James Webb Space Telescope Feed Post

Date: 7/11/2024

Arxiv: Coordinated JWST Imaging of Three Distance Indicators in a SN Host Galaxy and an Estimate of the TRGB Color Dependence Published: 7/10/2024 5:09:37 AM Updated: 7/10/2024 5:09:37 AM

Paper abstract: Boasting a 6.5m mirror in space, JWST can increase by several times thenumber of supernovae (SNe) to which a redshift-independent distance has beenmeasured with a precision distance indicator (e.g., TRGB or Cepheids); thelimited number of such SN calibrators currently dominates the uncertaintybudget in distance ladder Hubble constant (H0) experiments. JWST/NIRCAM imagingof the Virgo Cluster galaxy NGC4536 is used here to preview JWST programGO-1995, which aims to measure H0 using three stellar distance indicators(Cepheids, TRGB, JAGB/carbon stars). Each population of distance indicator washere successfully detected -- with sufficiently large number statistics,well-measured fluxes, and characteristic distributions consistent with ingoingexpectations -- so as to confirm that we can acquire distances from each methodprecise to about 0.05mag (statistical uncertainty only). We leverageoverlapping HST imaging to identify TRGB stars, cross-match them with the JWSTphotometry, and present a preliminary constraint on the slope of the TRGB'sF115W-(F115W}-F444W) relation equal to -0.99 +/- 0.16 mag/mag. This slope isconsistent with prior slope measurements in the similar 2MASS J-band, as wellas with predictions from the BASTI isochrone suite. We use the new TRGB slopeestimate to flatten the two-dimensional TRGB feature and measure a (blinded)TRGB distance relative to a set of fiducial TRGB colors, intended to representthe absolute fiducial calibrations expected from geometric anchors such asNGC4258 and the Magellanic Clouds. In doing so, we empirically demonstrate thatthe TRGB can be used as a standardizable candle at the IR wavelengthsaccessible with JWST.