Evolution of Dark Matter Phase-Space Density Distributions in Equal-Mass Halo Mergers

Vass, Ileana M.; Kazanzidis, Stelios; Valluri, Monica; Kravtsov, Andrey V.

doi:10.1088/0004-637x/698/2/1813

Cited by 9 publications

(7 citation statements)

References 40 publications

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“…The final remnants have been coloured by the relative energy parameter, κ. At small radii, the changes in the profile compared to the scaled ICs are subtle, and the inner slope is roughly conserved, in agreement with previous studies (Boylan-Kolchin & Ma 2004;Aceves & Velázquez 2006;Kazantzidis et al 2006;Zemp et al 2008;Vass et al 2009). At large radii, the changes in the density profile are more obvious, as mass has moved outwards, relative to the scaled ICs.…”

Section: General Resultssupporting

confidence: 91%

“…Previous studies of isolated major mergers have found that about 20-50 per cent of the mass lies outside the virial radius (e.g. Kazantzidis et al 2006;Valluri et al 2007;Vass et al 2009). Our results are consistent with these previous ones, but we have tested a much larger range of orbital parameters, including unrealistically low-energy mergers in which the virial mass increases more than expected from selfsimilar evolution.…”

Section: Discussionmentioning

confidence: 99%

“…Isolated major mergers between otherwise undisturbed systems are rare in a cosmological context, and thus the effects of major mergers are best studied through controlled simulations of isolated systems (e.g. Boylan-Kolchin & Ma 2004;Aceves & Velázquez 2006;Kazantzidis et al 2006;McMillan et al 2007;Zemp et al 2008;Vass et al 2009;Ogiya et al 2016;Drakos et al 2018). Most authors find that haloes are robust to major mergers; in particular, it appears that the slope of the steepest density profile is preserved (Boylan-Kolchin & Ma 2004;Aceves & Velázquez 2006;Kazantzidis et al 2006;Zemp et al 2008;Vass et al 2009), and there is also some suggestion that concentration does not change (Kazantzidis et al 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Boylan-Kolchin & Ma 2004;Aceves & Velázquez 2006;Kazantzidis et al 2006;McMillan et al 2007;Zemp et al 2008;Vass et al 2009;Ogiya et al 2016;Drakos et al 2018). Most authors find that haloes are robust to major mergers; in particular, it appears that the slope of the steepest density profile is preserved (Boylan-Kolchin & Ma 2004;Aceves & Velázquez 2006;Kazantzidis et al 2006;Zemp et al 2008;Vass et al 2009), and there is also some suggestion that concentration does not change (Kazantzidis et al 2006). However, the simulations of Moore et al (2004) suggest that concentration can decrease in major mergers, provided the initial encounter has sufficient angular momentum.…”

Section: Introductionmentioning

confidence: 99%

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Major mergers between dark matter haloes – II. Profile and concentration changes

Drakos

Taylor

Berrouet

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Several lines of evidence suggest that as dark matter haloes grow their scale radius increases, and that the density in their central region drops. Major mergers seem an obvious mechanism to explain both these phenomena, and the resulting patterns in the concentration-mass-redshift relation. To test this possibility, we have simulated equal-mass mergers between haloes with a variety of cosmological density profiles, placed on various different orbits. The remnants typically have higher densities than the initial conditions, but differ only slightly from self-similar scaling predictions. They are reasonably well fit by Einasto profiles, but have parameters distinct from those of the initial conditions. The net internal energy available to the merger remnant, relative to the internal energy of the initial conditions, κ, has the greatest influence on the properties of the final mass distribution. As expected, energetic encounters produce more extended remnants while mergers of strongly bound systems produce compact remnants. Surprisingly, however, the scale radius of the density profile shows the opposite trend, increasing in the remnants of low-energy encounters relative to energetic ones. Also even in the most energetic encounters, the density within the scale radius decreases only slightly (by 10-20%), while for very low-energy systems it increases significantly after the merger. We conclude that while major mergers can produce remnants that are more diffuse at large radii, they are relatively ineffective at changing the central densities of haloes, and seem unlikely to explain the mean trends in the concentration-mass-redshift relation.

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Section: General Resultssupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Major mergers between dark matter haloes – II. Profile and concentration changes

Drakos

Taylor

Berrouet

et al. 2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…We assume that the build-up of the galaxy occurs via a series of small, minor mergers (Bezanson et al 2009;Cook et al 2009;Naab et al 2009), not allowing for equal-mass mergers, which more violently disrupt the system. Indeed, it has been shown in dissipationless N-body simulations that equal-mass merger remnants will retain the profile of the steepest progenitor Dehnen 2005;Kazantzidis et al 2006;Vass et al 2009). Therefore, cuspy dark matter profiles are robust under major mergers.…”

Section: Discussionmentioning

confidence: 99%

Dissipational Versus Dissipationless Galaxy Formation and the Dark Matter Content of Galaxies

Lackner

Ostriker

2010

ApJ

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We examine two extreme models for the build-up of the stellar component of luminous elliptical galaxies. In one case, we assume the build-up of stars is dissipational, with centrally accreted gas radiating away its orbital and thermal energy; the dark matter halo will undergo adiabatic contraction and the central dark matter density profile will steepen. For the second model, we assume the central galaxy is assembled by a series of dissipationless mergers of stellar clumps that have formed far from the nascent galaxy. In order to be accreted, these clumps lose their orbital energy to the dark matter halo via dynamical friction, thereby heating the central dark matter and smoothing the dark matter density cusp. The central dark matter density profiles differ drastically between these models. For the isolated elliptical galaxy, NGC 4494, the central dark matter densities follow the power-laws r −0.2 and r −1.7 for the dissipational and dissipationless models, respectively. By matching the dissipational and dissipationless models to observations of the stellar component of elliptical galaxies, we examine the relative contributions of dissipational and dissipationless mergers to the formation of elliptical galaxies and look for observational tests that will distinguish between these models. Comparisons to strong lensing brightest cluster galaxies yield median (M * /L) B ratios of 2.1 ± 0.8 and 5.2 ± 1.7 at z ≈ 0.39 for the dissipational and dissipationless models, respectively. For NGC 4494, the best-fit dissipational and dissipationless models have (M * /L) B = 2.97 and 3.96. Comparisons to expected stellar mass-to-light ratios from passive evolution and population syntheses appear to rule out a purely dissipational formation mechanism for the central stellar regions of giant elliptical galaxies.

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Non-power law behavior of the radial profile of phase-space density of halos

Popolo

2011

J. Cosmol. Astropart. Phys.

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Abstract. We study the pseudo phase-space density, ρ(r)/σ 3 (r), of ΛCDM dark matter halos with and without baryons (baryons+DM, and pure DM), by using the model introduced in Del Popolo (2009), which takes into account the effect of dynamical friction, ordered and random angular momentum, baryons adiabatic contraction and dark matter baryons interplay. We examine the radial dependence of ρ(r)/σ 3 (r) over 9 orders of magnitude in radius for structures on galactic and cluster of galaxies scales. We find that ρ(r)/σ 3 (r) is approximately a power-law only in the range of halo radius resolved by current simulations (down to 0.1% of the virial radius) while it has a non-power law behavior below the quoted scale, with inner profiles changing with mass. The non-power-law behavior is more evident for halos constituted both of dark matter and baryons while halos constituted just of dark matter and with angular momentum chosen to reproduce a Navarro-Frenk-White (NFW) density profile, are characterized by an approximately power-law behavior. The results of the present paper lead to conclude that density profiles of the NFW type are compatible with a power-law behavior of ρ(r)/σ 3 (r), while those flattening to the halo center, like those found in Del Popolo (2009) or the Einasto profile, or the Burkert profile, cannot produce radial profile of the pseudo-phase-space density that are power-laws at all radii. The results argue against universality of the pseudo phase-space density and as a consequence argue against universality of density profiles constituted by dark matter and baryons as also discussed in Del Popolo (2009).

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Evolution of Dark Matter Phase-Space Density Distributions in Equal-Mass Halo Mergers

Cited by 9 publications

References 40 publications

Major mergers between dark matter haloes – II. Profile and concentration changes

Major mergers between dark matter haloes – II. Profile and concentration changes

Dissipational Versus Dissipationless Galaxy Formation and the Dark Matter Content of Galaxies

Non-power law behavior of the radial profile of phase-space density of halos

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