Polarized light from Sgr A* in the near-infrared $K_s$-band

Abstract

We present a statistical analysis of polarized near-infrared (NIR) light from Sgr A*, the radio source associated with the supermassive black hole at the center of the Milky Way. The observations have been carried out using the adaptive optics instrument NACO at the VLT UT4 in the infrared $K_{\mathrm{s}}$-band from 2004 to 2012. Several polarized flux excursions were observed during these years. Linear polarization at 2.2 $\mu m$, its statistics and time variation, can be used constrain the physical conditions of the accretion process onto this supermassive black hole. With an exponent of about 4 for the number density histogram of fluxes above 5~mJy, the distribution of polarized flux density is closely linked to the single state power-law distribution of the total $K_{\mathrm{s}}$-band flux densities reported earlier. We find typical polarization degrees of the order of 20\%$\pm$10\% and a preferred polarization angle of 13${}^o$$\pm$15${}^o$. Simulations show the uncertainties under a total flux density of $\sim 2\mathrm{mJy}$ are probably dominated by observational effects. At higher flux densities there are intrinsic variations of polarization degree and angle within rather well constrained ranges. Since the emission is most likely due to optically thin synchrotron radiation, this preferred polarization angle we find is very likely coupled to the intrinsic orientation of the Sgr A* system i.e. a disk or jet/wind scenario associated with the super massive black hole. If they are indeed linked to structural features of the source the data imply a rather stable geometry and accretion process for the Sgr A* system.

arXiv comment19 pages, 18 figures, 4 tables, submitted to Astronomy & Astrophysics

References in corpus (61)

• 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
• Closest Star Seen Orbiting the Supermassive Black Hole at the Centre of the Milky Way
• High Proper Motion Stars in the Vicinity of Sgr A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy
• 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 Accelerations of Stars Orbiting the Milky Way's Central Black Hole
• Analysis of isoplanatic high resolution stellar fields by Starfinder code
• A Geometric Determination of the Distance to the Galactic Center
• Interferometric Detection of Linear Polarization from Sagittarius A* at 230 GHz
• An extended scheme for fitting X-ray data with accretion disk spectra in the strong gravity regime
• 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*
• XMM-Newton observation of the brightest X-ray flare detected so far from SgrA*
• Evidence for X-ray synchrotron emission from simultaneous mid-IR to X-ray observations of a strong Sgr A* flare
• Polarimetry of near-infrared flares from Sagittarius A*
• On The Nature of the Variable Infrared Emission from Sgr A*
• Stellar Orbits Near Sagittarius A*
• First Simultaneous NIR/X-ray Detection of a Flare from SgrA*
• Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
• 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
• A near-IR variability study of the Galactic black hole: a red noise source with no detected periodicity
• A Magnetohydrodynamic Model for the Formation of Episodic Jets
• Modeling optical and UV polarization of AGNs I. Imprints of individual scattering regions
• The two states of Sgr A* in the near-infrared: bright episodic flares on top of low-level continuous variability
• The First Laser Guide Star Adaptive Optics Observations of the Galactic Center: Sgr A*'s Infrared Color and the Extended Red Emission in its Vicinity
• The Flare Activity of SgrA*; New Coordinated mm to X-Ray Observations
• A polarised infrared flare from Sagittarius A* and the signatures of orbiting plasma hotspots
• Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity
• Simultaneous Multi-Wavelength Observations of Sgr A* during 2007 April 1-11
• Source-intrinsic near-infrared properties of Sgr A*: Total intensity measurements
• Near-infrared polarimetry setting constraints on the orbiting spot model for Sgr A* flares
• Analysis of 6cm VLBI polarization observations of a complete sample of northern BL Lacertae Objects
• Variations in the spectral slope of Sgr A* during a NIR flare
• Detection of Circular Polarization in the Galactic Center Black Hole Candidate Sagittarius A*
• Polarized NIR and X-ray Flares from SgrA*
• Prospects for testing the nature of Sgr A*'s NIR flares on the basis of current VLT- and future VLTI-observations
• The Rotation Measure and 3.5mm Polarization of Sgr A*
• K-band polarimetry of an Sgr A* flare with a clear sub-flare structure
• Simultaneous NIR/sub-mm observation of flare emission from SgrA*
• The Linear Polarization of Sagittarius A* I. VLA Spectro-polarimetry at 4.8 and 8.4 GHz
• Near infrared flares of Sagittarius A*: Importance of near infrared polarimetry
• Synchrotron Radiation From Radiatively Inefficient Accretion Flow Simulations: Applications to Sgr A*
• Cometary shaped sources at the Galactic Center - Evidence for a wind from the central 0.2 pc
• VLBI Polarimetry of 177 Sources from the Caltech-Jodrell Bank Flat-spectrum Survey
• The Intrinsic Two-Dimensional Size of Sagittarius A*
• MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations, Outbursts, and Quasi-Periodicity
• On the orientation of the Sagittarius A* system
• Transient jet formation and state transitions from large-scale magnetic reconnection in black hole accretion discs
• The S-Star Cluster at the Center of the Milky Way: On the nature of diffuse NIR emission in the inner tenth of a parsec
• The instrumental polarization of the Nasmyth focus polarimetric differential imager NAOS/CONICA (NACO) at the VLT - Implications for time-resolved polarimetric measurements of Sgr A*
• The extreme luminosity states of Sagittarius A*
• Magnetic Fields of Agns and Standard Accretion Disk Model: Testing by Optical Polarimetry
• A Testable the Stochastic Acceleration Model for Flares in Sagittarius A*
• The Variability of Polarized Radiation from Sgr A*
• A formal method for identifying distinct states of variability in time-varying sources: SgrA* as an example
• Ks- and Lp-band polarimetry on stellar and bow-shock sources in the Galactic center
• Variation in the primary and reprocessed radiation from an orbiting spot around a black hole
• An evolving hot spot orbiting around Sgr A*
• Adaptive optics assisted near-infrared polarization measurements of sources in the Galactic Center
• Flare emission from Sagittarius A*

Cited by in corpus (30)

• Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*
• Flares in the Galactic center I: orbiting flux tubes in Magnetically Arrested Black Hole Accretion Disks
• The Milky Way's Supermassive Black Hole: How good a case is it? A Challenge for Astrophysics & Philosophy of Science
• 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
• Investigating the Relativistic Motion of the Stars Near the Supermassive Black Hole in the Galactic Center
• Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*
• A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating
• Dynamically important magnetic fields near the event horizon of Sgr A*
• Kinematic Structure of the Galactic Center S-cluster
• Simultaneous X-ray and Infrared Observations of Sagittarius A*'s Variability
• Effect of Electromagnetic Interaction on Galactic Center Flare Components
• Deep Images of the Galactic Center with GRAVITY
• A magnetohydrodynamic model for multi-wavelength flares from Sagittarius~A${}^{\star }$ (I): model and the near-infrared and X-ray flares
• Wisps in the Galactic center: NIR triggered observations of the radio source Sgr A* at 43 GHz
• ALMA Detection of Bipolar Outflows: Evidence for Low Mass Star Formation within 1pc of Sgr A*
• Polarized near-infrared light of the Dusty S-cluster Object (DSO/G2) at the Galactic Center
• A Deep Chandra View of A Candidate Parsec-Scale Jet from the Galactic Center Super-massive Black Hole
• Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*
• The 492 GHz emission of Sgr A* constrained by ALMA
• 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
• Monitoring the Galactic Centre with Australia Telescope Compact Array
• Synchrotron Polarization Radiative Transfer: Relativistic Thermal Electrons Contribution
• Multi-band polarimetry of post-asymptotic giant branch stars stars. Optical measurements
• Synchrotron Polarization of Relativistic Thermal Electrons
• Electromagnetic signatures of strong-field gravity from accreting black holes
• Possible evidence from the flaring activity of Sgr A* for a star at a distance of ~3.3 Schwarzscild radii from the blackhole
• Impact of intrinsic polarisation of Sgr A* historical flares on (polarisation) properties of their X-ray echoes
• The orbit and nature of the semi-detached stellar companion of Sgr A* super-massive blackhole
• The Center of the Milky Way from Radio to X-rays