X-ray observations of the hot phase in Sgr~A*

Abstract

We analyze 134 ks Chandra ACIS-I observations of the Galactic Centre (GC) performed in July 2011. The X-ray image with the field of view $17^{\prime }\times 17^{\prime }$ contains the hot plasma surrounding the Sgr~A*. The obtained surface brightness map allow us to fit Bondi hot accretion flow to the innermost hot plasma around the GC. We have fitted spectra from region up to $5"$ from Sgr~A* using a thermal bremsstrahlung model and four Gaussian profiles responsible for K${}_{\alpha }$ emission lines of Fe, S, Ar, and Ca. The X-ray surface brightness profile up to $3"$ from Sgr~A* found in our data image, was successfully fitted with the dynamical model of Bondi spherical accretion. By modelling the surface brightness profile, we derived the temperature and number density profiles in the vicinity of the black hole. The best fitted model of spherical Bondi accretion shows that this type of flow works only up to $3"$ and implies outer plasma density and temperature to be: $n_{\mathrm{e}}^{\mathrm{out}}=18.3\pm 0.1$ cm${}^{-3}$ and $T_{\mathrm{e}}^{\mathrm{out}}=3.5\pm 0.3$ keV respectively. We show that the Bondi flow can reproduce observed surface brightness profile up to $3"$ from Sgr~A* in the Galactic Center. This result strongly suggests the position of stagnation radius in the complicated dynamics around GC. The Faraday rotation computed from our model towards the pulsar PSR J1745-2900 near the GC agrees with the observed one, recently reported.

10 pages, 7 figures, accepted for publication in A&A

References in corpus (5)

• A strong magnetic field around the supermassive black hole at the centre of the Galaxy
• Dissecting X-ray-emitting Gas around the Center of our Galaxy
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• Dynamics of Ionized Gas at the Galactic Center: VLA Observations of the 3D Velocity Field and Location of the Ionized Streams in Sagittarius A West
• Multiple accretion events as a trigger for Sgr A* activity

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• Constraining the accretion flow density profile near Sgr A* using the $L^{\prime }$-band emission of the S2 star
• Multi-phase environment of compact galactic nuclei: the role of the Nuclear Star Cluster
• Red giant - jet collisions in galactic nuclei I: 3D hydrodynamical model of a few stellar orbits