A cooling flow in the giant, elliptical galaxy NGC 4472

NGC 4472 is shown to contain a large quantity (10 to the 10th solar mass) of X-ray-emitting gas which is cooling and flowing into the center. The binding of this hot gas in the outer regions of the galaxy requires a substantial halo, (3.5 + or 0.8) x 10 to the 10th (T/10 to the 7th K) solar mass/kpc, of dark matter. A one-phase model is developed for the cooling flow in NGC 4472 and compared with X-ray surface-brightness profiles. It is found that the supernova rate must be less than 0.00013/yr (10 to the 10th solar luminosity)- one twentieth of that given by Tamman (1974), that much of the mass lost from stars via winds or planetary nebulae is confined by the hot phase and rapidly condenses to form new stars, and that mass cools out of the hot phase at a rate of about 0.5 solar mass/yr and does so over the whole galaxy not just in the central regions. Some of this gas is supplied by an outer reservoir or intragroup medium.