Abstract
Galaxy halos and their globular cluster systems build up over time by the accretion of small satellites. We can learn about this process in detail by observing systems with ongoing accretion events and comparing the data with simulations. Elliptical shell galaxies are systems that are thought to be due to ongoing or recent minor mergers. We present preliminary results of an investigation of the baryonic halo—light profile, globular clusters, and shells/streams—of the shell galaxy NGC 3923 from deep Dark Energy Camera (DECam) g and i-band imaging. We present the 2D and radial distributions of the globular cluster candidates out to a projected radius of about 185 kpc, or ∼ 37 R e , making this one of the most extended cluster systems studied. The total number of clusters implies a halo mass of M h ∼ 3 × 10 13 M ⊙ . Previous studies had identified between 22 and 42 shells, making NGC 3923 the system with the largest number of shells. We identify 23 strong shells and 11 that are uncertain. Future work will measure the halo mass and mass profile from the radial distributions of the shell, N-body models, and line-of-sight velocity distribution (LOSVD) measurements of the shells using the Multi Unit Spectroscopic Explorer (MUSE).
Highlights
Galaxies at high redshift are much more compact at a given mass than in the local universe, implying that galaxies and their halos grow with time due to the accretion of mostly lower-mass galaxies [1,2,3]
At at distance of 21.3 Mpc, globular clusters (GCs) are unresolved from the ground in 1 arcsec seeing
We fit a plane to the source density of objects more than 30 arcmin from NGC 3923, and statistically subtracted this background
Summary
Galaxies at high redshift are much more compact at a given mass than in the local universe, implying that galaxies and their halos grow with time due to the accretion of mostly lower-mass galaxies [1,2,3]. Elliptical shell galaxies are other promising environments for studying the build-up of halos. Galaxies 2017, 5, 29 match the appearance of structures created during the accretion of low-mass satellites on near-radial orbits in simulations (Figure 1) [4]. In this contribution, we present preliminary results of a study of the globular cluster system and shells of the elliptical shell galaxy NGC 3923. NGC 3923 is one of the most studied shell galaxies because it has the largest number of detected shells. Mergers will bring in new globular clusters (GCs) so the distribution and total number of GCs can be used to estimate the halo mass.
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