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Monthly Notices of the Royal Astronomical Society


We study the edge-on galaxy NGC 5775, utilizing a 58.2 ks Chandra ACIS-S observation together with complementary Hubble Space Telescope (HST) ACS, Spitzer IRAC and other multi-wavelength data sets. This edge-on galaxy, with its disc-wide active star formation, is particularly well suited for studying the disc/halo interaction on subgalactic scales. We detect 27 discrete X-ray sources within the D25 region of the galaxy, including an ultra-luminous source with a 0.3–7 keV luminosity of ∼7 × 1040 erg s−1. The source-removed diffuse X-ray emission shows several prominent extraplanar features, including a ∼10 kpc diameter ‘shell-like’ feature and a ‘blob’ reaching a projected distance of ∼25 kpc from the galactic disc. The bulk of the X-ray emission in the halo has a scale height of ∼1.5 kpc and can be characterized by a two-temperature optically thin thermal plasma with temperatures of ∼0.2 and 0.6 keV and a total 0.3–2 keV luminosity of ∼3.5 × 1039 erg s−1. The high-resolution, multi-wavelength data reveal the presence of several extraplanar features around the disc, which appear to be associated with the in-disc star formation. We suggest that hot gas produced with different levels of mass loading can have different temperatures, which may explain the characteristic temperatures of hot gas in the halo. We have obtained a subgalactic scale X-ray-intensity–star-formation relation, which is consistent with the integrated version in other star-forming galaxies.


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