Dark matter concentrations and a search for cores in Milky Way dwarf satellites

Wolf, Joe; Bullock, James S.

doi:10.48550/arxiv.1203.4240

Cited by 8 publications

(9 citation statements)

References 47 publications

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“…Subsequent numerical results find haloes with steep inner density slopes and NFW or Einasto profiles (Dekel, Devor, & Hetzroni 2003a;Dekel et al 2003b;Reed et al 2005;Diemand et al 2008;Springel et al 2008;Navarro et al 2010). In contrast, observations have repeatedly found constant density 'cores,' where α ∼ 0 (de Blok et al 2001;de Blok & Bosma 2002;Swaters et al 2003;Strigari et al 2006;Walker et al 2009;Strigari, Frenk, & White 2010;Oh et al 2011;Walker & Peñarrubia 2011;Hayashi & Chiba 2012;Wolf & Bullock 2012).…”

Section: Introductionmentioning

confidence: 97%

Effects of baryon removal on the structure of dwarf spheroidal galaxies

Arraki¹,

Klypin²,

More³

et al. 2013

Monthly Notices of the Royal Astronomical Society

104

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Dwarf spheroidal galaxies (dSphs) are extremely gas-poor, dark matter-dominated galaxies, which make them ideal to test the predictions of the cold dark matter (CDM) model. We argue that the removal of the baryonic component from gas-rich dwarf irregular galaxies, the progenitors of dSphs, can substantially reduce their central density. Thus, it may play an important role in alleviating one of the problems of the CDM model related to the structure of relatively massive satellite galaxies of the Milky Way (MW). Traditionally, collisionless cosmological N-body simulations are used when confronting theoretical predictions with observations. However, these simulations assume that the baryon fraction everywhere in the Universe is equal to the cosmic mean, an assumption which is incorrect for dSphs. We find that the combination of (i) the lower baryon fraction in dSphs compared to the cosmic mean and (ii) the concentration of baryons in the inner part of the MW halo can go a long way towards explaining the observed circular velocity profiles of dSphs. We perform controlled numerical simulations that mimic the effects of baryons. From these we find that the blowing away of baryons by ram pressure, when the dwarfs fall into larger galaxies, decreases the circular velocity profile of the satellite and reduces the density in the central ∼200-500 pc by a factor of (1 − f b ) 4 ≈ 0.5, where f b is the cosmological fraction of baryons. Additionally, the enhanced baryonic mass in the central regions of the parent galaxy generates tidal forces, which are larger than those experienced by subhaloes in traditional N-body simulations. Increased tidal forces substantially alter circular velocity profiles for satellites with pericentres less than 50 kpc. We show that these two effects are strong enough to bring the predictions of subhaloes from CDM simulations into agreement with the observed structure of MW dSphs, regardless of the details of the baryonic processes.

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Section: Introductionmentioning

confidence: 97%

Effects of baryon removal on the structure of dwarf spheroidal galaxies

Arraki¹,

Klypin²,

More³

et al. 2013

Monthly Notices of the Royal Astronomical Society

104

View full text Add to dashboard Cite

show abstract

“…Determining precise and robust mass profiles is challenging, particularly if the goal is to separate the dark and baryonic components. Low surface brightness and dwarf spheroidal galaxies are often considered ideal targets for DM studies, since the mass fraction of baryons is minimal, and observations indicate that many of these galaxies have a DM core rather than the expected cusp (e.g., Simon et al 2005;de Blok et al 2008;Wolf & Bullock 2012). Due to their shallow potential wells, however, these are fragile systems and may be disrupted by supernovae (see references above).…”

Section: Introductionmentioning

confidence: 99%

The Density Profiles of Massive, Relaxed Galaxy Clusters. I. The Total Density Over Three Decades in Radius

Newman

Treu

Ellis

et al. 2013

ApJ

282

407

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Clusters of galaxies are excellent locations to probe the distribution of baryons and dark matter (DM) over a wide range of scales. We study a sample of seven massive (M 200 = 0.4 − 2 × 10 15 M ), relaxed galaxy clusters with centrally-located brightest cluster galaxies (BCGs) at z = 0.2 − 0.3. Using the observational tools of strong and weak gravitational lensing, combined with resolved stellar kinematics within the BCG, we measure the total radial density profile, comprising both dark and baryonic matter, over scales of 3−3000 kpc. We present Keck spectroscopy yielding seven new spectroscopic redshifts of multiply imaged sources and extended stellar velocity dispersion profiles of the BCGs. Lensingderived mass profiles typically agree with independent X-ray estimates within 15%, suggesting that departures from hydrostatic equilibrium are small and that the clusters in our sample (except A383) are not strongly elongated or compressed along the line of sight. The inner logarithmic slope γ tot of the total density profile measured over r/r 200 = 0.003 − 0.03, where ρ tot ∝ r −γtot , is found to be nearly universal, with a mean γ tot = 1.16 ± 0.05 (random) +0.05 −0.07 (systematic) and an intrinsic scatter σ γ < 0.13 (68% confidence). This is further supported by the very homogeneous shape of the observed velocity dispersion profiles, which are mutually consistent after a simple scaling. Remarkably, this slope agrees closely with high-resolution numerical simulations that contain only DM, despite the significant contribution of stellar mass on the scales we probe. The Navarro-Frenk-White profile characteristic of collisionless cold DM is a better description of the total mass density at radii 5 − 10 kpc than that of DM alone. Hydrodynamical simulations that include baryons, cooling, and feedback currently provide a poorer match. We discuss the significance of our findings for understanding the physical processes governing the assembly of BCGs and cluster cores, particularly the influence of baryons on the inner DM halo.

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“…The cold dark matter (CDM) paradigm (Blumenthal et al 1984) works extremely well on large scales (Seljak et al 2005;Percival et al 2007;Ferramacho et al 2009;Sánchez et al 2009;Komatsu et al 2011), but there remains the possibility of deviations from the CDM expectations on small scalesarising notably from the issue of cores vs. cusps and the inner slope of dark matter density profiles (Salucci 2001;Donato et al 2004;Newman et al 2009;Donato et al 2009 Newman et al 2011;Salucci et al 2012;Wolf & Bullock 2012) and the apparent paucity of bright satellites around the Milky Way (Boylan-Kolchin et al 2011, 2012. Several extensions to dark matter phenomenology E-mail: abenson@obs.carnegiescience.edu (Markevitch et al 2004;Boehm & Schaeffer 2005;Ahn & Shapiro 2005;Miranda & Macciò 2007;Randall et al 2008;Boyarsky et al 2009;Lovell et al 2012) and several different particle physics candidates for dark matter (Raffelt 1990;Turner 1990;Jungman et al 1996;Hogan & Dalcanton 2000;Spergel & Steinhardt 2000;Abazajian et al 2001;Cheng et al 2002;Feng et al 2003;Sigurdson & Kamionkowski 2004;Hubisz & Meade 2005;Feng et al 2009) have been put forward to explain these deviations, although it remains unclear if any of these proposals is able to fully explain observed phenomena (Kuzio de Naray et al 2010) or if they are even necessary, with the observed phenomena simpl...…”

Section: Introductionmentioning

confidence: 99%

Dark matter halo merger histories beyond cold dark matter – I. Methods and application to warm dark matter

Benson

Farahi

Cole

et al. 2012

Monthly Notices of the Royal Astronomical Society

181

239

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We describe a methodology to accurately compute halo mass functions, progenitor mass functions, merger rates and merger trees in non-cold dark matter universes using a self-consistent treatment of the generalized extended Press-Schechter formalism. Our approach permits rapid exploration of the subhalo population of galactic halos in dark matter models with a variety of different particle properties or universes with rolling, truncated, or more complicated power spectra. We make detailed comparisons of analytically derived mass functions and merger histories with recent warm dark matter cosmological N-body simulations, and find excellent agreement. We show that, once the accretion of smoothly distributed matter is accounted for, coarse-grained statistics such as the mass accretion history of halos can be almost indistinguishable between cold and warm dark matter cases. However, the halo mass function and progenitor mass functions differ significantly, with the warm dark matter cases being strongly suppressed below the free-streaming scale of the dark matter. We demonstrate the importance of using the correct solution for the excursion set barrier first-crossing distribution in warm dark matter-if the solution for a flat barrier is used instead the truncation of the halo mass function is much slower, leading to an overestimate of the number of low mass halos.

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Dark matter concentrations and a search for cores in Milky Way dwarf satellites

Cited by 8 publications

References 47 publications

Effects of baryon removal on the structure of dwarf spheroidal galaxies

Effects of baryon removal on the structure of dwarf spheroidal galaxies

The Density Profiles of Massive, Relaxed Galaxy Clusters. I. The Total Density Over Three Decades in Radius

Dark matter halo merger histories beyond cold dark matter – I. Methods and application to warm dark matter

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