ALMA Observations of the Terahertz Spectrum of Sagittarius A*

Abstract

We present ALMA observations at 233, 678, and 870 GHz of the Galactic Center black hole, Sagittarius A*. These observations reveal a flat spectrum over this frequency range with spectral index $\alpha \approx -0.3$, where the flux density $S\propto {\nu }^{\alpha }$. We model the submm and far infrared spectrum with a one zone synchrotron model of thermal electrons. We infer electron densities $n=(2-5)\times 10^6$ cm${}^{-3}$, electron temperatures $T_e=(1-3)\times 10^{11}$ K, and magnetic field strength $B=10-50$ G. The parameter range can be further constrained using the observed quiescent X-ray luminosity. The flat submm spectrum results in a high electron temperature and implies that the emitting electrons are efficiently heated. We also find that the emission is most likely optically thin at 233 GHz. These results indicate that millimeter and submillimeter wavelength very long baseline interferometry of Sgr A* including those of the Event Horizon Telescope should see a transparent emission region down to event horizon scales.

Accepted for publication in ApJL

References in corpus (86)

• emcee: The MCMC Hammer
• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• Hot Accretion Flows Around Black Holes
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• Viewing the Shadow of the Black Hole at the Galactic Center
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• HARM: A Numerical Scheme for General Relativistic Magnetohydrodynamics
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*
• Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*
• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images
• Magnetically Driven Accretion Flows in the Kerr Metric I: Models and Overall Structure
• Radiative Models of Sgr A* from GRMHD Simulations
• Dissecting X-ray-emitting Gas around the Center of our Galaxy
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• Interferometric Detection of Linear Polarization from Sagittarius A* at 230 GHz
• A size of ~1 AU for the radio source Sgr A* at the centre of the Milky Way
• Spectral Models of Advection-Dominated Accretion Flows with Winds
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• An X-ray, IR, and Submillimeter Flare of Sagittarius A*
• Rapid variability in the synchrotron self Compton model for blazars
• Non-thermal particle acceleration in collisionless relativistic electron-proton reconnection
• A public code for general relativistic, polarised radiative transfer around spinning black holes
• Constraining the Accretion Rate Onto Sagittarius A* Using Linear Polarization
• The simultaneous spectrum of Sgr A* from 20cm to 1mm and the nature of the mm-excess
• A Chandra/HETGS Census of X-ray Variability From Sgr A* During 2012
• Sagittarius A* Accretion Flow and Black Hole Parameters from General Relativistic Dynamical and Polarized Radiative Modeling
• The Intrinsic Size of Sagittarius A* from 0.35 cm to 6 cm
• A prescription for the turbulent heating of astrophysical plasmas
• Hybrid Thermal-Nonthermal Synchrotron Emission from Hot Accretion Flows
• Simulating the Emission and Outflows from Accretion Disks
• The central parsecs of M87: jet emission and an elusive accretion disc
• A Multi-Wavelength Study of Sgr A*: The Role of Near-IR Flares in Production of X-ray, Soft $\gamma$-ray and Sub-millimeter Emission
• Observational appearance of inefficient accretion flows and jets in 3D GRMHD simulations: Application to Sgr~A*
• The Disc-Jet Symbiosis Emerges: Modeling the Emission of Sagittarius A* with Electron Thermodynamics
• 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*
• Thermal disequilibration of ions and electrons by collisionless plasma turbulence
• Frequency-Dependent Shift in the Image Centroid of the Black Hole at the Galactic Center as a Test of General Relativity
• The two states of Sgr A* in the near-infrared: bright episodic flares on top of low-level continuous variability
• Variability of Sagittarius A* - Flares at 1 Millimeter
• Radio and Millimeter Monitoring of Sgr A*: Spectrum, Variability, and Constraints on the G2 Encounter
• Millimeter Flares and VLBI Visibilities from Relativistic Simulations of Magnetized Accretion onto the Galactic Center Black Hole
• Electron and proton heating in trans-relativistic magnetic reconnection
• Coupled jet-disk model for Sgr A*: explaining the flat-spectrum radio core with GRMHD simulations of jets
• Sgr A* Polarization: No ADAF, Low Accretion Rate, and Non-Thermal Synchrotron Emission
• Variability Timescale and Spectral Index of Sgr A* in the Near Infrared: Approximate Bayesian Computation Analysis of the Variability of the Closest Supermassive Black Hole
• Results from an extensive simultaneous broadband campaign on the underluminous active nucleus M81*: further evidence for mass-scaling accretion in black holes
• Polarimetric Imaging of the Massive Black Hole at the Galactic Center
• The Scattering and Intrinsic Structure of Sagittarius A* at Radio Wavelengths
• Faraday rotation in GRMHD simulations of the jet launching zone of M87
• Detection of Circular Polarization in the Galactic Center Black Hole Candidate Sagittarius A*
• Inflow-Outflow Model with Conduction and Self-Consistent Feeding for Sgr A*
• An 8 hour characteristic time-scale in submillimetre light curves of Sagittarius A*
• The Rotation Measure and 3.5mm Polarization of Sgr A*
• GRMHD simulations of accretion onto Sgr A*: How important are radiative losses?
• Detection of intrinsic source structure at ~3 Schwarzschild radii with Millimeter-VLBI observations of SAGITTARIUS A*
• ALMA Polarimetry of Sgr A*: Probing the Accretion Flow from the Event Horizon to the Bondi Radius
• Simulations of imaging the event horizon of Sagittarius A* from space
• The mean infrared emission of SagittariusA*
• Simultaneous NIR/sub-mm observation of flare emission from SgrA*
• The Variability of Sagittarius A* at Centimeter Wavelengths
• ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflow
• The X-ray Flux Distribution of Sagittarius A* as Seen by Chandra
• MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations, Outbursts, and Quasi-Periodicity
• The Intrinsic Two-Dimensional Size of Sagittarius A*
• The impact of Faraday effects on polarized black hole images of Sagittarius A*
• The Circular Polarization of Sagittarius A* at Submillimeter Wavelengths
• Self-consistent spectra from radiative GRMHD simulations of accretion onto Sgr A*
• Understanding the Radio Variability of Sgr A*
• Propagation Effects in Magnetized Transrelativistic Plasmas
• Disentangling the Circumnuclear Environs of Centaurus A: III. An Inner Molecular Ring, Nuclear Shocks and the CO to warm H2 interface
• Millimeter Radio Continuum Emissions as the Activity of Super Massive Black Holes in Nearby Early-Type Galaxies and Low-Luminosity Active Galactic Nuclei
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• Linearly Polarized Millimeter and Submillimeter Continuum Emission of Sgr A* Constrained by ALMA
• The millimeter-wave continuum spectrum of Centaurus A and its nucleus
• Polarized Emission of Sagittarius A*
• The 492 GHz emission of Sgr A* constrained by ALMA
• Far Infrared Variability of Sagittarius A*: 25.5 Hours of Monitoring with $Herschel$
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• A jet-dominated model for a broad-band spectral energy distribution of the nearby low-luminosity active galactic nucleus in M94

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• HOLESOM: Constraining the Properties of Slowly-Accreting Massive Black Holes with Self-Organizing Maps
• Radiative energy from a reconnection region around massive black hole