arXiv subjects

Tyann Dumerchat

Publications and source records attributed to Tyann Dumerchat.

5 recordsLinked to original sources

arXiv2026

Correlated residuals in Tully-Fisher and Fundamental Plane relations and their impact on peculiar velocity measurements

The Tully-Fisher (TF) and Fundamental Plane (FP) relations are widely used to infer extragalactic distances and peculiar velocities, enabling measurements of large-scale velocity statistics and cosmological parameters. Using the Millennium-TNG hydrodynamical simulation, we assess the accuracy of these methods in the presence of realistic galaxy formation physics. We find that, while the 2-point statistics of velocities are reliably inferred on scales larger than $\sim10\,\hMpc$, significant systematic deviations arise on smaller scales. These deviations originate from spatially correlated residuals in the TF and FP relations, driven by correlations between galaxy structural properties, star-formation history, and the local environment. As a result, TF- and FP-inferred velocity fields exhibit spurious correlations with the galaxy density field that cannot be explained by random scatter alone. We show that extending the TF and FP relations to include additional galaxy properties -- such as star formation rate, gas mass, and stellar mass -- mitigate these environmental correlations, particularly for late-type galaxies. Our results demonstrate that galaxy formation physics induces significant systematics in peculiar velocity measurements on non-linear scales, and that neglecting these effects may bias cosmological analyses.

astro-ph.CO↗

arXiv2024

The ACCEL$^2$ project: simulating Lyman-$\alpha$ forest in large-volume hydrodynamical simulations

Cosmological information is usually extracted from the Lyman-$\alpha$ forest correlations using only either large-scale information interpreted through linear theory or using small-scale information interpreted by means of expensive hydrodynamical simulations. A complete cosmological interpretation of the 3D correlations at all measurable scales is challenged by the need of more realistic models including the complex growth of non-linear small scales that can only be studied within large hydrodynamical simulations. Past work were often limited by the trade off between the simulated cosmological volume and the resolution of the low-density intergalactic medium from which the Lyman-$\alpha$ signal originates. We conduct a suite of hydrodynamical simulations of the intergalactic medium, including one of the largest Lyman-$\alpha$ simulations ever performed in terms of volume (640 $h^{-1}\mathrm{Mpc}$), alongside simulations in smaller volumes with resolutions up to 25 $h^{-1}\mathrm{kpc}$, which will be further improved to show resolution convergence in future studies. We compare the 3D Lyman-$\alpha$ power spectra predicted by those simulations to different non-linear models. The inferred Lyman-$\alpha$ bias and redshift space distortion (RSD) parameters, $b_\alpha$ and $\beta_\alpha$ are in remarkable agreement with those measured in SDSS and DESI data. We find that, contrary to intuition, the convergence of large-scale modes of the 3D Lyman-$\alpha$ power spectra, which determines $\beta_\alpha$, is primarily influenced by the resolution of the simulation box through mode coupling, rather than the box size itself. Finally, we study the BAO signal encoded in the 3D Lyman-$\alpha$ power spectra. For the first time with a hydrodynamical simulation, we clearly detect the BAO signal, however we only marginally detect its damping, associated with the non-linear growth of the structures.

astro-ph.CO↗

arXiv2023

Galaxy clustering multi-scale emulation

Simulation based inference has seen increasing interest in the past few years as a promising approach to model the non linear scales of galaxy clustering. The common approach using Gaussian process is to train an emulator over the cosmological and galaxy-halo connection parameters independently for every scales. We present a new Gaussian process model allowing to extend the input parameter space dimensions and to use non-diagonal noise covariance matrix. We use our new framework to emulate simultaneously every scales of the non-linear clustering of galaxies in redshift space from the AbacusSummit N-body simulations at redshift $z=0.2$. The model includes nine cosmological parameters, five halo occupation distribution (HOD) parameters and one scale dimension. Accounting for the limited resolution of the simulations, we train our emulator on scales from $0.3~h^{-1}\mathrm{Mpc}$ to $60~h^{-1}\mathrm{Mpc}$ and compare its performance with the standard approach of building one independent emulator for each scales. The new model yields more accurate and precise constraints on cosmological parameters compared to the standard approach. As the new model is able to interpolate over the scales space, we are also able to account for the Alcock-Paczynski distortion effect leading more accurate constraints on the cosmological parameters.

astro-ph.CO↗

arXiv2022

Baryon acoustic oscillations from a joint analysis of the large-scale clustering in Fourier and configuration space

Baryon acoustic oscillations (BAOs) are a powerful probe of the expansion history of our Universe and are typically measured in the two-point statistics of a galaxy survey, either in Fourier space or in configuration space. In this work, we report a first measurement of BAOs from a joint fit of power spectrum and correlation function multipoles. We tested our new framework with a set of 1000 mock catalogs and showed that our method yields smaller biases on BAO parameters than individually fitting power spectra or correlation functions, or when combining them with the Gaussian approximation method. Our estimated uncertainties are slightly larger than those from the Gaussian approximation, likely due to noise in our sample covariance matrix, the larger number of nuisance parameters, or the fact that our new framework does not rely on the assumption of Gaussian likelihoods for the BAO parameters. However, we argue that our uncertainties are more reliable since they rely on fewer assumptions, and because our method takes correlations between Fourier and configuration space at the level of the two-point statistics. We performed a joint analysis of the luminous red galaxy sample of the extended baryon oscillation spectroscopic survey (eBOSS) data release 16, obtaining $D_H/r_d = 19.27 \pm 0.48$ and $D_M/r_d = 17.77 \pm 0.37$, in excellent agreement with the official eBOSS consensus BAO-only results $D_H/r_d = 19.33 \pm 0.53$ and $D_M/r_d =17.86 \pm 0.33$.

astro-ph.CO↗

arXiv2021

Analysis of birefringence and dispersion effects from spacetime-symmetry breaking in gravitational waves

In this work, we review the effective field theory framework to search for Lorentz and CPT symmetry breaking during the propagation of gravitational waves. The article is written so as to bridge the gap between the theory of spacetime-symmetry breaking and the analysis of gravitational-waves signals detected by ground-based interferometers. The primary physical effects beyond General Relativity that we explore here are dispersion and birefringence of gravitational waves. We discuss their implementation in the open-source LIGO-Virgo algorithm library suite, as well as the statistical method used to perform a Bayesian inference of the posterior probability of the coefficients for symmetry-breaking. We present preliminary results of this work in the form of simulations of modified gravitational waveforms, together with sensitivity studies of the measurements of the coefficients for Lorentz and CPT violation. The findings show the high potential of gravitational wave sources across the sky to probe sensitively for these signals of new physics.

gr-qc↗