arXiv subjects

M. Chodorowski

Publications and source records attributed to M. Chodorowski.

4 recordsLinked to original sources

arXiv2022

Cross-correlation between $Planck$ CMB lensing potential and galaxy catalogues from HELP

We present the study of cross-correlation between Cosmic Microwave Background (CMB) gravitational lensing potential map released by the \textit{Planck} collaboration and photometric redshift galaxy catalogues from the \textit{Herschel} Extragalactic Legacy Project (HELP), divided into four sky patches: NGP, \textit{Herschel} Stripe-82, and two halves of SGP field, covering in total $\sim 660$ deg$^{2}$ of the sky. We estimate the galaxy linear bias parameter, $b_{0}$, from joint analysis of cross-power spectrum and galaxy auto-power spectrum using Maximum Likelihood Estimation technique to obtain values ranging from $0.70 \pm 0.01$ for SGP Part-2 to $1.02 \pm 0.02$ for SGP Part-1 field. We also estimate the amplitude of cross-correlation and find the values spanning from $0.67 \pm 0.18$ for SGP Part-2 to $0.80 \pm 0.23$ for SGP Part-1 field, respectively. For NGP and SGP Part-1 fields the amplitude is consistent with the expected value for the standard cosmological model within $\sim 1\,σ$, while for \textit{Herschel} Stripe-82 and SGP Part-2 we find the amplitude to be smaller than expected with $\sim 1.5\,σ$ and $\sim 2\,σ$ deviation, respectively. We perform several tests on various systematic errors to study the reason for the deviation, however, value of the amplitude turns out to be robust with respect to these errors. The only significant change in the amplitude is observed when we replace the minimum-variance CMB lensing map, used in the baseline analysis, by the lensing map derived from the CMB temperature map with deprojected thermal Sunyaev-Zeldovich signal.

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arXiv2004

Likelihood analysis of the Local Group acceleration revisited

We reexamine likelihood analyzes of the Local Group (LG) acceleration, paying particular attention to nonlinear effects. Under the approximation that the joint distribution of the LG acceleration and velocity is Gaussian, two quantities describing nonlinear effects enter these analyzes. The first one is the coherence function, i.e. the cross-correlation coefficient of the Fourier modes of gravity and velocity fields. The second one is the ratio of velocity power spectrum to gravity power spectrum. To date, in all analyzes of the LG acceleration the second quantity was not accounted for. Extending our previous work, we study both the coherence function and the ratio of the power spectra. With the aid of numerical simulations we obtain expressions for the two as functions of wavevector and σ_8. Adopting WMAP's best determination of σ_8, we estimate the most likely value of the parameter βand its errors. As the observed values of the LG velocity and gravity, we adopt respectively a CMB-based estimate of the LG velocity, and Schmoldt et al.'s (1999) estimate of the LG acceleration from the PSCz catalog. We obtain β= 0.66^{+0.21}_{-0.07}; thus our errorbars are significantly smaller than those of Schmoldt et al. This is not surprising, because the coherence function they used greatly overestimates actual decoherence between nonlinear gravity and velocity.

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arXiv2001

Local Group Velocity Versus Gravity: Nonlinear Effects

We use numerical simulations to study the relation between the velocity of the Local Group and its gravitational acceleration. This relation serves as a test for the kinematic origin of the CMB dipole and as a method for estimating beta. We calculate the misalignment angle between the two vectors and compare it to the observed value for the PSCz survey. The latter value is near the upper limit of the 95% confidence interval for the angle; therefore, the nonlinear effects are unlikely to be responsible for the whole observed misalignment. We also study the relation between the amplitudes of the LG velocity and gravity vectors. In an Omega=1 Universe, the smoothed gravity of the LG turns out to be a biased low estimator of the LG (unsmoothed) velocity. In an Omega=0.3 Universe, the estimator is biased high. The discussed biases are, however, only a few per cent, thus the linear theory works to good accuracy. The gravity-based estimator of the LG velocity has also a scatter that limits the precision of the estimate of beta in the LG velocity-gravity comparisons. The random error of beta due to nonlinear effects amounts to several per cent.

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arXiv1993

Weakly Non-Linear Gaussian Fluctuations and the Edgeworth Expansion

We calculate the cosmological evolution of the 1-point probability distribution function (PDF), using an analytic approximation that combines gravitational perturbation theory with the Edgeworth expansion of the PDF. Our method applies directly to a smoothed mass density field or to the divergence of a smoothed peculiar velocity field, provided that rms fluctuations are small compared to unity on the smoothing scale, and that the primordial fluctuations that seed the growth of structure are Gaussian. We use this `Edgeworth approximation' to compute the evolution of $<δ|δ|>$ and $<|delta|>$; these measures are similar to the skewness and kurtosis of the density field, but they are less sensitive to tails of the probability distribution, so they may be more accurately estimated from surveys of limited volume. We compare our analytic calculations to cosmological N-body simulations in order to assess their range of validity. When $σ\ll 1$, the numerical simulations and perturbation theory agree precisely, demonstrating that the N-body method can yield accurate results in the regime of weakly non-linear clustering. We show analytically that `biased' galaxy formation preserves the relation $<δ^3> \propto <δ^2>^2$ predicted by second-order perturbation theory, provided that the galaxy density is a local function of the underlying mass density.

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