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We examine 11 XMM-Newton observations of the giant spiral galaxy NGC 1961,allowing us to study the hot gaseous halo of a spiral galaxy in unprecedenteddetail. We perform a spatial and a spectral analysis; with the former, the hothalo is detected to at least 80 kpc and with the latter its properties can bemeasured in detail up to 42 kpc. We find evidence for a negative gradient inthe temperature profile as is common for elliptical galaxies. We measure arough metallicity profile, which is consistent with being flat at $Z \sim 0.2Z_{\odot}$. Converting to this metallicity, the deprojected density profile isconsistent with previous parametric fits, with no evidence for a break within42 kpc ($\sim$0.1R$_{\text{vir}}$). Extrapolating to the virial radius, weinfer a hot halo mass comparable to the stellar mass of the galaxy, and abaryon fraction from the stars and hot gas of around 30%. The cooling time ofthe hot gas is orders of magnitude longer than the dynamical time, making thehot halo stable against cooling instabilities, and we argue that an extendedstream of neutral Hydrogen seen to the NW of this galaxy is instead likely dueto accretion from the intergalactic medium. The low metallicity of the hot halosuggests it too was likely accreted. We compare the hot halo of NGC 1961 to hothalos around isolated elliptical galaxies, and show that the total massdetermines the hot halo properties better than the stellar mass.

A Deep XMM-Newton Study of the Hot Gaseous Halo Around NGC 1961