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arXiv · 1910.14057

Observational Properties of Field UDGs: Colours and Number Densities

Daniel J. Prole·Remco F. J. van der Burg·Michael Hilker·Jonathan I. Davies
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Abstract

While much of the focus around Ultra-Diffuse Galaxies (UDGs) has been given to those in galaxy groups and clusters, relatively little is known about them in less-dense environments. These isolated UDGs provide fundamental insights into UDG formation because environmentally driven evolution and survivability play less of a role in determining their physical and observable properties. We have recently conducted a statistical analysis of UDGs in the field using a new catalogue of sources detected in the deep Kilo-Degree Survey (KiDS) and Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) optical imaging surveys. Using an empirical model to assess our contamination from interloping sources, we show that a scenario in which cluster-like quiescent UDGs occupy a large fraction of the field UDG population is unlikely, with most being significantly bluer and some showing signs of localised star formation. We estimate an upper-limit on the total field abundance of UDGs of 8$\pm$3$\times10^{-3}$cMpc$^{-3}$ within our selection range. The mass formation efficiency of UDGs implied by this upper-limit is similar to what is measured in groups and clusters, meaning that secular formation channels may significantly contribute to the overall UDG population.

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Daniel J. Prole, Remco F. J. van der Burg, Michael Hilker, Jonathan I. Davies. 2019-10-30. Observational Properties of Field UDGs: Colours and Number Densities. https://arxiv.org/abs/1910.14057

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