Simulations of imaging the event horizon of Sagittarius A* from space

Abstract

It has been proposed that Very Long Baseline Interferometry (VLBI) at sub-millimeter waves will allow us to image the shadow of the black hole in the center of our Milky Way, Sagittarius A* (Sgr A*), and thereby test basic predictions of general relativity. This paper presents imaging simulations of a new Space VLBI mission concept. An initial design study of the concept has been presented as the Event Horizon Imager (EHI). The EHI may be suitable for imaging Sgr A* at high frequencies (up to ~690 GHz), which has significant advantages over performing ground-based VLBI at 230 GHz. The concept EHI design consists of two or three satellites in polar or equatorial circular Medium-Earth Orbits with slightly different radii. Due to the relative drift of the satellites along the individual orbits, this setup will result in a dense spiral-shaped uv-coverage with long baselines (up to ~60 Glambda), allowing for extremely high-resolution and high-fidelity imaging of radio sources. We simulate EHI observations of general relativistic magnetohydrodynamics models of Sgr A* and calculate the expected noise based on preliminary system parameters. On long baselines, where the signal-to-noise ratio may be low, fringes could be detected if the system is sufficiently phase stable and the satellite orbits can be reconstructed with sufficient accuracy. Averaging visibilities accumulated over multiple epochs of observations could then help improving the image quality. With three satellites, closure phases could be used for imaging. Our simulations show that the EHI could be capable of imaging the black hole shadow of Sgr A* with a resolution of 4 uas (about 8% of the shadow diameter) within several months of observing time. The EHI concept could thus be used to measure black hole shadows much more precisely than with ground-based VLBI, allowing for stronger tests of general relativity and accretion models.

19 pages, 14 figures, accepted for publication in A&A

References in corpus (25)

• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• Jet Launching Structure Resolved Near the Supermassive Black Hole in M87
• Apparent shape of super-spinning black holes
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• RadioAstron -- a Telescope with a Size of 300 000 km: Main Parameters and First Observational Results
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• Simulating the Emission and Outflows from Accretion Disks
• Observational appearance of inefficient accretion flows and jets in 3D GRMHD simulations: Application to Sgr~A*
• Plasma diagnostic potential of 2p4f in N${}^{+}$ -- accurate wavelengths and oscillator strengths
• The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observations of Sgr A*
• X-ray hiccups from SgrA* observed by XMM-Newton. The second brightest flare and three moderate flares caught in half a day
• Radio and Millimeter Monitoring of Sgr A*: Spectrum, Variability, and Constraints on the G2 Encounter
• 230 GHz VLBI observations of M87: event-horizon-scale structure at the enhanced very-high-energy $\gamma$-ray state in 2012
• The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA
• Imaging an Event Horizon: Mitigation of Scattering Toward Sagittarius A*
• TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet
• Dynamical Imaging with Interferometry
• The Intrinsic Two-Dimensional Size of Sagittarius A*
• Stochastic Optics: A Scattering Mitigation Framework for Radio Interferometric Imaging
• A power-law break in the near-infrared power spectrum of the Galactic center black hole
• The Chinese space millimeter-wavelength VLBI array - a step toward imaging the most compact astronomical objects
• Quantifying Intrinsic Variability of Sagittarius A* using Closure Phase Measurements of the Event Horizon Telescope
• Asymmetric structure in Sgr A* at 3mm from closure phase measurements with VLBA, GBT and LMT
• RadioAstron as a target and as an instrument: Enhancing the Space VLBI mission's scientific output
• System Design for the Event Horizon Imaging Experiment Using the PECMEO Concept

Cited by in corpus (37)

• The Shape of the Black Hole Photon Ring: A Precise Test of Strong-Field General Relativity
• Testing Generalized Einstein-Cartan-Kibble-Sciama Gravity using Weak Deflection Angle and Shadow Cast
• The Black Hole Explorer: Motivation and Vision
• Influence of an anisotropic matter field on the shadow of a rotating black hole
• Simulations of M87 and Sgr A* Imaging with the Millimetron Space Observatory on near-Earth orbits
• Testing Gravity with Black Hole Shadow Subrings
• Observational Signatures of Frame Dragging in Strong Gravity
• Using space-VLBI to probe gravity around Sgr A*
• Black hole parameter estimation with synthetic Very Long Baseline Interferometry data from the ground and from space
• Gravitational effect of plasma particles on the shadow of Schwarzschild black holes
• Shadows of rotating Einstein-Maxwell-dilaton black holes surrounded by a plasma
• Probing Quadratic Gravity with the Event Horizon Telescope
• Analysis of Orbital Configurations for Millimetron Space Observatory
• An Event Horizon Imager (EHI) Mission Concept Utilizing Medium Earth Orbit Sub-mm Interferometry
• The future ability to test theories of gravity with black-hole shadows
• Orbital configurations of spaceborne interferometers for studying photon rings of supermassive black holes
• First Space-VLBI Observations of Sagittarius A*
• Black Hole Shadow Observations with Space-Ground Interferometers
• Imaging the event horizon of M87* from space on different timescales
• Climbing out of the shadows: building the distance ladder with black hole images
• Laboratory Demonstration of the Local Oscillator Concept for the Event Horizon Imager
• Impact of the nonthermal electron radiation effects on the horizon scale image structure of Sagittarius A*
• Origin of the ring ellipticity in the black hole images of M87*
• Multi-frequency VLBI Observations of the M 84 Inner Jet/Counterjet
• Shadow of axisymmetric, stationary and asymptotically flat black holes in the presence of plasma
• Detecting Black Hole Occultations by Stars with Space Interferometric Telescopes
• Microlensing Black Hole Shadows
• Toward Optimisation of a Sub-Terahertz Spaceborne VLBI Mission
• Shadows cast by a class of rotating black bounces with an anisotropic fluid
• The science case and challenges of space-borne sub-millimeter interferometry
• Orbit design for mitigating interstellar scattering effects in Earth-space VLBI observations of Sgr A*
• High Resolution Imaging of a Black Hole Shadow with Millimetron Orbit around Lagrange Point L2
• Beyond Sgr A* and M87*: Sub-Microarcsecond Black Hole Shadow Detection via Lunar-based Extremely Long Baseline Interferometry
• First Very Long Baseline Interferometry Fringe Detection at 690GHz
• Spatially resolved spectral properties of M87* on event horizon scales
• Decoding a black hole metric from the interferometric pattern of the relativistic images of a compact source
• Visible shapes of black holes M87* and SgrA*