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

Journal Article · Wed Sep 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA8723· OSTI ID:22875760

Wood, R. A. ^[1]; Jones, C.; Machacek, M. E.; Forman, W. R.; Bogdan, A.; Andrade-Santos, F.; Kraft, R. P.; Paggi, A. ^[2]

---

1. University of Southampton, Southampton, SO17 1BJ (United Kingdom)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

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{sub ⊙} inside the edge and 1.37{sub −0.19}{sup +0.35} keV for an abundance of 0.1 Z{sub ⊙} in the Virgo ICM free stream region. We find that the observed jump in surface brightness yields a density ratio n{sub in}/n{sub out}=6.44{sub −0.67}{sup +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{sub −1.4}{sup +1.7} and Mach number of 1.7{sub −0.3}{sup +0.3}. For 1.37 keV Virgo gas, we find a total infall velocity for M60 of v{sub M60}=1030±180 km s{sup −1}. We calculate the motion in the plane of the sky to be v{sub tran}=1012{sub −192}{sup +183} km s{sup −1}, implying an inclination angle of ξ=11{sub −3}{sup +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.

• OSTI ID: 22875760
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 847; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BRIGHTNESS
COMPUTERIZED SIMULATION
DENSITY
GALAXY CLUSTERS
HELMHOLTZ INSTABILITY
INCLINATION
INTERGALACTIC SPACE
KEV RANGE 01-10
MACH NUMBER
STRIPPING
SURFACES
X RADIATION
X-RAY GALAXIES