Extended Star Clusters in NGC 1023 from HST/ACS Mosaic Imaging

TL;DR

This study uses HST/ACS imaging to analyze the star cluster system of NGC 1023, identifying various cluster types including faint fuzzies, globular clusters, and ultra compact dwarfs, revealing their spatial distribution and possible origins.

Contribution

First comprehensive analysis of NGC 1023's star clusters using ACS mosaic images, identifying faint fuzzies and their association with galaxy features and interactions.

Findings

Detected 81 red and 27 blue faint fuzzies.

Confirmed red FFs are associated with NGC 1023's disk.

Blue FFs are linked to NGC 1023A and surrounding HI gas.

Abstract

Faint fuzzies are a relatively new class of star cluster, first found in the nearby S0 galaxy NGC 1023 by Larsen & Brodie using WFPC2 images from the Hubble Space Telescope (HST). Here we investigate the star cluster system of NGC 1023 using an eight pointing mosaic of ACS images from HST. We identify blue and red normal globular clusters (two of which are particularly luminous and dense) and two ultra compact dwarf objects (with effective radius ~10 pc). With our more complete spatial coverage, we also find 81 red and 27 blue faint fuzzies (FFs). We confirm the association of the red FFs with the disk of NGC 1023, consistent with them being long-lived open clusters. Half of the blue FFs appear to be associated with the dwarf satellite galaxy NGC 1023A (which was largely absent from the original HST/WFPC2 coverage), while the remainder are spatially coincident with the densest HI gas that surrounds NGC 1023. The blue FFs have colours that are consistent with young (few 100 Myr old) star clusters that formed during the most recent interaction between NGC 1023 and its satellite NGC 1023A.