Near-IR TRGB Distance Modulus of Dwarf Irregular Galaxy IC 1613

Abstract

The JHK S magnitudes of the red giant branch tip (TRGB) and the distance moduli of the nearby dwarf irregular galaxy IC 1613 have been determined from the nearinfrared luminosity functions (LFs) of the resolved stars in the galaxy. Applying a Savitzky-Golay filtering, we derived the second derivatives of the LFs, and estimated the apparent magnitudes of the TRGB as m J = 19.1, m H = 18.4, and m Ks = 18.0. The mean values of the theoretical absolute magnitudes of the TRGB were measured by using the Yonsei-Yale isochrones with a metallicity range of −2.1 < [Fe/H] < −0.5 and age of 12 Gyr. The derived values of near-infrared TRGB distance moduli for IC 1613 are (m − M ) = 24.12 ± 0.25, 24.20 ± 0.44, and 24.00 ± 0.52 for J, H, and K S bands, respectively.

The AGB population in IC 1613 usingJHKphotometry

“…The poor AGB detection rate reported for Albert et al (2000) was repeated when comparing the IRAC data to other optical data sets in IC 1613 and in other dwarf galaxies (Jackson et al 2007a;Boyer et al 2009). As a result of the difficult of detecting redder AGB stars at optical wavelengths recent studies (e.g Borissova et al 2000;Jung et al 2009) have made use of NIR photometry to detect AGB stars; as these stars emit most of their light at these wavelengths (Frogel et al 1990) they are among the brightest objects in the NIR.…”

“…As a result of the difficult of detecting redder AGB stars at optical wavelengths recent studies (e.g Borissova et al 2000;Jung et al 2009) have made use of NIR photometry to detect AGB stars; as these stars emit most of their light at these wavelengths (Frogel et al 1990) they brightest are among the brightest objects in the NIR.…”

“…IC 1613 is a gas rich galaxy that appears to have experienced star formation over most of the life of the Universe as evidenced by the presence of an old (>10 Gyr) RR Lyrae population (Saha et al 1992;Dolphin et al 2001;Bernard et al 2010), an intermediate-age (1−10 Gyr) red giant branch (RGB) and asymptotic giant branch (AGB) population Full Tables 1 and 2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/573/A84 (Freedman 1988;Jung et al 2009) and a younger (<1 Gyr) blue population of stars (Hodge et al 1991;Tautvaišienė et al 2007). At present there seems to be only one recent and ongoing region of star formation, in the north east (NE) of the galaxy, but the hole in the H I gas in the south east (SE) suggests that there has been star formation in that region in the recent past (Lozinskaya 2002;Lake & Skillman 1989).…”