The Metallicity Distribution of the Milky Way Bulge

Understand

The Galactic bulge of the Milky Way is made up of stars with a broad range of metallicity, -3.0 < [Fe/H] < 1 dex.

• The mean of the Metallicity Distribution Function (MDF) decreases as a function of height z from the plane and, more weakly, with galactic radius.
• The most metal rich stars in the inner Galaxy are concentrated to the plane and the more metal poor stars are found predominantly further from the plane, with an overall vertical gradient in the mean of the MDF of about -0.45 dex/kpc.
• This vertical gradient is believed to reflect the changing contribution with height of different populations in the inner-most region of the Galaxy.