Speaker
Description
The morphological mix of dwarf galaxies (M < 10^9.5 MSun) outside the very local Universe is essentially unknown, due to the past unavailability of surveys that are both wide and deep. Here, we use 257 dwarf galaxies to present the first unbiased, statistical study of dwarf galaxy morphologies at cosmological distances (0.03 < z < 0.1), by combining physical parameters from the COSMOS2020 catalog with deep optical images from the Ultra-Deep layer of the HSC-SSP survey.
We combine quantitative morphological parameters (e.g. CAS, M_20 and Gini) with visual classification of 257 dwarf galaxies to show that dwarfs fall into three general classes: early-types i.e. E and S0 (43%), spirals (45%) and a third class which corresponds to a featureless flat profile with no noticeable spiral or bar features and low central concentration (10%). While the number fraction of early-types and spirals is comparable to that in the massive regime, the featureless galaxies are completely missing in the massive regime. Compared to their massive counterparts, dwarf early-types show a much lower incidence of interactions, are significantly less concentrated and share similar rest-frame colours as dwarf late-types. This suggests that the formation histories of dwarf and massive early-types are different, with dwarf early-types being shaped less by interactions and more by secular processes.
Our study serves as a pilot to what will be possible using the hundreds of thousands of dwarfs that will be imaged by revolutionary deep-wide surveys like the Legacy Survey of Space and Time (LSST).
