Jet-lag in Sgr A*: What size and timing measurements tell us about the central black hole in the Milky Way

Abstract

The black hole at the Galactic Center, Sgr A*, is the prototype of a galactic nucleus at a very low level of activity. Its radio through submm-wave emission is known to come from a region close to the event horizon, however, the source of the emission is still under debate. A successful theory explaining the emission is based on a relativistic jet model scaled down from powerful quasars. We want to test the predictive power of this established jet model against newly available measurements of wavelength-dependent time lags and the size-wavelength structure in Sgr A*. Using all available closure amplitude VLBI data from different groups, we again derived the intrinsic wavelength-dependent size of Sgr A*. This allowed us to calculate the expected frequency-dependent time lags of radio flares, assuming a range of in- and outflow velocities. Moreover, we calculated the time lags expected in the previously published pressure-driven jet model. The predicted lags are then compared to radio monitoring observations at 22, 43, and 350 GHz. The combination of time lags and size measurements imply a mildly relativistic outflow with bulk outflow speeds of gamma*beta ~ 0.5-2. The newly measured time lags are reproduced well by the jet model without any major fine tuning. The results further strengthen the case for the cm-to-mm wave radio emission in Sgr A* as coming from a mildly relativistic jet-like outflow. The combination of radio time lag and VLBI closure amplitude measurements is a powerful new tool for assessing the flow speed and direction in Sgr A*. Future VLBI and time lag measurements over a range of wavelengths will reveal more information about Sgr A*, such as the existence of a jet nozzle, and measure the detailed velocity structure of a relativistic jet near its launching point for the first time.

arXiv commentLatex, 7 pages, accepted for publication in Astronomy & Astrophysics

References in corpus (39)

• Closest Star Seen Orbiting the Supermassive Black Hole at the Centre of the Milky Way
• 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
• Stellar Orbits Around the Galactic Center Black Hole
• Near-infrared flares from accreting gas around the supermassive black hole at the Galactic Centre
• Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
• The Supermassive Black Hole at the Galactic Center
• Convection-Dominated Accretion Flows
• Advection-Dominated Accretion Model of Sagittarius A*: Evidence for a Black Hole at the Galactic Center
• A Geometric Determination of the Distance to the Galactic Center
• Magnetically Driven Jets in the Kerr Metric
• Radio Sources in Low-Luminosity Active Galactic Nuclei.IV. Radio Luminosity Function, Importance of Jet Power, and Radio Properties of the Complete Palomar Sample
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• A Jet-ADAF model for Sgr A*
• A size of ~1 AU for the radio source Sgr A* at the centre of the Milky Way
• Magnetically Driven Accretion in the Kerr Metric III: Unbound Outflows
• Imaging Optically-Thin Hot Spots Near the Black Hole Horizon of Sgr A* at Radio and Near-Infrared Wavelengths
• The Nature of the 10 Kilosecond X-ray Flare in Sgr A*
• An X-ray, IR, and Submillimeter Flare of Sagittarius A*
• 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
• The Flare Activity of SgrA*; New Coordinated mm to X-Ray Observations
• Intrinsic Size OF Sgr A*: 72 Schwarzschild Radii
• Variability of Sagittarius A* - Flares at 1 Millimeter
• Sgr A* Polarization: No ADAF, Low Accretion Rate, and Non-Thermal Synchrotron Emission
• Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity
• How to hide large scale outflows: size constraints on the jets of Sgr A*
• Intra-day Variability of Sagittarius A* at 3 Millimeters
• Structure of Sagittarius A* at 86 GHz using VLBI Closure Quantities
• Variable Linear Polarization from Sagittarius A*: Evidence for a Hot Turbulent Accretion Flow
• The Rotation Measure and 3.5mm Polarization of Sgr A*
• Black Hole Shadow Image and Visibility Analysis of Sagittarius A*
• The Variability of Sagittarius A* at Centimeter Wavelengths
• The Nuclear Jet in M81
• Intra-Day Variation of Sagittarius A* at Short Millimeter Wavelengths
• Understanding the Radio Variability of Sgr A*
• High-resolution Millimeter-VLBI Imaging of Sgr A*

Cited by in corpus (51)

• First Sagittarius A* Event Horizon Telescope Results. III: Imaging of the Galactic Center Supermassive Black Hole
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales
• A Chandra/HETGS Census of X-ray Variability From Sgr A* During 2012
• BlackHoleCam: fundamental physics of the Galactic center
• The Milky Way's Supermassive Black Hole: How good a case is it? A Challenge for Astrophysics & Philosophy of Science
• 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 Multi-Wavelength Observations of Sgr A* during 2007 April 1-11
• Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign
• Imaging an Event Horizon: Mitigation of Scattering Toward Sagittarius A*
• Determination of masses of the central black holes in NGC524 and NGC2549 using Laser Guide Star Adaptive Optics
• Rapid Variability of Sgr A* across the Electromagnetic Spectrum
• The Proper Motion of the Galactic Center Pulsar Relative to Sagittarius A*
• ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflow
• Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sgr A*
• The X-ray Flux Distribution of Sagittarius A* as Seen by Chandra
• X-ray and radio variability in the low luminosity Active Galactic Nucleus NGC 7213
• The Galactic Center Weather Forecast
• The Intrinsic Two-Dimensional Size of Sagittarius A*
• Multiwavelength VLBI observations of Sagittarius A*
• Constraining the charge of the Galactic centre black hole
• The Circular Polarization of Sagittarius A* at Submillimeter Wavelengths
• Probing the innermost accretion flow geometry of Sgr A* with Event Horizon Telescope
• Multiwavelength Light Curves of Two Remarkable Sagittarius A* Flares
• The Intrinsic Shape of Sagittarius A* at 3.5-mm Wavelength
• Asymmetric structure in Sgr A* at 3mm from closure phase measurements with VLBA, GBT and LMT
• A time-dependent jet model for the emission from Sagittarius A*
• Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA
• The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm
• The 492 GHz emission of Sgr A* constrained by ALMA
• Simultaneous Monitoring of X-ray and Radio Variability in Sagittarius A*
• Multi-Epoch VERA Observations of Sagittarius A*: I. Images and Structural Variability
• No asymmetric outflows from Sagittarius A* during the pericenter passage of the gas cloud G2
• Multi-wavelength Variability of Sagittarius A* in July 2019
• Is the plateau state in GRS 1915+105 equivalent to canonical hard states?
• The jet-disk symbiosis without maximal jets: 1-D hydrodynamical jets revisited
• Multi-wavelength torus-jet model for Sgr~A*
• Modelling the time dependence of the TeV Gamma-ray source at the Galactic Centre
• Intermediate-Mass Black Holes in Globular Clusters
• Magnetic flux eruptions at the root of time-lags in low-luminosity AGN
• Signatures of an Encounter Between the G2 Cloud and a Jet from Sgr A*
• Long-term monitoring of Sgr A* at 7 mm with VERA and KaVA
• Short Timescale Evolution of the Polarized Radio Jet during V404 Cygni's 2015 Outburst
• Time Lag in Intra-Day Variability of Sgr A* between the Light Curves at 90 and 102GHz
• The Point of Origin of the Radio Radiation from the Unresolved Cores of Radio-Loud Quasars
• Searching for Radio Outflows from M31* with VLBI Observations
• Radio Emission from Sgr A*: Pulsar Transits Through the Accretion Disc
• Variability of Sagittarius A* at 3 GHz on minute-scale with MeerKAT
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion
• A Model For The WMAP Anomalous Ecliptic Plane Signal