2005/08/31 by M. Macháček, M. Machacek, C. Jones +3 · 4 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Physics #Ram pressure #Star formation #Stellar, planetary, and galactic studies #Surface brightness #Virgo Cluster #astro-ph
paper · pdf · doi:10.1086/503350
31 pages, 12 figures, ApJ, in press; paper split into 2 parts, Paper I(sec 1-3) here, added figs and discussion to conform to published version; Paper II (sec. 4) in astro-ph/0604406
arxiv created 2006/04/20 · openalex publication_date 2006/06/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We use a 54.4 ks Chandra observation to study ram pressure stripping in NGC 4552 (M89), an elliptical galaxy in the Virgo Cluster. Chandra images in the 0.5-2 keV band show a sharp leading edge in the surface brightness 3.1 kpc north of the galaxy center, a cool ( kT = 0.51 keV) tail with mean density n e ~ × 10 -3 cm -3 extending ~10 kpc to the south of the galaxy, and two 3-4 kpc horns of emission extending southward away from the leading edge. These are all features characteristic of supersonic ram pressure stripping of galaxy gas, due to NGC 4552's motion through the surrounding Virgo ICM. Fitting the surface brightness profile and spectra across the leading edge, we find the galaxy gas inside the edge is cooler ( kT = 0.43 keV) and denser ( n e ~ 0.010 cm -3 ) than the surrounding Virgo ICM [ kT = 2.2 keV and n e = (3.0 ± 0.3) × 10 -4 cm -3 ]. The resulting pressure ratio between the free-streaming ICM and cluster gas at the stagnation point is ~7.6 for galaxy gas metallicities of 0.5 Z ☉ , which suggests that NGC 4552 is moving supersonically through the cluster with a velocity v ~ 1680 km s -1 (Mach 2.2 ) at an angle ξ ~ 35 ° ± 7 ° toward us with respect to the plane of the sky.