RR Lyrae Stars in the Newly Discovered Ultra-faint Dwarf Galaxy Centaurus i

C. E. Martínez-Vázquez, W. Cerny, A. K. Vivas, A. Drlica-Wagner, A. B. Pace, J. D. Simon, R. R. Munoz, A. R. Walker, S. Allam, D. L. Tucker, M. Adamów, J. L. Carlin, Y. Choi, P. S. Ferguson, A. P. Ji, N. Kuropatkin, T. S. Li, D. Martínez-Delgado, S. Mau, B. Mutlu-PakdilD. L. Nidever, A. H. Riley, J. D. Sakowska, D. J. Sand, G. S. Stringfellow

Research output: Contribution to journalArticlepeer-review

Abstract

We report the detection of three RR Lyrae (RRL) stars (two RRc and one RRab) in the ultra-faint dwarf (UFD) galaxy Centaurus I (Cen I) and two Milky Way (MW) δ Scuti/SX Phoenicis stars based on multi-epoch giz DECam observations. The two RRc stars are located within two times the half-light radius (r h ) of Cen I, while the RRab star (CenI-V3) is at ∼6 r h . The presence of three distant RRL stars clustered this tightly in space represents a 4.7σ excess relative to the smooth distribution of RRL in the Galactic halo. Using the newly detected RRL stars, we obtain a distance modulus to Cen I of μ 0 = 20.354 0.002 mag (σ = 0.03 mag), a heliocentric distance of D o˙ = 117.7 0.1 kpc (σ = 1.6 kpc), with systematic errors of 0.07 mag and 4 kpc. The location of the Cen I RRL stars in the Bailey diagram is in agreement with other UFD galaxies (mainly Oosterhoff II). Finally, we study the relative rate of RRc+RRd (RRcd) stars (f cd) in UFD and classical dwarf galaxies. The full sample of MW dwarf galaxies gives a mean of f cd = 0.28. While several UFD galaxies, such as Cen I, present higher RRcd ratios, if we combine the RRL populations of all UFD galaxies, the RRcd ratio is similar to the one obtained for the classical dwarfs (f cd ∼ 0.3). Therefore, there is no evidence for a different fraction of RRcd stars in UFD and classical dwarf galaxies.

Original languageEnglish (US)
Article number253
JournalAstronomical Journal
Volume162
Issue number6
DOIs
StatePublished - Dec 1 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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