# seestar: Selection functions for spectroscopic surveys of the Milky Way

## TL;DR

This paper introduces a Bayesian Poisson likelihood method for calculating and combining selection functions in spectroscopic surveys of the Milky Way, enabling better understanding of observational biases and intrinsic stellar properties.

## Contribution

It presents a generalizable, robust approach for determining and transforming selection functions applicable to various multi-object spectrographs and survey overlaps.

## Key findings

- Successfully recreates synthetic spectroscopic samples from mock catalogues.
- Handles overlapping survey fields and combined samples effectively.
- Transforms sky-based selection functions into intrinsic stellar property functions.

## Abstract

Selection functions are vital for understanding the observational biases of spectroscopic surveys. With the wide variety of multi-object spectrographs currently in operation and becoming available soon, we require easily generalisable methods for determining the selection functions of these surveys. Previous work, however, has largely been focused on generating individual, tailored selection functions for every data release of each survey. Moreover, no methods for combining these selection functions to be used for joint catalogues have been developed. We have developed a Poisson likelihood estimation method for calculating selection functions in a Bayesian framework, which can be generalised to any multi-object spectrograph. We include a robust treatment of overlapping fields within a survey as well as selection functions for combined samples with overlapping footprints. We also provide a method for transforming the selection function that depends on the sky positions, colour, and apparent magnitude of a star to one that depends on the galactic location, metallicity, mass, and age of a star. This `intrinsic' selection function is invaluable for chemodynamical models of the Milky Way. We demonstrate that our method is successful at recreating synthetic spectroscopic samples selected from a mock galaxy catalogue.