Duration: 1 year rotation, with option to expand into a thesis
PI name: Karoline Gilbert (kgilbert@stsci.edu) and Erik Tollerud (etollerud@stsci.edu)
Project description:
The Andromeda Galaxy (M31) provides a vital connection between studies of galaxies near and far, and a principal data point for using local objects for placing constraints on cosmological theories. Due to its proximity (∼ 780 kpc), M31 can be resolved into individual stas like the Milky Way (MW). Unlike the MW, we have the advantage of a global view of M31, enabling M31 to be observed with techniques that also apply to more distant galaxies. Moreover, recent evidence suggests that M31 may have survived a major merger within the last several billion years, shaping its stellar halo and triggering a burst of star formation, while leaving the stellar disk largely intact. The MW and M31 provide complementary opportunities for in-depth studies of the disks, halos, and satellites of large spiral galaxies. Moreover, M33, a satellite of M31, is the only dwarf Spiral in the Local Group. With a mass ten times lower than M31’s or the MW’s and a star formation rate 10 times higher, M33 is the best local analog for high redshift galaxies. M33 is also relatively isolated, making it an excellent laboratory for studying a low-mass stellar disk in detail.
A large number of spectra of individual stars have been obtained in disk, halo, and dwarf galaxy satellites of M31, including M31’s largest satellite, M33. This allows us to investigate the kinematics (line of sight velocity distributions) and abundances of stellar populations throughout the M31 system, yielding insights into how the disk, halo, and satellites of M31 have formed and evolved. We have recently acquired a large number of spectra of stars in M33’s disk. The kinematics of M33’s extended stellar disk can be used to constrain models of M33’s orbit around M31, yielding insights into whether M33 is on its first infall into M31’s halo or if it has interacted substantially with M31 in the past.
Specific work you imagine the grad student will be doing.
Several projects are possible, depending on the interests and experience of the student, but generally will involve analyzing the line of sight velocities and/or measuring chemical abundances for stars in M31 or M33’s disk, M31’s stellar streams, or in specific dwarf galaxies of M31, or creating improvements to existing spectral reduction software to make use of the large amount of archival data that exist in the M31 system. The expectation is that projects will result in a paper being led by the student.
Caption: On the underlying star count map, you can see the streams and large structures in the halo of M31. Each of the cyan points represents a spectroscopic mask, on which a few to hundreds of stars were observed (depending on the density of stars at the location of the mask).
