Relativistic effect in Large Scale Structure
We studied several relativistic effects like gravitational redshift, special relativistic beaming, transverse Doppler redshift, light cone effect, luminosity distance perturbation and other second order effects, which can affect large scale structure as observed by galaxies, using simple phenomenology modelling with tools such as N-body simulation, general relativistic perturbation theory and halo models. We have studied relative amplitude of these effects, detected a signal in SDSS DR12 data and compared linear vs nonlinear predictions. You can find simple descriptions of these things in here.
This project resulted in following papers:
- Modelling with N-body simulations
- Measurement in SDSS sample
- Special Relativistic beaming study
- Modeling in perturbation theory
Combining Weak Gravitational Lensing and RSD with LSS (EG)
I have been involved in the study of a unique combination of gravitational lensing with large scale structure and redshift space distortions (RSD) to measure a quantity called EG. This has some unique features. For example, it is independent of galaxy bias and amplitude of matter fluctuation. This also has a very simple theoretical prediction and it is easy to extend this prediction for a wide range of modified gravity theories. This provides a unique test of General Relativity at Large Scale. I have published several papers with my collaborators related to theoretical prediction and measurement of EG. Following is the list of papers I have on the above topic.
- Theoretical development and forecast to extend the idea of EG to use CMB lensing in place of initially proposed galaxy-galaxy lensing and forecast for all the future surveys.
- First Measurement of EG with CMB lensing
- Measurement of EG with CFHTLS and high redshift SDSS data
- Measurement of EG with CMB and low redshift SDSS data
The first constraints on many of the Hordenski's model parameters with RSD
We looked at an extension to LCDM by including dark energy and modified gravity. We focused on Hordensiki theories for modified gravity with linear perturbation regime and used the RSD data from 6 Large Scale Structure surveys to provide some of the first constraints on a few model classes. We also improved latest constraints at that time on many of the model parameters. We also clarified some of the inconsistencies while constraining such models in the literature and pointed out how such data can also provide an indirect constraint on redshift of reionization. I have also contributed to a similar analysis focusing on different aspects of such an extension. The following are papers coming out of these contributions:
- An extensive constraints on modified gravity
- Another look at constraining modified gravity models
Redshift Space Distortion in Large Scale Structure
I have led and contributed to several of the analyses on Large Scale Structure focusing on various aspects of modelling galaxy velocity fields. These studies also contributed to the SDSS-III final cosmological results and folded into SDSS-III latest precision cosmology constraints. You can find further description about this effect and how this helps us constrain cosmology over here. The papers from these works are as follows:
- The RSD study on DR11 sample
- The RSD study contributing to final SDSS sample
- Final cosmology results from SDSS-III
The current best constraint on neutrino mass comes from cosmological data sets. I have been pondering about some aspects of neutrino mass's effect on large scale structure. Some animations and descriptions are available here. https://sites.google.com/site/salamcosmology/research/neutrino-mass