Iron gradients in cooling flow galaxies and groups

Previous studies of the Fe abundances in the hot gas of galaxies and groups have reported conflicting results with most studies finding very subsolar Fe abundances that disagree with standard theory. To investigate the possib le role of Fe abundance gradients on these measurements we present deprojec tion analysis of the ROSAT PSPC data of 10 of the brightest cooling flow ga laxies and groups. The PSPC allows for spatially resolved spectral analysis on a half-arcminute scale, and interesting constraints on both the tempera tures and Fe abundances are possible because the similar to 1 keV temperatu res of these systems are well matched to the bandpass of the PSPC. In nine out of 10 systems we find clear evidence that the Fe abundance decreases wi th increasing radius: Z(Fe) similar to 1-several Z. within the central radi al bin (r less than or similar to 10 kpc), which decreases to Z(Fe) similar to 0.5 . at the largest radii examined (r similar to 50-100 kpc). The Fe a bundances (and temperatures) are consistent with the average values for the se systems that we obtained in our previous analyses of the ASCA data using multitemperature models, which confirms that previous inferences of very s ubsolar Fe abundances from ASCA arise from the incorrect assumption of isot hermal gas and not the presence of Fe abundance gradients. We discuss why t his "Fe bias" affects much more seriously the measurements of Z(Fe) from AS CA data than from ROSAT data. We show that the Fe abundance profiles for th ese galaxies and groups are consistent with a gasdynamical model where the gas is enriched by stellar ejecta and supernovae in the "solar supernova pr oportion;" the stars formed with a Galactic initial mass function, and the gas is diluted by mixing with primordial gas at large radii.