Globular Cluster Counts around 700 Nearby Galaxies

Abstract Empirically, the total number (or total mass) of globular clusters (GCs) bound in a single galactic system correlates with the virial mass of the system. The form of this relation and its intrinsic scatter are potentially valuable constraints on theories of GC formation and galaxy evolution. In this work, we use the DESI Legacy Imaging Survey (DESI-LS) to make a large-scale, homogeneous estimate of GC abundance around 707 galaxies at distances ≲30 Mpc with luminosities <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>8</mml:mn> <mml:mo>≤</mml:mo> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mi mathvariant="italic">L</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo>≤</mml:mo> <mml:mn>11.5</mml:mn> </mml:math> . The combination of depth and sky coverage in DESI-LS allow us to extend the techniques used by previous ground-based photometric GC surveys to a larger and potentially more representative sample of galaxies. We find average GC counts and radial profiles that are broadly consistent with the literature on individual galaxies, including good agreement with the distribution of GCs in the Milky Way, demonstrating the viability of DESI-LS images for this purpose. We find a relation between GC counts and virial mass in agreement with previous estimates based on heterogenous data sets, except at the lowest masses we probe, where we find a larger scatter in the number of cluster candidates and a slightly higher average count.