Abstract
Studies of resolved stellar populations in the Milky Way and nearby galaxies reveal an amazingly detailed and clear picture of galaxy evolution. Within the Local Group, the ability to probe the stellar populations of small and large galaxies opens up the possibility of exploring key questions such as the nature of dark matter, the detailed formation history of different galaxy components, and the role of accretion in galactic formation. Upcoming wide-field surveys promise to extend this ability to all galaxies within 10 Mpc, drastically increasing our capability to decipher galaxy evolution and enabling statistical studies of galaxies’ stellar populations. To facilitate the optimum use of these upcoming capabilities, we develop a simple formalism to predict the density of resolved stars for an observation of a stellar population at fixed surface brightness and population parameters. We provide an interface to calculate all quantities of interest to this formalism via a public release of the code walter. This code enables calculation of (i) the expected number density of detected stars; (ii) the exposure time needed to reach certain population features, such as the horizontal branch; and (iii) an estimate of the crowding limit, among other features. We provide a limited test of the code and formalism of the paper against existing resolved star observations. These calculations will be very useful for planning surveys with NASA’s upcoming Nancy Grace Roman Space Telescope (Roman, formerly WFIRST), which we use for example calculations throughout this work.
| Original language | English (US) |
|---|---|
| Article number | 142 |
| Journal | Astronomical Journal |
| Volume | 164 |
| Issue number | 4 |
| DOIs | |
| State | Published - Oct 1 2022 |
Funding
The authors thank the anonymous referee for their helpful feedback on the article. L.L. thanks David Sand, Johnny Greco, Scott Carlsten, and Rachael Beaton for helpful discussions. The authors thank Leo Girardi for providing access to the low-metallicity and F213 predictions for the Padova isochrones. Support for S.P. was provided by NASA through the NASA Hubble Fellowship grant No. HST-HF2-51466.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. The Flatiron Institute is supported by the Simons Foundation. Support for B.F.W., K.V.J., and A.S. was provided through NASA contract NNG16PJ28C as part of the Roman Science Investigation Team funded through ROSES call NNH15ZDA001N-WFIRST. The authors thank the anonymous referee for their helpful feedback on the article. L.L. thanks David Sand, Johnny Greco, Scott Carlsten, and Rachael Beaton for helpful discussions. The authors thank Leo Girardi for providing access to the low-metallicity and F213 predictions for the Padova isochrones. Support for S.P. was provided by NASA through the NASA Hubble Fellowship grant No. HST-HF2-51466.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. The Flatiron Institute is supported by the Simons Foundation. Support for B.F.W., K.V.J., and A.S. was provided through NASA contract NNG16PJ28C as part of the Roman Science Investigation Team funded through ROSES call NNH15ZDA001N-WFIRST.
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science