The Andromeda galaxy, our nearest neighbour

The galaxy M31 or Andromeda is the largest galaxy within the local group. It has a stellar mass of 1011 M and a dark matter halo mass of 1012 M. It is at a distance of 770 kpc from the Sun, has an inclination of 77o to the plane of the sky and is classified as an Sab galaxy. M31 is therefore the only galaxy within several Mpc radius that is comparable in mass and type to our own Milky Way.

A possible coverage of the M31 disk using the GAMAICA instrument. During the course of the project an in-depth study will be carried out to determine the optimal footprint of the survey, taking into account the locations of the spiral arms, expectations for kinematic pecularities in the M31 disk and our main science goals.
Stars and gas in NGC300, observed with MUSE over a 3×1 arcmin2 field-of-view. The physical spatial resolution is 5pc, similar to what GAMACA would obtain for M31. However, NGC300 is more than one order of magnitude less massive than the Milky Way and M31. Also, the area covered by our dedicated GAMACA survey in M31 would be two orders of magnitude larger, allowing to probe radial gradients and other local variations in a statistical manner Top: RGB image created by collapsing the datacubes within V, R, I broadband filter curves. Bottom: composite narrowband images, highlighting Hα in red, [OIII] in green, and [SII] in blue hues. Numerous distinct objects are apparent, e.g. blue and red supergiants in the top panel, HII regions (purple), supernova remnants (blue), planetary nebulae as green dots, and emission line stars as faint red dots in the bottom panel.