Chapter V

Tolstoy, Leo

doi:10.1093/owc/9780199555765.003.0007

Cited by 9 publications

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“…As Figure 1(a) shows, it is only below a circular velocity ~30 km s -1 that the number of dark matter halos definitely begins to exceed the number of observed satellites. Figure 1(b) shows that suppression of star formation in small dwarf galaxies after reionization can account for the observed satellite abundance [11] in ΛCDM, as suggested by several authors [12][13][14][15], although the extended star formation histories [16,17] show that star formation continued in these galaxies long after reionization. It remains to be seen whether better understanding of baryonic physics can explain the recent discovery [18] that all the local faint satellites have roughly the same dynamical mass m 0.3 within their central 0.3 kpc of about 10 7 M  despite having a large range of ~10 4 in luminosity.…”

Section: Subhalos and Satellitessupporting

confidence: 63%

Cosmology: Small Scale Issues

Primack¹,

Cline²

2009

AIP Conference Proceedings

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Abstract. The abundance of dark matter satellites and subhalos, the existence of density cusps at the centers of dark matter halos, and problems producing realistic disk galaxies in simulations are issues that have raised concerns about the viability of the standard cold dark matter (ΛCDM) scenario for galaxy formation. This talk reviews these issues, and considers the implications for cold vs. various varieties of warm dark matter (WDM). The current evidence appears to be consistent with standard ΛCDM, although improving data may point toward a rather tepid version of ΛWDM -tepid since the dark matter cannot be very warm without violating observational constraints. Keywords DARK MATTER IS OUR FRIENDDark matter preserved the primordial fluctuations in cosmological density on galaxy scales that were wiped out in baryonic matter by momentum transport (viscosity) as radiation decoupled from baryons in the first few hundred thousand years after the big bang. The growth of dark matter halos started early enough to result in the formation of galaxies that we see even at high redshifts z > 6. Dark matter halos provide most of the gravitation within which stable structures formed in the universe. Dark matter halos preserve these galaxies, groups, and clusters as the dark energy tears apart unbound structures and expands the space between bound structures such as the Local Group of galaxies. Thus we owe our existence and future to dark matter.Cold dark matter theory [1] including cosmic inflation has become the basis for the standard modern ΛCDM cosmology, which is favored by analysis of the available cosmic microwave background data and large scale structure data over even more complicated variant theories having additional parameters [2]. Most of the cosmological density is nonbaryonic dark matter (about 23%) and dark energy (about 72%), with baryonic matter making up only about 4.6% and the visible baryons only about 0.5% of the cosmic density. The fact that dark energy and dark matter are dominant suggests a popular name for the modern standard cosmology: the "double dark" theory, as Nancy Abrams and I suggested in our recent book about modern cosmology and its broader implications [3].The physical nature of dark matter remains to be discovered. The two most popular ideas concerning the identity of the dark matter particles remain the lightest supersymmetric partner particle [4], also called supersymmetric weakly interacting

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Section: Subhalos and Satellitessupporting

confidence: 63%

Cosmology: Small Scale Issues

Primack¹,

Cline²

2009

AIP Conference Proceedings

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“…stars throughout their evolution, although the majority of stars may be formed in several main episodes spread over ten or more billion years [47,48,49,50], and have at least some fraction of stars that formed in the first two billion years of the evolution of the universe. In terms of their SFHs, the main difference between the dwarf irregular and dwarf spheroidal galaxies is in the presence or absence of star formation in the last two billion years [49].…”

Section: Introductionmentioning

confidence: 99%

Dark Matter Substructure and Dwarf Galactic Satellites

Kravtsov

2010

Advances in Astronomy

168

175

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A decade ago cosmological simulations of increasingly higher resolution were used to demonstrate that virialized regions of Cold Dark Matter (CDM) halos are filled with a multitude of dense, gravitationally-bound clumps. These dark matter subhalos are central regions of halos that survived strong gravitational tidal forces and dynamical friction during the hierarchical sequence of merging and accretion via which the CDM halos form. Comparisons with observations revealed that there is a glaring discrepancy between abundance of subhalos and luminous satellites of the Milky Way and Andromeda as a function of their circular velocity or bound mass within a fixed aperture. This large discrepancy, which became known as the "substructure" or the "missing satellites" problem, begs for an explanation. In this paper I review the progress made during the last several years both in quantifying the problem and in exploring possible scenarios in which it could be accommodated and explained in the context of galaxy formation in the framework of the CDM paradigm of structure formation. In particular, I show that the observed luminosity function, radial distribution, and the remarkable similarity of the inner density profiles of luminous satellites can be understood within hierarchical CDM framework using a simple model in which efficiency of star formation monotonically decreases with decreasing virial mass satellites had before their accretion without any actual sharp galaxy formation threshold. 1

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“…In any case, a subset of the low-mass elliptical population shows ages that are identical to old massive galaxies (e.g. Kuntschner et al 2002;Koleva et al 2009;Mendel et al 2009;Tolstoy et al 2009).…”

Section: Acsvcs Data Samplementioning

confidence: 99%

The first gigayear of bulge star formation in Virgo ellipticals: constraints from their globular cluster systems

Spitler¹

2010

Monthly Notices of the Royal Astronomical Society

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Data products from the Advanced Camera for Surveys Virgo cluster survey are used to understand the bulge star formation history in early‐type galaxies at redshifts z≳2. A new technique is developed whereby observed high‐redshift age–metallicity relationships are utilized to constrain the typical formation epochs of metal‐rich or ‘bulge’ globular clusters. This analysis supports a model where massive Virgo galaxies underwent an extremely intense mode of bulge globular cluster formation at z∼ 3.5 that was followed by an era of significant bulge growth and little globular cluster production. Intermediate‐mass galaxies showed a less intense period of globular cluster formation at z∼ 2.5 that was synchronized with the bulk of bulge star growth. The transition between the massive and intermediate‐mass galaxy star formation modes occurs at a galaxy stellar mass of Mstellar∼ 3 × 1010 M⊙, the mass where many other galaxy properties are observed to change. Dwarf early‐type galaxies in Virgo may have experienced no significant period of bulge globular cluster formation, thus the intense starbursts associated with globular cluster formation may be difficult to directly observe at redshifts z≲ 4. Although the above conclusions are preliminary because they are based upon uncertain relationships between age and metallicity, the technique employed will yield more stringent constraints as high‐redshift galaxy observations and theoretical models improve.

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Chapter V

Abstract: The corridors of the Court were already full of activity. The attendants, out of breath, shuffling their feet along the ground, hurried backwards and forwards with all sorts of messages and papers. Ushers, advocates, and law officers passed hither and thither. Plaintiffs, and the...

Cited by 9 publications

References 0 publications

Cosmology: Small Scale Issues

Cosmology: Small Scale Issues

Dark Matter Substructure and Dwarf Galactic Satellites

The first gigayear of bulge star formation in Virgo ellipticals: constraints from their globular cluster systems

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