Mário G. Santos
A5005834624- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Scientific Research and Discoveries
- Antenna Design and Optimization
- Superconducting and THz Device Technology
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Dark Matter and Cosmic Phenomena
- Radio Wave Propagation Studies
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Particle Accelerators and Free-Electron Lasers
- Millimeter-Wave Propagation and Modeling
- Geophysics and Gravity Measurements
- Electromagnetic Compatibility and Measurements
- Spectroscopy and Laser Applications
- Black Holes and Theoretical Physics
- GNSS positioning and interference
- Microwave Engineering and Waveguides
- Gyrotron and Vacuum Electronics Research
South African Radio Astronomy Observatory
2019-2025
University of the Western Cape
2016-2025
Indian Institute of Technology Madras
2024
West Virginia University
2022
Yale University
2022
University of California, Berkeley
2021
University of Lisbon
1999-2020
SKA Telescope, South Africa
2014-2020
Institute of Astrophysics and Space Sciences
2019-2020
University of Oxford
2001-2018
We present a framework for forecasting cosmological constraints from future neutral hydrogen intensity mapping experiments at low to intermediate redshifts. In the process, we establish simple way of comparing such surveys with optical galaxy redshift surveys. explore wide range experimental configurations and assess how well number observables (the expansion rate, growth angular diameter distance) parameters densities dark energy matter, spatial curvature, equation state, etc.) will be...
Abstract We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 Square Kilometre Array (SKA1) and science they will enable. highlight three main surveys: medium-deep continuum weak lensing low-redshift spectroscopic HI galaxy survey over 5 000 deg 2 ; wide deep intensity mapping (IM) 20 from $z = 0.35$ 3; deep, high-redshift IM 100 3$ 6. Taken together, these achieve an array important scientific goals: measuring equation state dark energy \sim...
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new 400-800MHz radio interferometer under development for deployment in South Africa. HIRAX will comprise 1024 six meter parabolic dishes on compact grid map most of the southern sky over course four years. has two primary science goals: to constrain Dark Energy measure structure at high redshift, study transients pulsars. observe unresolved sources neutral hydrogen via their redshifted 21-cm emission line (`hydrogen...
Following the first two annual intensity mapping workshops at Stanford in March 2016 and Johns Hopkins June 2017, we report on recent advances theory, instrumentation observation that were presented these meetings some of opportunities challenges identified looking forward. With preliminary detections CO, [CII], Lya low-redshift 21cm, a host experiments set to go online next few years, field is rapidly progressing all fronts, with great anticipation for flood new exciting results. This...
Abstract Recently, the Hydrogen Epoch of Reionization Array (HERA) has produced experiment’s first upper limits on power spectrum 21 cm fluctuations at z ∼ 8 and 10. Here, we use several independent theoretical models to infer constraints intergalactic medium (IGM) galaxies during epoch reionization from these limits. We find that IGM must have been heated above adiabatic-cooling threshold by 8, uncertainties about ionization radio background. Combining HERA with complementary observations...
Abstract We report the most sensitive upper limits to date on 21 cm epoch of reionization power spectrum using 94 nights observing with Phase I Hydrogen Epoch Reionization Array (HERA). Using similar analysis techniques as in previously reported limits, we find at 95% confidence that Δ 2 ( k = 0.34 h Mpc −1 ) ≤ 457 mK z 7.9 and 0.36 3496 10.4, an improvement by a factor 2.1 2.6, respectively. These are mostly consistent thermal noise over wide range after our data quality cuts, despite...
We study the prospects for extracting detailed statistical properties of neutral hydrogen distribution during era reionization using brightness temperature fluctuations from redshifted 21 cm line emission. Detection this signal is complicated by contamination foreground sources such as diffuse Galactic synchrotron and free-free emission at low radio frequencies, extragalactic ionized regions, point sources. model these foregrounds to determine extent which can be detected with upcoming...
The atomic C ii fine-structure line is one of the brightest lines in a typical star-forming galaxy spectrum with luminosity ∼0.1%–1% bolometric luminosity. It potentially reliable tracer dense gas distribution at high redshifts and could provide an additional probe to era reionization. By taking into account spontaneous, stimulated, collisional emission line, we calculate spin temperature mean intensity as function redshift. When averaged over cosmologically large volume, find that from...
While limited to low spatial resolution, the next generation low-frequency radio interferometers that target 21 cm observations during era of reionization and prior will have instantaneous fields-of-view are many tens square degrees on sky. Predictions related various statistical measurements brightness temperature must then be pursued with numerical simulations correspondingly large volume box sizes, order 1000 Mpc one side. We pursue a semi-numerical scheme simulate signal Reionization by...
HI intensity mapping (IM) is a novel technique capable of the large-scale structure Universe in three dimensions and delivering exquisite constraints on cosmology, by using as biased tracer dark matter density field.This achieved measuring redshifted 21cm line over sky range redshifts without requirement to resolve individual galaxies.In this chapter, we investigate potential SKA1 deliver maps broad frequencies substantial fraction sky.By pinning down baryon acoustic oscillation redshift...
The Square Kilometre Array (SKA) will produce spectroscopic surveys of tens to hundreds millions neutral hydrogen (H I) galaxies, eventually covering 30 000 deg2 and reaching out redshift z≳2. huge volumes probed by the SKA allow for some best constraints on primordial non-Gaussianity, based measurements large-scale power spectrum.We investigate various observational set-ups HI galaxy surveys, compatible with Phase 1 2 (full SKA) configurations.We use corresponding number counts bias each...
We produce simulations of the atomic C ii line emission in large sky fields order to determine current and future prospects for mapping this during high-redshift epoch reionization. calculate intensity, redshift evolution, spatial fluctuations using observational relations between galaxy star formation rate over frequency range 200–300 GHz. estimate an averaged intensity . Observations will suffer contamination from lines at lower redshifts, particular CO rotational lines. Using simulations,...
Next-generation cosmological surveys will probe ever larger volumes of the universe, including largest scales, near and beyond horizon. On these galaxy power spectrum carries signatures local primordial non-Gaussianity (PNG) horizon-scale general relativistic (GR) effects. However, cosmic variance limits detection Combining different via multi-tracer method allows us to reduce effect variance. This benefits from large bias differences between two tracers underlying dark matter distribution,...
We make use of a large set fast simulations an intensity mapping experiment with characteristics similar to those expected the Square Kilometre Array (SKA) in order study viability and limits blind foreground subtraction techniques. In particular, we consider different approaches: polynomial fitting, principal component analysis (PCA) independent (ICA). review motivations algorithms for three methods, show that they can all be described, using same mathematical framework, as approaches...
Future surveys of large-scale structure will be able to measure perturbations on the scale cosmological horizon, and so could potentially probe a number novel relativistic effects that are negligibly small sub-horizon scales. These leave distinctive signatures in power spectra clustering observables and, if measurable, would open new window cosmology. We quantify size detectability for most relevant future experiments: spectroscopic photometric galaxy redshift surveys, intensity mapping...
ABSTRACT MIGHTEE is a galaxy evolution survey using simultaneous radio continuum, spectropolarimetry, and spectral line observations from the South African MeerKAT telescope. When complete, will image ∼20 deg2 over COSMOS, E-CDFS, ELAIS-S1, XMM-Newton Large Scale Structure field (XMM-LSS) extragalactic deep fields with central frequency of 1284 MHz. These were selected based on extensive multiwavelength data sets numerous existing forthcoming observational campaigns. Here, we describe...
While most purpose-built 21cm intensity mapping experiments are close-packed interferometer arrays, general-purpose dish arrays should also be capable of measuring the cosmological signal. This can achieved efficiently if array is used as a collection scanning autocorrelation dishes rather than an interferometer. As first step towards demonstrating feasibility this observing strategy, we show that able to successfully calibrate dual-polarisation data from 64 MeerKAT in L-band (856-1712 MHz,...
We present a detection of correlated clustering between MeerKAT radio intensity maps and galaxies from the WiggleZ Dark Energy Survey. find $7.7\sigma$ cross-correlation power spectrum, amplitude which is proportional to product HI density fraction ($\Omega_{\rm HI}$), bias ($b_{\rm HI}$) coefficient ($r$). therefore obtain constraint $\Omega_{\rm HI} b_{\rm r\,{=}\,[0.86\,{\pm}\,0.10\,({\rm stat})\,{\pm}\,0.12\,({\rm sys})]\,{\times}\,10^{-3}$, at an effective scale $k_{\rm...
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element to be deployed at the South African Radio Astronomy Observatory (SARAO) Square Kilometer Array (SKA) site Africa. Each of 6m, $f/0.23$ dishes will instrumented dual-polarisation feeds operating over frequency range 400-800 MHz. Through intensity mapping 21 cm emission line neutral hydrogen, HIRAX provide cosmological survey distribution...
Abstract This paper presents the design and deployment of Hydrogen Epoch Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements Reionization. First results from I array are published early 2022, system nearing completion. We describe discuss progress on commissioning future upgrades. As designated Square Kilometre pathfinder instrument, we also show number “case studies” that investigate systematics seen while system, which...
Twenty-one centimeter tomography is emerging as a powerful tool to explore the end of cosmic dark ages and reionization epoch, but it will only be good our ability accurately model remove astrophysical foreground contamination. Previous treatments this problem have focused on angular structure signal foregrounds what can achieved with limited spectral resolution (bandwidths in 1 MHz range). In paper we introduce evaluate ``blind'' method extract multifrequency 21cm by taking advantage smooth...
We study contributions from inhomogeneous (patchy) reionization to arcminute-scale (1000 < l 10,000) cosmic microwave background (CMB) anisotropies. show that inhomogeneities in the ionization fraction, rather than mean density, dominate both temperature and polarization power spectra. Depending on history clustering bias of ionizing sources, we find rms fluctuations range 2 8 μK corresponding values for are over orders magnitude smaller. Reionization can significantly cosmological parameter...
We measure several properties of the reionization process and corresponding low-frequency 21-cm signal associated with neutral hydrogen distribution, using a large volume, high resolution simulation cosmic reionization. The brightness temperature is derived by post-processing this numerical semi-analytical prescription. Our study extends to redshifts (z ~ 25) where, in addition collisional coupling, our post-processed simulations take into account inhomogeneities heating gas X-rays effect an...