My work on SMBHs takes up most of my life right now. The work I do in this area is frequently as a part of the Nuker collaboration (PI Doug Richstone).

Recent SMBH Projects

  1. Disk–Jet Coupling in NGC 4395
  2. What’s on Tap?
  3. Swift Galactic Plane Survey Discovery of a Galactic Supernova Remnant
  4. Regulation of Black Hole Winds and Jets
  5. What does an accretion disk with a gap in it look like?
  6. Discovery of a gigantic black hole (1.7 × 1011 M) in NGC 1277, a modestly sized galaxy
  7. Discovery of a QPO in a Tidal Disruption Event
  8. A Survey of SMBHs with Chandra
  9. Is There a Black Hole in NGC 4382?
  10. Orbit Based Dynamical Models of the Sombreo Galaxy
  11. X-Ray and Radio Constraints on the Mass of the Black Hole in Swift J164449.3+573451
  12. Observational Selection Effects and the M–σ Relation
  13. The Black Hole Mass in M87 from Gemini/NIFS Adaptive Optics Observations
  14. A Distinctive Disk-Jet Coupling in the Seyfert-1 Active Galactic Nucleus NGC 4051
  15. The Fundamental Plane of Black Hole Accretion
  16. The Intrinsic Scatter in Black Hole Scaling Relations
  17. Five Black Hole Mass Measurements.

G306.3−0.9: A newly discovered young galactic supernova remnant

Reynolds, M. et al. (2013), G306.3−0.9: A Newly Discovered Young Galactic Supernova Remnant ApJ, 766, 112.

<i>Swift</i> image of G306.3−0.9.

We discovered a new supernova remnant (SNR), G306.3-0.9, with the Swift Galactic Plane Survey. We followed it up with new Chandra and radio observations. Chandra imaging reveals a complex morphology, dominated by a bright shock. The X-ray spectrum is broadly consistent with a young SNR in the Sedov phase, implying an age of 2500 yr for a distance of 8 kpc, plausibly identifying this as one of the 20 youngest Galactic SNRs. Australia Telescope Compact Array (ATCA) imaging reveals a prominent ridge of radio emission that correlates with the X-ray emission. We find a flux density of ~160 mJy at 1 GHz, which is the lowest radio flux recorded for a Galactic SNR to date. The remnant is also detected at 24 μm, indicating the presence of irradiated warm dust. The data reveal no compelling evidence for the presence of a compact stellar remnant. I recognize that this is not a supermassive black hole, but I didn't have anywhere else obvious to put it. Besides, have you seen the image below?

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Composite image of supernova remnant G306.3-0.9 near a young stellar nursery.
Composite X-ray (Chandra 0.3–7 keV, blue), infraread (Spitzer 24 μm, red), and radio (ATCA 5 GHz, purple) of G306.3-0.9, a young Galactic supernova remnant.

What does an accretion disk with a gap in it look like?

Gültekin & Mïllër (2012), “Observable Consequences of Merger-Driven Gaps and Holes in Black Hole Accretion Disks,” ApJ, 761, 90.

Schematic illustration of gapped accretion disk

We calculate the observable signature of a black hole (BH) accretion disk with a gap or a hole created by a secondary BH embedded in the disk. We find that for an interesting range of parameters of BH masses (~106–109 M), orbital separation (~1 AU to ~0.1 pc), and gap width (10-190 disk scale heights), the missing thermal emission from a gap manifests itself in an observable decrement in the spectral energy distribution (SED). We present observational diagnostics in terms of power-law forms that can be fit to line-free regions in active galactic nucleus (AGN) spectra or in fluxes from sequences of broad filters. Most interestingly, the change in slope in the broken power law is almost entirely dependent on the width of the gap in the accretion disk, which in turn is uniquely determined by the mass ratio of the BHs, such that it scales roughly as q5/12. Thus, one can use spectral observations of the continuum of bright AGNs to infer not only the presence of a closely separated BH binary, but also the mass ratio. When the BH merger opens an entire hole (or cavity) in the inner disk, the broadband SED of the AGNs or quasar may serve as a diagnostic. Such sources should be especially luminous in optical bands but intrinsically faint in X-rays (i.e., not merely obscured). We briefly note that viable candidates may have already been identified, though extant detailed modeling of those with high-quality data have not yet revealed an inner cavity.

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SED of accretion disk with gaps of varying width.
Simulated SEDs with gaps of increasing the gap width with values w/h = 0, 10, 60, 80, 100, 140, and 180. The figure shows the depth of the dip in the SED increasing as well as the differences in the slopes on either side of the local minimum increasing as w/h increases. Empirically, we find that the change in slope scales approximately as (w/h)5/4, allowing one to infer the mass ratio of the binary from just the change in the slopes.

Discovery of a gigantic black hole in a modestly sized galaxy

van den Bosch, R. et al. (2012), “An over-massive black hole in the compact lenticular galaxy NGC1277, ” Nature, 491, 729.

Image of 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 NGC4486B. Here we report observations of the stellar kinematics of NGC1277, 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 NGC1277 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.

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Black hole mass vs. galaxy luminosity relation showing that NGC 1277 is a huge upward outlier
The black line shows the mass–luminosity relation for galaxies with a directly measured black-hole mass. NGC 1277 is a significant positive outlier. In addition to the galaxies (black dots) to which the relation has been fitted8, eight black-hole masses (NGC 4486B9, triangles16, squares19) have been added with 2MASS K-band bulge luminosities. The error bars denote 1-s.d. uncertainties, except for the NGC 1277 bulge luminosity, where we use its total luminosity as a conservative upper limit.

Discovery of a Quasi Periodic Oscillation in a Tidal Disruption Event

Reis, R. et al. (2012), A 200-Second Quasi-Periodicity After the Tidal Disruption of a Star by a Dormant Black Hole Science, 337, 949.

Artist’s impression of accretion disk with QPO-producing spot

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.

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Power spectra for Suzaku and XMM observations in the 2-10 keV energy range, showing QPO at 4.8 mHz.
(A) Power spectra for Suzaku and (B) for XMM #1, in the 2–10 keV energy range. The power spectra are normalized so that their integral gives the squared RMS fractional variability. The Poisson noise level expected from the data errors is shown as the dashed horizontal line. We checked that the peak is robust to a variety of frequency and time resolutions. The arrow in both panels mark the presence of a QPO with a centroid frequency of νsuzaku ~ 4.8 mHz. The solid curves enclose the range of the best fit to the underlying continuum as described in table S1 (model 2). The dotted curves show the 99.99 and 99.73% (3σ) threshold for significant detection.

A Chandra Survey of SMBHs with Dynamically Determined Masses

Gültekin et al. (2012), “A Chandra Survey of Supermassive Black Holes with Dynamical Mass Measurements,” ApJ, 749, 129.

DSS image of NGC 1300 with new Chandra X-ray point sources identified

We present Chandra observations of 12 galaxies that contain supermassive black holes (SMBHs) with dynamical mass measurements. Each galaxy was observed for 30 ks and resulted in a total of 68 point-source detections in the target galaxies including SMBH sources, ultraluminous X-ray sources (ULXs), and extragalactic X-ray binaries. Based on our fits of the X-ray spectra, we report fluxes, luminosities, Eddington ratios, and slope of the power-law spectrum. Normalized to the Eddington luminosity, the 2–10 keV band X-ray luminosities of the SMBH sources range from 10–8 to 10–6, and the power-law slopes are centered at ~2 with a slight trend toward steeper (softer) slopes at smaller Eddington fractions, implying a change in the physical processes responsible for their emission at low accretion rates. We find 20 ULX candidates, of which 6 are likely (>90% chance) to be true ULXs. The most promising ULX candidate has an isotropic luminosity in the 0.3–10 keV band of 1.0+0.6−0.3           × 1040 erg s−1.

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Figure showing Gamma, the X-ray photon index, as a function of the 2-10 keV X-ray luminosity as a fraction of Eddington.  There is a slight trend to negative slope.
Slope of the spectral power law (Γ) as a function of hard X-ray Eddington fraction (L2–10/LEdd). Large red circles are new results from this paper, and small gray squares are results from Gültekin et al. (2009a). The slope of the best-fit relation to these two data sets, which is drawn as a solid black line, is 0.24 ± 0.12. The dark shaded region shows the 1σ confidence band, and the light shaded region shows the 1σ confidence band plus the rms intrinsic scatter. Error bars on each point are 1σ uncertainties. For reference we show similar data based primarily on secondary mass estimates from Gu & Cao (2009), Shemmer et al. (2008), Winter et al. (2009), and Younes et al. (2011) as indicated in the legend drawn as small open triangles.

Is the M–σ Relation an Upper Limit Relation?

Gültekin et al. (2011), “Observational Selection Effects and the M–σ Relation,” ApJ, 738, 17.

p-values as a funtion of minimum mass

We examine the possibility that the observed relation between black hole mass and host-galaxy stellar velocity dispersion (the M–σ relation) is biased by an observational selection effect, the difficulty of detecting a black hole whose sphere of influence is smaller than the telescope resolution. In particular, we critically investigate recent claims that the M–σ relation only represents the upper limit to a broad distribution of black hole masses in galaxies of a given velocity dispersion. We find that this hypothesis can be rejected at a high confidence level, at least for the early-type galaxies with relatively high velocity dispersions (median 268 km s−1) that comprise most of our sample. We also describe a general procedure for incorporating observational selection effects in estimates of the properties of the M–σ relation. Applying this procedure we find results that are consistent with earlier estimates that did not account for selection effects, although with larger error bars. In particular, (1) the width of the M–σ relation is not significantly increased, (2) the slope and normalization of the M–σ relation are not significantly changed, and (3) most or all luminous early-type galaxies contain central black holes at zero redshift. Our results may not apply to late-type or small galaxies, which are not well represented in our sample.

The Fundamental Plane of Accretion onto Black Holes with Dynamical Masses

Gültekin, K. et al. (2009c), Fundamental Plane of Accretion onto Black Holes with Dynamical Masses ApJ, 706, 404.

Plot of edge-on view of fundamental plane

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-σ relation. If obscured active galactic nuclei are excluded, the plane is potentially a better predictor than other scaling measures.

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Figure 5 from Gultekin et al. (2009c), showing the edge-on view of the fundamental plane.
Fundamental plane relation: the edge-on view of our best-fit relation: ξM=0.78 and ξX=0.67. Error bars on the x-axis are calculated as σi2 = ξM2 σM,i2 + ξX2 σX,i2. This view is for comparison with Merloni et al. (2003) and with Falcke et al. (2004). Red circles are Seyferts. Blue circles are LINERs and unclassified LLAGN.

The M–σ and ML Relations in Galactic Bulges, and Determinations of Their Intrinsic Scatter

Gültekin, K. et al. (2009b), The M–σ and ML Relations in Galactic Bulges, and Determinations of Their Intrinsic Scatter ApJ, 698, 198.

Zoom-in on portion of <i>M</i>–σ diagram

We derive improved versions of the relations between supermassive black hole mass (MBH) and host-galaxy bulge velocity dispersion (σ) and luminosity (L; the M–σ and ML relations), based on 49 MBH measurements and 19 upper limits. Particular attention is paid to recovery of the intrinsic scatter (ε0) in both relations. We find log(MBH / M) = α + β * log(σ / 200 km/s) with (α, β, ε0) = (8.12 ± 0.08, 4.24 ± 0.41, 0.44 ± 0.06) for all galaxies and (α, β, ε0) = (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-sigma relation, and further implies that there may be substantial selection bias in studies of the evolution of the M–σ relation. We estimate the ML relationship as log(MBH / M) = α + β * log(LV / 1011 L⊙,V) of (α, β, ε0) = (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 hole’s sphere of influence biases the relations to larger mean masses, larger slopes, and incorrect intrinsic residuals.

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Figure 1 from Gultekin et al. (2009b), showing the M–σ relation.
The M–σ relation for galaxies with dynamical measurements. The symbol indicates the method of BH mass measurement: stellar dynamical (pentagrams), gas dynamical (circles), masers (asterisks). Arrows indicate 3σ68 upper limits to BH mass. If the 3σ68 limit is not available, we plot it at 3 times the 1σ68 or at 1.5 times the 2σ68 limits. For clarity, we only plot error boxes for upper limits that are close to or below the best-fit relation. The color of the error ellipse indicates the Hubble type of the host galaxy: elliptical (red), S0 (green), and spiral (blue). The saturation of the colors in the error ellipses or boxes is inversely proportional to the area of the ellipse or box. Squares are galaxies that we do not include in our fit. The line is the best fit relation to the full sample: MBH = 108.12 M(σ / 200 km/s)4.24. The mass uncertainty for NGC 4258 has been plotted much larger than its actual value so that it will show on this plot. For clarity, we omit labels of some galaxies in crowded regions.

A Quintet of Black Hole Mass Determinations

Gültekin, K. et al. (2009a), A Quintet of Black Hole Mass Determinations ApJ, 695, 1577.

Image of NGC 3945

We report five new measurements of central black hole masses based on Space Telescope Imaging Spectrograph (STIS) and Wide Field Planetary Camera 2 (WFPC2) 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 galaxy’s 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, MBH = 3.4 (+1.5, -0.6) × 108 M;
NGC 3607, MBH = 1.2 (+0.4, -0.4) × 108 M;
NGC 4026, MBH = 2.1 (+0.7, -0.4) × 108 M; and
NGC 5576, MBH = 1.8 (+0.3, -0.4) × 108 M,

all significantly excluding MBH = 0. For

NGC 3945, MBH = 9 (+17, -21) × 106 M,

which is significantly below predictions from M–σ and ML relations and consistent with MBH = 0, though the presence of a double bar in this galaxy may present problems for our axisymmetric code.

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Figure 4 from Gultekin et al. (2009a), showing LOSVDs for NGC 4026.
Gauss–Hermite moments of line-of-sight velocity distributions (LOSVDs) for NGC 4026 for HST STIS data (blue crosses), ground-based data long the major axis (red diamonds) and minor axis (green triangles). Ground-based data are from Fisher (1997), for which the h3 and h4 moments have been interpolated. Because of the interpolation, the scatter in the data is less than the error bars. The LOSVDs show a sharp increase in velocity dispersion toward the center. The jagged black lines (solid for major axis, dashed for minor axis) are from the best-fit model, which has MBH = 2.2 × 108 M and Υ = 4.6. The best-fit model without a black hole (red dotted line) has Υ = 5.6.