RESCUER: Cosmological K-corrections for star clusters

TL;DR

This paper develops and provides tools for calculating K-corrections for star clusters observed at high redshift, accounting for their unique spectral energy distributions.

Contribution

It derives star cluster K-corrections across various ages and metallicities and introduces the RESCUER webtool for custom calculations.

Findings

K-corrections vary significantly with age and metallicity.

Results are tailored for HST/ACS and JWST/NIRCam filters.

The RESCUER tool enables personalized K-correction computations.

Abstract

The advent of JWST (the James Webb Space Telescope) now allows entire star cluster populations to be imaged in galaxies at cosmologically significant redshifts, bringing with it the need to apply K-corrections to their magnitudes and colour indices. Since the stellar populations within star clusters can be well approximated by a single age and metallicity, their spectral energy distributions are very different from those of galaxies or supernovae, and their K-corrections behave differently. We derive the photometric K-corrections versus redshift for model star clusters that cover a wide range of ages and metallicities, illustrating the results particularly for the broadband filters on the HST/ACS and the JWST/NIRCam cameras that are most commonly being used for imaging of populations of star clusters in distant galaxies. In an Appendix, we introduce a simple webtool called RESCUER that can generate K-values for any user-defined combination of cluster properties.