Looking into the faintEst WIth MUSE (LEWIS): on the nature of ultra-diffuse galaxies in the Hydra I cluster. V. Integrated stellar population properties
Authors
Goran Doll
Chiara Buttitta
Enrichetta Iodice
Anna Ferré-Mateu
Jesus Falcòn-Barroso
Ignacio Martìn-Navarro
Maurizio Paolillo
Luca Rossi
Duncan A. Forbes
Chiara Spiniello
Johanna Hartke
Marco Gullieuszik
Magda Arnaboldi
Michele Cantiello
Enrico Maria Corsini
Giuseppe D'Ago
Michael Hilker
Antonio La Marca
Steffen Mieske
Marco Mirabile
Marina Rejkuba
Marilena Spavone
Abstract
Context: This paper presents new results from the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS). The sample consists of low-surface brightness (LSB) and ultra-diffuse galaxies (UDGs) located inside 0.4 R$_{vir}$ of the Hydra I cluster. Integral field spectroscopy is acquired for 24 galaxies with the MUSE spectrograph mounted on the Very Large Telescope (VLT). Aims: Our main objective is to analyse possible correlations between the environment and the integrated stellar population properties. Methods: For each galaxy, we extract the 1D stacked spectrum in an aperture of one effective radius and adopt previously published stellar kinematics to derive age, metallicity and [Mg/Fe] through a full spectral fitting technique. Results: We find that the analysed LEWIS sample has a mean metallicity of [M/H] = -0.9 dex, a mean age of 10 Gyr, comparable to results of UDGs in other clusters. According to the projected phase-space, galaxies can be classified into two groups: early infallers, with slightly higher metallicities ([M/H]$_{early} = -0.8 \pm 0.1$ dex), and late infallers, with slightly lower values ([M/H]$_{late} = -1.0 \pm 0.1$ dex). Two types of galaxies are found in the early-infall region: half of them have metallicities consistent with the dwarf mass-metallicity relation, while the other half show higher values. Moreover, they display different timescales for stellar mass assembly. Conclusions: We identified different classes of UDGs in the Hydra I cluster, which suggest different formation mechanisms taking place. Almost all of the UDGs and LSBs in the cluster are consistent with the puffed-up dwarf formation scenario, having dwarf-like metallicities and being consistent with the dwarf mass-metallicity relation. In the innermost regions of the cluster, where metal-richer UDGs lie, tidal or environmental effects might have influenced their formation and evolution.
