S. Nadathur
A5025432371- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Scientific Research and Discoveries
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Remote Sensing in Agriculture
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- CCD and CMOS Imaging Sensors
- Adaptive optics and wavefront sensing
- Particle physics theoretical and experimental studies
- Black Holes and Theoretical Physics
- Calibration and Measurement Techniques
- Astrophysical Phenomena and Observations
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Advanced Vision and Imaging
- Statistical and numerical algorithms
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Advanced Physical and Chemical Molecular Interactions
- Impact of Light on Environment and Health
University of Portsmouth
2016-2025
University of Edinburgh
2024
Australian Astronomical Observatory
2024
Macquarie University
2024
Marconi University
2024
University College London
2021-2023
Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
2023
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati
2023
École Polytechnique Fédérale de Lausanne
2023
RWTH Aachen University
2023
We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Ly$\alpha$ forests completed Sloan Digital Sky Survey (SDSS) lineage experiments in large-scale structure. These experiments, composed data SDSS, SDSS-II, BOSS, eBOSS, offer independent baryon acoustic oscillation (BAO) angular-diameter distances Hubble relative to sound horizon, $r_d$, eight different samples six growth rate parameter, $f\sigma_8$, redshift-space distortions (RSD)....
We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift $z=0.001$ to 2.26. This work features an increased sample size, span, and improved treatment systematic uncertainties comparison original Pantheon results a factor two improvement constraining power. For Flat$\Lambda$CDM model, we find $\Omega_M=0.334\pm0.018$ SNe alone. Flat$w_0$CDM measure $w_0=-0.90\pm0.14$ alone, H$_0=73.5\pm1.1$...
We present the cosmological analysis of configuration-space anisotropic clustering in completed Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic (eBOSS) DR16 galaxy sample. This sample consists luminous red galaxies (LRGs) spanning redshift range $0.6 < z 1$, at an effective $z_{\rm eff}=0.698$. It combines 174 816 eBOSS LRGs and 202 642 BOSS CMASS galaxies. extract model baryon acoustic oscillations (BAO) redshift-space distortions (RSD) features from...
We analyse the clustering of Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Data Release 16 luminous red galaxy sample (DR16 eBOSS LRG) in combination with high redshift tail III 12 (DR12 BOSS CMASS). measure space distortions (RSD) and also extract longitudinal transverse baryonic acoustic oscillation (BAO) scale from anisotropic power spectrum signal inferred 377,458 galaxies between redshifts 0.6 1.0, effective $z_{\rm eff}=0.698$ comoving volume $2.72\,{\rm...
We analyse the large-scale clustering in Fourier space of emission line galaxies (ELG) from Data Release 16 Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey. The ELG sample contains 173,736 covering 1,170 square degrees redshift range $0.6 < z 1.1$. perform a BAO measurement post-reconstruction power spectrum monopole, and study distortions (RSD) first three even multipoles. Photometric variations yield fluctuations both angular radial survey selection functions....
Abstract A key component of the Dark Energy Spectroscopic Instrument (DESI) survey validation (SV) is a detailed visual inspection (VI) optical spectroscopic data to quantify metrics. In this paper we present results from VI quasar using deep coadded SV spectra. We show that majority (≈70%) main-survey targets are spectroscopically confirmed as quasars, with ≈16% galaxies, ≈6% stars, and ≈8% low-quality spectra lacking reliable features. nonnegligible fraction quasars misidentified by...
Abstract The Dark Energy Spectroscopic Instrument (DESI) Survey has obtained a set of spectroscopic measurements galaxies to validate the final survey design and target selections. To assist in these tasks, we visually inspect DESI spectra approximately 2500 bright galaxies, 3500 luminous red (LRGs), 10,000 emission-line (ELGs) obtain robust redshift identifications. We then utilize inspected information characterize performance operation. Based on visual inspection (VI) catalogs, our...
ABSTRACT We present the first comprehensive halo occupation distribution (HOD) analysis of Dark Energy Spectroscopic Instrument (DESI) One-Percent Survey luminous red galaxy (LRG) and Quasi Stellar Object (QSO) samples. constrain HOD each sample test possible extensions by fitting redshift-space 2-point correlation functions in 0.15 &lt; r 32 h−1 Mpc a set fiducial redshift bins. use AbacusSummit cubic boxes at Planck 2018 cosmology as model templates forward clustering with AbacusHOD...
Abstract In anticipation of forthcoming data releases current and future spectroscopic surveys, we present the validation tests analysis systematic effects within velocileptors modeling pipeline when fitting mock from AbacusSummit N-body simulations. We compare constraints obtained parameter compression methods to direct (Full-Modeling) approaches galaxy power spectra, show that ShapeFit extension traditional template method is consistent with Full-Modeling standard ΛCDM space. dependence on...
Abstract We present the technical details on how large-scale structure (LSS) catalogs are constructed from redshifts measured spectra observed by Dark Energy Spectroscopic Instrument (DESI). The LSS provide information needed to determine relative number density of DESI tracers as a function redshift and celestial coordinates and, e.g., clustering statistics. produce that weighted subsamples data, each matched `random' catalog forms an unclustered sampling probability could have those data...
Abstract Baryon acoustic oscillations (BAO) provide a robust standard ruler to measure the expansion history of Universe through galaxy clustering. Density-field reconstruction is now widely adopted procedure for increasing precision and accuracy BAO detection. With goal finding optimal settings be used in DESI 2024 analysis, we assess sensitivity post-reconstruction constraints different choices our analysis configuration, performing tests on blinded data from first year observations (DR1),...
Abstract The Dark Energy Spectroscopic Instrument (DESI) will provide precise measurements of Baryon Acoustic Oscillations (BAO) to constrain the expansion history Universe and set stringent constraints on dark energy. Therefore, control global error budget due various systematic effects is required for DESI 2024 BAO analysis. In this work, we estimate level systematics induced in analysis assumed Halo Occupation Distribution (HOD) model Emission Line Galaxy (ELG) tracer. We make use mock...
Abstract In this paper, we present the estimation of systematics related to halo occupation distribution (HOD) modeling in baryon acoustic oscillations (BAO) distance measurement Dark Energy Spectroscopic Instrument (DESI) 2024 analysis. This paper focuses on study HOD for luminous red galaxies (LRG). We consider three different models LRGs, including base 5-parameter vanilla model and two extensions it, that refer as baseline extended models. The is described by 5 parameters, an...
Abstract In the contemporary era of high-precision spectroscopic surveys, led by projects like DESI, there is an increasing demand for optimizing extraction cosmological information from clustering data. This work conducts a thorough comparison various methodologies modeling full shape two-point statistics in configuration space. We investigate performance both direct fits ( Full Modeling ) and parameter compression approaches ShapeFit Standard ). utilize ABACUS-SUMMIT simulations, tailored...
Abstract When measuring the Baryon Acoustic Oscillations (BAO) scale from galaxy surveys, one typically assumes a fiducial cosmology when converting redshift measurements into comoving distances and also defining input parameters for reconstruction algorithm. A parameterised template model to be fitted is created based on (possibly different) cosmology. This reliance can considered form of data compression, then analysed allowing that true answer different assumed. In this study, we evaluate...
Abstract In preparation for the next generation of galaxy redshift surveys, and in particular year-one data release from Dark Energy Spectroscopic Instrument (DESI), we investigate consistency a variety effective field theory models that describe galaxy-galaxy power spectra space into quasi-linear regime using 1-loop perturbation theory. These are employed pipelines velocileptors , PyBird Folps ν . While these have been validated independently, detailed comparison with consistent choices has...
Abstract The Dark Energy Spectroscopic Instrument (DESI) will provide unprecedented information about the large-scale structure of our Universe. In this work, we study robustness theoretical modelling power spectrum Folps , a novel effective field theory-based package for evaluating redshift space in presence massive neutrinos. We perform validation by fitting AbacusSummit high-accuracy N -body simulations Luminous Red Galaxies, Emission Line Galaxies and Quasar tracers, calibrated to...
Abstract In the era of precision cosmology, ensuring integrity data analysis through blinding techniques is paramount — a challenge particularly relevant for Dark Energy Spectroscopic Instrument (DESI). DESI represents monumental effort to map cosmic web, with goal measure redshifts tens millions galaxies and quasars. Given volume impact findings, potential confirmation bias poses significant challenge. To address this, we implement validate comprehensive blind strategy Data Release 1 (DR1),...
Abstract DESI aims to provide one of the tightest constraints on cosmological parameters by analysing clustering more than thirty million galaxies. However, obtaining such requires special care in validating methodology and efforts reduce computational time required through data compression emulation techniques. In this work, we perform a rigorous validation PyBird power spectrum modelling code with both traditional emulated Full-Modelling approach model-independent ShapeFit approach. By...
We present the Emission Line Galaxy (ELG) sample of extended Baryon Oscillation Spectroscopic Survey (eBOSS) from Sloan Digital Sky IV Data Release 16 (DR16). After describing observations and redshift measurement for 269,243 observed ELG spectra over 1170 deg$^2$, we large-scale structure catalogues, which are used cosmological analysis. These catalogues contain 173,736 reliable spectroscopic redshifts between 0.6 1.1, along with associated random quantifying extent observations,...
Cosmic voids are usually identified in spectroscopic galaxy surveys, where 3D information about the large-scale structure of Universe is available. Although an increasing amount photometric data being produced, its potential for void studies limited since redshifts induce line-of-sight position errors ≥50 Mpc h−1which can render many undetectable. We present a new finder designed validate it using simulations, and apply to high-quality photo-z redMaGiC sample DES Science Verification data....
We consider decaying dark matter (DDM) as a resolution to the possible tension between cosmic microwave background (CMB) and weak lensing (WL) based determinations of amplitude fluctuations, σ8. perform N-body simulations in model where decays into radiation develop an accurate fitting formula for non-linear power spectrum, which enables us test DDM by combined measurements CMB, WL baryon acoustic oscillation (BAO). employ Markov chain Monte Carlo analysis examine overlap posterior...
We present a measurement of the anisotropic void-galaxy cross-correlation function in CMASS galaxy sample BOSS DR12 data release. perform joint fit to for redshift space distortions (RSD) due peculiar velocities and anisotropies Alcock-Paczynski (AP) effect, first time using velocity field reconstruction technique remove complicating effects RSD void centre positions themselves. Fits give 1% AP parameter combination $D_A(z)H(z)/c = 0.4367\pm 0.0045$ at $z=0.57$, where $D_A$ is angular...
ABSTRACT We present reconstructed convergence maps, mass from the Dark Energy Survey (DES) third year (Y3) weak gravitational lensing data set. The maps are weighted projections of density field (primarily dark matter) in foreground observed galaxies. use four reconstruction methods, each is a maximum posteriori estimate with different model for prior probability map: Kaiser–Squires, null B-mode prior, Gaussian and sparsity prior. All methods implemented on celestial sphere to accommodate...