Aavso paper Session I sunday Sunday, May 22, 2011, 9: 30 am – 12: 00 pm

229

Black Holes

Poster Session

Essex Ballroom

229.01

8:00 AM - 7:00 PM

Using hydrodynamic cosmological simulations that directly follow black hole growth we investigate the halo occupation distribution (HOD) of black holes. Similar to the HOD of galaxies/subhalos, we find that the black hole occupation number can be described by the power law N_BH proportional to 1+(M_Host)^α where α evolves mildly with redshift, indicating that a given mass halo at low redshift tends to host fewer BHs than at high redshift (as expected as a result of galaxy and BH mergers). We further show how to divide the occupation number into contributions from black holes residing in central and satellite galaxies within the halo. The distribution of black holes masses and luminosities within halos tends to consist of a single massive, bright BH (distributed about a peak mass strongly correlated with the host mass), and a collection of relatively low-mass secondary BHs with weaker correlation to host mass. We examine the spatial distribution of black holes within their host halos, and find they typically follow a power-law radial distribution that is much more centrally concentrated than the subhalo distribution. We further show that black hole feedback becomes increasingly important at low redshifts, which can lead to suppression of the central quasar luminosity and increased scatter in the correlation between quasar luminosity and host halo mass. Overall, this HOD formalism provides the most complete tool for characterizing the distribution of black holes within host halos and galaxies, and can be used in semi-analytic and theoretical models and as a framework for interpreting observational black hole measurements.

229.02

8:00 AM - 7:00 PM

We reported the results of the time-dependent simulations of large amplitude oscillations of advective, viscous, sub-Keplerian disks with a proper trement of angular momentum transfer in one-dimensional, quasi-spherical transonic accretion flow around a non-rotating black hole using the Lagrangian Total Variation Diminising (TVD) and a remap routine.Our code has a shock-capturing capability better than both standard Eulerian code and Lagrangian SPH code. It could well follow the angular momentum transfer of the viscous, subsonic, analytical solution. Hence, we present a simulation of a rotating, viscous, transonic fluid with shocks. Oscillation of the accretion shock was produced due to the different rates of angular momentum transfer across the shock and the heat dissipated due to the presence of high viscosity parameter. Moreover, as the shock drifts to larger distances, a secondary inner shock develops. We showed that the inner shock is the direct consequence of expansion of the outer shock, as well as creation of regions with dl / dr < 0 due to more efficient angular momentum transfer near the inner sonic point. The oscillatory motion of the shock induced oscillation in all the disk parameters such as emission, rate of matter consumed by the black hole, and the rate of angular momentum consumed by the black hole. Our simulation may have implication for low and high frequency QPOs.

229.03

8:00 AM - 7:00 PM

The microquasar XTE J1550-564 produced the very first X-ray jets to be observed from a black-hole X-ray binary. Chandra imaging data obtained for these jets during 2000-2003 offer a near-unique opportunity to test whether the black hole's spin axis is tilted or aligned with respect to the plane of the binary orbit. To this end, we apply a kinematic relativistic blast-wave model to position measurements of the expanding jet. A comparison of the derived orientation of the jet to the optically measured binary inclination angle has important implications for the measurement of black hole spin. We present our results in the context of ongoing studies of the spins of several black holes, including XTE J1550-564.

229.04

The Local Environments of Ultra-Luminous X-Ray Sources in Interacting Galaxies

Beverly Smith¹, O. Miller¹, M. Nowak², C. Struck^3
1East Tennessee State Univ., ²Massachusetts Institute of Technology, ³Iowa State University.

8:00 AM - 7:00 PM

In the last several years, the Chandra X-Ray Observatory has discovered hundreds of ultra-luminous X-ray (ULX) point sources in nearby galaxies. These may be either intermediate mass (100 - 1000 solar mass) black holes or stellar mass black holes with anisotropic X-ray emission. To help distinguish between these possibilities, we are conducting a statistical analysis of the local environments of a sample of several hundred ULXs in nearby interacting galaxies. Using GALEX UV, SDSS optical, and Spitzer IR images, we investigate the stellar populations within the galaxies in the local vicinity of the ULXs. We also investigate whether the ULXs are more likely to be found in tidal features or in the inner disks of these galaxies. This research is supported by NASA Chandra grant AR9-0010A.

229.05

Long Term Monitoring of Black Hole Binaries with SMARTS

Charles D. Bailyn¹, M. Buxton^1
1Yale Univ..

8:00 AM - 7:00 PM

We have been monitoring black hole X-ray binaries (BHXRBs) for over ten years with the SMARTS consortium telescopes (and its precursor YALO) at CTIO. We will present lightcurves of a variety of well-known systems including A0620-00, GX 339-4, V4641 Sgr (=SAX 1819-2525), GRO J1915+105, GRO J1655-40 and others. The use of the ANDICAM instrument allows us to monitor these sources in both optical and IR bandpasses. We show that it is possible in many cases to divide the observed flux between flux from the secondary star and flux from the accretion flow, and in some cases between thermal emission from the accretion flow and a non-thermal component that presumably originates in a jet.

229.06

Evidence for Black Hole Growth in Local Analogs to Lyman Break Galaxies

Jianjun Jia¹, A. Ptak², T. M. Heckman¹, R. A. Overzier³, A. Hornschemeier², S. M. LaMassa^1
1The Johns Hopkins University, ²Goddard Space Flight Center, ³Max-Planck Institute for Astrophysics, Germany.

8:00 AM - 7:00 PM

We have used XMM-Newton to observe six Lyman Break Analogs (LBAs): members of the rare population of local galaxies that have properties that are very similar to distant Lyman Break Galaxies. Our six targets were specifically selected because they have optical emission-line properties that are intermediate between starbursts and Type 2 (obscured) AGN. Our new X-ray data provide an important diagnostic of the presence of an AGN. We find X-ray luminosities of order 10^{42} erg/s and ratios of X-ray to far-IR luminosities that are higher than values in pure starburst galaxies by factors ranging from ~3 to 30. This strongly suggests the presence of an AGN in at least some of the galaxies. The ratios of the luminosities of the hard (2-10 keV) X-ray to [O III]5007 emission-line are low by about an order-of-magnitude compared to Type 1 AGN, but are consistent with the broad range seen in Type 2 AGN. Either the AGN hard X-rays are significantly obscured or the [O III] emission is dominated by the starburst. We searched for an iron emission line at 6.4 keV, which is a key feature of obscured AGN, but only detected emission at the 2\sigma level. Finally, we find that the ratios of the mid-infrared (24 micron) continuum to [O III] luminosities in these LBAs are higher than the values for Type 2 AGN by an average of 0.8 dex. Combining all these clues, we conclude that an AGN is likely to be present, but that the bolometric luminosity is produced primarily by an intense starburst. If these black holes are radiating at the Eddington limit, their masses would lie in the range of 10^5 to 10^6 solar masses. These objects may offer ideal local laboratories to investigate the processes by which black holes grew in the early universe.

229.07

Testing General Relativity with the Event Horizon Telescope

Jessica Ruprecht¹, T. Johannsen², V. L. Fish³, A. E. Broderick⁴, S. S. Doeleman³, A. Loeb⁵, A. E. E. Rogers^3
1MIT, ²University of Arizona, ³MIT Haystack Observatory, ⁴CITA, Canada, ⁵Harvard CFA.

8:00 AM - 7:00 PM

General relativity (GR) predicts that light near a black hole will be lensed so as to produce a nearly circular photon orbit at a well-defined radius around the black hole. When embedded in an accretion flow, the emission profile will resemble all or part of a ring with a dark "shadow" within the photon orbit. Detecting the size and shape of a black hole shadow would serve as a test of GR. In particular,

229.08

8:00 AM - 7:00 PM

The Event Horizon Telescope (EHT) is an array of millimeter-wavelength telescopes that participate in very long baseline interferometry (VLBI) observations of supermassive black holes at extremely high angular resolution. For the Galactic Center black hole Sgr A*, the resolution of the EHT is a few Schwarzschild radii, sufficient to probe the inner accretion flow. Since the orbital period of material at the innermost stable circular orbit (ISCO) is a strong function of the spin of the black hole, measuring periodicity in the accretion flow provides a lower limit on the black hole spin. Recent general relativistic magnetohydrodynamic models (GRMHD) of the accretion flow are capable of qualitatively reproducing the variability in flux density seen at millimeter wavelengths. These models exhibit significant variability on scales near the ISCO. We examine prospects for detection of (quasi-)periodicity in the millimeter VLBI signatures of GRMHD models given expected performance parameters of the EHT. These simulations inform the feasibility of measuring the spin of the black hole in Sgr A* assuming a realistic model of the accretion flow around the black hole.

229.09

8:00 AM - 7:00 PM

The goal of the Event Horizon Telescope (EHT) project is to understand the physical and astrophysical processes of supermassive black holes though extremely high angular resolution observations. The EHT consists of existing millimeter-wavelength telescopes that participate in very long baseline interferometry (VLBI) observations of Sagittarius A*, M87, and active galactic nuclei. For the nearest sources, the EHT is uniquely capable of providing a resolution of a few Schwarzschild radii. Prior EHT observations have demonstrated very compact structure in Sgr A* and have been used to constrain the orientation of the black hole spin vector, strengthen the case for the existence of an event horizon, and examine the spatial characteristics of the variable millimeter emission. The sensitivity and angular resolution of the array are increasing due to the inclusion of new telescopes and several technical developments currently underway. We will summarize the most recent observations as well as the outlook for further enhancements of the capabilities of the EHT in the near future.