James Webb Space Telescope Feed Post

Date: 6/10/2024

Harvard ADS: The RGB tip in the SDSS, PS1, JWST, NGRST and Euclid photometric systems. Calibration in optical passbands using Gaia DR3 synthetic photometry

Paper abstract: We use synthetic photometry from Gaia DR3 BP and RP spectra for a large selected sample of stars in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) to derive the magnitude of the Red Giant Branch (RGB) tip for these two galaxies in several passbands in various widely used optical photometric systems, including those of space missions that have not yet started operations. The RGB tip is estimated by fitting a well-motivated model to the RGB luminosity function (LF) within a fully Bayesian framework, allowing for a proper representation of the uncertainties of all the involved parameters and their correlations. Adopting the best available distance and interstellar extinction estimates we provide a calibration of the RGB tip as a standard candle for the following passbands: Johnson-Kron-Cousins I (mainly used for validation purposes), Hubble Space Telescope F814W, Sloan Digital Sky Survey i and z, PanSTARRS1 y, James Webb Space Telescope F090W, Nancy Grace Roman Space Telescope Z087, and Euclid I_E, with an accuracy of a few per cent, depending on the case. The trend of the absolute magnitude of the tip as a function of colour in the different passbands, beyond the range spanned by the LMC and SMC, as well as its dependency on age, is explored by means of theoretical models. These calibrations can be very helpful to obtain state-of-the-art RGB tip distance estimates to stellar systems in a very large range of distances directly from data in the natural photometric system of these surveys and/or missions, without recurring to photometric transformations. [abridged]