Abstract
X-ray emitting gaseous coronae around massive galaxies are a basic prediction
of galaxy formation models. Although the coronae around spiral galaxies offer a
fundamental test of these models, observational constraints on their
characteristics are still scarce. While the presence of extended hot coronae
has been established around a handful of massive spiral galaxies, the short
X-ray observations only allowed to measure the basic characteristics of the
coronae. In this work, we utilize deep XMM-Newton observations of NGC 6753 to
explore its extended X-ray corona in unprecedented detail. Specifically, we
establish the isotropic morphology of the hot gas, suggesting that it resides
in hydrostatic equilibrium. The temperature profile of the gas shows a decrease
with increasing radius: it drops from $kT\approx0.7$ keV in the innermost parts
to $kT\approx0.4$ keV at 50 kpc radius. The temperature map reveals the complex
temperature structure of the gas. We study the metallicity distribution of the
gas, which is uniform at $Z\approx0.1$ Solar. This value is about an order of
magnitude lower than that obtained for elliptical galaxies with similar dark
matter halo mass, hinting that the hot gas in spiral galaxies predominantly
originates from external gas inflows rather than from internal sources. By
extrapolating the density profile of the hot gas out to the virial radius, we
estimate the total gas mass and derive the total baryon mass of NGC 6753. We
conclude that the baryon mass fraction is $f_b 0.06$, implying
that about half of the baryons are missing.
Description
[1710.07286] Probing the Hot X-ray Corona around the Massive Spiral Galaxy, NGC 6753, Using Deep XMM-Newton observations
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