Table 2.
Stellar populations properties of early and late UDG populations in Hydra I.
| Properties | Very early infallers | Late infallers |
|---|---|---|
| (1) | (2) | (3) |
| Number of galaxies | 6 galaxies | 4 galaxies |
| Metallicity | [M/H]= − 0.8 ± 0.1 dex | [M/H]= − 1.0 ± 0.1 dex |
| α abundances | [α/Fe] = 0.0 ± 0.2 dex | [α/Fe]= − 0.1 ± 0.1 dex |
| Mass-metallicity relation(a) | Dwarf-like & metal-richer | Dwarf-like |
| Star formation history(b) | Dwarf-like: Δt50 ∼ 6 Gyr, Δt90 ∼ 0.5 Gyr | Dwarf-like: Δt50 ∼ 5 Gyr, Δt90 ∼ 1 Gyr |
| Metal-richer: Δt50 ∼ 0.5 Gyr, Δt90 ∼ 12 Gyr | ||
| Stellar rotation(c) | Rotation & pressure-supported | Rotation-supported |
Notes. Column 1 reports the properties of stellar population analysis from this work and stellar kinematics analysis from Paper II. Columns 2 and 3 report the values for the very early and late infallers. Superscript (a) refers to galaxies in LEWIS for which the value of metallicity is similar (dwarf-like) or higher (metal-richer) than metallicity of dwarf galaxies of similar stellar mass according to the Kirby et al. (2013) relation. Superscript (b) means we do not consider UDG4 since it has a peculiar SFH (see Fig. 3, top left panel). Superscript (c) refers to our finding that, in the late-infallers, three out of four galaxies have hints of stellar rotation, while the remaining one is pressure-supported. The reported classification refers to the majority of the objects in this class, although the sample size is not statistically significant.
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