scholarly journals The impact of modified gravity on the Sunyaev-Zel’dovich effect

2020 ◽  
Author(s):  
Myles A Mitchell ◽  
Christian Arnold ◽  
César Hernández-Aguayo ◽  
Baojiu Li
Keyword(s):  
Galaxy Formation ◽  
Modified Gravity ◽  
Power Spectra ◽  
Substantial Effect ◽  
Formation Model ◽  
Modified Gravity Theories ◽  
Sunyaev Zel'dovich Effect ◽  
Normal Branch ◽  
Using Data ◽  
The Impact

Abstract We study the effects of two popular modified gravity theories, which incorporate very different screening mechanisms, on the angular power spectra of the thermal (tSZ) and kinematic (kSZ) components of the Sunyaev-Zel’dovich effect. Using the first cosmological simulations that simultaneously incorporate both screened modified gravity and a complete galaxy formation model, we find that the tSZ and kSZ power spectra are significantly enhanced by the strengthened gravitational forces in Hu-Sawicki f(R) gravity and the normal-branch Dvali-Gabadadze-Porrati model. Employing a combination of non-radiative and full-physics simulations, we find that the extra baryonic physics present in the latter acts to suppress the tSZ power on angular scales l ≳ 3000 and the kSZ power on all tested scales, and this is found to have a substantial effect on the model differences. Our results indicate that the tSZ and kSZ power can be used as powerful probes of gravity on large scales, using data from current and upcoming surveys, provided sufficient work is conducted to understand the sensitivity of the constraints to baryonic processes that are currently not fully understood.

Probing screened modified gravity with nonlinear structure formation

2018 ◽  
Vol 27 (04) ◽  
pp. 1830003 ◽  
Author(s):  
David F. Mota
Keyword(s):  
Structure Formation ◽  
Modified Gravity ◽  
Equivalence Principle ◽  
Velocity Dispersion ◽  
Power Spectra ◽  
Nonlinear Structure ◽  
Fifth Force ◽  
Modified Gravity Theories ◽  
Halo Masses ◽  
Screening Scale

We review the effects of modified gravity theories, in particular the symmetron and [Formula: see text] gravity, on the nonlinear regime of structure formation. In particular, we investigate the velocity dispersion of galaxy clusters as a function of the halo masses, how the matter power spectra depend on the coupling, range, and screening scale of the fifth force, and on possible ways of detecting violations of the equivalence principle using the mass inferred via lensing methods versus the mass inferred via dynamical methods. Furthermore, we show how one could use different voids statistics as one of the most promising probes of modified gravity.

scholarly journals Large-scale structure probes of modified gravity

2018 ◽  
Vol 27 (15) ◽  
pp. 1848005 ◽  
Author(s):  
Catherine Heymans ◽  
Gong-Bo Zhao
Keyword(s):  
Gravitational Lensing ◽  
Modified Gravity ◽  
Large Scale ◽  
Information Gain ◽  
Einstein Gravity ◽  
Large Scale Structures ◽  
Modified Gravity Theories ◽  
Scale Structures ◽  
The Impact ◽  
The Universe

Observations of the evolution of large-scale structures in the Universe provides unique tools to confront Einstein’s theory of General Relativity on cosmological scales. We review weak gravitational lensing and galaxy clustering studies, discussing how these can be used in combination in order to constrain a range of different modified gravity theories. We argue that in order to maximise the future information gain from these probes, theoretical effort will be required in order to model the impact of beyond-Einstein gravity in the nonlinear regime of structure formation.

scholarly journals N-body simulations for parametrized modified gravity

2020 ◽  
Vol 497 (2) ◽  
pp. 1885-1894
Author(s):  
Farbod Hassani ◽  
Lucas Lombriser
Keyword(s):  
Modified Gravity ◽  
Full Range ◽  
Percent Level ◽  
Power Spectra ◽  
Large Field ◽  
Spherical Collapse ◽  
Non Linear ◽  
Normal Branch ◽  
Braneworld Model ◽  
Tests Of Gravity

ABSTRACT We present MG-evolution, an N-body code simulating the cosmological structure formation for parametrized modifications of gravity. It is built from the combination of parametrized linear theory with a parametrization of the deeply non-linear cosmological regime extrapolated from modified spherical collapse computations that cover the range of known screening mechanisms. We test MG-evolution, which runs at the speed of conventional ΛCDM simulations, against a suit of existing exact model-specific codes, encompassing linearized and chameleon f(R) gravity as well as the normal branch of the Dvali–Gabadadz–Porrati braneworld model, hence covering both large-field value and large-derivative screening effects. We compare the non-linear power spectra produced by the parametrized and model-specific approaches over the full range of scales set by the box size and resolution of our simulations, k = (0.05 − 2.5) $h\, \mathrm{Mpc}^{-1}$, and for two redshift slices, z = 0 and z = 1. We find sub-percent to one-percent level recovery of all the power spectra generated with the model-specific codes for the full range of scales. MG-evolution can be used for generalized and accurate tests of gravity and dark energy with the increasing wealth of high-precision cosmological survey data becoming available over the next decade.

scholarly journals Imaging systematics and clustering of DESI main targets

2020 ◽  
Vol 496 (2) ◽  
pp. 2262-2291 ◽  
Author(s):  
Ellie Kitanidis ◽  
Martin White ◽  
Yu Feng ◽  
David Schlegel ◽  
Julien Guy ◽  
...  
Keyword(s):  
Power Spectra ◽  
Luminous Red Galaxies ◽  
Cross Correlations ◽  
Emission Line Galaxies ◽  
Using Data ◽  
Red Galaxies ◽  
The Impact ◽  
Stellar Density ◽  
North Galactic ◽  
Good Agreement

ABSTRACT We evaluate the impact of imaging systematics on the clustering of luminous red galaxies (LRG), emission-line galaxies (ELG), and quasars (QSO) targeted for the upcoming Dark Energy Spectroscopic Instrument (DESI) survey. Using Data Release 7 of the DECam Legacy Survey, we study the effects of astrophysical foregrounds, stellar contamination, differences between north galactic cap and south galactic cap measurements, and variations in imaging depth, stellar density, galactic extinction, seeing, airmass, sky brightness, and exposure time before presenting survey masks and weights to mitigate these effects. With our sanitized samples in hand, we conduct a preliminary analysis of the clustering amplitude and evolution of the DESI main targets. From measurements of the angular correlation functions, we determine power law fits $r_0 = 7.78 \pm 0.26\, h^{-1}$Mpc, γ = 1.98 ± 0.02 for LRGs and $r_0 = 5.45 \pm 0.1\, h^{-1}$Mpc, γ = 1.54 ± 0.01 for ELGs. Additionally, from the angular power spectra, we measure the linear biases and model the scale-dependent biases in the weakly non-linear regime. Both sets of clustering measurements show good agreement with survey requirements for LRGs and ELGs, attesting that these samples will enable DESI to achieve precise cosmological constraints. We also present clustering as a function of magnitude, use cross-correlations with external spectroscopy to infer dN/dz and measure clustering as a function of luminosity, and probe higher order clustering statistics through counts-in-cells moments.

scholarly journals Galaxy formation in the brane world I: overview and first results

2021 ◽  
Author(s):  
César Hernández-Aguayo ◽  
Christian Arnold ◽  
Baojiu Li ◽  
Carlton M Baugh
Keyword(s):  
Dark Matter ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Modified Gravity ◽  
Formation Rate ◽  
Brane World ◽  
Stellar Content ◽  
Braneworld Model ◽  
Hydrodynamical Simulations ◽  
The Impact

Abstract We carry out “full-physics” hydrodynamical simulations of galaxy formation in the normal-branch Dvali-Gabadadze-Porrati (nDGP) braneworld model using a new modified version of the Arepo code and the IllustrisTNG galaxy formation model. We simulate two nDGP models (N5 and N1) which represent, respectively, weak and moderate departures from GR, in boxes of sizes 62 h−1Mpc and 25 h−1Mpc using 2 × 5123 dark matter particles and initial gas cells. This allows us to explore, for the first time, the impact of baryonic physics on galactic scales in braneworld models of modified gravity and to make predictions on the stellar content of dark matter haloes and galaxy evolution through cosmic time in these models. We find significant differences between the GR and nDGP models in the power spectra and correlation functions of gas, stars and dark matter of up to ∼25 per cent on large scales. Similar to their impact in the standard cosmological model (ΛCDM), baryonic effects can have a significant influence over the clustering of the overall matter distribution, with a sign that depends on scale. Studying the degeneracy between modified gravity and galactic feedback in these models, we find that these two physical effects on matter clustering can be cleanly disentangled, allowing for a method to accurately predict the matter power spectrum with baryonic effects included, without having to run hydrodynamical simulations. Depending on the braneworld model, we find differences compared with GR of up to ∼15 per cent in galaxy properties such as the stellar-to-halo-mass ratio, galaxy stellar mass function, gas fraction and star formation rate density. The amplitude of the fifth force is reduced by the presence of baryons in the very inner part of haloes, but this reduction quickly becomes negligible above ∼0.1 times the halo radius.

Nonlinear structure formation in gravity theories beyond general relativity

2016 ◽  
Vol 31 (21) ◽  
pp. 1640007
Author(s):  
David F. Mota
Keyword(s):  
Structure Formation ◽  
Modified Gravity ◽  
Equivalence Principle ◽  
Velocity Dispersion ◽  
Power Spectra ◽  
Nonlinear Structure ◽  
Modified Gravity Theories ◽  
Gravity Theories ◽  
Halo Masses ◽  
Screening Scale

We investigate the effects of modified gravity theories, in particular, the symmetron and f(R) gravity, on the nonlinear regime of structure formation. In particular, we investigate the velocity dispersion of galaxy clusters as a function of the halo masses, how the matter power spectra depend on the coupling, range and screening scale of the fifth force, and on possible ways of detecting violations of the equivalence principle using the mass inferred via lensing methods versus the mass inferred via dynamical methods.

scholarly journals Predicting halo occupation and galaxy assembly bias with machine learning

2021 ◽  
Vol 507 (4) ◽  
pp. 4879-4899 ◽  
Author(s):  
Xiaoju Xu ◽  
Saurabh Kumar ◽  
Idit Zehavi ◽  
Sergio Contreras
Keyword(s):  
Machine Learning ◽  
Galaxy Formation ◽  
Critical Role ◽  
Dark Matter Halo ◽  
Formation Model ◽  
Galaxy Clustering ◽  
The Galaxy ◽  
Galaxy Halo ◽  
Galaxy Assembly ◽  
The Impact

Abstract Understanding the impact of halo properties beyond halo mass on the clustering of galaxies (namely galaxy assembly bias) remains a challenge for contemporary models of galaxy clustering. We explore the use of machine learning to predict the halo occupations and recover galaxy clustering and assembly bias in a semi-analytic galaxy formation model. For stellar mass selected samples, we train a random forest algorithm on the number of central and satellite galaxies in each dark matter halo. With the predicted occupations, we create mock galaxy catalogues and measure the clustering and assembly bias. Using a range of halo and environment properties, we find that the machine learning predictions of the occupancy variations with secondary properties, galaxy clustering, and assembly bias are all in excellent agreement with those of our target galaxy formation model. Internal halo properties are most important for the central galaxies prediction, while environment plays a critical role for the satellites. Our machine learning models are all provided in a usable format. We demonstrate that machine learning is a powerful tool for modelling the galaxy–halo connection, and can be used to create realistic mock galaxy catalogues which accurately recover the expected occupancy variations, galaxy clustering, and galaxy assembly bias, imperative for cosmological analyses of upcoming surveys.

Accent Policy and Accent Modification Enterprises as Potential Indicators of Intercultural Power Relations: A Call for an Updated Research Agenda

2013 ◽  
Vol 3 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Brynne D. Ovalle ◽  
Rahul Chakraborty
Keyword(s):  
International Relations ◽  
Identity Construction ◽  
Social Theory ◽  
Power Relations ◽  
Linguistic Diversity ◽  
Cultural Organization ◽  
Using Data ◽  
The Individual ◽  
The Impact ◽  
The Relationship

This article has two purposes: (a) to examine the relationship between intercultural power relations and the widespread practice of accent discrimination and (b) to underscore the ramifications of accent discrimination both for the individual and for global society as a whole. First, authors review social theory regarding language and group identity construction, and then go on to integrate more current studies linking accent bias to sociocultural variables. Authors discuss three examples of intercultural accent discrimination in order to illustrate how this link manifests itself in the broader context of international relations (i.e., how accent discrimination is generated in situations of unequal power) and, using a review of current research, assess the consequences of accent discrimination for the individual. Finally, the article highlights the impact that linguistic discrimination is having on linguistic diversity globally, partially using data from the United Nations Educational, Scientific and Cultural Organization (UNESCO) and partially by offering a potential context for interpreting the emergence of practices that seek to reduce or modify speaker accents.

Sign in / Sign up

Export Citation Format

Share Document