH-σ. Although the data are sparse, there appears to be more scatter in the correlation for both σ and Vc at the low-mass end. This is not unexpected given our current understanding of galaxy and black hole assembly. In fact, there are several compelling reasons that account for this: (1) supermassive black hole (SMBH) formation is likely less efficient in low-mass galaxies with large angular momentum content, (2) SMBH growth is less efficient in low-mass disk galaxies that have not experienced major mergers, and (3) dynamical effects, such as gravitational recoil, increase scatter preferentially at the low-mass end. Therefore, the recent observational claim of the absence of central SMBHs in bulgeless, low-mass galaxies, or deviations from the correlations defined by high-mass black holes in large galaxies today is, in fact, predicated by current models of black hole growth. We show how this arises as a direct consequence of the coupling between dark matter halos and central black holes at the earliest epochs.

A 200-second quasi-periodicity after the tidal disruption of a star by a dormant black hole.

Oscillating Black Hole The massive black holes that reside in the centers of galaxies can occasionally capture and tidally disrupt stars that wander too close. One such tidal disruption event was detected last year by the Swift satellite. Follow-up x-ray observations analyzed by Reis et al. (p. 949, published online 2 August; see the Perspective by McKinney) show quasi-periodic oscillations that suggest that an accretion disk formed around the black hole shortly after the tidal disruption event. This type of oscillation is commonly seen in the x-ray light from the much lighter black holes that result from the gravitational collapse of stars, but has been seen only once in a massive black hole residing in the center of a galaxy. Oscillations in x-ray emission from a galaxy’s central black hole imply that a disc formed after the hole captured a star. Supermassive black holes (SMBHs; mass is greater than or approximately 105 times that of the Sun) are known to exist at the center of most galaxies with sufficient stellar mass. In the local universe, it is possible to infer their properties from the surrounding stars or gas. However, at high redshifts we require active, continuous accretion to infer the presence of the SMBHs, which often comes in the form of long-term accretion in active galactic nuclei. SMBHs can also capture and tidally disrupt stars orbiting nearby, resulting in bright flares from otherwise quiescent black holes. Here, we report on a ~200-second x-ray quasi-periodicity around a previously dormant SMBH located in the center of a galaxy at redshift z = 0.3534. This result may open the possibility of probing general relativity beyond our local universe.