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Journal Club
Ultra-Diffuse Galaxies – a Distinct Population? Dwarf Galaxies in the Coma Cluster and Abell 262 from Deep u’–g’–r’ Wendelstein Imaging Data
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Europe/Rome
0/0-3 - Sala Rosino (Dipartimento di Fisica e Astronomia - Edificio ex-Rizzato)
Description
Speakers: Nicola Bellucco (Università degli Studi di Padova)
In this study, we compare the structural parameters of Ultra-Diffuse Galaxies (UDGs) to those of other dwarf galaxies and investigate whether UDGs form a distinct population. We observed deep u′-, g′-, and r′-band images (maximum limiting surface brightness [3σ, 10”×10”] u’ and g’: ≈ 30 mag arcsec−2; r’: ≈ 29 mag arcsec−2) of Abell 1656 (Coma cluster) and Abell 262 with the Wendelstein Wide Field Imager at the 2.1 m Fraunhofer telescope on the Wendelstein Observatory. We measure u′ −g′ and g′ −r′ colors and structural parameters using parametric fitting of tens of thousands of potential UDGs and other dwarf galaxies. Cluster members are identified and separated from diffuse background galaxies based on red sequence membership and location in the u′ −g′ vs. g′ −r′ color–color diagram. We find 11 UDGs in Abell 262 and 48 UDGs in Abell 1656. The latter is 6 times more than van Dokkum et al. found in the overlapping region. By comparing the structural parameters of UDGs to non-UDGs in our sample and to spheroidals from the literature, we do not find any separation in all tested parameter spaces. Instead, UDGs form the diffuse end of the already well-known spheroidal population and slightly extend it. Furthermore, we find that the UDG definition used by Koda et al. and Yagi et al. mainly extends the definition by van Dokkum et al. toward ordinary spheroidals.
