We present the first V, B - V color-magnitude diagram of the Leo IV dwarf spheroidal galaxy, a faint Milky Way satellite recently discovered by the Sloan Digital Sky Survey. We have obtained B, V time-series photometry reaching about half a magnitude below the Leo IV turnoff, which we detect at V = 24.7 mag, and have performed the first study of the variable star population. We have identified three RR Lyrae stars (all fundamental-mode pulsators, RRab) and one SX Phoenicis variable in the galaxy. In the period-amplitude diagram the Leo IV RR Lyrae stars are located close to the loci of Oosterhoff type I systems and the evolved fundamental-mode RR Lyrae stars in the Galactic globular cluster M3. However, their mean pulsation period, langPabrang = 0.655 days, would suggest an Oosterhoff type II classification for this galaxy. The RR Lyrae stars trace very well the galaxy's horizontal branch, setting its average magnitude at langV RRrang = 21.48 ± 0.03 mag (standard deviation of the mean). This leads to a distance modulus of μ0 = 20.94 ± 0.07 mag, corresponding to a distance of 154 ± 5 kpc, by adopting for the Leo IV dSph a reddening E(B - V) = 0.04 ± 0.01 mag and a metallicity of [Fe/H] = -2.31 ± 0.10. Based on data collected at the 2.5 m Isaac Newton Telescope, La Palma, Canary Island, Spain, at the 4.2 m William Herschel Telescope, Roche de los Muchachos, Canary Islands, Spain, and at the 4.1 m Southern Astrophysical Research Telescope, Cerro Pachón, Chile.
Moretti M. I., Dall'Ora M., Ripepi V., Clementini G., Di Fabrizio L., Smith H. A., et al. (2009). The Leo IV Dwarf Spheroidal Galaxy: Color-Magnitude Diagram and Pulsating Stars. THE ASTROPHYSICAL JOURNAL LETTERS, 699, L125-L129.
The Leo IV Dwarf Spheroidal Galaxy: Color-Magnitude Diagram and Pulsating Stars
MORETTI, MARIA IDA;
2009
Abstract
We present the first V, B - V color-magnitude diagram of the Leo IV dwarf spheroidal galaxy, a faint Milky Way satellite recently discovered by the Sloan Digital Sky Survey. We have obtained B, V time-series photometry reaching about half a magnitude below the Leo IV turnoff, which we detect at V = 24.7 mag, and have performed the first study of the variable star population. We have identified three RR Lyrae stars (all fundamental-mode pulsators, RRab) and one SX Phoenicis variable in the galaxy. In the period-amplitude diagram the Leo IV RR Lyrae stars are located close to the loci of Oosterhoff type I systems and the evolved fundamental-mode RR Lyrae stars in the Galactic globular cluster M3. However, their mean pulsation period, langPabrang = 0.655 days, would suggest an Oosterhoff type II classification for this galaxy. The RR Lyrae stars trace very well the galaxy's horizontal branch, setting its average magnitude at langV RRrang = 21.48 ± 0.03 mag (standard deviation of the mean). This leads to a distance modulus of μ0 = 20.94 ± 0.07 mag, corresponding to a distance of 154 ± 5 kpc, by adopting for the Leo IV dSph a reddening E(B - V) = 0.04 ± 0.01 mag and a metallicity of [Fe/H] = -2.31 ± 0.10. Based on data collected at the 2.5 m Isaac Newton Telescope, La Palma, Canary Island, Spain, at the 4.2 m William Herschel Telescope, Roche de los Muchachos, Canary Islands, Spain, and at the 4.1 m Southern Astrophysical Research Telescope, Cerro Pachón, Chile.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
