Observational properties of ultra-diffuse galaxies in low-density environments: field UDGs are predominantly blue and star forming

Abstract

<jats:title>Abstract</jats:title> <jats:p>While we have learnt much about ultradiffuse galaxies (UDGs) in groups and clusters, relatively little is known about them in less dense environments. More isolated UDGs are important for our understanding of UDG formation scenarios because they form via secular mechanisms, allowing us to determine the relative importance of environmentally driven formation in groups and clusters. We have used the public Kilo-Degree Survey together with the Hyper Suprime-Cam Subaru Strategic Program to constrain the abundance and properties of UDGs in the field, targeting sources with low surface brightness (24.0 ≤ $\bar{\mu }_{\mathrm{ e},r}$ ≤ 26.5) and large apparent sizes (3.0 arcsec ≤ $\bar{r}_{\mathrm{ e},r}$ ≤ 8.0 arcsec). Accounting for several sources of interlopers in our selection based on canonical scaling relations, and using an empirical UDG model based on measurements from the literature, we show that a scenario in which cluster-like red-sequence UDGs occupy a significant number of field galaxies is unlikely, with most field UDGs being significantly bluer and showing signs of localized star formation. An immediate conclusion is that UDGs are much more efficiently quenched in high-density environments. We estimate an upper limit on the total field abundance of UDGs of 8 ± 3 × 10−3 cMpc−3 within our selection range. We also compare the total field abundance of UDGs to a measurement of the abundance of H i-rich UDGs from the literature, suggesting that they occupy at least one-fifth of the overall UDG population. The mass formation efficiency of UDGs implied by this upper limit is similar to what is measured in groups and clusters.</jats:p>

Low surface brightness galaxies in z > 1 galaxy clusters: HST approaching the progenitors of local ultra diffuse galaxies

“…An approximately linear dependence between the abundance of UDGs in galaxy clusters and the cluster mass was found (van der Burg et al 2017;Janssens et al 2017;Román & Trujillo 2017). Within clusters, UDGs appear to be found on the red sequence (van Dokkum et al 2015a;van der Burg et al 2016), while UDG-like galaxies found in the field typically appear to be bluer (Leisman et al 2017;Prole et al 2019).…”

One Hundred SMUDGes in S-PLUS: Ultra-diffuse Galaxies Flourish in the Field

“…In the limited available examples of field UDGs, however, the reported luminosity-weighted ages have consistently been younger, with ages ranging from 1 to 3 Gyr (Martínez-Delgado et al 2016;Greco et al 2018;Martín-Navarro et al 2019). In fact, the UDG population in the field is expected to have a larger variety of colors than that of the clusters (Di Cintio et al 2017) and there is observational support for this trend (van der Burg et al 2016;Prole et al 2019).…”

“…Photometric information, such as broadband colors (e.g. Prole et al 2019), are available for many UDGs but are of limited value in determining the properties of the stellar populations, while spectroscopy, which can provide the necessary information, is only available for a small number of galaxies (e.g. Martínez-Delgado et al 2016;Kadowaki et al 2017;Ruiz-Lara et al 2018;Ferré-Mateu et al 2018;Gu et al 2018).…”

Abundance of dwarf galaxies around low-mass spiral galaxies in the Local Volume

“…Novel development of automated detection algorithms show promising results. One of the best software packages available today is MTObjects (Teeninga et al 2013(Teeninga et al , 2015, a max-tree based algorithm developed for medical image analysis and rewritten for astronomical purposes (see, e.g., Prole et al 2019). It is non-parametric; that is, it automatically searches for the best parameters for a given image, which makes MTObjects straightforward to use.…”

“…Several surveys have targeted the more prominent of these giant galaxies like M 83 (Müller et al 2015), Centaurus A (Crnojević et al 2014(Crnojević et al , 2016Müller et al 2017;Taylor et al 2018), and others (Merritt et al 2014;Karachentsev et al 2015;Javanmardi et al 2016;Park et al 2017;Smercina et al 2018;Bennet et al 2019;Carlsten et al 2020;Davis et al 2020). Furthermore, dwarf galaxy surveys reach even more distant galaxy clusters (Venhola et al 2017;Wittmann et al 2019), groups (Geha et al 2017;Cohen et al 2018;Habas et al 2020), and the field (Greco et al 2018;Prole et al 2019).…”