ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflow

Abstract

Radio and mm-wavelength observations of Sagittarius A* (Sgr A*), the radio source associated with the supermassive black hole at the center of our Galaxy, show that it behaves as a partially self-absorbed synchrotron-emitting source. The measured size of Sgr A* shows that the mm-wavelength emission comes from a small region and consists of the inner accretion flow and a possible collimated outflow. Existing observations of Sgr A* have revealed a time lag between light curves at 43 GHz and 22 GHz, which is consistent with a rapidly expanding plasma flow and supports the presence of a collimated outflow from the environment of an accreting black hole. Here we wish to measure simultaneous frequency-dependent time lags in the light curves of Sgr A* across a broad frequency range to constrain direction and speed of the radio-emitting plasma in the vicinity of the black hole. Light curves of Sgr A* were taken in May 2012 using ALMA at 100 GHz using the VLA at 48, 39, 37, 27, 25.5, and 19 GHz. As a result of elevation limits and the longitude difference between the stations, the usable overlap in the light curves is approximately four hours. Although Sgr A* was in a relatively quiet phase, the high sensitivity of ALMA and the VLA allowed us to detect and fit maxima of an observed minor flare where flux density varied by ~10%. The fitted times of flux density maxima at frequencies from 100 GHz to 19 GHz, as well as a cross-correlation analysis, reveal a simple frequency-dependent time lag relation where maxima at higher frequencies lead those at lower frequencies. Taking the observed size-frequency relation of Sgr A* into account, these time lags suggest a moderately relativistic (lower estimates: 0.5c for two-sided, 0.77c for one-sided) collimated outflow.

arXiv comment10 pages, 9 figures. Accepted for publication in A&A. Updated acknowledgements

References in corpus (33)

• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits
• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• A fundamental plane of black hole activity
• Viewing the Shadow of the Black Hole at the Galactic Center
• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• The Proper Motion of Sgr A*: II. The Mass of Sgr A*
• A Scheme to Unify Low-Power Accreting Black Holes - Jet-Dominated Accretion Flows and the Radio/X-Ray Correlation
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*
• A Geometric Determination of the Distance to the Galactic Center
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• A size of ~1 AU for the radio source Sgr A* at the centre of the Milky Way
• The Nature of the 10 Kilosecond X-ray Flare in Sgr A*
• Using the Fundamental Plane of Black Hole Activity to Distinguish X-ray Processes from Weakly Accreting Black Holes
• Detection of the Intrinsic Size of Sagittarius A* through Closure Amplitude Imaging (includes Online Supporting Material)
• The simultaneous spectrum of Sgr A* from 20cm to 1mm and the nature of the mm-excess
• Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
• The Intrinsic Size of Sagittarius A* from 0.35 cm to 6 cm
• Hybrid Thermal-Nonthermal Synchrotron Emission from Hot Accretion Flows
• Observational appearance of inefficient accretion flows and jets in 3D GRMHD simulations: Application to Sgr~A*
• Towards the event horizon -- the supermassive black hole in the Galactic Center
• Coupled jet-disk model for Sgr A*: explaining the flat-spectrum radio core with GRMHD simulations of jets
• Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity
• Time Dependent Models of Flares from Sagittarius A*
• An 8 hour characteristic time-scale in submillimetre light curves of Sagittarius A*
• Variable Linear Polarization from Sagittarius A*: Evidence for a Hot Turbulent Accretion Flow
• Jet-lag in Sgr A*: What size and timing measurements tell us about the central black hole in the Milky Way
• Evidence for A Parsec-scale Jet from The Galactic Center Black Hole: Interaction with Local Gas
• The Location of the Core in M81
• A Three Parsec-Scale Jet-Driven Outflow from Sgr A*
• The jet-disk symbiosis. I. Radio to X-ray emission models for quasars
• Time Lag in Intra-Day Variability of Sgr A* between the Light Curves at 90 and 102GHz
• Exploring the Jet/Accretion Flow Relationship in Low Disk Luminosity Sources

Cited by in corpus (48)

• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multi-wavelength Observations, Data Processing, and Calibration
• BlackHoleCam: fundamental physics of the Galactic center
• A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission
• The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA
• Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign
• General relativistic resistive magnetohydrodynamics with robust primitive variable recovery for accretion disk simulations
• Fast Variability and mm/IR flares in GRMHD Models of Sgr A* from Strong-Field Gravitational Lensing
• Rapid Variability of Sgr A* across the Electromagnetic Spectrum
• Dynamical Imaging with Interferometry
• Constraining particle acceleration in Sgr A* with simultaneous GRAVITY, Spitzer, NuSTAR and Chandra observations
• The Flux Distribution of Sgr A*
• General relativistic MHD simulations of non-thermal flaring in Sagittarius A*
• Relativistic resistive magnetohydrodynamic reconnection and plasmoid formation in merging flux tubes
• ALMA Observations of the Terahertz Spectrum of Sagittarius A*
• Physical laboratory at the center of the Galaxy
• A Detection of Sgr A* in the far infrared
• Statistics of X-ray flares of Sagittarius A*: evidence for solar-like self-organized criticality phenomenon
• Magnetic reconnection plasmoid model for Sagittarius A* flares
• Variations in emission from episodic plasmoid ejecta around black holes
• Fundamental Plane of Black Hole Activity in Quiescent Regime
• Multiwavelength Light Curves of Two Remarkable Sagittarius A* Flares
• Linearly Polarized Millimeter and Submillimeter Continuum Emission of Sgr A* Constrained by ALMA
• Multiwavelength study of the flaring activity of Sgr A* in 2014 February-April
• A magnetohydrodynamic model for multi-wavelength flares from Sagittarius~A${}^{\star }$ (I): model and the near-infrared and X-ray flares
• Quantifying Intrinsic Variability of Sagittarius A* using Closure Phase Measurements of the Event Horizon Telescope
• Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA
• Probing spacetime and accretion model for the Galactic Center: Comparison of Kerr and dilaton black hole shadows
• The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm
• Galactic Center Mini-spiral by ALMA - Possible Origin of the Central Cluster
• Simultaneous Monitoring of X-ray and Radio Variability in Sagittarius A*
• Far Infrared Variability of Sagittarius A*: 25.5 Hours of Monitoring with $Herschel$
• General relativistic effects and the near-infrared and X-ray variability of Sgr A* I
• Black Holes Up Close
• Multi-wavelength Variability of Sagittarius A* in July 2019
• Sgr A* and its Environment: Low Mass Star Formation, the Origin of X-ray Gas and Collimated Outflow
• Fermi LAT observations of Sagittarius A*: Imaging Analysis
• The jet-disk symbiosis without maximal jets: 1-D hydrodynamical jets revisited
• Multi-wavelength torus-jet model for Sgr~A*
• A first search of transients in the Galactic Center from 230 GHz ALMA observations
• Polarized signatures of adiabatically expanding hotspots in Sgr A*'s accretion flow
• Magnetic flux eruptions at the root of time-lags in low-luminosity AGN
• Constraining cosmic-ray acceleration in the magnetospheric gaps of Sgr A*
• The Core-shift of Sagittarius A* as a Discriminant between Disk and Jet Emission Models with millimeter-VLBI
• Radiative energy from a reconnection region around massive black hole
• Variability of Sagittarius A* at 3 GHz on minute-scale with MeerKAT
• Sagittarius A* near-infrared flares polarization as a probe of space-time I: Non-rotating exotic compact objects
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion