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Register a new userProspects for measuring supermassive black hole masses with future extremely large telescopes
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The next generation of giant-segmented mirror telescopes ($>$ 20 m) will enable us to observe galactic nuclei at much higher angular resolution and sensitivity than ever before. These capabilities will introduce a revolutionary shift in our understanding of the origin and evolution of supermassive black holes by enabling more precise black hole mass measurements in a mass range that is unreachable today. We present simulations and predictions of the observations of nuclei that will be made with the Thirty Meter Telescope (TMT) and the adaptive optics assisted integral-field spectrograph IRIS, which is capable of diffraction-limited spectroscopy from $Z$ band (0.9 $mu$m) to $K$ band (2.2 $mu$m). These simulations, for the first time, use realistic values for the sky, telescope, adaptive optics system, and instrument, to determine the expected signal-to-noise ratio of a range of possible targets spanning intermediate mass black holes of $sim10^4$ msun to the most massive black holes known today of $>10^{10}$ $M_odot$. We find that IRIS will be able to observe Milky Way-mass black holes out the distance of the Virgo cluster, and will allow us to observe many more brightest cluster galaxies where the most massive black holes are thought to reside. We also evaluate how well the kinematic moments of the velocity distributions can be constrained at the different spectral resolutions and plate scales designed for IRIS. We find that a spectral resolution of $sim8000$ will be necessary to measure the masses of intermediate mass black holes. By simulating the observations of galaxies found in SDSS DR7, we find that over $10^5$ massive black holes will be observable at distances between $0.005 < z < 0.18$ with the estimated sensitivity and angular resolution provided by access to $Z$-band (0.9 $mu$m) spectroscopy from IRIS and the TMT adaptive optics system. (Abridged)
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The anticipated discovery of a pulsar in orbit with a black hole is expected to provide a unique laboratory for black hole physics and gravity. In this context, the next generation of radio telescopes, like the Five-hundred-metre Aperture Spherical radio Telescope (FAST) and the Square Kilometre Array (SKA), with their unprecedented sensitivity, will play a key role. In this paper, we investigate the capability of future radio telescopes to probe the spacetime of a black hole and test gravity theories, by timing a pulsar orbiting a stellar-mass-black-hole (SBH). Based on mock data simulations, we show that a few years of timing observations of a sufficiently compact pulsar-SBH (PSR-SBH) system with future radio telescopes would allow precise measurements of the black hole mass and spin. A measurement precision of one per cent can be expected for the spin. Measuring the quadrupole moment of the black hole, needed to test GRs no-hair theorem, requires extreme system configurations with compact orbits and a large SBH mass. Additionally, we show that a PSR-SBH system can lead to greatly improved constraints on alternative gravity theories even if they predict black holes (practically) identical to GRs. This is demonstrated for a specific class of scalar-tensor theories. Finally, we investigate the requirements for searching for PSR-SBH systems. It is shown that the high sensitivity of the next generation of radio telescopes is key for discovering compact PSR-SBH systems, as it will allow for sufficiently short survey integration times.
The Galactic center offers us a unique opportunity to test General Relativity (GR) with the orbits of stars around a supermassive black hole. Observations of these stars have been one of the great successes of adaptive optics on 8-10 m telescopes, driving the need for the highest angular resolution and astrometric precision. New tests of gravitational physics in the strong gravity regime with stellar orbits will be made possible through the leap in angular resolution and sensitivity from the next generation of extremely large ground-based telescopes. We present new simulations of specific science cases such as the detection of the GR precession of stars, the measurement of extended dark mass, and the distance to the Galactic center. We use realistic models of the adaptive optics system for TMT and the IRIS instrument to simulate these science cases. In additions, the simulations include observational issues such as the impact of source confusion on astrometry and radial velocities in the dense environment of the Galactic center. We qualitatively show how improvements in sensitivity, astrometric and spectroscopic precision, and increasing the number of stars affect the science with orbits at the Galactic center. We developed a tool to determine the constraints on physical models using a joint fit of over 100 stars that are expected to be observable with TMT. These science cases require very high astrometric precision and stability, thus they provide some of the most stringent constraints on the planned instruments and adaptive optics systems.
The field of time-domain astrophysics has entered the era of Multi-messenger Astronomy (MMA). One key science goal for the next decade (and beyond) will be to characterize gravitational wave (GW) and neutrino sources using the next generation of Extremely Large Telescopes (ELTs). These studies will have a broad impact across astrophysics, informing our knowledge of the production and enrichment history of the heaviest chemical elements, constrain the dense matter equation of state, provide independent constraints on cosmology, increase our understanding of particle acceleration in shocks and jets, and study the lives of black holes in the universe. Future GW detectors will greatly improve their sensitivity during the coming decade, as will near-infrared telescopes capable of independently finding kilonovae from neutron star mergers. However, the electromagnetic counterparts to high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus demand ELT capabilities for characterization. ELTs will be important and necessary contributors to an advanced and complete multi-messenger network.
We determine the spin of a supermassive black hole in the context of discseismology by comparing newly detected quasi-periodic oscillations (QPOs) of radio emission in the Galactic centre, Sagittarius A* (Sgr A*), as well as infrared and X-ray emissions with those of the Galactic black holes. We find that the spin parameters of black holes in Sgr A* and in Galactic X-ray sources have a unique value of $approx 0.44$ which is smaller than the generally accepted value for supermassive black holes, suggesting evidence for the angular momentum extraction of black holes during the growth of supermassive black holes. Our results demonstrate that the spin parameter approaches the equilibrium value where spin-up via accretion is balanced by spin-down via the Blandford-Znajek mechanism regardless of its initial spin. We anticipate that measuring the spin of black holes by using QPOs will open a new window for exploring the evolution of black holes in the Universe.
We test the recently proposed (Mediavilla et al. 2018) black hole mass scaling relationship based on the redshift {with respect to the quasars rest frame} of the Fe III$lambdalambda$2039-2113 line blend. To this end, we fit this feature in the spectra of a well suited sample of quasars, observed with X-shooter at the Very Large Telescope (VLT), whose masses have been independently estimated using the virial theorem. For the quasars of this sample we consistently confirm the redshift of the Fe III$lambdalambda$2039-2113 blend and find that it correlates with the squared widths of H$beta$, H$alpha$ and Mg II, which are commonly used as a measure of $M_{BH}/R$ to determine masses from the virial theorem. The average differences between virial and Fe III$lambdalambda$2039-2113 redshift based masses are 0.18$pm 0.21$ dex, 0.18$pm 0.22$ dex and 0.14$pm 0.21$ dex, when the full widths at half maximum (FWHM) of the H$beta$, H$alpha$ and MgII lines are, respectively, used. The difference is reduced to 0.10$pm 0.16$ dex when the standard deviation, $sigma$, of {the} MgII line is used, instead. We also study the high S/N composite quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS), finding that the Fe III$lambdalambda$2039-2113 redshifts and Mg II squared widths, $FWHM_{MgII}^2$, match very well the correlation found for the individual quasar spectra observed with X-shooter. This correlation is expected if the redshift is gravitational.
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