Relevant publication:
2015, AJ, 150:90 (← click to see the publication at ADS/arXiv)
We present distance modulus to the Carina dwarf spheroidal galaxy obtained from single-phase near-infrared magnitudes in the J- and K-band for a sample of 33 RR Lyrae (RRL) stars. The sample was carefully chosen from data published by Dall’Ora et al. (2003, AJ, 126, 197), who provided also RRL pulsational periods.
![]() |
---|
Near-infrared (NIR) photometry of RRLs, while minimizing the influence of both interstellar extinction and metallicity on the RRL luminosity, reveals a linear relationship between the luminosity and the metallicity and the logarithm of pulsational period, i.e. the PLZ relation.
We used five semi-theoretical and empirical, J- and K-band PLZ relations from the literature (Bono et al. 2003, MNRAS, 344, 1097; Catelan et al. 2004, ApJS, 154, 633; Sollima et al. 2008, MNRAS, 384, 1583; Dékány et al. 2013, ApJL, 776, L19) in order to perform the linear least squares fitting with a slope value fixed. This way, only one parameter – zero point of the calibration – was free, and therefore the uncertainty of the entire fit could be substantially reduced.
![]() |
---|
The zero point of the calibration, corrected for the effect of metallicity and interstellar extinction (both from literature), yielded the true distance modulus of 20.118 ± 0.017(stat) ± 0.110(sys) mag.
![]() |
---|
Our results are consistent with other distance determinations obtained within the Araucaria Project from NIR photometry of red clump stars (20.165 ± 0.015 mag) and the tip of red giant branch (20.09 ± 0.03 ± 0.12 mag in the J-band, 20.14 ± 0.04 ± 0.14 mag in the K-band), as well as with most independent distance determinations to the Carina galaxy. The NIR RRL method once more proves to be a reliable tool for accurate distance determination at the 5% level or better, particularly for galaxies and globular clusters that lack young standard candles, like Cepheids.