Messier 82, also called M82, is a nearby starburst galaxy used to study how intense star formation drives a large galactic outflow. Its bright stellar disk, obscuring interstellar dust and extended gas emission trace different components; a bright feature in one wavelength band need not represent most of the outflow's mass or energy.
A concrete measurement is to compare diffuse X-ray emission above the disk with compact sources inside it. ROSAT imaging and spectroscopy detected the wind's X-rays to roughly six kiloparsecs from the plane. The observations separated point sources from diffuse emission and found that the latter was not well described as a freely expanding wind: shocked material interacting with the flow could instead account for the emission.[ref]
ROSAT Observations of the Galactic Wind in M82 by Dave Strickland and others. Abstract, spatial/spectral separation and comparison of wind models
This makes M82 an illuminating stellar feedback laboratory. The inference runs from spatially resolved spectra to gas conditions and then to a physical outflow model; a photograph of gas extending away from the disk does not by itself determine its temperature, energy source or escape rate.
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