The stellar population content of the thick disc and halo of the Milky Way analogue NGC 891

Abstract

We present deep VI images obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope, covering three fields in the north-east side of the edge-on disc galaxy NGC 891. The observed fields span a wide range of galactocentric distances along the eastern minor axis, extending from the plane of the disc to 12 kpc, and out to ∼25 kpc along the major axis. The photometry of individual stars reaches ∼2.5 mag below the tip of the red giant branch. We use the astrophotometric catalogue to probe the stellar content and metallicity distribution across the thick disc and spheroid of NGC 891.