The distribution of dark matter at large scales and in gravitational lenses

The nature of dark matter and dark energy is one of the most important unsolved problems in cosmology. The distribution of dark matter at cosmological scales, galactic scales and subgalactic scales all reveal complementary aspects of the physics of dark matter. The broadest set of probes for dark energy are necessary to constrain the dark energy equation of state and to distinguish dark energy models. In this thesis, I review the application of counts-in-cells probability distribution functions in measuring the clustering of large-scale structures in cosmology. I examine the counts-in-cells probability distribution functions that describe dark matter halos in the Dark Energy Universe Simulations (DEUS) and describe the measurements between redshifts $z=0$ to $z=4$ on both linear and non-linear scales. The best-fits of the gravitational quasi-equilibrium distribution (GQED), the negative binomial distribution (NBD), the Poisson-Lognormal distribution (PLN), and the Poisson-Lognormal distribution with a bias parameter (PLNB) are compared to simulations. The distributions agree reasonably well over a range of redshifts and scales. To distinguish quintessence (RPCDM) and phantom ($w$CDM) dark energy from $\Lambda$ dark energy, I present a new method that compares the model parameters of the counts-in-cells probability distribution functions. I find that the mean and variance of the halo counts-in-cells on 2-25h^-1Mpc scales within a redshift range of $0.65<z<4$ show significant percentage differences for different dark energy cosmologies. On 15-25h^-1Mpc scales, the $g$ parameter in NBD, ω parameter in PLN, $b$ and C_b parameters in PLNB show larger percentage differences for different dark energy cosmologies than on smaller scales. On 2-6h^-1Mpc scales, kurtosis and the $b$ parameter in the GQED show larger percentage differences for different dark energy cosmologies than on larger scales. For cosmologies explored in the DEUS simulations, the percentage differences between these statistics for the RPCDM and $w$CDM dark energy cosmologies relative to $\Lambda$CDM generally increases with redshift from a few percent to significantly larger percentages at $z=4$. Applying our method to simulations and galaxy surveys can provide a useful way to distinguish among dark energy models and cosmologies in general. The second research study presented here concerns the flux ratio anomaly in the quadruply imaged strong gravitational lens, B1422+231, in which the contribution of 10-10³M_\odot primordial black holes (PBHs) as a potential dark matter constituent is examined. I review the theory of gravitational lensing, the current state of galaxy-galaxy lens modeling, and the causes of anomalous flux density ratios between strongly lensed image components, including dark matter substructure (DMS) millilensing and PBH microlensing. I describe the first flux density ratio measurement of B1422+231 in the millimeter wave band using the Atacama Large Millimeter Array (ALMA). We find a flux density ratio for B1422+231 at 233 GHz similar to those measured in radio and mid-infrared bands, which cannot be explained by a simple smooth mass model of the lens galaxy. I then examine the probability of the flux ratio anomaly arising from PBH microlensing using ray tracing simulations. The simulations consider the cases where 10\% and 50\% of dark matter are 10-10³M_\odot PBHs with power law mass functions. Our analysis of the ALMA observations and PBH microlensing simulations shows that the anomalous flux density ratio for B1422+231 can be explained by a lens model with a significant fraction of dark matter being PBHs. Multi-component mass models can predict the flux ratio anomaly more accurately and are reserved for future work. This study demonstrates the potential for new constraints on PBH dark matter using ALMA observations of multiply imaged strong gravitational lenses.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Astronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2021

Author dc:creator

• Wen, Di

Contributors dc:contributor

• Kemball, Athol J
• Fields, Brian D
• Shen, Yue
• Liu, Xin

• cosmology
• dark matter
• dark energy
• counts-in-cells
• large-scale structure
• gravitational lensing
• primordial black hole
• flux ratio anomaly

Statement dc:rights

• Copyright 2020 Di Wen

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/109630

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/109630