MEASURING THE DIRECTION AND ANGULAR VELOCITY OF A BLACK HOLE ACCRETION DISK VIA LAGGED INTERFEROMETRIC COVARIANCE

We show that interferometry can be applied to study irregular, rapidly rotating structures, as are expected in the turbulent accretion flow near a black hole. Specifically, we analyze the lagged covariance between interferometric baselines of similar lengths but slightly different orientations. For a flow viewed close to face-on, we demonstrate that the peak in the lagged covariance indicates the direction and angular velocity of the emission pattern from the flow. Even for moderately inclined flows, the covariance robustly estimates the flow direction, although the estimated angular velocity can be significantly biased. Importantly, measuring the direction of the flow as clockwise or counterclockwise on the sky breaks a degeneracy in accretion disk inclinations when analyzing time-averaged images alone. We explore the potential efficacy of our technique using three-dimensional, general relativistic magnetohydrodynamic (GRMHD) simulations, and we highlight several baseline pairs for the Event Horizon Telescope (EHT) that are well-suited to this application. These results indicate that the EHT may be capable of estimating the direction and angular velocity of the emitting material near Sagittarius A*, and they suggest that a rotating flow may even be utilized to improve imaging capabilities.

[1]  P. Young,et al.  Time series analysis, forecasting and control , 1972, IEEE Transactions on Automatic Control.

[2]  William H. Press,et al.  Rotating Black Holes: Locally Nonrotating Frames, Energy Extraction, and Scalar Synchrotron Radiation , 1972 .

[3]  B. Dewitt,et al.  Black holes (Les astres occlus) , 1973 .

[4]  V. Moncrief,et al.  Relativistic fluid disks in orbit around Kerr black holes , 1976 .

[5]  Roger D. Blandford,et al.  Relativistic jets as compact radio sources , 1979 .

[6]  T. Geballe,et al.  The central parsec of the Galaxy , 1979 .

[7]  R Edelson,et al.  The Discrete Correlation Function: a New Method for Analyzing Unevenly Sampled Variability Data , 1988 .

[8]  R. Narayan,et al.  The shape of a scatter-broadened image. II: Interferometric visibilities , 1989 .

[9]  R. Narayan,et al.  The shape of a scatter-broadened image – I. Numerical simulations and physical principles , 1989 .

[10]  D. H. Roberts,et al.  Linear Polarization Radio Imaging at Milliarcsecond Resolution , 1994 .

[11]  Ramesh Narayan,et al.  Advection-dominated Accretion: A Self-similar Solution , 1994 .

[12]  Hot One-Temperature Accretion Flows Around Black Holes , 1996, astro-ph/9601074.

[13]  Intrinsic Size of Sagittarius A*: 72 Schwarzschild Radii , 1998, astro-ph/9809222.

[14]  Roger D. Blandford,et al.  On the fate of gas accreting at a low rate on to a black hole , 1998, astro-ph/9809083.

[15]  Holland,et al.  Detection of Polarized Millimeter and Submillimeter Emission from Sagittarius A* , 2000, The Astrophysical journal.

[16]  The Astrophysical Journal , 2000 .

[17]  E. Quataert,et al.  Constraining the Accretion Rate onto Sagittarius A* Using Linear Polarization , 2000, astro-ph/0004286.

[18]  Eric Agol,et al.  Viewing the Shadow of the Black Hole at the Galactic Center. , 2000 .

[19]  UCLA,et al.  Chandra X-Ray Spectroscopic Imaging of Sagittarius A* and the Central Parsec of the Galaxy , 2001, astro-ph/0102151.

[20]  Ramesh Narayan,et al.  Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A* , 2003, astro-ph/0304125.

[21]  Geoffrey C. Bower,et al.  Interferometric Detection of Linear Polarization from Sagittarius A* at 230 GHz , 2003, astro-ph/0302227.

[22]  Charles F. Gammie,et al.  HARM: A NUMERICAL SCHEME FOR GENERAL RELATIVISTIC MAGNETOHYDRODYNAMICS , 2003 .

[23]  Rohta Takahashi,et al.  Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin Parameters of Black Holes , 2004, astro-ph/0405099.

[24]  Avery E. Broderick,et al.  Imaging bright-spots in the accretion flow near the black hole horizon of Sgr A* , 2005, astro-ph/0506433.

[25]  H. Falcke,et al.  The Intrinsic Size of Sagittarius A* from 0.35 to 6 cm , 2006, astro-ph/0608004.

[26]  Harvard University,et al.  Imaging optically-thin hotspots near the black hole horizon of Sgr A* at radio and near-infrared wavelengths , 2005, astro-ph/0509237.

[27]  C. Gammie,et al.  Primitive Variable Solvers for Conservative General Relativistic Magnetohydrodynamics , 2005, astro-ph/0512420.

[28]  J. Moran,et al.  To appear in the Astrophysical Journal Letters Preprint typeset using L ATEX style emulateapj v. 10/09/06 AN UNAMBIGUOUS DETECTION OF FARADAY ROTATION IN SAGITTARIUS A* , 2006 .

[29]  P. K. Leung,et al.  Simulating the emission and outflows from accretion discs , 2007, astro-ph/0701778.

[30]  A. Loeb,et al.  Properties of the radio-emitting gas around Sgr A* , 2007, astro-ph/0702043.

[31]  A. Niell,et al.  Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre , 2008, Nature.

[32]  Jessica R. Lu,et al.  Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits , 2008, 0808.2870.

[33]  Canadian Institute for Theoretical Astrophysics,et al.  DETECTING FLARING STRUCTURES IN SAGITTARIUS A* WITH HIGH-FREQUENCY VLBI , 2008, 0809.3424.

[34]  George E. P. Box,et al.  Time Series Analysis: Box/Time Series Analysis , 2008 .

[35]  R. Genzel,et al.  MONITORING STELLAR ORBITS AROUND THE MASSIVE BLACK HOLE IN THE GALACTIC CENTER , 2008, 0810.4674.

[36]  V. F. Vdovin,et al.  Millimetron—a large Russian-European submillimeter space observatory , 2009 .

[37]  S. Trippe,et al.  PROSPECTS FOR TESTING THE NATURE OF Sgr A*'s NEAR-INFRARED FLARES ON THE BASIS OF CURRENT VERY LARGE TELESCOPE—AND FUTURE VERY LARGE TELESCOPE INTERFEROMETER—OBSERVATIONS , 2009 .

[38]  P. K. Leung,et al.  RADIATIVE MODELS OF SGR A* FROM GRMHD SIMULATIONS , 2009, 0909.5431.

[39]  Signatures of Relativistic Helical Motion in the Rotation Measures of AGN Jets , 2009, 0908.2999.

[40]  Alan E. E. Rogers,et al.  DETECTING CHANGING POLARIZATION STRUCTURES IN SAGITTARIUS A* WITH HIGH FREQUENCY VLBI , 2009 .

[41]  G. Perrin,et al.  GRAVITY: Astrometry on the galactic center and beyond , 2009 .

[42]  Abraham Loeb,et al.  THE EVENT HORIZON OF SAGITTARIUS A* , 2009, 0903.1105.

[43]  T. Paumard,et al.  Performance of astrometric detection of a hotspot orbiting on the innermost stable circular orbit of the galactic centre black hole , 2010, 1011.5439.

[44]  Reinhard Genzel,et al.  The galactic center massive black hole and nuclear star cluster , 2010, 1006.0064.

[45]  P. Chris Fragile,et al.  THE SUBMILLIMETER BUMP IN Sgr A* FROM RELATIVISTIC MHD SIMULATIONS , 2010, 1005.4062.

[46]  M. Wright,et al.  1.3 mm WAVELENGTH VLBI OF SAGITTARIUS A*: DETECTION OF TIME-VARIABLE EMISSION ON EVENT HORIZON SCALES , 2010, 1011.2472.

[47]  Harvard,et al.  EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A* , 2010, 1011.2770.

[48]  Sven Koenig,et al.  Multiwavelength VLBI observations of Sagittarius A , 2010, 1010.1287.

[49]  Alan E. E. Rogers,et al.  Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87 , 2012, Science.

[50]  C. Gammie,et al.  A gas cloud on its way towards the supermassive black hole at the Galactic Centre , 2011, Nature.

[51]  C. Gammie,et al.  NEAR-INFRARED AND X-RAY QUASI-PERIODIC OSCILLATIONS IN NUMERICAL MODELS OF Sgr A* , 2012, 1201.1917.

[52]  R. Penna,et al.  SAGITTARIUS A* ACCRETION FLOW AND BLACK HOLE PARAMETERS FROM GENERAL RELATIVISTIC DYNAMICAL AND POLARIZED RADIATIVE MODELING , 2010, 1007.4832.

[53]  R. Shcherbakov,et al.  SUBMILLIMETER QUASI-PERIODIC OSCILLATIONS IN MAGNETICALLY CHOKED ACCRETION FLOW MODELS OF SgrA* , 2013, 1304.7768.

[54]  J. A. Zensus,et al.  “RadioAstron”-A telescope with a size of 300 000 km: Main parameters and first observational results , 2013, 1303.5013.

[55]  M. Johnson,et al.  DISCOVERY OF SUBSTRUCTURE IN THE SCATTER-BROADENED IMAGE OF SGR A* , 2014, 1409.0530.

[56]  Michael D. Johnson,et al.  RELATIVE ASTROMETRY OF COMPACT FLARING STRUCTURES IN Sgr A* WITH POLARIMETRIC VERY LONG BASELINE INTERFEROMETRY , 2014, 1408.6241.

[57]  H. Falcke,et al.  THE INTRINSIC TWO-DIMENSIONAL SIZE OF SAGITTARIUS A* , 2014, 1405.1456.

[58]  Victor Pankratius,et al.  IMAGING AN EVENT HORIZON: MITIGATION OF SCATTERING TOWARD SAGITTARIUS A* , 2014, 1409.4690.

[59]  R. Narayan,et al.  Hot Accretion Flows Around Black Holes , 2014, 1401.0586.

[60]  Canada.,et al.  IMAGING THE SUPERMASSIVE BLACK HOLE SHADOW AND JET BASE OF M87 WITH THE EVENT HORIZON TELESCOPE , 2014, 1404.7095.

[61]  A. Loeb,et al.  EVENT HORIZON TELESCOPE EVIDENCE FOR ALIGNMENT OF THE BLACK HOLE IN THE CENTER OF THE MILKY WAY WITH THE INNER STELLAR DISK , 2014, 1409.5447.

[62]  Andreas Burkert,et al.  THE GALACTIC CENTER CLOUD G2 AND ITS GAS STREAMER , 2014 .

[63]  H. Falcke,et al.  RADIO AND MILLIMETER MONITORING OF Sgr ?> A⋆: SPECTRUM, VARIABILITY, AND CONSTRAINTS ON THE G2 ENCOUNTER , 2015, 1502.06534.

[64]  Stephanie Thalberg,et al.  Interferometry And Synthesis In Radio Astronomy , 2016 .