Neelima Sehgal
A5058817864- Galaxies: Formation, Evolution, Phenomena
- Cosmology and Gravitation Theories
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Dark Matter and Cosmic Phenomena
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Superconducting and THz Device Technology
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Particle physics theoretical and experimental studies
- Computational Physics and Python Applications
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Precipitation Measurement and Analysis
- Astrophysical Phenomena and Observations
- Advanced Thermodynamics and Statistical Mechanics
- Acute Ischemic Stroke Management
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Particle Detector Development and Performance
- Pulsars and Gravitational Waves Research
- Neurological Disorders and Treatments
- Soil Moisture and Remote Sensing
Stony Brook University
2015-2025
University of Chicago
2014-2024
Flatiron Health (United States)
2020-2021
Flatiron Institute
2020-2021
University of KwaZulu-Natal
2021
Stony Brook Medicine
2019
Kavli Institute for the Physics and Mathematics of the Universe
2017
California Institute of Technology
2017
The University of Tokyo
2017
University at Buffalo, State University of New York
2017
The dwarf spheroidal satellite galaxies of the Milky Way are some most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack astrophysical backgrounds, widely considered be among promising targets for indirect detection via $\ensuremath{\gamma}$ rays. Here we report on $\ensuremath{\gamma}$-ray observations 25 based 4 years Fermi Large Area Telescope (LAT) data. None significantly detected in rays, present flux upper limits between 500 MeV GeV. We...
This book lays out the scientific goals to be addressed by next-generation ground-based cosmic microwave background experiment, CMB-S4, envisioned consist of dedicated telescopes at South Pole, high Chilean Atacama plateau and possibly a northern hemisphere site, all equipped with new superconducting cameras. CMB-S4 will dramatically advance cosmological studies crossing critical thresholds in search for B-mode polarization signature primordial gravitational waves, determination number...
We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz 218 made by the Atacama Cosmology Telescope (ACT) in three seasons of observations 2008 to 2010. A model primary secondary foreground is fit map power spectra lensing deflection spectrum, including contributions both thermal Sunyaev-Zeldovich (tSZ) effect kinematic (kSZ) effect, Poisson correlated anisotropy unresolved infrared sources, radio correlation between tSZ...
[Abridged] We present a catalog of 68 galaxy clusters, which 19 are new discoveries, detected via the Sunyaev-Zel'dovich effect (SZ) at 148 GHz in Atacama Cosmology Telescope (ACT) survey 504 square degrees on celestial equator. A subsample 48 clusters within 270 degree region overlapping SDSS Stripe 82 is estimated to be 90% complete for M_500c > 4.5e14 Msun and 0.15 < z 0.8. While matched filters used detect sample studied further through "Profile Based Amplitude Analysis" using...
We present cosmological parameters derived from the angular power spectrum of cosmic microwave background (CMB) radiation observed at 148 GHz and 218 over 296 deg2 with Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations scales 500 < ℓ 10, 000. fit a model for lensed CMB, Sunyaev–Zel'dovich (SZ), foreground contribution to spectra, including thermal kinetic SZ, Poisson radio infrared point sources, clustered sources. At = 3000, about half comes primary CMB...
We present the temperature power spectra of cosmic microwave background (CMB) derived from three seasons data Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well cross-frequency spectrum between two channels. detect correct for contamination due to Galactic cirrus in our equatorial maps. results a number tests possible systematic error conclude that any effects are not significant compared statistical errors we quote. Where they overlap, cross-correlate ACT South Pole (SPT)...
We report the first detection of gravitational lensing cosmic microwave background through a measurement four-point correlation function in temperature maps made by Atacama Cosmology Telescope. verify our calculating levels potential contaminants and performing number null tests. The resulting convergence power spectrum at 2° angular scales measures amplitude matter density fluctuations on comoving length around 100 Mpc redshifts 0.5 to 3. measured signal agrees with Lambda cold dark...
Using high-resolution microwave sky maps made by the Atacama Cosmology Telescope, we for first time present strong evidence motions of galaxy clusters and groups via background temperature distortions due to kinematic Sunyaev-Zel'dovich effect. Galaxy are identified their constituent luminous galaxies observed Baryon Oscillation Spectroscopic Survey, part Sloan Digital Sky Survey III. We measure mean pairwise momentum clusters, with a probability signal being random errors 0.002, is...
We present the temperature and polarization angular power spectra measured by Atacama Cosmology Telescope Polarimeter (ACTPol). analyze night-time data collected during 2013-14 using two detector arrays at 149 GHz, from 548 deg$^2$ of sky on celestial equator. use these spectra, with MBAC camera ACT 2008-10, in combination Planck WMAP to estimate cosmological parameters temperature, polarization, temperature-polarization cross-correlations. find new ACTPol be consistent LCDM model. The...
Due to their proximity, high dark-matter content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection dark matter. Recently, eight new dSph candidates were discovered using first year data from Dark Energy Survey (DES). We searched gamma-ray emission coincident with positions these objects in six years Fermi Large Area Telescope data. found no significant excesses emission. Under assumption that...
The imprint left on the cosmic microwave background (CMB) from CMB photons scattering off high-energy electrons in galaxies and clusters is known as Sunyaev-Zel'dovich (SZ) effect subject of these two papers Atacama Cosmology Telescope (ACT). ACT measurements combined with those Planck BOSS are shown to provide a rich picture electron gas thermodynamics galactic cluster medium. This can be used test improve cosmological simulations relevant for upcoming experiments.
The early dark energy (EDE) scenario aims to increase the value of Hubble constant (${H}_{0}$) inferred from cosmic microwave background (CMB) data over that found in standard cosmological model ($\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$), via introduction a new form density Universe. EDE component briefly accelerates expansion just prior recombination, which reduces physical size sound horizon imprinted CMB. Previous work has nonzero is not preferred by Planck CMB power spectrum alone,...
Abstract We present tomographic measurements of structure growth using cross-correlations Atacama Cosmology Telescope (ACT) DR6 and Planck cosmic microwave background (CMB) lensing maps with the unWISE Blue Green galaxy samples, which span redshift ranges 0.2 ≲ z 1.1 0.3 1.8, respectively. improve on prior not just by making use new, high-precision ACT maps, but also including additional spectroscopic data for calibration analyzing our a more flexible theoretical model. determine amplitude...
Abstract We investigate the impact and mitigation of extragalactic foregrounds for cosmic microwave background (CMB) lensing power spectrum analysis Atacama Cosmology Telescope (ACT) data release 6 (DR6) data. Two independent sky simulations are used to test a range strategies. demonstrate that finding then subtracting point sources, models clusters, using profile bias-hardened estimator together reduce fractional biases well below statistical uncertainties, with inferred amplitude, A lens ,...
We report on 23 clusters detected blindly as Sunyaev–ZEL'DOVICH (SZ) decrements in a 148 GHz, 455 deg2 map of the southern sky made with data from Atacama Cosmology Telescope 2008 observing season. All SZ detections announced this work have confirmed optical counterparts. Ten are new discoveries. One newly discovered cluster, ACT-CL J0102−4915, redshift 0.75 (photometric), has an decrement comparable to most massive systems at lower redshifts. Simulations cluster recovery method reproduce...
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915 "El Gordo," likely most massive, hottest, X-ray luminous and brightest Sunyaev-Zeldovich (SZ) effect known at z>0.6. The Atacama Cosmology Telescope collaboration discovered El Gordo as significant SZ decrement in sky survey area 755 deg^2. Our VLT/FORS2 spectra 89 member galaxies yield redshift, z=0.870, velocity dispersion, s=1321+/-106 km/s. Chandra reveal hot system...
We create realistic, full-sky, half-arcminute resolution simulations of the microwave sky matched to most recent astrophysical observations. The primary purpose these is test data reduction pipeline for Atacama Cosmology Telescope (ACT) experiment; however, we have widened frequency coverage beyond ACT bands and utilized easily accessible HEALPix map format make applicable other current near future background experiments. Some novel features are that radio infrared galaxy populations...
Updated constraints on dark matter cross section and mass are presented combining CMB power spectrum measurements from Planck, WMAP9, ACT, SPT as well several low-redshift datasets (BAO, HST, supernovae). For the datasets, we combine WMAP9 temperature polarization data for l <= 431 with Planck 432 < 2500, ACT > four-point lensing measurements. We allow redshift-dependent energy deposition annihilation by using a `universal' absorption curve. also include an updated treatment of excitation,...
We report on measurements of the cosmic microwave background (CMB) and celestial polarization at 146 GHz made with Atacama Cosmology Telescope Polarimeter (ACTPol) in its first three months observing. Four regions sky covering a total 270 square degrees were mapped an angular resolution $1.3'$. The map noise levels four are between 11 17 $\mu$K-arcmin. present TT, TE, EE, TB, EB, BB power spectra from these regions. observed E-mode spectrum, displaying six acoustic peaks range...
The Atacama Cosmology Telescope has measured the angular power spectra of microwave fluctuations to arcminute scales at frequencies 148 and 218 GHz, from three seasons data. At small in primordial Cosmic Microwave Background (CMB) become increasingly obscured by extragalactic foregounds secondary CMB signals. We present results a nine-parameter model describing these effects, including thermal kinematic Sunyaev-Zel'dovich (tSZ kSZ) power; clustered Poisson-like Infrared (CIB) sources, their...
We present measurements of the cosmic microwave background (CMB) power spectrum made by Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well cross-frequency between two channels. Our results clearly show second through seventh acoustic peaks in CMB spectrum. The these higher-order provide an additional test {\Lambda}CDM cosmological model. At l > 3000, we detect excess primary anisotropy CMB. lower multipoles 500 < find evidence for gravitational lensing 2.8{\sigma} level. also a low...