Year: 2021
Type: review
Abstract: The central engines of active galactic nuclei (AGNs) are powered by accreting supermassive black holes, and while AGNs are known to play an important role in galaxy evolution, the key physical processes occur on scales that are too small to be resolved spatially (aside from a few exceptional cases). Reverberation mapping is a powerful technique that overcomes this limitation by using echoes of light to determine the geometry and kinematics of the central regions. Variable ionizing radiation from close to the black hole drives correlated variability in surrounding gas/dust but with a time delay due to the light travel time between the regions, allowing reverberation mapping to effectively replace spatial resolution with time resolution. Reverberation mapping is used to measure black hole masses and to probe the innermost X-ray emitting region, the UV/optical accretion disk, the broad emission line region, and the dusty torus. In this article, we provide an overview of the technique and its varied applications.
Source: iScience
Authors: Edward M. Cackett, Misty C. Bentz, Erin Kara
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,000
Awards: G1956696903, Are Active Galactic Nuclei accretion disks too big?, SUPERMASSIVE BLACK HOLES ARE CRUCIAL TO COSMOLOGY. THEIR POWERFUL JETS AND WINDS SHAPE GALAXIES VIA FEEDBACK. THEY ARE HOWEVER HARD TO STUDY BECAUSE THEY ARE DIM AND SCARCELY VARY ON A HUMAN TIMESCALE. LUCKILY SUPERMASSIVE BLACK HOLES CAN BE EFFECTIVELY STUDIED BY OBSERVING THEIR STELLAR-MASS COUSINS IN X-RAY BINARIES BECAUSE TIMESCALES AND SIZE-SCALES OF KEY PHENOMENA ARE DIRECTLY PROPORTIONAL TO THE BLACK HOLE'S MASS. AS A SINGLE STELLAR BLACK HOLE CYCLES BETWEEN QUIESCENCE AND ITS EDDINGTON LUMINOSITY IT EXHIBITS THE SAME WIDE RANGE OF BEHAVIOR THAT IS OBSERVED IN AN AGGREGATE OF ITS SUPERMASSIVE COUSINS. PROFOUNDLY A BLACK HOLE IS COMPLETELY DEFINED BY ITS MASS AND SPIN. MASS SIMPLY SETS THE SCALE WHILE THE SPIN LARGELY DETERMINES HOW A BLACK HOLE INTERACTS WITH ITS ENVIRONMENT. A CENTRAL OBJECTIVE OF THIS PROPOSAL IS TO ADVANCE THE QUALITY OF BLACK HOLE SPIN MEASUREMENTS. OUR OBSERVATIONS FOCUS ON THE OHIO-SIZED INNER REGION OF THE BLACK HOLE'S ACCRETION DISK WHERE GAS ORBITS AT RELATIVISTIC SPEEDS. REMINISCENT OF THE SUN THE X-RAY SOURCE IS COMPRISED OF A 10 K ACCRETION-DISK PHOTOSPHERE WHICH IS VEILED BY 10 K CORONAL GAS. THE CORONA ILLUMINATES THE COLD DISK PRODUCING A RICH ATOMIC "REFLECTION" SPECTRUM WHOSE FEATURES ARE GROSSLY BLURRED AND DISTORTED BY GRAVITATIONAL REDSHIFT AND DOPPLER EFFECTS. THE SPECTRAL FEATURE THAT WE SPOTLIGHT IS THE FE KLINE AND EDGE. WE PROPOSE GLOBAL STUDIES OF X-RAY REFLECTION SPECTRA USING THE VAST ARCHIVE OF 15 000 BLACK HOLE SPECTRA COLLECTED BY NASXS ROSSI X-RAY TIMING EXPLORER (RXTE) DURING ITS 16- YEAR MISSION. TWO METHODOLOGIES MAKE OUR STUDY UNIQUE: (1) OUR GROUP IS LEADING THE DEVELOPMENT OF DISK REFLECTION MODELS WHICH ARE THE BASIS FOR "FE-LINE MEASUREMENTS" OF BLACK HOLE SPIN; WE WILL EMPLOY AND CONTINUE TO EXTEND THESE MODELS. (2) A CALIBRATION TOOL THAT INCREASES THE SENSITIVITY OF THE RXTE DETECTORS FOR BRIGHT SOURCES BY AN ORDER OF MAGNITUDE -THE SAME FACTOR THAT THE COSTAR OPTICS SYSTEM BOOSTED THE SPATIAL RESOLUTION OF HST THREE YEARS AFTER ITS LAUNCH. FOR SPECTROSCOPY OF BLACK HOLES THIS LEAP IN SENSITIVITY EFFECTIVELY CREATES A QUALITATIVELY NEW DATA ARCHIVE WHICH WE REFER TO AS RXTE-11. WE HAVE SELECTED SIX BLACK HOLES WHICH WERE EACH OBSERVED SEVERAL HUNDRED TIMES ON A NEAR-DAILY BASIS. DURING OUTBURSTS THESE SOURCES DISPLAY THE FULL REPERTOIRE OF ACCRETING BLACK HOLE BEHAVIOR TRANSITIONING BETWEEN STATES AS THEIR LUMINOSITIES RAMP UP TO THE EDDINGTON LIMIT AND THEN DECAY. OVER THE COURSE OF AN OUTBURST THEY ALTERNATELY PRODUCE STEADY AND BALLISTIC JETS QUASI PERIODIC OSCILLATIONS (QPOS) AND SPECTRA THAT EXTEND UP TO SEVERAL MEV. WHILE WE WILL STRIVE TO RELATE OUR RESULTS TO ALL BLACK HOLE PHENOMENA OUR IMMEDIATE GOAL IS TO ANALYZE FOR EACH BLACK HOLE HUNDREDS OF SPECTRA SAMPLING COMPLETE OUTBURST CYCLES, G2866920699, G2924158848, Direct Comparisons of Black Hole Mass Measurements, G7470702609, G8672899949, G8978642021
OpenAlex ID: W3160011729