The large-scale structure of globular clusters in the NGC 1052 group

Abstract

Prompted by the many controversial claims involving the NGC 1052 group, including that it hosts two dark matter-free galaxies with overluminous and monochromatic globular cluster (GC) systems, here we map out the large-scale structure (LSS) of GCs over the entire group. To recover the LSS, we use archival optical CFHT imaging data. We recover two GC density maps, one based on universal photometric properties of GCs from simple stellar population models, and one based on the properties of spectroscopically confirmed GCs in DF2 and DF4 (the two dwarf galaxies with overluminous GC populations). Both selection methods reveal overdensities around the massive galaxies in the group, as well as around NGC 1052 itself, that are coincident with the positions of previously identified stellar streams and tidal features. No intragroup GCs are found connecting these structures to any of the dwarf galaxies. We find, however, two other dwarfs in the group hosting GC systems. These include RCP32 with 2 GCs with ages equivalent to the GCs around NGC 1052, and DF9 with 3 GCs with ages similar to the GCs around DF2 and DF4. We conclude that the GC distribution in the group does not strongly support any formation scenario in particular. It favours, nonetheless, scenarios relying on galaxy-galaxy interactions and on the coeval formation of GCs around the DM-free dwarf galaxies. These may include the recently proposed bullet-dwarf formation, as well as high-redshift tidal dwarf galaxy models.

Multiple Beads on a String: Dark-matter-deficient Galaxy Formation in a Mini-Bullet Satellite–Satellite Galaxy Collision

“…van Dokkum et al (2022a) postulated that NGC 1052-DF7 (hereafter DF7) and RCP32, located at the farthest end of the UDG trail, represent the remnants of the progenitor galaxies. Notably, a follow-up study showed that the identified GCs near RCP32 exhibit stellar populations that are more similar to those of the host galaxy NGC 1052, in contrast to the GCs associated with DF2 and DF4 (Buzzo et al 2023). This finding provides support for the notion that RCP32 may be the preserved remnant of a post-collision satellite galaxy.…”

“…More recently, Buzzo et al (2023) studied the large-scale structure of GCs in the NGC 1052 group and found that the GC distribution is consistent with scenarios involving a single galaxy-galaxy interaction event and subsequent coeval formation of the GCs and the DMDGs, which includes the tidal dwarf galaxy scenario and the Mini-Bullet scenario. To distinguish the two scenarios, a possible smoking gun signature of the Mini-Bullet scenario was suggested by Gannon et al (2023), a linear relation between the line-of-sight velocities of the aligned DMDGs produced by the collision and their distance from their common point of origin in the collision; the farther a galaxy was from this point, the higher must its launch velocity have been to reach that distance in the same elapsed time.…”