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Distances to PHANGS Galaxies: New Tip of the Red Giant Branch Measurements

Published onJun 01, 2020
Distances to PHANGS Galaxies: New Tip of the Red Giant Branch Measurements

PHANGS-HST is a five-band survey of 38 nearby galaxies within ~20 Mpc. Combined with the PHANGS-ALMA survey and other multiwavelength data, it will provide an unprecedented look into the connections between young stars and cold gas in these nearby star-forming galaxies. Accurate distances are needed to transform measured quantities from these programs into physical parameters (e.g. brightness to luminosity). PHANGS-HST also provides parallel ACS imaging of the galaxy halos in F606W+F814W. This imaging provides an ideal sample of Population II stars from which to construct color-magnitude diagrams (CMDs). From these CMDs, we identify the tip of the red giant branch (TRGB), the point in the evolution of low-mass stars just before the onset of the helium flash. It has been shown that this feature acts as a remarkably consistent standard-candle, with only small corrections required for metallicity. Here we present first results of TRGB distances obtained from the parallel imaging, and compare them to existing measurements from the literature.

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