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The Infall of the Virgo Elliptical Galaxy M60 toward M87 and the Gaseous Structures Produced by Kelvin-Helmholtz Instabilities

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Abstract

  • We present Chandra observations of hot gas structures, which are characteristic of gas-stripping during infall, in the Virgo cluster elliptical galaxy M60 (NGC4649) located 1 Mpc east of M87. Chandra X-ray images at 0.5-2 keV show a sharp leading edge in the surface brightness that is 12.4 ± 0.1 kpc north and west of the galaxy center in the direction of M87 and characteristic of a merger cold front due to M60's motion through the Virgo ICM. We measured a temperature of 1.00 ± 0.02 keV for an abundance of 0.5 {Z}? inside the edge and {1.37}-0.19 0.35 {keV} for an abundance of 0.1 {Z}? in the Virgo ICM free stream region. We find that the observed jump in surface brightness yields a density ratio {n}{in}/{n}{out}={6.44}-0.67 1.04 between gas inside the edge and in the cluster free stream region. If the edge is a cold front due solely to the infall of M60 in the direction of M87, we find a pressure ratio of {4.7}-1.4 1.7 and Mach number of {1.7}-0.3 0.3. For 1.37 keV Virgo gas, we find a total infall velocity for M60 of {v}{{M}60}=1030 /- 180 {km} {{{s}}}-1. We calculate the motion in the plane of the sky to be {v}{tran}={1012}-192 183 {km} {{{s}}}-1, implying an inclination angle of ? ={11}-3 3°. Surface brightness profiles also show the presence of a faint, diffuse gaseous tail. We identify filamentary gaseous wing structures caused by the galaxy's motion through the ICM. The structure and dimensions of these wings are consistent with simulations of Kelvin-Helmholtz instabilities, as expected if the gas-stripping is close to inviscid.

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  • 2017

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