Leo II: a distant dwarf spheroidal galaxy

University essay from Lunds universitet/Astronomi; Lunds universitet/Institutionen för astronomi och teoretisk fysik

Abstract: In this project aperture photometry has been performed for stars in the direction of the dwarf spheroidal galaxy Leo II. The observations were carried out using the Stro ̈mgren filters v, b and y, during three consecutive nights in 2003, out of which all but the first one turned out to be non-photometric. The data was reduced and calibrated (using the metallicity calibration of Calamida et al. (2007)) to yield magnitudes and metallicities for in total 2364 stars. Errors were estimated by means of Monte Carlo simulations. 152 stars correlate with stars observed in spectroscopic surveys, and are confirmed members of Leo II based on their radial velocity. We find an asymmetric metallicity distribution function, which extends towards lower metallicities, peaks at [Fe/H] = −2.4 dex, and has a spread of 1 dex. We also find signs of metallicity-dependent substructure within the galaxy, and a radial metallicity gradient of −0.220 ± 0.016 dex/rc. We generally find fainter magnitudes and lower metallicities for the stars in the galaxy than previous studies have done.

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