University of Michigan
Department of Astronomy
+1 (734) 615-1585
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Date of Birth: January 22, 1977
Place of Birth: Hanover, New Hampshire

Ph.D. in Astronomy, University of Maryland, College Park -- August 2006
Advisor: Dr. M. Coleman Miller
Thesis: "Growing Intermediate-Mass Black Holes with Gravitational Waves" (Download PDF)
Ph.D. Candidate in Astronomy, University of Maryland, College Park -- March 2002
M.S. in Astronomy, University of Maryland, College Park -- December 2002
B.A. with Distinction in Physics (Astrophysics concentration), University of Pennsylvania -- May 1999
Advisor: Dr. David Koerner - Thesis: "A Circumstellar Disk around the High-Mass Protostar L1206A"

1. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Gültekin, Kayhan, Richstone, Douglas O., Gebhardt, Karl, Faber, S. M., Lauer, Tod R., Bender, Ralf, Kormendy, John, & Pinkney, Jason (Nov 2011), “Is There a Black Hole in NGC 4382?,” The Astrophysical Journal, Volume 741, Issue 1, article id. 38 (2011). [2 citations]
   
   We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of the galaxy NGC 4382 (M85) and axisymmetric models of the galaxy to determine mass-to-light ratio (Upsilon V ) and central black hole mass (M BH). We find Upsilon V = 3.74 ± 0.1 M sun/L sun and M BH = 1.3+5.2 - 1.2 × 107 M sun at an assumed distance of 17.9 Mpc, consistent with no black hole. The upper limit, M BH < 9.6 × 107 M sun(2σ) or M BH < 1.4 × 108(3σ), is consistent with the current M-σ relation, which predicts M BH = 8.8 × 107 M sun at σ e = 182 km s-1, but low for the current M - L relation, which predicts M BH = 7.8 × 108 M sun at LV = 8.9 × 1010 L sun, V . HST images show the nucleus to be double, suggesting the presence of a nuclear eccentric stellar disk, analogous to the Tremaine disk in M31. This conclusion is supported by the HST velocity dispersion profile. Despite the presence of this non-axisymmetric feature and evidence of a recent merger, we conclude that the reliability of our black hole mass determination is not hindered. The inferred low black hole mass may explain the lack of nuclear activity. Based on observations made with the Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with GO proposals 5999, 6587, 6633, 7468, and 9107.
   
2. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Jardel, John R. et al. (Sep 2011), “Orbit-based Dynamical Models of the Sombrero Galaxy (NGC 4594),” The Astrophysical Journal, Volume 739, Issue 1, article id. 21 (2011). [1 citations]
   
   We present axisymmetric, orbit-based models to study the central black hole (BH), stellar mass-to-light ratio (M/L), and dark matter (DM) halo of NGC 4594 (M104, the Sombrero Galaxy). For stellar kinematics, we use published high-resolution kinematics of the central region taken with the Hubble Space Telescope, newly obtained Gemini long-slit spectra of the major axis, and integral field kinematics from the Spectroscopic Areal Unit for Research on Optical Nebulae instrument. At large radii, we use globular cluster kinematics to trace the mass profile and apply extra leverage to recovering the DM halo parameters. We find a BH of mass M • = (6.6 ± 0.4) × 108 M sun and determine the stellar M/LI = 3.4 ± 0.05 (uncertainties are the 68% confidence band marginalized over the other parameters). Our best-fit DM halo is a cored logarithmic model with asymptotic circular speed Vc = 376 ± 12 km s-1 and core radius rc = 4.7 ± 0.6 kpc. The fraction of dark to total mass contained within the half-light radius is 0.52. Taking the bulge and disk components into account in our calculation of σ e puts NGC 4594 squarely on the M-σ relation. We also determine that NGC 4594 lies directly on the M-L relation.
   
3. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Mïller, J. M., & Gültekin, K. (Sep 2011), “X-Ray and Radio Constraints on the Mass of the Black Hole in Swift J164449.3+573451,” The Astrophysical Journal Letters, Volume 738, Issue 1, article id. L13 (2011). [6 citations]
   
   Swift J164449.3+573451 is an exciting transient event, likely powered by the tidal disruption of a star by a massive black hole. The distance to the source, its transient nature, and high internal column density serve to complicate several means of estimating the mass of the black hole. Utilizing newly refined relationships between black hole mass, radio luminosity, and X-ray luminosity, and de-beaming the source flux, a weak constraint on the black hole mass is obtained: log(M BH/M sun) = 5.5 ± 1.1 (1σ confidence). The confidence interval is determined from the current intrinsic scatter in the relation, which includes effects from X-ray variability and accretion modes. This mass range is broad, but it includes low values that are consistent with some variability arguments, and it safely excludes high-mass values where it becomes impossible for black holes to disrupt stars. Future refinements in relationships between black hole mass, radio luminosity, and X-ray luminosity will be able to reduce the uncertainty in related mass estimates by a factor of two, making this technique comparable to estimates based on the M-σ relationship. Possible difficulties in placing such events on the fundamental plane, a potential future test of their suitability, and uncertainties in mass stemming from variable X-ray emission are discussed. As near- and longer-term survey efforts such as Pan-STARRS, LSST, LOFAR, the Square Kilometer Array, and eROSITA begin to detect many tidal disruption events, black hole mass estimates from combined X-ray and radio observations may prove to be very pragmatic.
   
4. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Gültekin, Kayhan, Tremaine, Scott, Loeb, Abraham, & Richstone, Douglas O. (Sep 2011), “Observational Selection Effects and the M-σ Relation,” The Astrophysical Journal, Volume 738, Issue 1, article id. 17 (2011). [5 citations]
   
   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.
   
5. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Volonteri, Marta, Natarajan, Priyamvada, & Gültekin, Kayhan (Aug 2011), “How Important is the Dark Matter Halo for Black Hole Growth?,” The Astrophysical Journal, Volume 737, Issue 2, article id. 50 (2011). [9 citations]
   
   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.
   
6. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Gebhardt, Karl, Adams, Joshua, Richstone, Douglas, Lauer, Tod R., Faber, S. M., Gültekin, Kayhan, Murphy, Jeremy, & Tremaine, Scott (Mar 2011), “The Black Hole Mass in M87 from Gemini/NIFS Adaptive Optics Observations,” The Astrophysical Journal, Volume 729, Issue 2, article id. 119 (2011). [15 citations]
   
   We present the stellar kinematics in the central 2'' of the luminous elliptical galaxy M87 (NGC 4486), using laser adaptive optics to feed the Gemini telescope integral-field spectrograph, Near-infrared Integral Field Spectrograph (NIFS). The velocity dispersion rises to 480 km s-1 at 0farcs2. We combine these data with extensive stellar kinematics out to large radii to derive a black hole mass equal to (6.6 ± 0.4) × 109 M sun, using orbit-based axisymmetric models and including only the NIFS data in the central region. Including previously reported ground-based data in the central region drops the uncertainty to 0.25 × 109 M sun with no change in the best-fit mass; however, we rely on the values derived from the NIFS-only data in the central region in order to limit systematic differences. The best-fit model shows a significant increase in the tangential velocity anisotropy of stars orbiting in the central region with decreasing radius, similar to that seen at the centers of other core galaxies. The black hole mass is insensitive to the inclusion of a dark halo in the models—the high angular resolution provided by the adaptive optics breaks the degeneracy between black hole mass and stellar mass-to-light ratio. The present black hole mass is in excellent agreement with the Gebhardt & Thomas value, implying that the dark halo must be included when the kinematic influence of the black hole is poorly resolved. This degeneracy implies that the black hole masses of luminous core galaxies, where this effect is important, may need to be re-evaluated. The present value exceeds the prediction of the black hole-dispersion and black hole-luminosity relations, both of which predict about 1 × 109 M sun for M87, by close to twice the intrinsic scatter in the relations. The high end of the black hole correlations may be poorly determined at present.
   
7. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   King, A. L. et al. (Mar 2011), “A Distinctive Disk-Jet Coupling in the Seyfert-1 Active Galactic Nucleus NGC 4051,” The Astrophysical Journal, Volume 729, Issue 1, article id. 19 (2011). [9 citations]
   
   We report on the results of a simultaneous monitoring campaign employing eight Chandra X-ray (0.5-10 keV) and six Very Large Array/Extended Very Large Array (8.4 GHz) radio observations of NGC 4051 over seven months. Evidence for compact jets is observed in the 8.4 GHz radio band; this builds on mounting evidence that jet production may be prevalent even in radio-quiet Seyferts. Assuming comparatively negligible local diffuse emission in the nucleus, the results also demonstrate an inverse correlation of L radio ∝ L -0.72±0.04 X-ray . If the A configuration is excluded in the case where diffuse emission plays a significant role, the relation is still L_radio ∝ L_{X-ray}^{-0.12 ± 0.05}. Current research linking the mass of supermassive black holes and stellar-mass black holes in the "low/hard" state to X-ray luminosities and radio luminosities suggests a "fundamental plane of accretion onto black holes" that has a positive correlation of L radio ∝ L 0.67±0.12 X-ray . Our simultaneous results differ from this relation by more than 11σ (6σ excluding the A configuration), indicating that a separate mode of accretion and ejection may operate in this system. A review of the literature shows that the inverse correlation seen in NGC 4051 is seen in three other black hole systems, all of which accrete at near 10% of their Eddington luminosity, perhaps suggesting a distinct mode of disk-jet coupling at high Eddington fractions. We discuss our results in the context of disks and jets in black holes and accretion across the black hole mass scale.
   
8. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Volonteri, Marta, Gültekin, Kayhan, & Dotti, Massimo (Jun 2010), “Gravitational recoil: effects on massive black hole occupation fraction over cosmic time,” Monthly Notices of the Royal Astronomical Society, Volume 404, Issue 4, pp. 2143-2150. [22 citations]
   
   We assess the influence of massive black hole (MBH) ejections from galaxy centres due to gravitational radiation recoil, along the cosmic merger history of the MBH population. We discuss the `danger' of recoil for MBHs as a function of different MBH spin-orbit configurations and of the host halo cosmic bias, and on how that reflects on the occupation fraction of MBHs. We assess ejection probabilities for mergers occurring in a gas-poor environment, in which the MBH binary coalescence is driven by stellar dynamical processes and the spin-orbit configuration is expected to be isotropically distributed. We contrast this case with the `aligned' case. The latter is the more realistic situation for gas-rich, i.e. `wet', mergers, which are expected for high-redshift galaxies. We find that if all haloes at z > 5-7 host an MBH, the probability of the Milky Way (or similar size galaxy) to host an MBH today is less than 50 per cent, unless MBHs form continuously in galaxies. The occupation fraction of MBHs, intimately related to halo bias and MBH formation efficiency, plays a crucial role in increasing the retention fraction. Small haloes, with shallow potential wells and low escape velocities, have a high ejection probability, but the MBH merger rate is very low along their galaxy formation merger hierarchy: MBH formation processes are likely inefficient in such shallow potential wells. Recoils can decrease the overall frequency of MBHs in small galaxies to ~60 per cent, while they have little effect on the frequency of MBHs in large galaxies (at most a 20 per cent effect).
   
9. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
   Gültekin, Kayhan, Cackett, Edward M., Miller, Jon M., Di Matteo, Tiziana, Markoff, Sera, & Richstone, Douglas O. (Nov 2009), “The Fundamental Plane of Accretion onto Black Holes with Dynamical Masses,” The Astrophysical Journal, Volume 706, Issue 1, pp. 404-416 (2009). [32 citations]
   
   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.
   
10. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
    Gültekin, Kayhan et al. (Jun 2009), “The M-σ and M-L Relations in Galactic Bulges, and Determinations of Their Intrinsic Scatter,” The Astrophysical Journal, Volume 698, Issue 1, pp. 198-221 (2009). [232 citations]
    
    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 (epsilon0) in both relations. We find log(M BH/M sun) = α + βlog(σ/200 km s-1) with (α, β, epsilon0) = (8.12 ± 0.08, 4.24 ± 0.41, 0.44 ± 0.06) for all galaxies and (α, β, epsilon0) = (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 sun) = α + βlog(LV /1011 L sun,V ) of (α, β, epsilon0) = (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.
    
11. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
    Gültekin, Kayhan et al. (Apr 2009), “A Quintet of Black Hole Mass Determinations,” The Astrophysical Journal, Volume 695, Issue 2, pp. 1577-1590 (2009). [24 citations]
    
    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 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, M BH = 3.4+1.5 -0.6 × 108 M sun; NGC 3607, M BH = 1.2+0.4 -0.4 × 108 M sun; NGC 4026, M BH = 2.1+0.7 -0.4 × 108 M sun; and NGC 5576, M BH = 1.8+0.3 -0.4 × 108 M sun, all significantly excluding M BH = 0. For NGC 3945, M BH = 9+17 -21 × 106 M sun, 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. Based on observations made with the Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with GO proposals 5999, 6587, 6633, 7468, and 9107.
    
12. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
    Holley-Bockelmann, Kelly, Gültekin, Kayhan, Shoemaker, Deirdre, & Yunes, Nicolas (Oct 2008), “Gravitational Wave Recoil and the Retention of Intermediate-Mass Black Holes,” The Astrophysical Journal, Volume 686, Issue 2, pp. 829-837. [24 citations]
    
    During the inspiral and merger of a binary black hole, gravitational radiation is emitted anisotropically due to asymmetries in the merger configuration. This anisotropic radiation leads to a gravitational wave kick, or recoil velocity, as large as ~4000 km s-1. We investigate the effect gravitational recoil has on the retention of intermediate-mass black holes (IMBHs) within the population of Galactic globular clusters by simulating the response of IMBHs to black hole mergers. Assuming that our current understanding of IMBH formation is correct and yields an IMBH seed in every globular cluster, we find a significant problem in retaining low-mass IMBHs (<~1000 Msolar) in the typical merger-rich globular cluster environment. Given a uniform black hole spin distribution and orientation and a stellar-mass black hole mass function generated in a low-metallicity system, we find that only three of the Milky Way globular clusters can retain an IMBH with an initial mass of 200 Msolar. Even if IMBHs have an initial mass of 1000 Msolar, only 60 would remain within Milky Way globular clusters, and each would reside only in the most massive clusters. Our calculations show that if there are black holes of mass M>50 Msolar in a cluster, repeated IMBH-black hole encounters will eventually eject a M=1000 Msolar IMBH with greater than 30% probability. As a consequence, a large population of rogue black holes may exist in our Milky Way halo. We briefly discuss the dynamical implications of this process and its possible connection to ultraluminous X-ray sources (ULXs).
    
13. [+] Abstract - ADS - arXiv - Reprint - BibTeX
    Volonteri, Marta, Haardt, Francesco, & Gültekin, Kayhan (Mar 2008), “Compact massive objects in Virgo galaxies: the black hole population,” Monthly Notices of the Royal Astronomical Society, Volume 384, Issue 4, pp. 1387-1392. [17 citations]
    
    We investigate the distribution of massive black holes (MBHs) in the Virgo cluster. Observations suggest that active galactic nuclei activity is widespread in massive galaxies (M* >~ 1010Msolar), while at lower galaxy masses star clusters are more abundant, which might imply a limited presence of central black holes in these galaxy-mass regimes. We explore if this possible threshold in MBH hosting is linked to nature, nurture or a mixture of both. The nature scenario arises naturally in hierarchical cosmologies, as MBH formation mechanisms typically are efficient in biased systems, which would later evolve into massive galaxies. Nurture, in the guise of MBH ejections following MBH mergers, provides an additional mechanism that is more effective for low mass, satellite galaxies. The combination of inefficient formation, and lower retention of MBHs, leads to the natural explanation of the distribution of compact massive objects in Virgo galaxies. If MBHs arrive to the correlation with the host mass and velocity dispersion during merger-triggered accretion episodes, sustained tidal stripping of the host galaxies creates a population of MBHs which lie above the expected scaling between the holes and their host mass, suggesting a possible environmental dependence.
    
14. [+] Abstract - ADS - Reprint - BibTeX
    Gultekin, Kayhan (Jun 2006), “Growing intermediate-mass black holes with gravitational waves,” PhD Thesis, Proquest Dissertations And Theses 2006. Section 0117, Part 0606 126 pages; [Ph.D. dissertation].United States -- Maryland: University of Maryland, College Park; 2006. Publication Number: AAT 3222352. Source: DAI-B 67/06, Dec 2006
    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 [Special characters omitted.] and compare purely Newtonian simulations with a relativistic endpoint, simulations in which Newtonian encounters are interspersed with gravitational wave emission from the binary, and simulations 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. In all cases, the sequence is terminated when the binary's merger time due to gravitational radiation is less than the arrival time of the next interloper. We also examine the role of gravitational waves during an encounter and show that close approach cross-sections for three 1 [Special characters omitted.] 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). We find that black hole binaries typically merge with a very high eccentricity- --extremely high when gravitational waves are included during the encounter such that when the gravitational waves are detectable by LISA, most of the binaries will have eccentricities e > 0.9 though 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. The simulations show that the Miller & Hamilton (2002b) model of IMBH formation is a viable method if it is modified to start with a larger seed mass.
    
15. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
    Gültekin, Kayhan, Miller, M. Coleman, & Hamilton, Douglas P. (Mar 2006), “Three-Body Dynamics with Gravitational Wave Emission,” The Astrophysical Journal, Volume 640, Issue 1, pp. 156-166. [38 citations]
    
    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 Msolar 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.
    
16. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
    Gültekin, Kayhan, Miller, M. Coleman, & Hamilton, Douglas P. (Nov 2004), “Growth of Intermediate-Mass Black Holes in Globular Clusters,” The Astrophysical Journal, Volume 616, Issue 1, pp. 221-230. [53 citations]
    
    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 Msolar and 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 binary's 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.
    
17. [+] Abstract - ADS - arXiv - PDF - Reprint - BibTeX
    Koerner, D. W., Jensen, E. L. N., Cruz, K. L., Guild, T. B., & Gultekin, K. (Apr 2000), “A Single Circumbinary Disk in the HD 98800 Quadruple System,” The Astrophysical Journal, Volume 533, Issue 1, pp. L37-L40. [31 citations]
    
    We present subarcsecond thermal infrared imaging of HD 98800, a young quadruple system composed of a pair of low-mass spectroscopic binaries separated by 0.8" (38 AU), each with a K-dwarf primary. Images at wavelengths ranging from 5 to 24.5 μm show unequivocally that the optically fainter binary, HD 98800B, is the sole source of a comparatively large infrared excess on which a silicate emission feature is superposed. The excess is detected only at wavelengths of 7.9 μm and longer, peaks at 25 μm, and has a best-fit blackbody temperature of 150 K, indicating that most of the dust lies at distances greater than the orbital separation of the spectroscopic binary. We estimate the radial extent of the dust with a disk model that approximates radiation from the spectroscopic binary as a single source of equivalent luminosity. Given the data, the most likely values of disk properties in the ranges considered are Rin=5.0+/-2.5 AU, ΔR=13+/-8 AU, λ0=2+4-1.5 μm, γ=0+/-2.5, and σtotal=16+/-3 AU2, where Rin is the inner radius, ΔR is the radial extent of the disk, λ0 is the effective grain size, γ is the radial power-law exponent of the optical depth τ, and σtotal is the total cross section of the grains. The range of implied disk masses is 0.001-0.1 times that of the Moon. These results show that, for a wide range of possible disk properties, a circumbinary disk is far more likely than a narrow ring.
    

1. [+] Abstract - ADS - BibTeX
   King, Ashley L. et al. (Sep 2011), “The Jet and Winds in Seyfert-1, NGC 4051.,” American Astronomical Society, HEAD meeting #12, #35.10
   We present our work on outflows in the Seyfert-1 AGN, NGC 4051. The joint study of both winds and jets allows us to address the total outflowing power and feedback of this AGN. Evidence for compact jet production is observed in the EVLA 8.4 GHz band, while the warm absorbing winds are observed in Chandra HETG spectra. Counter to the expectations of the fundamental plane of accretion, accretion power (traced by X-ray flux) and jet power (traced by radio flux) are only weakly correlated in our simultaneous EVLA and Chandra data, or perhaps even anti-correlated. This may represent a separate mode of disk-jet coupling that obtains at high Eddington fractions. Both XSTAR and Cloudy models for the X-ray warm absorbers require only two absorption zones. The closer of the two gives a wind launching radius of just 100 gravitational radii, perhaps suggesting a role for magnetic driving of the wind. Evidence for simultaneous jet and wind production is significantly different from stellar mass black holes. These results will be discussed in terms of wind and jet production across the black hole mass scale.
   
2. [+] Abstract - ADS - BibTeX
   Reynolds, Mark et al. (Sep 2011), “The Swift Galactic Plane Survey,” American Astronomical Society, HEAD meeting #12, #27.01
   The Swift Galactic Plane Survey (SGPS) is a 240 square degree survey of the Galactic plane, covering the region |b| < 1 deg and |l| < 60 deg. The survey is designed to obtain 100% overlap with the Spitzer (GLIMPSE/MIPSGAL) and Herschel (HiGal) Galactic plane surveys in the 0.3 -- 10 keV band, crucially including the dust penetrating 2 -- 10 keV hard X-ray band. In addition, we will take advantage of the multi-wavelength capabilities of Swift to obtain simultaneuous ultra-violet (UV) imaging with the UVM2 filter ( 2246 Angstrom), resulting in the first large area survey of the Galactic plane at UV wavelengths. This survey complements the ongoing and completed surveys of the Galactic plane, filling in the crucial high energy region, and will facilitate a truly multi-wavelength study of the Milky Way galaxy. The survey area is 6 times larger than that previously imaged by ASCA, and the order of magnitude improvement in spatial resolution provided by the Swift X-ray telescope will enable follow-up identification of unique multi-wavelength counterparts. We will discuss the current status of the survey and present preliminary results.
   
3. [+] Abstract - ADS - BibTeX
   Miller, J. M. et al. (Jun 2011), “Discovery of a New Supernova Remnant in the Swift Galactic Plane Survey,” The Astronomer's Telegram, #3415
   We report the discovery of a new supernova remnant. Following the detection of an extended source in a Swift/XRT exposure in the Galactic plane, we requested a short 5 ks exposure with Chandra. The Swift observation was obtained on 22 February 2011 (observation 00042184001), and the Chandra ACIS-S observation was obtained on 03 June 2011 (observation 13419). If characterized with a circle, the center of the remnant could be approximated with the following coordinates: 13:21:50.9, -63:33:50 (J2000), or (l,b) = 306.309034, -0.891719, with a radius of approximately 110 arcseconds.
   
4. [+] Abstract - ADS - BibTeX
   Maitra, D., Reynolds, M. T., Curran, P. A., Gultekin, K., Miller, J. M., Kennea, J. A., & Russell, D. M. (May 2011), “Rebrightening of MAXI J0556-332,” The Astronomer's Telegram, #3327
   We report a rebrightening of the newly discovered transient MAXI J0556-332 (ATEL #3102, #3103, #3104, #3106, #3110, #3112, #3116, #3119) in optical through soft-X-ray wavelengths. The source is being monitored regularly in the I-band using the SMARTS 1.3m telescope in CTIO, and the I-band light curve has been showing a monotonically increasing trend since 55670.9748 (2011 April 19.97, when the I-band magnitude was 18.39 ± 0.15).
   
5. [+] Abstract - ADS - BibTeX
   Gebhardt, Karl, Adams, J., Richstone, D., Lauer, T., Gultekin, K., Murphy, J., Faber, S., & Tremaine, S. (Jan 2011), “The Black Hole Mass in M87 from Gemini/AO Observations,” American Astronomical Society, AAS Meeting #217, #422.05; Bulletin of the American Astronomical Society, Vol. 43, 2011
   We present results from an adaptive optics study of the central region of M87 using NIFS on Gemini. The kinematics show a dramatic rise in the velocity dispersion with the AO data. The best-fit dynamical model requires the most massive black hole yet measured with spatially-resolved kinematics at 6.6e9 solar masses. The AO data provides a robust measure of the black hole mass since it so well resolves its sphere of influence. This also allows us to probe the stellar orbital structure reliably, where we find a significant increase in tangential orbital anisotropy. Current and future AO data will provide a significant advance for the field.
   
6. [+] Abstract - ADS - BibTeX
   Gultekin, Kayhan (Oct 2010), “Putting Faint M-sigma Black Holes on the Fundamental Plane,” XMM-Newton Proposal ID #06727604
   There is a relation between radio and X-ray luminosities and SMBH mass: the Fundamental Plane. If radio and X-ray are proxies for jet and accretion power, a broad link between them can be inferred. The relation may be used as a proxy for M_BH measurement, but the scatter is big (0.75 dex; sample of 18). Without Seyferts it is tighter than the M-sigma relation (0.25; sample of 8). It is vital to determine if this is from small numbers or a stronger link between accretion and jets at low Eddington rates. We propose to increase the sample with 37-68 ks observations (197 tot.) of 5 SMBHs with dynamical masses ideal for XMM. Together with VLA data, we can increase the total sample by 25% and the LLAGN sample by 50%, advancing our understanding of accretion, jets, and AGN feedback.
   
7. [+] Abstract - ADS - BibTeX
   Maitra, Dipankar, Reynolds, Mark, Miller, Jon M., & Gultekin, Kayhan (Jul 2010), “X-ray, UV, Optical and NIR Observations of Aql X-1,” The Astronomer's Telegram, #2744
   Aql X-1 was observed using Swift between 2010 July 16.8965 and 2010 July 16.9083. The source was recently found to start a new outburst as inferred from Swift/BAT and MAXI/GSC monitoring data (ATEL #2742). Preliminary analyses of the XRT (WT mode) "quicklook" data suggests that the 0.6-10 keV spectrum can be well modeled (chi2/dof=565.2/400) by a phenomenological absorbed power law model with column density of (3.4 ± 0.02) E21 per cm2 and photon index 1.65 ± 0.05.
   
8. [+] Abstract - ADS - BibTeX
   Gultekin, Kayhan, Maitra, Dipankar, Miller, Jon M., & Reynolds, Mark (Jul 2010), “New X-ray Activity from Aql X-1,” The Astronomer's Telegram, #2742
   Recent MAXI/GSC and Swift/BAT data show a significant increase in X-ray activity. On 13 July 2010, the Swift/BAT count rate increased from quiescence to 0.0047 ± 0.0012 counts/sec, to 0.0073 ± 0.0010 on 14 July 2010, and to 0.0106 ± 0.0018 on 15 July 2010. This is an average increase of 0.003 counts/sec per day, and the flux has increased by 2.3 since 13 July 2010. The most recent observation is 5.9 sigma above the quiescent level. Between 12.5 July 2010 and 14.5 July 2010 The MAXI/GSC 2-20 keV count rate also appears to have increased from 0.024 ± 0.010 to 0.048 ± 0.012 counts/sec from, an increase in flux by a factor of 2. Optical and NIR observations are planned.
   
9. [+] Abstract - ADS - BibTeX
   Gültekin, Kayhan (May 2010), “Determination of the Intrinsic Scatter in the MBH-σ and MBH-Lbulge Relations,” Co-Evolution of Central Black Holes and Galaxies, Proceedings of the International Astronomical Union, IAU Symposium, Volume 267, p. 189-194 [2 citations]
   
   We derive improved versions of the relations between supermassive black hole mass MBH and host-galaxy bulge velocity dispersion σ and luminosity L (the MBH-σ and MBH-Lbulge relations), based on ~ 50 MBH measurements and ~ 20 upper limits. Particular attention is paid to recovery of the intrinsic scatter (ɛ0) in both relations. We find the scatter to be significantly larger than estimated in most previous studies. The large scatter requires revision of the local black hole mass function, and it implies that there may be substantial selection bias in studies of the evolution of the MBH-σ and MBH-Lbulge relations. When only considering ellipticals, the scatter decreases. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We also investigate the effects on the fits of culling the sample according to the resolution of the black hole's sphere of influence.
   
10. [+] Abstract - ADS - BibTeX
    Benson, Amanda, Holley-Bockelmann, K., & Gultekin, K. (Jan 2010), “The Distribution of Stars around a Super Massive Black Hole Binary Due to Three-Body Scattering,” American Astronomical Society, AAS Meeting #215, #404.16; Bulletin of the American Astronomical Society, Vol. 42, p.227
    Shortly after a galaxy merger, the supermassive black holes from each galaxy are thought to form a binary at the center of the merger remnant. The binary orbit shrinks via three-body scattering of stars until the black holes are close enough to strongly emit gravitational radiation and merge. Since a substantial fraction of the scattered stars are ejected with enough energy to escape the host galaxy, three-body encounters with a supermassive binary black hole are a viable mechanism to generate hypervelocity stars. We investigate the 3-d spatial and kinematic distribution of the stars that are scattered by interacting with a supermassive binary black hole. We simulate each three body encounter explicitly, including gravitational radiation, until the stellar interloper has either been ejected or has merged with a black hole. Then, we evolve the positions and velocities of the scattered stars self-consistently within an N-body galactic model. By mapping the motion of these scattered stars as they traverse the galactic potential, we can characterize their distribution and how it evolves with time. We discuss how the anisotropic distribution of the scattered stars could allow us to determine characteristics of the black hole binary, as well as aid in the search for hypervelocity stars.
    
11. [+] Abstract - ADS - BibTeX
    Gultekin, Kayhan, Cackett, E. M., Miller, J. M., Di Matteo, T., Markoff, S., & Richstone, D. O. (Jan 2010), “The Fundamental Plane of Accretion onto Black Holes with Dynamical Masses,” American Astronomical Society, AAS Meeting #215, #336.08; Bulletin of the American Astronomical Society, Vol. 42, p.440
    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 luminosity 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 Lr = (4.59 +/- 0.23) + (0.80 +/- 0.26) MBH + (0.67 +/- 0.12) 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-sigma relation. If obscured AGN are excluded, the plane is potentially a better predictor than other scaling measures.
    
12. [+] Abstract - ADS - arXiv - Reprint - BibTeX
    Gultekin, Kayhan (Dec 2009), “Determination of the intrinsic scatter in the M-sigma and M-L relations,” eprint arXiv:0912.3898
    We report on recently derived improved versions of the relations between supermassive black hole mass (M_BH) and host-galaxy bulge velocity dispersion (sigma) and luminosity (L) (the M-sigma and M-L relations), based on ~50 M_BH measurements and ~20 upper limits. Particular attention is paid to recovery of the intrinsic scatter (epsilon_0) in both relations. The scatter was found to be significantly larger than estimated in most previous studies. The large scatter requires revision of the local black hole mass function, and it implies that there may be substantial selection bias in studies of the evolution of the M-sigma and M-L relations. When only considering ellipticals, the scatter appears to decrease. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We also report on the effects on the fits of culling the sample according to the resolution of the black hole's sphere of influence.
    
13. [+] Abstract - ADS - BibTeX
    Gultekin, Kayhan (Sep 2009), “COMBH: Chandra Observations of M-sigma Black Holes,” Chandra proposal ID #11900514
    Galaxies with dynamically-measured central BH masses allow us to understand BH accretion, jets, and interactions between BHs and host galaxies with a clarity not possible in random surveys. By measuring true Eddington fractions, we can calculate the energy in radiation vs mechanical jet energy and the efficacy of BHs in heating nuclear regions and affecting star formation. Remarkably, 1/3 of SMBHs making up the M-sigma relation have been poorly observed or totally unobserved with Chandra. We propose a survey of 15 M-sigma galaxies to complete the sample of reliable M-sigma SMBHs. For each galaxy we propose to obtain 30-60 ks exposures and an hour-long VLA observation. This survey will test and extend the fundamental plane of BH activity and facilitate studies of the origin of M-sigma.
    
14. [+] Abstract - ADS - BibTeX
    Gultekin, Kayhan, & Richstone, D. O. (Dec 2007), “The Fundamental Plane for Nuclear Black Hole Masses,” American Astronomical Society, AAS Meeting #211, #144.07; Bulletin of the American Astronomical Society, Vol. 39, p.997
    We present the latest analysis of the relationship between nuclear black hole mass and properties of the host galaxy or bulge, notably stellar velocity dispersion. This analysis includes six new measurements of black hole masses based on observations with HST using STIS and WFPC2 as well as the most recent results from the literature for a total of about 50 dynamical black hole mass measurements. We also include in our analysis, for the first time, 15 measured upper limits on black hole mass. Studies of supermassive black holes in galaxy centers have led to the discoveries that most or all hot galaxies contain massive dark objects at their centers, presumably black holes; and that there is a remarkably tight correlation between the black-hole mass and the luminosity-weighted velocity dispersion of the hot component of the galaxy. This M-sigma relationship suggests a strong link between black-hole formation, AGN activity, and galaxy formation, and once it is understood, this link should advance our understanding of all three processes. In this work we (1) present the most current fit to the M-sigma relation; (2) measure the scatter in the relation, which previous studies claim to be consistent with zero scatter; and (3) investigate the role of possible second parameters in predicting black hole mass, that is a fundamental plane relationship.
    
15. [+] Abstract - ADS - BibTeX
    Holley-Bockelmann, Kelly, Gultekin, K., Shoemaker, D., & Yunes, N. (Dec 2007), “Gravitational Wave Recoil and the Retention of Intermediate Mass Black Holes,” American Astronomical Society, AAS Meeting #211, #49.02; Bulletin of the American Astronomical Society, Vol. 39, p.811
    During the inspiral and merger of a binary black hole, gravitational radiation is emitted anisotropically due to asymmetries in the merger configuration. This anisotropic radiation leads to a gravitational wave kick, or recoil velocity, as large as 4000 km/sec. We investigate the effect gravitational recoil has on the retention of intermediate mass black holes (IMBH) within Galactic globular clusters. Assuming that our current understanding of IMBH-formation is correct and yields an IMBH-seed in every globular cluster, we find a significant problem retaining low mass IMBHs in the typical merger-rich globular cluster environment. Given a uniform black hole spin distribution and orientation and a Kroupa IMF, we find that at most 3 percent of the globular clusters can retain an IMBH larger than 1000 solar masses today. For a population of black holes that better approximates mass loss from winds and supernovae, we find that 16 percent of globulars can retain an IMBH larger than 1000 solar masses. Our calculations show that if there are black holes larger than 60 solar masses in a cluster, repeated IMBH-BH encounters will eventually eject a 1000 solar mass IMBH with greater than 30 percent probability. As a consequence, a large population of rogue black holes may exist in our Milky Way halo. We discuss the dynamical implications of this subpopulation, and its possible connection to ultraluminous X-ray sources (ULXs).
    
16. [+] Abstract - ADS - BibTeX
    Gultekin, Kayhan, Holley-Bockelmann, K., Miller, M. C., Shoemaker, D., & Yunes, N. (Jul 2007), “Gravitational Wave Kicks of Intermediate-Mass Black Holes,” American Astronomical Society, DDA meeting #38, #2.02
    Recent numerical relativistic simulations have found that recoil from gravitational wave emission of merging black holes can produce kicks up to 1000 km/s. Because intermediate-mass black holes (IMBHs) are thought to form in dense stellar clusters, their ejection from the cluster becomes a real possibility. In this talk we present results on the retention probability of IMBHs as they interact with the host cluster's stellar-mass black hole population. We consider the ramifications of gravitational wave recoil and potential for further growth as the IMBHs merge with stellar mass black holes. We consider IMBHs that are the evolution of Population III stars, core-collapse runaway merger remnants (including multiples), and those built up from mergers of stellar-mass black holes.
    
17. [+] Abstract - ADS - BibTeX
    Gultekin, K., Miller, M. C., & Hamilton, D. P. (Dec 2005), “Three-Body Interactions of Black Holes with Gravitational Wave Emission,” American Astronomical Society Meeting 207, #102.02; Bulletin of the American Astronomical Society, Vol. 37, p.1331
    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. Building on previous work, we simulate sequences of high-mass-ratio three-body encounters as they would occur in a dense stellar system. 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 though all will have circularized by the time they are detectable by LIGO. We also investigate the implications for the formation and growth of intermediate-mass black holes (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.
    
18. [+] Abstract - ADS - arXiv - Reprint - BibTeX
    Gültekin, Kayhan, Miller, M. Coleman, & Hamilton, Douglas P. (Oct 2003), “Three-Body Encounters of Black Holes in Globular Clusters,” THE ASTROPHYSICS OF GRAVITATIONAL WAVE SOURCES. AIP Conference Proceedings, Volume 686, pp. 135-140 (2003). [5 citations]
    
    Evidence has been mounting for the existence of black holes with masses from 102 to 104 Msolar associated with stellar clusters. Such intermediate-mass black holes (IMBHs) will encounter other black holes in the dense cores of these clusters. The binaries produced in these interactions will be perturbed by other objects as well thus changing the orbital characteristics of the binaries. These binaries and their subsequent mergers due to gravitational radiation are important sources of gravitational waves. We present the results of numerical simulations of high mass ratio encounters, which help clarify the interactions of intermediate-mass black holes in globular clusters and help determine what types of detectable gravitational wave signatures are likely.
    
19. [+] Abstract - ADS - BibTeX
    Gultekin, K., Miller, M. C., & Hamilton, D. P. (Dec 2001), “Three Body Interactions of Black Holes in Globular Clusters,” American Astronomical Society, 199th AAS Meeting, #05.02; Bulletin of the American Astronomical Society, Vol. 33, p.1308
    Recent x-ray observations suggest that a number of galaxies may harbor black holes with masses between 102 and 103-4 MSun. These intermediate-mass black holes may require a formation mechanism different from those of stellar-mass black holes and supermassive black holes. Several models have been proposed to account for their origin, one of which proposes that stellar-mass black holes in dense globular clusters may grow to the required masses through mergers. We investigate this scenario numerically, by examining the role of interactions between binary black holes and single black holes. We present results of numerical simulations of these encounters and discuss their implications for the formation of intermediate-mass black holes and for their detectability with gravitational wave detectors such as LISA and LIGO-II.
    
20. [+] Abstract - ADS - BibTeX
    Koerner, D. W., Jensen, E. L. N., Cruz, K., Guild, T. B., & Gultekin, K. (Dec 1999), “A Single Circumbinary Disk in the HD 98800 Quadruple System,” American Astronomical Society, 195th AAS Meeting, #25.02; Bulletin of the American Astronomical Society, Vol. 31, p.1409
    We present sub-arcsecond thermal infrared imaging of HD 98800, a young quadruple system composed of a pair of low-mass spectroscopic binaries separated by 0.8'', each with a K-dwarf primary. Images at wavelengths ranging from 5 to 24.5 microns show unequivocally that the optical secondary, HD 98800B, is the sole source of a comparatively large infrared excess upon which a silicate emission feature is superposed. The excess is detected only at wavelengths of 7.9 microns and longer, peaks at 25 microns, and has a best-fit black-body temperature of 146 K. With the assumption that the dust is in radiative equilibrium with the central stars, these characteristics require its location to be in a configuration that is circumbinary to the spectroscopic pair. A simple black-body fit underpredicts emission in the region of the broad silicate feature, however, and the feature itself requires a dust component with temperatures higher than 146 K by at least a factor of two. Further, the spectral slope at sub-millimeter wavelengths is flatter than expected for a collision-induced size-distribution of grains, suggesting a range of temperatures present at longer wavelengths. These facts suggest that the circumbinary dust is not confined to a narrow ring but is wide enough to exhibit a range of temperatures.
    
21. [+] Abstract - ADS - BibTeX
    Gultekin, K., Koerner, D. W., & Ressler, M. E. (Dec 1998), “A Circumstellar Disk around the High-Mass Protostar L1206A,” American Astronomical Society, 193rd AAS Meeting, #72.07; Bulletin of the American Astronomical Society, Vol. 30, p.1360
    We present aperture synthesis mapping of a circumstellar disk around the high-mass protostellar source, L1206A. A contour map at 110 GHz reveals dust emission with peak flux density 32.5 +/-3 mJy in a circular 2'' beam, and integrated intensity 62 +/-6 mJy. The emission is elongated perpendicular to a bipolar reflection nebula with a nominal FWHM diameter of 2.3+/-0.05'' (deconvolved), corresponding to 2300 AU at the 1 kpc distance estimated for the Lynds 1206 cloud. Visibility amplitudes are well-matched by those predicted from a model of dust radiation arising from a circumstellar disk. Preliminary model-fitting suggests the disk has outer radius 4000 AU and mass greater than 0.3M_sun.
    

1. AAS International Travel Grant Award Winner - 2006
2. Jacob K. Goldhaber Travel Grant Award Winner - 2006
3. American Astronomical Society Member - 1999 - Present

1. August 12, 2009 “The Scatter in the M–σ and M–L Relations,” IAU, Rio, Brazil.
2. April 2, 2009 “The IMBH–SMBH Connection,” IMBH Workshop, UC Irvine, CA.
3. December 4, 2008 “Scatting about M–σ,” Astronomy Department Colloquium, University of Michigan, Ann Arbor.
4. September 21, 2006 “Growing Intermediate-Mass Black Holes with Gravitational Waves,” Extra-Galactic Astronomy Seminar, University of Texas, Austin.
5. July 27, 2006 “Growing Black Holes in Globular Clusters,” Galactic Nuclei Workshop, Lorentz Center, Leiden, The Netherlands.
6. September 14, 2005 “Growth of Intermediate-Mass Black Holes in Globular Clusters and their Gravitational Waves,” Space Sciences Seminar, George Mason University, Fairfax, VA.
7. December 6, 2004 “Making IMBHs and Gravitational Waves in Globular Clusters,” Astronomy Seminar, Caltech, Pasadena, CA.
8. November 16, 2004 “The Role of Three-Body Encounters in IMBH Formation,” Center for Astrophysical Sciences Seminar, Johns Hopkins University, Baltimore, MD.
9. October 20, 2004 “From Newtonian Dynamics to Gravitational Waves,” University of Pennsylvania Astrophysics Seminar, Philadelphia, PA.
10. October 19, 2004 “Growing IMBHs in Globular Clusters,” University of Virginia and NRAO Seminar, Charlottesville, VA.
11. October 15, 2004 “The Role of Three-Body Dynamics in IMBH Formation and their Gravitational Waves,” LHEA Seminar, GSFC, Greenbelt, MD.
12. March 3, 2003 “Close Encounters of the Three-Body Kind,” Penn State Astronomy Seminar, State College.

Postdoctoral Fellow for Douglas O. Richstone, University of Michigan, August 2006-Present
   Modelled mass distribution and stellar kinematics of galactic nuclei to compare with HST and ground-based data to determine masses of supermassive black holes in galactic centers.

Research Assistant for M. Coleman Miller, University of Maryland, College Park, June 2001-August 2006
   Investigated interactions of black hole dynamics in cluster cores, developed and adapted code to perform numerical simulations of sequences of three-body encounters, and used the data from these simulations to test intermediate-mass black hole formation models and to predict likely gravitational wave signatures.

Beowulf Cluster Co-Administrator, VAMPIRE, University of Maryland, June 2001-August 2006
   Installed and currently maintain Condor job management software on department computers to utilize unused computing power of over thirty desktop workstations to create a combined 21 GFlop cluster, created tutorial for use of cluster, and assisted faculty and students in use of cluster.

Observer, Berkeley Illinois Maryland Association (BIMA), Hat Creek, CA 2000-2001
   Operate telescope, scheduled observing queue, verified data quality, and responded to telescope alarms.

Research Assistant for Laboratory for Millimeter-Wave Astronomy, University of Maryland, College Park, Summer 2000
   Assisted in design of water vapor radiometers planned for use with BIMA millimeter-wave radio interferometer antennae (now part of CARMA), analyzed data from prototype radiometers to evaluate efficacy, and assisted in installation of prototype radiometers on antennae.

Undergraduate Research Assistant for Dr. David Koerner, Planetary Origins Research Group, University of Pennsylvania, 1998-1999.
   Reduced Keck MIRLIN infrared data of debris disk in quadruple system, and developed code to model OVRO millimeter data of the circumstellar disk around a high-mass protostar.

2007 - 2009 Mentor for University of Michigan undergraduate student research projects.
2004 - Guest lecturer for graduate astronomy courses Numerical Astrophysics and Introduction to Research.
2000 - 2001 Instructor for astronomy observing class. Planned, facilitated, and taught class for undergraduate non-majors in use of small telescopes and naked-eye observations.
1999 - Telescope operator, facilitator, and educational reference for department open houses and special public events.
1999 - 2000 Teaching Assistant for introductory astronomy classes. Taught discussion session, graded, and led special review sessions for undergraduate classes.