Ultradiffuse galaxies: the high-spin tail of the abundant dwarf galaxy population

By Nicola C. Amorisco, Abraham Loeb. 2016

174 citations recorded by the source corpus.

Recent observations have revealed the existence of an abundant population of faint, low surface brightness (SB) galaxies, which appear to be numerous and ubiquitous in nearby galaxy clusters, including the Virgo, Coma and Fornax clusters. With median stellar masses of dwarf galaxies, these ultra-diffuse galaxies (UDGs) have unexpectedly large sizes, corresponding to a mean SB of $24\lesssim\langle\mu_e\rangle_r\ {\rm mag}^{-1} {\rm arcsec}^2\lesssim27$ within the effective radius. We show that the UDG population represents the tail of galaxies formed in dwarf-sized haloes with higher-than-average angular momentum. By adopting the standard model of disk formation -- in which the size of galaxies is set by the spin of the halo -- we recover both the abundance of UDGs as a function of the host cluster mass and the distribution of sizes within the UDG population. According to this model, UDGs are not failed $L_*$ galaxies, but genuine dwarfs, and their low SB is not uniquely connected to the harsh cluster environment. We therefore expect a correspondingly abundant population of UDGs in the field, with likely different morphologies and colours.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/8d0bb8b293944ff79062882ffef53ef7aa647abd

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In Astronomy and Astrophysics

Citations in the corpus

Ultra-diffuse galaxies outside clusters: clues to their formation and evolution (2016, methodology): “This angular size is roughly the pixel size (2.8 arcsec) of the Dragonfly lens array (the telescope used to define this galaxy population; van Dokkum et al. 2015). et al. 2016; Beasley & Trujillo 2016; Amorisco & Loeb 2016; Di Cintio et al. 2017; Amorisco et al. 2016).”
NIHAO - XI. Formation of ultra-diffuse galaxies by outflows (2016, background): “Such dwarf halo mass range is also advocated in Amorisco & Loeb (2016), although their model requires high halo spin, unlike what we see in our simulated UDGs.”
Illuminating Low Surface Brightness Galaxies with the Hyper Suprime-Cam Survey (2017, result): “…as a function of environment can be explained if they preferentially form in dwarf-mass halos (Mvirial ∼ 1010 M ) with higher than average angular momentum (Amorisco & Loeb 2016), a view which is consistent with recent weak-lensing (Sifón et al. 2018) and H I (Leisman et al. 2017) observations.”
(Almost) Dark Galaxies in the ALFALFA Survey: Isolated H i-bearing Ultra-diffuse Galaxies (2017, background): “Amorisco & Loeb (2016) suggest they likely represent sources in halos in the high end tail of the spin parameter distribution, and Di Cintio et al. (2017) reproduce the extended stellar distributions of UDGs in isolated dwarf halos using gas outflows.”
A HIGH STELLAR VELOCITY DISPERSION AND ∼100 GLOBULAR CLUSTERS FOR THE ULTRA-DIFFUSE GALAXY DRAGONFLY 44 (2016, background): “Another idea is that UDGs represent the most rapidly-rotating tail of the distribution of dwarf galaxies, as the size and surface brightness of a galaxy are thought to be related to its spin (Amorisco & Loeb 2016).”