Arya Farahi

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

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 haloes 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 haloes 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 haloes.

A model for multiproperty galaxy cluster statistics

The massive dark matter halos that host groups and clusters of galaxies have observable properties that appear to be log-normally distributed about power-law mean scaling relations in halo mass. Coupling this assumption with either quadratic or cubic approximations to the mass function in log space, we derive closed-form expressions for the space density of halos as a function of multiple observables as well as forms for the low-order moments of properties of observable-selected samples. Using a Tinker mass function in a CDM cosmology, we show that the cubic analytic model reproduces results obtained from direct, numerical convolution at the 10% level or better over nearly the full range of observables covered by current observations and for redshifts extending to z = 1:5. The model provides an ecient framework for estimating eects arising from selection and covariance among observable properties in survey samples.

Galaxy cluster mass estimation from stacked spectroscopic analysis

We use simulated galaxy surveys to study: i) how galaxy membership in redMaPPer clusters maps to the underlying halo population, and ii) the accuracy of a mean dynamical cluster mass,

Gravitational collapse, chaos in CFT correlators and the information paradox

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Excursion set theory for correlated random walks

, derived from stacked pairwise spectroscopy of clusters with richness

A Data Science Approach to Understanding Residential Water Contamination in Flint

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Modelling projection effects in optically selected cluster catalogues

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Localized massive halo properties in bahamas and MACSIS simulations: scalings, lognormality, and covariance

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Holographic p-wave superconductor with disorder

galaxy pairs patterned after the SDSS redMaPPer cluster sample study of Rozo et al. (2015 RMIV), we show that the pairwise velocity PDF of central--satellite pairs with

Flint Water Crisis: Data-Driven Risk Assessment Via Residential Water Testing.

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