DARK MATTER SUBHALOS IN THE URSA MINOR DWARF GALAXY

ABSTRACT We use cosmological hydrodynamical galaxy formation simulations from the NIHAO project to investigate the response of cold dark matter (CDM) haloes to baryonic processes. Previous work has shown that the halo response is primarily a function of the ratio between galaxy stellar mass and total virial mass, and the density threshold above which gas is eligible to form stars, n[cm−3]. At low n all simulations in the literature agree that dwarf galaxy haloes are cuspy, but at high n ≳ 100 there is no consensus. We trace halo contraction in dwarf galaxies with n ≳ 100 reported in some previous simulations to insufficient spatial resolution. Provided the adopted star formation threshold is appropriate for the resolution of the simulation, we show that the halo response is remarkably stable for n ≳ 5, up to the highest star formation threshold that we test, n = 500. This free parameter can be calibrated using the observed clustering of young stars. Simulations with low thresholds n ≤ 1 predict clustering that is too weak, while simulations with high star formation thresholds n ≳ 5, are consistent with the observed clustering. Finally, we test the CDM predictions against the circular velocities of nearby dwarf galaxies. Low thresholds predict velocities that are too high, while simulations with n ∼ 10 provide a good match to the observations. We thus conclude that the CDM model provides a good description of the structure of galaxies on kpc scales provided the effects of baryons are properly captured.

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A constraint on light primordial black holes from the interstellar medium temperature

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab1222 ◽

2021 ◽

Author(s):

Hyungjin Kim

Keyword(s):

Black Holes ◽

Dark Matter ◽

Dwarf Galaxy ◽

Dark Matter Candidate ◽

Primordial Black Hole ◽

Primordial Black Holes ◽

Substantial Fraction ◽

Interstellar Gas ◽

Medium Temperature ◽

Fast Electrons

Abstract Primordial black holes are a viable dark matter candidate. They decay via Hawking evaporation. Energetic particles from the Hawking radiation interact with interstellar gas, depositing their energy as heat and ionization. For a sufficiently high Hawking temperature, fast electrons produced by black holes deposit a substantial fraction of energy as heat through the Coulomb interaction. Using the dwarf galaxy Leo T, we place an upper bound on the fraction of primordial black hole dark matter. For M < 5 × 10−17M⊙, our bound is competitive with or stronger than other bounds.

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The Large Range of Dark Matter content in Dwarf Galaxies and its Implications

Symposium - International Astronomical Union ◽

10.1017/s0074180900233536 ◽

1996 ◽

Vol 171 ◽

pp. 435-435

Author(s):

S.A. Pustilnik ◽

V.A. Lipovetsky ◽

J.-M. Martin ◽

T.X. Thuan

Keyword(s):

Dark Matter ◽

Galaxy Formation ◽

Large Range ◽

Dwarf Galaxy ◽

Rotational Velocity ◽

Matter Content ◽

Optical Observations ◽

Strong Interactions ◽

Formation Mechanisms ◽

Mass Ratio

We present the analysis of a new set of radio and optical observations of a large sample of Byurakan Blue Compact Galaxies. HI spectra were obtained with the Nançay 300-m and Green Bank 43-m radio telescopes. CCD-images were taken with the KPNO 0.9-m and Whipple Observatory 1.2-m telescopes. Dark Matter (DM) to luminous mass ratios in these BCGs were found to vary from about less than 0.5 up to 14. Recent data taken from the literature indicate this same range. This result has important consequences on models of dwarf galaxy formation, indicating possibly different formation mechanisms. The standard CDM model of dwarfs formation requires large DM halos. However the formation of dwarfs as tidal debris resulting from strong interactions of massive spirals leads naturally to dwarfs with low content of DM. On Fig.1 we show DM to luminous mass ratio versus rotational velocity for our BCGs and some other galaxies.

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Embedding globular clusters in dark matter minihaloes solves the cusp–core and timing problems in the Fornax dwarf galaxy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa011 ◽

2020 ◽

Vol 492 (3) ◽

pp. 3169-3178 ◽

Cited By ~ 1

Author(s):

Pierre Boldrini ◽

Roya Mohayaee ◽

Joseph Silk

Keyword(s):

Dark Matter ◽

Globular Clusters ◽

Dwarf Galaxy ◽

Large Fraction ◽

Star Clusters ◽

Circumstantial Evidence ◽

Core Size ◽

Core Problem ◽

Good Agreement

ABSTRACT We use a fully GPU N-body code to demonstrate that dark matter (DM) minihaloes, as a new component of globular clusters (GCs), resolve both the timing and cusp–core problems in Fornax if the (five or six) GCs were recently accreted (≤3 Gyr ago) by Fornax. Under these assumptions, infall of these GCs does not occur and no star clusters form in the centre of Fornax in accordance with observations. We find that crossings of GCss that have DM minihaloes near the Fornax centre induce a cusp-to-core transition of the DM halo and hence resolve the cusp–core problem in this dwarf galaxy. The DM core size depends on the frequency of GC crossings. Our simulations clearly demonstrate also that between the passages, the DM halo can regenerate its cusp. Moreover, our models are in good agreement with constraints on the DM masses of GCs as our clusters lose a large fraction of their initial DM minihaloes. These results provide circumstantial evidence for the universal existence of DM haloes in GCs.

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The Search for Dark Matter in Draco and Ursa Minor: A Three Year Progress Report

Symposium - International Astronomical Union ◽

10.1017/s0074180900150120 ◽

1987 ◽

Vol 117 ◽

pp. 153-160 ◽

Cited By ~ 1

Author(s):

M. Aaronson ◽

E. Olszewski

Keyword(s):

Dark Matter ◽

Velocity Dispersion ◽

Progress Report ◽

Radial Velocities ◽

Circumstantial Evidence ◽

Dwarf Spheroidal Galaxies ◽

Ursa Minor ◽

Stellar Velocity ◽

Atmospheric Motions ◽

Matter Component

We report the cumulative results of an on-going effort to measure the stellar velocity dispersion in two nearby dwarf spheroidal galaxies. Radial velocities having an accuracy ≲ 2 km s−1 have now been secured for ten stars in Ursa Minor and eleven stars in Draco (including 16 K giants and 5 C types). Most objects have been observed at two or more epochs. Stars having non-variable velocities yield in both dwarfs a large (∼ 10 km s−1) dispersion. These results cannot be explained by atmospheric motions, and circumstantial evidence suggests that the effects of undetected binaries are also not likely to be important. Instead, it seems that both spheroidals contain a substantial dark matter component, which therefore must be “cold” in form.

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Refracting into ultra-diffuse galaxy NGC 1052-DF2 by passing near the centre of NGC 1052

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa071 ◽

2020 ◽

Vol 495 (1) ◽

pp. L144-L148 ◽

Cited By ~ 1

Author(s):

Ran Huo

Keyword(s):

Dark Matter ◽

Physical Mechanism ◽

Dwarf Galaxy ◽

Recent Observation ◽

Tidal Effect ◽

Natural Consequence ◽

Formation Theory ◽

The Galaxy ◽

Standard Structure ◽

Flat Distribution

ABSTRACT The recent observation of the ultra-diffuse galaxy NGC 1052-DF2 shows a galaxy may lack dark matter, which becomes a challenge to the standard structure formation theory. Here, we show that such phenomena can be a natural consequence if the NGC 1052-DF2 had experienced a single passage within a few kpc to the centre of the galaxy NGC 1052. The tidal effect of NGC 1052 in the encounter will heat the NGC 1052-DF2, and stretch the previous dwarf galaxy significantly into its current size. The relative lack of dark matter in the observed region is a natural consequence of the dark matter limited total amount in the corresponding small central region before the encounter, together with a systematic underestimation of the trace mass estimator method during revirialization after the encounter. The observed flat distribution of the ultra-diffuse galaxy can be reproduced with a cored initial star profile, which is a major improvement compared with the previous work. Our results show no need for introducing any new physical mechanism, as well as an alternative origin of an ultra-diffuse galaxy without repeated pericentre passage.

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The Dark Blue Compact Dwarf Galaxy NGC 2915

Publications of the Astronomical Society of Australia ◽

10.1071/as97077 ◽

1997 ◽

Vol 14 (1) ◽

pp. 77-80 ◽

Cited By ~ 2

Author(s):

Gerhardt R. Meurer

Keyword(s):

Dark Matter ◽

Mass Distribution ◽

Dwarf Galaxy ◽

Dark Matter Halo ◽

High Mass ◽

Mass Star ◽

Normal Galaxies ◽

The Galaxy ◽

Dark Blue ◽

Blue Compact Dwarf Galaxy

AbstractRecent results on NGC 2915, the first blue compact dwarf galaxy to have its mass distribution modelled, are summarised. NGC 2915 is shown to have HI well beyond its detected optical extent. Its rotation curve is well determined and fit with maximum disk mass models. The dark matter halo dominates the mass distribution at nearly all radii, and has a very dense core compared to those of normal galaxies. High-mass star formation energises the HI in the centre of the galaxy, but appears to be maintained in viriai equilibrium with the dark matter halo. The implications of these results are briefly discussed.

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Globular cluster ejection, infall, and the host dark matter halo of the Pegasus dwarf galaxy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa004 ◽

2020 ◽

Vol 492 (4) ◽

pp. 5102-5120

Author(s):

Ryan Leaman ◽

Tomás Ruiz-Lara ◽

Andrew A Cole ◽

Michael A Beasley ◽

Alina Boecker ◽

...

Keyword(s):

Dark Matter ◽

Relaxation Time ◽

Density Profile ◽

Globular Cluster ◽

Dwarf Galaxy ◽

Orbital Evolution ◽

Dark Matter Halo ◽

Host Galaxy ◽

Structural Constraints ◽

The Galaxy

ABSTRACT Recent photometric observations revealed a massive, extended (MGC ≳ 105 M⊙; Rh ∼ 14 pc) globular cluster (GC) in the central region (D3D ≲ 100 pc) of the low-mass (M* ∼ 5 × 106 M⊙) dwarf irregular galaxy Pegasus. This massive GC offers a unique opportunity to study star cluster inspiral as a mechanism for building up nuclear star clusters, and the dark matter (DM) density profile of the host galaxy. Here, we present spectroscopic observations indicating that the GC has a systemic velocity of ΔV = 3 ± 8 km s−1 relative to the host galaxy, and an old, metal-poor stellar population. We run a suite of orbital evolution models for a variety of host potentials (cored to cusped) and find that the GC’s observed tidal radius (which is ∼3 times larger than the local Jacobi radius), relaxation time, and relative velocity are consistent with it surviving inspiral from a distance of Dgal ≳ 700 pc (up to the maximum tested value of Dgal = 2000 pc). In successful trials, the GC arrives to the galaxy centre only within the last ∼1.4 ± 1 Gyr. Orbits that arrive in the centre and survive are possible in DM haloes of nearly all shapes, however to satisfy the GC’s structural constraints a galaxy DM halo with mass MDM ≃ 6 ± 2 × 109 M⊙, concentration c ≃ 13.7 ± 0.6, and an inner slope to the DM density profile of −0.9 ≤ γ ≤ −0.5 is preferred. The gas densities necessary for its creation and survival suggest the GC could have formed initially near the dwarf’s centre, but then was quickly relocated to the outskirts where the weaker tidal field permitted an increased size and relaxation time – with the latter preserving the former during subsequent orbital decay.

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ETHOS – an effective theory of structure formation: formation of the first haloes and their stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz766 ◽

2019 ◽

Vol 485 (4) ◽

pp. 5474-5489 ◽

Cited By ~ 6

Author(s):

Mark R Lovell ◽

Jesús Zavala ◽

Mark Vogelsberger

Keyword(s):

Dark Matter ◽

Power Spectrum ◽

Galaxy Formation ◽

Cold Dark Matter ◽

Dwarf Galaxy ◽

Mass Scale ◽

Effective Theory ◽

Matter Power Spectrum ◽

Hydrodynamical Simulations ◽

Stellar Masses

Abstract A cut-off in the linear matter power spectrum at dwarf galaxy scales has been shown to affect the abundance, formation mechanism and age of dwarf haloes, and their galaxies at high and low redshifts. We use hydrodynamical simulations of galaxy formation within the ETHOS framework in a benchmark model that has such a cut-off and that has been shown to be an alternative to the cold dark matter (CDM) model that alleviates its dwarf-scale challenges. We show how galaxies in this model form differently to CDM, on a halo-by-halo basis, at redshifts z ≥ 6. We show that when CDM haloes with masses around the ETHOS half-mode mass scale are resimulated with the ETHOS matter power spectrum, they form with 50 per cent less mass than their CDM counterparts due to their later formation times, yet they retain more of their gas reservoir due to the different behaviour of gas and dark matter during the monolithic collapse of the first haloes in models with a galactic-scale cut-off. As a result, galaxies in ETHOS haloes near the cut-off scale grow rapidly between z = 10 and 6 and by z = 6 end up having very similar stellar masses, higher gas fractions and higher star formation rates relative to their CDM counterparts. We highlight these differences by making predictions for how the number of galaxies with old stellar populations is suppressed in ETHOS for both z = 6 galaxies and for gas-poor Local Group fossil galaxies. Interestingly, we find an age gradient in ETHOS between galaxies that form in high- and low-density environments.

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The dark matter halos of Draco and Ursa Minor

The Astronomical Journal ◽

10.1086/115496 ◽

1990 ◽

Vol 100 ◽

pp. 127 ◽

Cited By ~ 47

Author(s):

Carlton Pryor ◽

John Kormendy

Keyword(s):

Dark Matter ◽

Dark Matter Halos ◽

Ursa Minor

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