A High Stellar Velocity Dispersion and ∼100 Globular Clusters for the Ultra-Diffuse Galaxy Dragonfly 44

Dokkum, Pieter van; Abraham, Roberto; Brodie, Jean P.; Conroy, Charlie; Danieli, Shany; Merritt, Allison; Mowla, Lamiya; Romanowsky, Aaron J.; Zhang, Jielai

doi:10.3847/2041-8205/828/1/l6

Cited by 236 publications

(141 citation statements)

References 44 publications

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“…Thus, a UDG population is an important indicator of dynamic processes in clusters and groups. From the data in [31,32], ultra-diffuse galaxies have a high darkto-stellar mass ratio, which can reach M DM /M * about 10 2 -10 3 for them.…”

Section: Resultsmentioning

confidence: 99%

KDG218, a nearby ultra-diffuse galaxy

et al. 2017

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We present properties of the low-surface-brightness galaxy KDG 218 observed with the HST/ACS. The galaxy has a half-light (effective) diameter of a e = 47′′ and a central surface brightness of SB V (0) = 24. m 4/⊓ ⊔ ′′ . The galaxy remains unresolved with the HST/ACS, which implies its distance of D > 13.1 Mpc and linear effective diameter of A e > 3.0 kpc. We notice that KDG 218 is most likely associated with a galaxy group around the massive lenticular NGC 4958 galaxy at approximately 22 Mpc, or with the Virgo Southern Extension filament at approximately 16.5 Mpc. At these distances, the galaxy is classified as an ultra-diffuse galaxy (UDG) similar to those found in the Virgo, Fornax, and Coma clusters. We also present a sample of 15 UDG candidates in the Local Volume. These sample galaxies have the following mean parameters: D = 5.1 Mpc, A e = 4.8 kpc, and SB B (e) = 27. m 4/⊓ ⊔ ′′ . All the local UDG candidates reside near massive galaxies located in the regions with the mean stellar mass density (within 1 Mpc) about 50 times greater than the average cosmic density. The local fraction of UDGs does not exceed 1.5% of the Local Volume population. We notice that the presented sample of local UDGs is a heterogeneous one containing irregular, transition, and tidal types, as well as objects consisting of an old stellar population.

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Section: Resultsmentioning

confidence: 99%

KDG218, a nearby ultra-diffuse galaxy

et al. 2017

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“…of M h ∼ 10 12 M , i.e., similar to the halo of the Milky Way (van Dokkum et al 2016; but see also Di Cintio et al 2017). and Beasley & Trujillo (2016) have also inferred very high dynamical-to-stellar mass ratios for the UDGs VCC 1287 and Dragonfly-17, but argue that their host halos have dwarf-scale masses (M h ∼ 10 11 M ).…”

Section: Introductionmentioning

confidence: 84%

The HI content of isolated ultra-diffuse galaxies: A sign of multiple formation mechanisms?

Papastergis

Adams

Romanowsky

2017

A&A

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We report on the results of radio observations in the 21 cm emission line of atomic hydrogen (HI) of four relatively isolated ultradiffuse galaxies (UDGs): DGSAT I, R-127-1, M-161-1, and SECCO-dI-2. Our Effelsberg observations resulted in non-detections for the first three UDGs, and a clear detection for the last. DGSAT I, R-127-1, and M-161-1 are quiescent galaxies with gas fractions that are much lower than those of typical field galaxies of the same stellar mass. On the other hand, SECCO-dI-2 is a star forming gas-rich dwarf, similar to two other field UDGs that have literature HI data: SECCO-dI-1 and UGC 2162. This group of three gas-rich UDGs have stellar and gaseous properties that are compatible with a recently proposed theoretical mechanism for the formation of UDGs, based on feedback-driven outflows. In contrast, the physical characteristics of R-127-1 and M-161-1 are puzzling, given their isolated nature. We interpret this dichotomy in the gaseous properties of field UDGs as a sign of the existence of multiple mechanisms for their formation, with the formation of the quiescent gas-poor UDGs remaining a mystery.

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“…We estimate a halo mass from the best fitting profiles from Di Cintio et al (2017) (Wang et al 2015). The dynamical mass estimates from and van Dokkum et al (2016) are marked by grey circles and a grey triangle respectively. The measured and predicted profiles show good agreement, suggesting halo masses below 10 11 M .…”

Section: The Halo Profile and Massmentioning

confidence: 99%

(Almost) Dark Galaxies in the ALFALFA Survey: Isolated H i-bearing Ultra-diffuse Galaxies

Leisman

Haynes

Janowiecki

et al. 2017

ApJ

230

409

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We present a sample of 115 very low optical surface brightness, highly extended, H i-rich galaxies carefully selected from the ALFALFA survey that have similar optical absolute magnitudes, surface brightnesses, and radii to recently discovered "ultra-diffuse" galaxies (UDGs). However, these systems are bluer and have more irregular morphologies than other UDGs, are isolated, and contain significant reservoirs of H i. We find that while these sources have normal star formation rates for H i selected galaxies of similar stellar mass, they have very low star formation efficiencies. We further present deep optical and H i synthesis follow up imaging of three of these H i-bearing ultra-diffuse sources. We measure H i diameters extending to ∼40 kpc, but note that while all three sources have large H i diameters for their stellar mass, they are consistent with the H i mass -H i radius relation. We further analyze the H i velocity widths and rotation velocities for the unresolved and resolved sources respectively, and find that the sources appear to inhabit halos of dwarf galaxies. We estimate spin parameters, and suggest that these sources may exist in high spin parameter halos, and as such may be potential H i-rich progenitors to the ultra-diffuse galaxies observed in cluster environments.

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A High Stellar Velocity Dispersion and ∼100 Globular Clusters for the Ultra-Diffuse Galaxy Dragonfly 44

Cited by 236 publications

References 44 publications

KDG218, a nearby ultra-diffuse galaxy

KDG218, a nearby ultra-diffuse galaxy

The HI content of isolated ultra-diffuse galaxies: A sign of multiple formation mechanisms?

(Almost) Dark Galaxies in the ALFALFA Survey: Isolated H i-bearing Ultra-diffuse Galaxies

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