GHOSTS: the resolved stellar outskirts of massive disk galaxies

Roelof S. De Jong*, A. C. Seth, E. F. Bell, T. M. Brown, J. S. Bullock, S. Courteau, J. J. Dalcanton, H. C. Ferguson, P. Goudfrooij, S. Holfeltz, C. Purcell, D. Radburn-Smith, D. Zucker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We show initial results from our ongoing HST/ACS GHOSTS survey of the resolved stellar envelopes of 14 nearby, massive disk galaxies. In hierarchical galaxy formation the stellar halos and thick disks of galaxies are formed by accretion of minor satellites and therefore contain valuable information about the (early) assembly process of galaxies. We detect for the first time the very small halo of NGC 4244, a low mass edge-on galaxy. We find that massive galaxies have very extended halos, with equivalent surface brightnesses of 28-29 V-mag arcsec2 at 20-30 kpc from the disk. The old RGB stars of the thick disk in the NGC 891 and NGC 4244 edge-on galaxies truncate at the same radius as the young thin disk stars, providing insights into the formation of both disk truncations and thick disks. We furthermore present the stellar populations of a very low surface brightness stream around M83, the first such a stream resolved into stars beyond those of the Milky Way and M31.

Original languageEnglish
Pages (from-to)503-504
Number of pages2
JournalProceedings of the International Astronomical Union
Issue numberS241
Publication statusPublished - Dec 2006
Externally publishedYes


  • Galaxies: evolution
  • Galaxies: halos
  • Galaxies: individual (M83, NGC 891, NGC 4244)
  • Galaxies: spiral
  • Galaxies: stellar content
  • Galaxies: structure


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