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Date and Time of the Query: 2019-05-23 T20:54:55 PDT
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For refcode 2000MNRAS.314..557B:
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Copyright by Royal Astronomical Society. 2000MNRAS.314..557B Diffuse X-ray emission from late-type galaxy haloes A. J. Benson, R. G. Bower, C. S. Frenk and S. D. M. White Accepted 1999 December 17. Received 1999 September 24; in original form 1999 March 15 ABSTRACT Current theories of galaxy formation predict that spiral galaxies are embedded in a reservoir of hot gas. This gas is able to cool on to the galaxy, replenishing cold gas that is consumed by star formation. Estimates of the X-ray luminosity emitted in the cooling region suggest a bolometric luminosity of the order of 10 x 10^41^ erg s^-1^ in massive systems. We have used ROSAT PSPC data to search for extended X-ray emission from the haloes of three nearby, massive, late-type galaxies: NGC 2841, 4594 and 5529. We infer 95 per cent upper limits on the bolometric X-ray luminosities of the haloes of NGC 2841, 4594 and 5529 of 0.4, 1.2 and 3.8 x 10^41^ erg s^-1^ respectively. Thus, the true luminosity lies well below the straightforward theoretical prediction. We discuss this discrepancy and suggest a number of ways in which the theoretical model might be brought into agreement with the observational results. A possible solution is that the gravitational potentials of the dark matter haloes of these galaxies are weaker than assumed in the current model. Alternatively, the present-day accretion may be substantially less than is required on average to build the disc over the Hubble time. Our results are, however, based on only three galaxies, none of which is ideal for this kind of study. A larger data set is required to explore this important problem further. Keywords: cooling flows - galaxies: formation - galaxies: individual: NGC 2841 - galaxies: individual: NGC 4594 - galaxies: individual: NGC 5529 - X- rays: galaxies
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