NOAO >   Observing Info >   Approved Programs >   2017B-0222

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Program Information for 2017B-0222


PI: Joanne D Hughes, Seattle University, jhughes@seattleu.edu
Address: Physics Department, 901 12th Ave, Seattle, WA 98122 U.S.A.

CoI: Charli Sakari, U. of Washington
CoI: Peter Frinchaboy, Texas Christian U.
CoI: George Wallerstein, U. of Washington

Title: Segue 3: A Cluster Born in an LMC-like System?

Abstract: As part of a study of satellite galaxies and (possibly) accreted star clusters around the Milky Way, we have identified some additional members of the system, Segue 3, which require confirmation with a multiobject spectrograph because some of the stars are faint. Using Washington and SDSS colors, combined with archival VI-observations, we find that the photometric metallicity is Z=0.005, which becomes a solar- scaled iron abundance of $[Fe/H] = -0.6pm 0.1$ dex. We have found a new (and younger) age for the system of .6pm 0.4$ Gyr, E(B-V)=0.09 and a distance modulus of $(m-M)_0=17.31 pm 0.1$ (about 29 kpc). All available data indicates mass-segregation has occurred in this cluster with the binary fraction approaching 40%. There are stars beyond the tidal radius of $sim 0.04^circ$, which Hydra will allow us to observe at the same time as the cluster center. Its youth and location place it in a sample of unusual stellar systems which have likely been stripped from external dwarf galaxies as they are being accreted by the Milky Way, or formed during such an event. It is of vital importance to confirm the age and metallicity of the cluster with spectroscopy.

Program Type: ITAC

Scheduled Nights:
Run 1 (2017B):  WIYN/HYDR -- 2n on Oct 07 - Oct 10 2017


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