<i>Chandra</i>observation of the edge-on spiral NGC 5775: probing the hot galactic disc/halo connection

Abstract

We study the edge-on galaxy NGC 5775, utilizing a 58.2 ks {\\sl Chandra}\nACIS-S observation together with complementary {\\sl HST} ACS, {\\sl Spitzer}\nIRAC and other multi-wavelength data sets. This edge-on galaxy, with its\ndisk-wide active star formation, is particularly well-suited for studying the\ndisk/halo interaction on sub-galactic scales. We detect 27 discrete X-ray\nsources within the $D_{25}$ region of the galaxy, including an ultra-luminous\nsource with a 0.3-7 keV luminosity of $\\sim7\\times10^{40}\\rm ergs s^{-1}$. The\nsource-removed diffuse X-ray emission shows several prominent extraplanar\nfeatures, including a $\\sim10\\rm kpc$ diameter ``shell-like'' feature and a\n``blob'' reaching a projected distance of $\\sim25\\rm kpc$ from the galactic\ndisk. The bulk of the X-ray emission in the halo has a scale height of\n$\\sim$1.5 kpc and can be characterized by a two-temperature optically thin\nthermal plasma with temperatures of $\\sim$ 0.2 and 0.6 keV and a total 0.3-2\nkeV luminosity of $\\sim3.5\\times10^{39}\\rm ergs s^{-1}$. The high-resolution,\nmulti-wavelength data reveal the presence of several extraplanar features\naround the disk, which appear to be associated with the in-disk star formation.\nWe suggest that hot gas produced with different levels of mass loading can have\ndifferent temperatures, which may explain the characteristic temperatures of\nhot gas in the halo. We have obtained a sub-galactic scale X-ray-intensity-star\nformation relation, which is consistent with the integrated version in other\nstar forming galaxies.\n