FORTY-SEVEN MILKY WAY-SIZED, EXTREMELY DIFFUSE GALAXIES IN THE COMA CLUSTER

By P. V. van Dokkum, R. Abraham, A. Merritt, Jielai Zhang, M. Geha, C. Conroy. 2014

294 citations recorded by the source corpus.

We report the discovery of 47 low surface brightness objects in deep images of a 3° × 3° field centered on the Coma cluster, obtained with the Dragonfly Telephoto Array. The objects have central surface brightness μ(g, 0) ranging from 24–26 mag arcsec−2 and effective radii reff = 3″–10″, as measured from archival Canada–France–Hawaii Telescope images. From their spatial distribution we infer that most or all of the objects are galaxies in the Coma cluster. This relatively large distance is surprising as it implies that the galaxies are very large: with reff = 1.5–4.6 kpc their sizes are similar to those of L* galaxies even though their median stellar mass is only ∼6 × 107 M☉. The galaxies are relatively red and round, with 〈g − i〉 = 0.8 and 〈b/a〉 = 0.74. One of the 47 galaxies is fortuitously covered by a deep Hubble Space Telescope Advanced Camera for Surveys (ACS) observation. The ACS imaging shows a large spheroidal object with a central surface brightness μ475 = 25.8 mag arcsec−2, a Sérsic index n = 0.6, and an effective radius of 7″, corresponding to 3.4 kpc at the distance of Coma. The galaxy is not resolved into stars, consistent with expectations for a Coma cluster object. We speculate that these “ultra-diffuse galaxies” may have lost their gas supply at early times, possibly resulting in very high dark matter fractions.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/13ab71af20413f0886dbdc040541b9d1edc970d1

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Citations in the corpus

Illuminating Low Surface Brightness Galaxies with the Hyper Suprime-Cam Survey (2017, methodology): “…we also show the family of early-type galaxies (Brodie et al. 2011), representative giant LSB spiral galaxies (Sprayberry et al. 1995), UDGs in intermediate to high density environments (van Dokkum et al. 2015; Román & Trujillo 2017a), and H I-bearing UDGs in the field (Leisman et al. 2017).”
GALAXIES AT THE EXTREMES: ULTRA-DIFFUSE GALAXIES IN THE VIRGO CLUSTER (2015, background): “This was demonstrated most recently through deep wide-field imaging of the Coma Cluster (van Dokkum et al. 2015a; vD15a, Koda et al. 2015; K15), which found a population of large (re=2 − 5 kpc; i.e., Milky Way-sized) and extremely diffuse galaxies with central surface brightnesses µ0,V = 24 − 26.”
Ultra-diffuse galaxies outside clusters: clues to their formation and evolution (2016, methodology): “This is ∼1.2 mag deeper than the Dragonfly images used to explore UDGs (van Dokkum et al. 2015) and a similar depth like in Koda et al. (2015).”
Ultradiffuse galaxies: the high-spin tail of the abundant dwarf galaxy population (2016, methodology): “Using the Dragonfly array (Abraham & van Dokkum 2014), van Dokkum et al. (2015a) (vD15) first identified 47 extended, roundish, quiescent galaxies, with central surface brightness (SB) of µg,0 = 24 − 26 mag arcsec−2, in imaging data of the Coma cluster.”
(Almost) Dark Galaxies in the ALFALFA Survey: Isolated H i-bearing Ultra-diffuse Galaxies (2017, methodology): “…of 115 sources with rr,eff > 1.5 kpc, 〈µ(r, reff)〉 > 24 mag arcsec−2, and Mr > −17.6 (corresponding to the surface brightness and radius limits from van Dokkum et al. 2015 and van der Burg et al. 2016 respectively; since these papers do not give explicit absolute magnitude limits, we chose the…”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, background): “For example, the so-called ultra diffuse galaxies (van Dokkum et al. 2015) have sizes similar to Ant 2, but are typically ∼6 mag brighter.”
NIHAO - XI. Formation of ultra-diffuse galaxies by outflows (2016, methodology): “Deep imaging of nearby clusters have revealed a sizeable population of faint, MR∼>−16.5, low surface brightness, µe=24-28 mag/arcsec2, and unusually large, 0.8<re/kpc<5 galaxies, named Ultra-Diffuse Galaxies or UDGs (van Dokkum et al. 2015a).”
Constraining the galaxy–halo connection over the last 13.3 Gyr: star formation histories, galaxy mergers and structural properties (2017, background): “…studies that the evolution of the structural properties of the galaxies played a key role in the quenching of galaxies (Kauffmann et al. 2003a; van Dokkum et al. 2010; Bell et al. 2012; Cheung et al. 2012; Patel et al. 2013; van Dokkum et al. 2014; Barro et al. 2013, 2015; van Dokkum et al. 2015b).”
The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater (2016, background): “For example, recently, a discovery of an entire population of ultra diffuse galaxies (UDGs) was reported by van Dokkum et al. (2015) in the Coma cluster.”
APPROXIMATELY A THOUSAND ULTRA-DIFFUSE GALAXIES IN THE COMA CLUSTER (2015, methodology): “These results are consistent with van Dokkum et al. (2015a) when the difference in the adopted bands, SDSS g and Subaru R, is taken into account (roughly g − R ∼0.8 mag for the red-sequence in Coma).”
The Local Group on FIRE: dwarf galaxy populations across a suite of hydrodynamic simulations (2018, background): “If ultra-diffuse galaxies (UDGs) are prevalent in the field (as predicted by Di Cintio et al. 2017 and Chan et al. 2017), with central surface brightnesses 24–26 mag arcsec−2 (van Dokkum et al. 2015), then some of this incompleteness may even arise at M∗ ∼ 107 M .”
A HIGH STELLAR VELOCITY DISPERSION AND ∼100 GLOBULAR CLUSTERS FOR THE ULTRA-DIFFUSE GALAXY DRAGONFLY 44 (2016, methodology): “This amount of dark matter is sufficient to prevent disruption of the galaxy by the Coma tidal field, at least at distances & 100 kpc from the center of the cluster (Gnedin 2003; van Dokkum et al. 2015a; van der Burg et al. 2016).”
CATALOG OF ULTRA-DIFFUSE GALAXIES IN THE COMA CLUSTERS FROM SUBARU IMAGING DATA (2016, methodology): “Except for the faintest one (DF27), DF-UDGs are easily identified with enough S/N in the image of ∼20 minutes integration by Suprime-Cam in the R-band using the coordinates given in van Dokkum et al. (2015a).”