Kavli Affiliate: Wendy L. Freedman
| First 5 Authors: Taylor J. Hoyt, In Sung Jang, Wendy L. Freedman, Barry F. Madore, Abigail J. Lee
| Summary:
Boasting a 6.5m mirror in space, JWST can increase by several times the
number of supernovae (SNe) to which a redshift-independent distance has been
measured with a precision distance indicator (e.g., TRGB or Cepheids); the
limited number of such SN calibrators currently dominates the uncertainty
budget in distance ladder Hubble constant (H0) experiments. JWST/NIRCAM imaging
of the Virgo Cluster galaxy NGC4536 is used here to preview JWST program
GO-1995, which aims to measure H0 using three stellar distance indicators
(Cepheids, TRGB, JAGB/carbon stars). Each population of distance indicator was
here successfully detected — with sufficiently large number statistics,
well-measured fluxes, and characteristic distributions consistent with ingoing
expectations — so as to confirm that we can acquire distances from each method
precise to about 0.05mag (statistical uncertainty only). We leverage
overlapping HST imaging to identify TRGB stars, cross-match them with the JWST
photometry, and present a preliminary constraint on the slope of the TRGB’s
F115W-(F115W}-F444W) relation equal to -0.99 +/- 0.16 mag/mag. This slope is
consistent with prior slope measurements in the similar 2MASS J-band, as well
as with predictions from the BASTI isochrone suite. We use the new TRGB slope
estimate to flatten the two-dimensional TRGB feature and measure a (blinded)
TRGB distance relative to a set of fiducial TRGB colors, intended to represent
the absolute fiducial calibrations expected from geometric anchors such as
NGC4258 and the Magellanic Clouds. In doing so, we empirically demonstrate that
the TRGB can be used as a standardizable candle at the IR wavelengths
accessible with JWST.
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