The Stellar Initial Mass Function in Early-Type Galaxies from Absorption Line Spectroscopy. III. Radial Gradients

Understand

There is good evidence that the centers of massive early-type galaxies have a bottom-heavy stellar initial mass function (IMF) compared to the IMF of the Milky Way.

• Here we study the radial variation of the IMF within such galaxies, using a combination of high quality Keck spectroscopy and a new suite of stellar population synthesis models that cover a wide range in metallicity.
• As in the previous studies in this series, the models are fitted directly to the spectra and treat all elemental abundance ratios as free parameters.
• Using newly obtained spectroscopy for six galaxies, including deep data extending to ~1Re for the galaxies NGC1407, NGC1600, and NGC2695, we find that the IMF varies strongly with galactocentric radius.