Lunch talk on Oct. 28, 2024

The Binary Fraction of Stars in the Dwarf Galaxy Ursa Minor via Dark Energy Survey Instrument

Speaker: Tian Qiu (SJTU)

Venue: SWIFAR Building 2111

Time: 12:45 PM, Monday, Oct. 28, 2024

Abstract: 

We utilize the Milky Way Survey (MWS) tertiary program of the Dark Energy Spectroscopic Instrument (DESI), which provides multi-epoch observations of individual stars, to estimate the binary fraction for the dwarf spheroidal galaxy Ursa Minor. Our dataset comprises 1,280 distinct objects, with a total of 7,358 observations collected over approximately one year. Adopting the precise radial velocity measurements from DESI, we constrain the binary fraction for Ursa Minor to be 0.48+0.04−0.04 and 0.52+0.05−0.04, based on the models by Duquennoy & Mayor in 1991 and Moe & Stefano in 2017, respectively. Furthermore, by dividing our data into two subsamples based on metallicity, we identify a difference in the binary fraction between the metal-rich and metal-poor populations, which roughly represent the younger and older stellar populations in the dwarf galaxy. The binary fraction for the metal-rich population is higher than that of the metal-poor population, measured at 0.62+0.06−0.08 and 0.46+0.05−0.05 based on Moe & Stefano’s model, respectively. After a thorough examination, this offset cannot be attributed to observational biases, suggesting that the binaries may be destructed during the dynamical interactions during the evolutionary processes of dwarf galaxies.