A DECam view of the diffuse dwarf galaxy Crater II - Variable stars

A. Katherina Vivas, Alistair R. Walker, Clara E. Martinez-Vazquez, Matteo Monelli, Giuseppe Bono, Antonio Dorta, David L. Nidever, Giuliana Fiorentino, Carme Gallart, Gloria Andreuzzi, Vittorio F. Braga, Massimo Dall'Ora, Knut Olsen, Peter B. Stetson

Research output: Contribution to journalReview articlepeer-review

15 Citations (Scopus)


Time series observations of a single dithered field centred on the diffuse dwarf satellite galaxy Crater II were obtained with the Dark Energy Camera (DECam) at the 4m Blanco Telescope at Cerro Tololo Inter-American Observatory, Chile, uniformly covering up to two half-light radii. Analysis of the g and i time series results in the identification and characterization of 130 periodic variable stars, including 98 RR Lyrae stars, 7 anomalous Cepheids, and 1 SX Phoenicis star belonging to the Crater II population, and 24 foreground variables of different types. Using the large number of ab-type RR Lyrae stars present in the galaxy, we obtained a distance modulus to Crater II of (m - M)0 = 20.333 ± 0.004 (stat) ± 0.07 (sys). The distribution of the RR Lyrae stars suggests an elliptical shape for Crater II, with an ellipticity of 0.24 and a position angle of 153°. From the RR Lyrae stars, we infer a small metallicity dispersion for the old population of Crater II of only 0.17 dex. There are hints that the most metal-poor stars in that narrow distribution have a wider distribution across the galaxy, while the slightly more metal-rich part of the population is more centrally concentrated. Given the features in the colour-magnitude diagram of Crater II, the anomalous Cepheids in this galaxy must have formed through a binary evolution channel of an old population.

Original languageEnglish
Pages (from-to)1061-1077
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 1 Feb 2020


  • Galaxies: dwarf
  • Galaxies: individual: (Crater II)
  • Galaxies: stellar content
  • Local Group
  • Stars: variables: general
  • Stars: variables: RR Lyrae

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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