A Search for Intergalactic Globular Clusters in the Local Group

• Main Authors: Zinn, Graziella di Tullio, Zinn, Robert
• Format: Journal Article
• Language: English
• Published: 10-03-2015
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.1503.02963

The whole Sloan Digital Sky Survey (SDSS, 14,555 deg^2 has been searched for
intergalactic globular clusters (IGCs) in the Local Group (LG). Using optical,
infrared, and ultraviolet photometric selection criteria and photometric
redshifts, the 2.1x10^8 of objects in the SDSS Galaxy Catalogue were reduced to
only 183,791 brighter than r_o = 19 that might be GCs. Visual examination of
their SDSS images recovered 84 percent of the confirmed GCs in M31 and M33 and
yielded 17 new GC candidates, 5 of them of high confidence, which we could
confirm as GCs in MegaPrime images from the Canada, France, Hawaii Telescope.
These 5 GCs are within M31's halo, but the other 12 candidates are not close to
LG galaxies or galaxies within 3 Mpc of the LG. Even though this search covers
only one-third of the sky and some GCs could have been missed, it suggests that
the LG does not contain a large population of IGCs more luminous than Mv ~ -6.
In the direction of the M81 Group, the search yielded five candidate GCs,
probable members of that group.