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The Near-Infrared Tip of the Red Giant Branch. II. An Absolute Calibration in the Large Magellanic Cloud

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 نشر من قبل Taylor Hoyt
 تاريخ النشر 2018
  مجال البحث فيزياء
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We present a new empirical (JHK) absolute calibration of the tip of the red giant branch (TRGB) in the Large Magellanic Cloud (LMC). We use published data from the extensive emph{Near-Infrared Synoptic Survey} containing 3.5 million stars, of which 65,000 are red giants that fall within one magnitude of the TRGB. Adopting the TRGB slopes from a companion study of the isolated dwarf galaxy IC,1613 as well as an LMC distance modulus of (mu_0 = )~18.49~mag from (geometric) detached eclipsing binaries, we derive absolute (JHK) zero-points for the near-infrared TRGB. For comparison with measurements in the bar alone, we apply the calibrated (JHK) TRGB to a 500 degtextsuperscript{2} area of the 2MASS survey. The TRGB reveals the 3-dimensional structure of the LMC with a tilt in the direction perpendicular to the major axis of the bar, in agreement with previous studies.



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Based on observations from the emph{FourStar} near-infrared camera on the 6.5m Baade-Magellan telescope at Las Campanas, Chile, we present calibrations of the $JHK$ luminosities of stars defining the tip of the red giant branch (TRGB) in the halo of the Local Group dwarf galaxy IC 1613. We employ metallicity-independent (rectified) T-band magnitudes---constructed using $J,H$ and $K$-band magnitudes and both $(J-H)~ & ~(J-K)$ colors in order to flatten the upward-sloping red giant branch tips as otherwise seen in their apparent color-magnitude diagrams. We describe and quantify the advantages of working at these particular near-infrared wavelengths, which are applicable to both emph{HST} and emph{JWST}. We also note that these same wavelengths can be accessed from the ground for an eventual tie-in to emph{Gaia} for absolute astrometry and parallaxes to calibrate the intrinsic luminosity of the TRGB. Adopting the color terms derived from the IC 1613 data, as well as the zero-points from a companion study of the Large Magellanic Cloud whose distance is anchored to the geometric distances of detached eclipsing binaries, we find a true distance modulus of 24.32 $pm$ 0.02~ (statistical) $pm$ 0.06~mag (systematic) for IC 1613, which compares favorably with the recently published multi-wavelength, multi-method consensus modulus of 24.30 $pm$ 0.05~mag by Hatt et al. (2017).
144 - Taylor J. Hoyt 2021
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