James Webb Space Telescope Feed Post

Harvard ADS: Extending the cosmic distance ladder two orders of magnitude with strongly lensed Cepheids, carbon AGB, and RGB stars

Paper abstract: Extreme magnification of stars near the caustics of clusters allow to detect individual luminous stars at high redshift. We show how deep exposures of caustic crossing galaxies at z<~1 with IR telescopes such as JWST, can detect non-explosive distance calibrators, such as Cepheids, carbon stars in the asymptotic giant branch or stars in the tip of the red giant branch. A large number of such detections, combined with careful modelling of the magnification affecting these stars (including microlensing), opens the door to using them as alternative standard candles to SNe in a redshift range that would extend the cosmic distance ladder two orders of magnitude for these distance calibrators. As a bonus, strongly lensed stars detected in deep exposures provide also a robust method of mapping small dark matter substructures since they cluster around the critical curves of small scale dark matter halos.