"Globular Cluster Systems in Dwarf Galaxies: Linking Dark Matter and Star Formation"

Abstract:

Globular clusters (GCs) in massive galaxies have proven to be powerful tracers of merger histories, star formation episodes, and the conditions of the early Universe. These insights mainly arise from scaling relations between host galaxy properties and GC system parameters. However, massive galaxies, contrary to dwarfs, have assembled most of their stellar mass via ex situ formation, implying that a substantial fraction of their GC systems originated outside the main galaxy. To perform the study in a clean regime where ex-situ processes are minimized, we focus on dwarf galaxies (DGs, M⋆ < 109.5M⊙), where stellar mass forms predominantly in situ, thereby providing a perspective directly tied to the galaxy’s intrinsic formation history. Therefore, we expect that DGs host GCs systems that reflect the initial conditions of galaxy formation. In this context, we select a sample of irregular DGs, located outside the Local Group but within 20 Mpc. These objects are in low-density environments (isolated or in small groups) and have stellar masses ranging from 107.5 − 109.0 M⊙. We also adopt a multi-wavelength approach, combining optical (griz, DELVE), mid-infrared (3.6 and 4.5 µm, S4G), and radio (21 cm, HIPASS) data. We select GC candidates using griz photometry and SSP-based color cuts. Preliminary results indicate an average of 6 GCs per galaxy and a GC luminosity function that deviates from the gaussian shape typically bserved in massive galaxies. We find a linear correlation between GC system mass and dark matter halo mass, as predicted for massive galaxies, an indicative of a co-evolution between the two. We report hints of bimodality in the GC populations, which is unexpected for such systems. This feature may indicate past merger events, earlier episodes of enhanced star formation, or a combination of both. To confirm this finding we analyse multi-object spectroscopic observations from Gemini/GMOS and present preliminary results. Finally, we perform SED fitting on the GCs to constrain their ages and metallicities. The results are consistent with the bimodality. Our results suggest that GC populations in dwarf galaxies may be more complex than previously thought. These complexities may offer valuable insights into mass assembly of low mass systems, and the importance of mergers in low-density environments.