arXiv subjects

Vitali Halenka

Publications and source records attributed to Vitali Halenka.

6 recordsLinked to original sources

arXiv2024

Escape Velocity Mass of Abell S1063

We measure the radius-velocity phase-space edge profile for Abell S1063 using galaxy redshifts from arXiv:1409.3507 and arXiv:2109.03305. Combined with a cosmological model and after accounting for interlopers and sampling effects, we infer the escape velocity profile. Using the Poisson equation, we then directly constrain the gravitational potential profile and find excellent agreement between three different density models. For the NFW profile, we find log$_{10}$(M$_{200},{\rm crit}$)= $15.40^{+0.06}_{-0.12}$M$_{\odot}$, consistent to within $1σ$ of six recently published lensing masses. We argue that this consistency is due to the fact that the escape technique shares no common systematics with lensing other than radial binning. These masses are 2-4$σ$ lower than estimates using X-ray data, in addition to earlier velocity dispersion estimates. We measure the 1D velocity dispersion within r$_{200}$ to be $σ_{v} = 1477^{+87}_{-99}$ km/s, which combined with our escape velocity mass, brings the dispersion for AS1063 in-line with hydrodynamic cosmological simulations for the first time.

astro-ph.CO↗

arXiv2022

Quantifying the Projected Suppression of Cluster Escape Velocity Profiles

The 3D radial escape-velocity profile of galaxy clusters has been suggested to be a promising and competitive tool for constraining mass profiles and cosmological parameters in an accelerating universe. However, the observed line-of-sight escape profile is known to be suppressed compared to the underlying 3D radial (or tangential) escape profile. Past work has suggested that velocity anisotropy in the phase-space data is the root cause. Instead, we find that the observed suppression is from the statistical undersampling of the phase spaces and that the 3D radial escape edge can be accurately inferred from projected data. We build an analytical model for this suppression that only requires the number of observed galaxies $N$ in the phase-space data within the sky-projected range $0.3 \le r_\perp/R_{200, \text{critical}} \le 1$. The radially averaged suppression function is an inverse power law $\langle Z_\text{v} \rangle = 1 + (N_0/N)^λ$ with $N_0 = 17.818$ and $λ= 0.362$. We test our model with $N$-body simulations, using dark matter particles, subhalos, and semianalytic galaxies as the phase-space tracers, and find excellent agreement. We also assess the model for systematic biases from cosmology ($Ω_Λ$, $H_0$), cluster mass ($M_{200, \text{critical}}$), and velocity anisotropy ($β$). We find that varying these parameters over large ranges can impart a maximal additional fractional change in $\langle Z_\text{v} \rangle$ of $2.7\%$. These systematics are highly subdominant (by at least a factor of 13.7) to the suppression from $N$.

astro-ph.CO↗

arXiv2021

Testing the theory of gravity with DESI: estimators, predictions and simulation requirements

Shortly after its discovery, General Relativity (GR) was applied to predict the behavior of our Universe on the largest scales, and later became the foundation of modern cosmology. Its validity has been verified on a range of scales and environments from the Solar system to merging black holes. However, experimental confirmations of GR on cosmological scales have so far lacked the accuracy one would hope for -- its applications on those scales being largely based on extrapolation and its validity sometimes questioned in the shadow of the unexpected cosmic acceleration. Future astronomical instruments surveying the distribution and evolution of galaxies over substantial portions of the observable Universe, such as the Dark Energy Spectroscopic Instrument (DESI), will be able to measure the fingerprints of gravity and their statistical power will allow strong constraints on alternatives to GR. In this paper, based on a set of $N$-body simulations and mock galaxy catalogs, we study the predictions of a number of traditional and novel estimators beyond linear redshift distortions in two well-studied modified gravity models, chameleon $f(R)$ gravity and a braneworld model, and the potential of testing these deviations from GR using DESI. These estimators employ a wide array of statistical properties of the galaxy and the underlying dark matter field, including two-point and higher-order statistics, environmental dependence, redshift space distortions and weak lensing. We find that they hold promising power for testing GR to unprecedented precision. The major future challenge is to make realistic, simulation-based mock galaxy catalogs for both GR and alternative models to fully exploit the statistic power of the DESI survey and to better understand the impact of key systematic effects. Using these, we identify future simulation and analysis needs for gravity tests using DESI.

astro-ph.CO↗

arXiv2021

Emergent gravity fails to explain color-dependent galaxy-galaxy lensing signals from SDSS Dr7

We test the Emergent Gravity(EG) theory using the galaxy-galaxy lensing technique based on SDSS DR7 data. In the EG scenario, we do not expect color dependence of the galaxy sample in the 'apparent dark matter' predicted by EG, which is exerted only by the baryonic mass. If the baryonic mass is similar, then the predicted lensing profiles from the baryonic mass should be similar according to the EG, regardless of the color of the galaxy sample. We use the stellar mass of the galaxy as a proxy of its baryonic mass. We divide our galaxy sample into 5 stellar mass bins, and further classify them as red and blue subsamples in each stellar mass bin. If we set halo mass and concentration as free parameters, $Λ$CDM is favored by our data in terms of the reduced $χ^2$ while EG fails to explain the color dependence of ESDs from the galaxy-galaxy lensing measurement.

astro-ph.GA↗

arXiv2020

Testing emergent gravity with mass densities of galaxy clusters

We use a sample of 23 galaxy clusters to test the predictions of emergent gravity (EG) as alternative to dark matter. Our sample has both weak-lensing inferred total mass profiles as well as x-ray inferred baryonic gas mass profiles. Using nominal assumptions about the weak-lensing and x-ray mass profiles, we find that the EG predictions (based on no dark matter) are acceptable fits only near the virial radius. In the cores and in the outskirts, the mass profile shape differences allow us to confirm previous results that the EG model can be ruled out at $>5σ$. However, when we account for systematic uncertainties in the observed weak-lensing and x-ray profiles, we find good agreement for the EG predictions. For instance, if the weak-lensing total mass profiles are shallow in the core and the x-ray gas density profiles are steep in the outskirts, EG can predict the observed dark matter profile in $0.3 \le r \le 1$R$_{200}$, where R$_{200}$ is the radius which encloses 200$\times$ the critical density of the Universe. The required x-ray and lensing shapes are within the current observational systematics-limited errors on cluster profiles. We also show that EG itself allows flexibility in its predictions, which can allow for good agreement between the observations and the predictions. We conclude that we cannot formally rule our EG as an alternative to dark matter on the cluster scale and that we require better constraints on the weak-lensing and gas mass profile shapes in the region $0.3 \le r \le 1$R$_{200}$.

astro-ph.CO↗

arXiv2019

Deriving galaxy cluster velocity anisotropy profiles from a joint analysis of dynamical and weak lensing data

We present an analytic approach to lift the mass-anisotropy degeneracy in clusters of galaxies by utilizing the line-of-sight velocity dispersion of clustered galaxies jointly with weak lensing inferred masses. More specifically, we solve the spherical Jeans equation by assuming a simple relation between the line-of-sight velocity dispersion and the radial velocity dispersion and recast the Jeans equation as a Bernoulli differential equation that has a well-known analytic solution. We first test our method in cosmological N-body simulations and then derive the anisotropy profiles for 35 archival data galaxy clusters with an average redshift of $\langle {z}_{c}\rangle =0.25$. The resulting profiles yield a weighted average global value of $\langle β(0.2\leqslant R/{R}_{200}\leqslant 1)\rangle =0.35\pm 0.28$ (stat) \pm 0.15 (sys). This indicates that clustered galaxies tend to globally fall on radially anisotropic orbits. We note that this is the first attempt to derive velocity anisotropy profiles for a cluster sample of this size utilizing joint dynamical and weak lensing data

astro-ph.CO↗