Origins of ultradiffuse galaxies in the Coma cluster – I. Constraints from velocity phase space

Alabi, Adebusola B.; Ferré-Mateu, Anna; Romanowsky, Aaron J.; Brodie, Jean P.; Forbes, Duncan A.; Wasserman, Asher; Bellstedt, Sabine; Martín-Navarro, Ignacio; Pandya, Viraj; Stone, M.; Okabe, Nobuhiko

doi:10.1093/mnras/sty1616

Cited by 62 publications

(68 citation statements)

References 59 publications

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“…Local dwarfs are relevant as UDGs may have formed their GCs in low density environments before falling into clusters, e.g. Alabi et al (2018). If UDGs are simply puffed-up dwarfs, then it is relevant to compare them to a sample of Coma early-type dwarf galaxies.…”

Section: Dwarf Galaxy Comparison Samplesmentioning

confidence: 99%

Globular clusters in Coma cluster ultra-diffuse galaxies (UDGs): evidence for two types of UDG?

Forbes

Alabi

Romanowsky

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Ultra diffuse galaxies (UDGs) reveal extreme properties. Here we compile the largest study to date of 85 globular cluster (GC) systems around UDGs in the Coma cluster, using new deep ground-based imaging of the known UDGs and existing imaging from the Hubble Space Telescope of their GC systems. We find that the richness of GC systems in UDGs generally exceeds that found in normal dwarf galaxies of the same stellar mass. These GC-rich UDGs imply halos more massive than expected from the standard stellar mass-halo mass relation. The presence of such overly massive halos presents a significant challenge to the latest simulations of UDGs in cluster environments. In some exceptional cases, the mass in the GC system is a significant fraction of the stellar content of the host galaxy. We find that rich GC systems tend to be hosted in UDGs of lower luminosity, smaller size and fainter surface brightness. Similar trends are seen for normal dwarf galaxies in the Coma cluster. A toy model is presented in which the GC-rich UDGs are assumed to be 'failed' galaxies within massive halos that have largely old, metal-poor, alpha-element enhanced stellar populations. On the other hand, GC-poor UDGs are more akin to normal, low surface brightness dwarfs that occupy less massive dark matter halos. Additional data on the stellar populations of UDGs with GC systems will help to further refine and test this simplistic model.

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Section: Dwarf Galaxy Comparison Samplesmentioning

confidence: 99%

Globular clusters in Coma cluster ultra-diffuse galaxies (UDGs): evidence for two types of UDG?

Forbes

Alabi

Romanowsky

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Three other low surface brightness galaxies in the vicinity of Dragonfly 44 (Dragonfly 42, DFX1, and DFX2) have redshifts, all from the DEIMOS multi-slit spectroscopy described in van Dokkum et al (2016van Dokkum et al ( , 2017a, and Alabi et al (2018). Of this sample of four faint galaxies, three (Dragonfly 42, Dragonfly 44, and DFX2) are within ≈ 100 km s −1 of each other (see van Dokkum et al 2017a;Alabi et al 2018). The velocity dispersion of the Coma cluster is ∼ 1000 km s −1 (Colless & Dunn 1996), and the probability that three out of four randomly selected galaxies have a velocity range ∆v < 100 km s −1 is 3 × 10 −3 .…”

Section: Robustness Of the Radial Dispersion Profilementioning

confidence: 99%

Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits

Dokkum

Wasserman

Danieli

et al. 2019

ApJ

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We present spatially-resolved stellar kinematics of the well-studied ultra diffuse galaxy (UDG) Dragonfly 44, as determined from 25.3 hrs of observations with the Keck Cosmic Web Imager. The luminosity-weighted dispersion within the half-light radius is σ 1/2 = 33 +3 −3 km s −1 , lower than what we had inferred before from a DEIMOS spectrum in the Hα region. There is no evidence for rotation, with V max / σ < 0.12 (90 % confidence) along the major axis, in possible conflict with models where UDGs are the high-spin tail of the normal dwarf galaxy distribution. The spatially-averaged line profile is more peaked than a Gaussian, with Gauss-Hermite coefficient h 4 = 0.13 ± 0.05. The mass-to-light ratio within the effective radius is (M dyn /L I )(< R e ) = 26 +7 −6 M /L , similar to other UDGs and higher by a factor of six than smaller galaxies of the same luminosity. This difference between UDGs and other galaxies is, however, sensitive to the aperture that is used, and is much reduced when the M/L ratios are measured within a fixed radius of 10 kpc. Dragonfly 44 has a rising velocity dispersion profile, from σ = 26 +4 −4 km s −1 at R = 0.2 kpc to σ = 41 +8 −8 km s −1 at R = 5.1 kpc. The profile can only be fit with a cuspy NFW profile if the orbital distribution has strong tangential anisotropy, with β = −0.8 +0.4 −0.5 . An alternative explanation is that the dark matter profile has a core: a Di Cintio et al. (2014) density profile with a mass-dependent core provides a very good fit to the kinematics for a halo mass of log(M 200 /M ) = 11.2 +0.6 −0.6 and β = −0.1 +0.2 −0.3 , i.e. isotropic orbits. This model predicts a slight positive kurtosis, in qualitative agreement with the measured h 4 parameter. UDGs such as Dragonfly 44 are dark matter dominated even in their centers, and can constrain the properties of dark matter in a regime where baryons usually dominate the kinematics: small spatial scales in massive halos. In a companion paper (Wasserman et al. 2019) we provide constraints on the axion mass in the context of "fuzzy" dark matter models.

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“…UDGs in clusters are typically on the red sequence (Koda et al 2015;van der Burg et al 2016;RS et al 2019) and show little evidence for tidal interaction even close to the cluster centres (Mowla et al 2017), suggesting relatively high mass-to-light ratios. There is tentative evidence that UDGs tend to be bluer towards the outskirts of galaxy groups (Román & Trujillo 2017b;Alabi et al 2018;Zaritsky et al 2019) (and more generally in lower-density environments cf. Greco et al 2018a,b), suggesting that interactions with the environment during in-fall can diminish star formation in the UDGs.…”

Section: Introductionmentioning

confidence: 99%

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

Prole

Burg

Hilker

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Abstract 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.

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Origins of ultradiffuse galaxies in the Coma cluster – I. Constraints from velocity phase space

Cited by 62 publications

References 59 publications

Globular clusters in Coma cluster ultra-diffuse galaxies (UDGs): evidence for two types of UDG?

Globular clusters in Coma cluster ultra-diffuse galaxies (UDGs): evidence for two types of UDG?

Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits

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

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