The Carnegie-Chicago Hubble Program. IV. The Distance to NGC 4424, NGC 4526, and NGC 4356 via the Tip of the Red Giant Branch

Dylan Hatt, Wendy L. Freedman, Barry F. Madore, Rachael L. Beaton, Taylor J. Hoyt, In Sung Jang, Myung Gyoon Lee, Andrew J. Monson, Jeffrey A. Rich, Victoria Scowcroft, Mark Seibert

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The Carnegie-Chicago Hubble Program is undertaking a re-calibration of the extragalactic distance scale, using SNe Ia that are tied to Tip of the Red Giant Branch (TRGB) distances to local galaxies. We present here deep Hubble Space Telescope ACS/WFC imaging of the resolved stellar populations in the metal-poor halos of the SN Ia-host galaxies NGC 4424, NGC 4526, and NGC 4536. These three Virgo constellation galaxies are prime targets for calibrating the extragalactic distance scale given their relative proximity in the local universe and their low line-of-sight reddenings. Anchoring the TRGB zero-point to the geometric distance to the Large Magellanic Cloud via detached eclipsing binaries, we measure extinction-corrected distance moduli of 31.00 ± 0.03stat ± 0.06sys mag, 30.98 ± 0.03stat ± 0.06sys mag, and 30.99 ± 0.03stat ± 0.06sys mag for NGC 4424, NGC 4526, and NGC 4536, respectively, or 15.8 ± 0.2stat ± 0.4sys Mpc, 15.7 ± 0.2stat ± 0.4sys Mpc, and 15.8 ± 0.2stat ± 0.4sys Mpc. For these three galaxies, the distances are the first that are based on the TRGB, and for NGC 4424 and NGC 4526, they are the highest-precision distances published to date, each measured to 3%. Finally, we report good agreement between our TRGB distances and the available Cepheid distances for NGC 4424 and NGC 4536, demonstrating consistency between the distance scales currently derived from stars of Population I and II.
Original languageEnglish
Article number104
Pages (from-to)1-10
Number of pages10
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 11 Jul 2018


  • distance scale
  • galaxies: individual (NGC 4424, NGC 4526, NGC 4536)
  • stars: Population II

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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