1998/12/17 by S. Pellegrini, Silvia Pellegrini, Pellegrini, S.
Engineering · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #Atomic and Molecular Physics #CCD and CMOS Imaging Sensors #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9812325
12 pages, including 3 postscript figures, 1 table. To appear in Astronomy and Astrophysics
arxiv created 1998/12/17 · openalex publication_date 1998/12/17 · arxiv updated 2009/12/01 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/28
We present the results of the analysis of the BeppoSAX LECS and MECS pointed\nobservation of the E4 galaxy NGC 3923, for which previous X-ray measurements\nhad given a medium X-ray to optical ratio Lx/Lb. The spectral analysis over\n(0.5-10) keV reveals that the best representation of the data is the\nsuperposition of two thermal components at temperatures of 0.4 keV and 6-8 keV.\nThe total emission is roughly equally divided between the two components, over\n(0.5-4.5) keV. The harder component is consistent with an origin from stellar\nsources; the softer component likely comes from hot gas. Lx of this hot gas is\nnot as large as expected for a global inflow, in a galaxy of an optical\nluminosity as high as that of NGC3923. So, it is suggested that a substantial\namount of hot gas was removed by internal agents, and that this process was\nhelped by the flat mass distribution of the galaxy. Another possibility is that\ngas was lost as a consequence of the episod of interaction or merger that\nproduced the system of shells visible in the optical band. Finally, the\npossible origins of the large scatter in the X-ray emission shown by galaxies\nof similar Lb are also reviewed. Like NGC 3923, many other low and medium Lx/Lb\ngalaxies reside in small groups, in which the ambient medium (if present)\ncannot strip them of their hot gas; so, if only environmental factors are\ninvoked to lower Lx/Lb, the most effective mechanism must be galaxy\ninteractions. The lower Lx/Lb galaxies, though, are seen to occur across the\nwhole range of galaxy densities. Another possibility, to remove some or all of\nthe hot gas, appeals to mechanisms internal to the galaxies, ...\n