EDGE-INFERNO: Simulating every observable star in faint dwarf galaxies and their consequences for resolved-star photometric surveys

TL;DR

This paper introduces EDGE-INFERNO, a simulation method that models all observable stars in faint dwarf galaxies, enabling more accurate interpretation of their structural and chemical properties from limited observational data.

Contribution

The study presents the first cosmological simulations resolving all stars above 0.5 solar masses, predicting detailed observable properties of faint dwarf galaxies from initial conditions.

Findings

Simulations predict complex light profiles with multiple components.

Observational measures can underestimate total magnitudes by up to 0.5 mag.

Shot noise significantly affects measurements when few stars are observed.

Abstract

Interpretation of data from faint dwarf galaxies is made challenging by observations limited to only the brightest stars. We present a major improvement to tackle this challenge by undertaking zoomed cosmological simulations that resolve the evolution of all individual stars more massive than $0.5\,{\rm M}_{\odot}$, thereby explicitly tracking all observable stars for the Hubble time. For the first time, we predict observable color-magnitude diagrams and the spatial distribution of $\approx 100,000$ stars within four faint ($M_{\star} \approx 10^5 \, \,{\rm M}_{\odot}$) dwarf galaxies directly from their cosmological initial conditions. In all cases, simulations predict complex light profiles with multiple components, implying that typical observational measures of structural parameters can make total V-band magnitudes appear up to 0.5 mag dimmer compared to estimates from simulations. Furthermore, when only small ($\lessapprox100$) numbers of stars are observable, shot noise from realizations of the color-magnitude diagram introduces uncertainties comparable to the population scatter in, e.g., total magnitude, half-light radius, and mean iron abundance measurements. Estimating these uncertainties with fully self-consistent mass growth, star formation and chemical enrichment histories paves the way for more robust interpretation of dwarf galaxy data.