Galaxy Evolution in the Local Group
Probing Galaxy Evolution with Structures, Chemo-dynamics and Star Formation Histories of resolved galaxies

We use wide field photometric and spectroscopic surveys, such as the SMASH project, where we have a leading role in deriving the LMC and SMC SFHs  from deep CMD. We have shown that the LMC and SMC SFHs are correlated at recent times, when enhancements of star formation are localized in the northern spiral arm of the LMC, and globally across the SMC, indicating an influence of the interactions between both galaxies in their SFH (Massana et al. 2022). See related press releases: ( LMC ; SMC )

 Using mostly HST data, we study the SFHs of Milky Way and M31 satellites, as well as those of more distant isolated galaxies.  We have obtained interesting results for individual galaxies such as Fornax (Rusakov et al), Eridanus II (Gallart et al ) and Leo I (Ruiz-Lara et al), which provide insight on the possible role of interactions in dwarf galaxy evolution. See related press release ( Leo I ) 

Variable stars provide complementary information on the evolution of galaxies, since the most ancient epochs. We investigate the variable star content in all the bright Local Group galaxies, using both HST and wide-field ground-based data (Monelli et al. 2018, Neeley et al. 2021, Martínez-Vázquez et al. 2021). Also, RR Lyrae stars and Cepheids are fundamental distance indicators that allow us to study the 3D structure of the Local Group (Monelli & Fiorentino 2022).

In our work we focus on both Milky Way satellite galaxies and isolated Local Group dwarf galaxies (see e.g. invited review article  Battaglia & Nipoti 2022  on the stellar dynamics and dark matter halo properties, and  Taibi et al. 2022  for a comprehensive analysis of metallicity gradients). In some of our most recent articles we have shown that a few of these systems have peculiar structural and internal kinematic properties likely due to mergers with smaller galaxies (e.g. Phoenix in  Kacharov et al. 2017  , Sextans in  Cicuendez & Battaglia 2018 ), as supported by the analysis of cosmological simulations (Cardona-Barrero et al. 2021): these structures might be therefore telling us about the hierarchical accretion process down to the smallest galactic scales. 

In the process of assembling the pieces of the puzzle needed to interpret the internal dynamics of dwarf galaxies in the context of dark matter properties, we have studied the binary stellar population properties of seven Milky Way classical dwarf spheroidals, finding that for now, there is no evidence that the properties of the binary star population in satellite galaxies of the Local Group are different from those in the solar neighborhood (Arroyo-Polonio et al. 2023). However, the uncertainties are large, and samples such as those that can be provided by WEAVE will be key to clarifying possible differences. Additionally, we have shown that the dark matter distribution of the Milky Way satellite galaxy Sculptor is inconsistent, at the 3-sigma level across a wide radial range, with N-body simulations of the Cold Dark Matter model—although we cannot rule out that feedback effects from supernovae are the cause of these differences (Arroyo-Polonio et al. 2025).

We have made use of data from the ESA Gaia mission for the determination of the systemic motions of Local Group galaxies out to a distance of 1.4Mpc using the early DR3 (Battaglia et al. 2022) and previously from Gaia DR2 data for the system of Milky Way satellites (Fritz, Battaglia et al. 2018). Please visit the website https://research.iac.es/proyecto/GaiaDR3LocalGroup/ for catalogues, videos and an interactive animation of the Milky Way system of satellite galaxies.

We place particular emphasis on the properties of small, dwarf galaxies. There is mounting observational evidence that black hole feedback is important also at the scales of the faintest objects, and this topic has so far been ignored by the theoretical community. Using a suite of AURIGA dwarf galaxies run with and without black holes it is possible to make a proper comparison of the effect of AGN feedback in those galaxies.