# SBF: multi-wavelength data and models

## TL;DR

This paper demonstrates the use of Surface Brightness Fluctuations (SBF) as a reliable distance indicator and a tool for analyzing stellar populations' properties in external galaxies, presenting new observational data and models.

## Contribution

It provides new B-band SBF measurements for galaxies beyond 10 Mpc and evaluates optimized SSP models for analyzing stellar populations.

## Key findings

- First B-band SBF data for galaxies beyond 10 Mpc
- Detection of I-band SBF gradients in six ellipticals
- Availability of tailored SBF models at the web platform

## Abstract

Recent applications have proved that the Surface Brightness Fluctuations (SBF) technique is a reliable distance indicator in a wide range of distances, and a promising tool to analyze the physical and chemical properties of unresolved stellar systems, in terms of their metallicity and age. We present the preliminary results of a project aimed at studying the evolutionary properties and distance of the stellar populations in external galaxies based on the SBF method. On the observational side, we have succeeded in detecting I-band SBF gradients in six bright ellipticals imaged with the ACS, for these same objects we are now presenting also B-band SBF data. These B-band data are the first fluctuations magnitude measurements for galaxies beyond 10 Mpc. To analyze the properties of stellar populations from the data, accurate SBF models are essential. As a part of this project, we have evaluated SBF magnitudes from Simple Stellar Population (SSP) models specifically optimized for the purpose. A wide range of chemical compositions and ages, as well as different choices of the photometric system have been investigated. All models are available at the Teramo-Stellar Populations Tools web site: www.oa-teramo.inaf.it/SPoT.