X-ray observations of the massive spiral galaxy NGC 5746 reveal a spherical halo of hot gas (blue) extending 60,000 light-years on either side of the galaxy’s visible disk (seen edge on as a large white streak).
Because NGC 5746, which is 100 million light-years from Earth, doesn’t form stars prodigiously or have an energetic core, it’s not likely that the halo is gas streaming from the galaxy.