A5071294469- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Superconducting and THz Device Technology
- Cosmology and Gravitation Theories
- Radio Wave Propagation Studies
- Astrophysics and Star Formation Studies
- Antenna Design and Optimization
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Scientific Research and Discoveries
- Astronomical Observations and Instrumentation
- Electromagnetic Compatibility and Measurements
- Millimeter-Wave Propagation and Modeling
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Particle Accelerators and Free-Electron Lasers
- Soil Moisture and Remote Sensing
- Precipitation Measurement and Analysis
- Microwave Engineering and Waveguides
- Particle Detector Development and Performance
- Statistical and numerical algorithms
Scuola Normale Superiore
2016-2025
Computing Center
2023-2024
Commonwealth Scientific and Industrial Research Organisation
2023
Studieförbundet Näringsliv och Samhälle
2015-2019
University of Groningen
2015
Princeton University
2008-2011
University of California, Los Angeles
2008
Yale University
2007-2008
Columbia University
2004-2008
Yale Cancer Center
2008
We introduce a powerful semi-numeric modeling tool, 21cmFAST, designed to efficiently simulate the cosmological 21-cm signal. Our code generates 3D realizations of evolved density, ionization, peculiar velocity, and spin temperature fields, which it then combines compute brightness temperature. Although physical processes are treated with approximate methods, we compare our results state-of-the-art large-scale hydrodynamic simulation, find good agreement on scales pertinent upcoming...
The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization ($z=6-12$), and explore earlier epochs our Cosmic Dawn ($z\sim30$). During these epochs, early stars black holes heated ionized IGM, introducing fluctuations in emission. HERA designed characterize evolution power spectrum constrain timing morphology reionization, properties first galaxies, large-scale structure,...
We present new upper limits on the volume-weighted neutral hydrogen fraction, <xHI>, at z~5-6 derived from spectroscopy of bright quasars. The fraction Lyman-alpha and Lyman-beta forests that is "dark" (with zero flux) provides only model-independent limit requiring no assumptions about physical conditions in intergalactic medium or quasar's unabsorbed UV continuum. In this work we update our previous results using a larger sample (22 objects) medium-depth (~ few hours) spectra high-redshift...
Detailed theoretical studies of the high-redshift universe, and especially reionization, are generally forced to rely on time-consuming N-body codes and/or radiative transfer algorithms. We present a method construct seminumerical "simulations," which can efficiently generate realizations halo distributions ionization maps at high redshifts. Our procedure combines an excursion-set approach with first-order Lagrangian perturbation theory operates directly linear density velocity fields. As...
We introduce 21 CMMC: a parallelized, Monte Carlo Markov Chain analysis tool, incorporating the epoch of reionization (EoR) seminumerical simulation CMFAST. CMMC estimates astrophysical parameter constraints from cm EoR experiments, accommodating variety models, as well priors on model parameters and history. To illustrate its utility, we consider two different scenarios, one with single population galaxies (with mass-independent ionizing efficiency) second, more general different,...
The properties of the first galaxies, expected to drive Cosmic Dawn and Epoch Reionization, are encoded in 3D structure cosmic 21-cm signal. Parameter inference from upcoming observations promises revolutionize our understanding these unseen galaxies. However, prior was done using models with several simplifying assumptions. Here we introduce a flexible, physically motivated parametrization for high-|$z$| galaxy properties, implementing it public code 21cmfast. In particular, allow their...
The presence of excess scatter in the Ly-$\alpha$ forest at $z\sim 5.5$, together with existence sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late end hydrogen reionisation. However, low data quality and systematic uncertainties complicate use transmission as precision probe reionisation's stages. In this paper, we assemble sample 67 quasar sightlines $z>5.5$ high signal-to-noise ratios $>10$ per $\leq 15$ km s$^{-1}$ spectral pixel, relying...
Abstract We report upper limits on the Epoch of Reionization 21 cm power spectrum at redshifts 7.9 and 10.4 with 18 nights data (∼36 hr integration) from Phase I Hydrogen Array (HERA). The show evidence for systematics that can be largely suppressed systematic models down to a dynamic range ∼10 9 respect peak foreground power. This yields 95% confidence limit <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi...
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...
ABSTRACT The formation of the first galaxies during cosmic dawn and reionization (at redshifts z = 5–30), triggered last major phase transition our universe, as hydrogen evolved from cold neutral to hot ionized. 21-cm line will soon allow us map these milestones study that drove them. To aid in interpreting observations, we upgrade publicly available code 21cmFAST. We introduce a new, flexible parametrization additive feedback from: an inhomogeneous, H2-dissociating (Lyman–Werner; LW)...
ABSTRACT The final phase of the reionization process can be probed by rest-frame UV absorption spectra quasars at z ≳ 6, shedding light on properties diffuse intergalactic medium within first Gyr Universe. ESO Large Programme ‘XQR-30: ultimate XSHOOTER legacy survey ≃ 5.8–6.6’ dedicated ∼250 h observations VLT to create a homogeneous and high-quality sample 30 luminous ∼ covering rest wavelength range from Lyman limit beyond Mg ii emission. Twelve quasar similar quality archive were added...
ABSTRACT Lyman-alpha (Ly α) emission from galaxies is currently our most promising probe for constraining when and how reionization began, thus the first formed. At z &gt; 7, majority of detected with Ly α are in candidate overdensities. Here, we quantify probability these residing large ionized bubbles. We create (1.6 Gpc)3 intergalactic medium (IGM) simulations: sufficient volume to robustly measure bubble size distributions around UV-bright rare find ${M_{\small UV}}\lesssim -16$...
[abridged] With their long mean free paths and efficient heating of the intergalactic medium (IGM), X-rays could have a dramatic impact on thermal ionization history Universe. We explore this in various signals: (i) Reionization history: including results an earlier, more extended reionization. Efficient feedback from X-ray yield extended, ~10% ionized epoch. (ii) morphology: sizable (~10%) contribution to reionization uniform morphology, though is modest when compared at same global neutral...
The earliest generation of stars and black holes must have established an early 'Lyman-Werner' background (LWB) at high redshift, prior to the epoch reionization. Because long mean free path photons with energies E<13.6 eV, LWB was nearly uniform. However, some variation in is expected due discrete nature sources, their highly clustered spatial distribution. In this paper, we compute probability distribution function (PDF) LW flux that irradiates dark matter (DM) halos collapsing...
We compare the predictions of four different algorithms for distribution ionized gas during Epoch Reionization. These are all used to run a 100 Mpc h−1 simulation reionization with same initial conditions. Two state-of-the-art ray-tracing radiative transfer codes that use disparate methods calculate ionization history. The other two fast but more approximate schemes based on iterative applications smoothing filter underlying source and density fields. these algorithms' resulting 21-cm fields...
We present new results from our search for z~7 galaxies deep spectroscopic observations of candidate z-dropouts in the CANDELS fields. Despite extremely low flux limits achieved by sensitive observations, only 2 have robust redshift identifications, one its Lyalpha emission line at z=6.65, other Lyman-break, i.e. continuum discontinuity wavelength consistent with a 6.42, but no line. In addition, 23 we EW derived non detections ultra-deep observations. Using this data as well previous...
The large cross-section of the Lyman alpha (Lya) line makes it a sensitive probe ionization state intergalactic medium (IGM). Here we present most complete study to date IGM Lya opacity, and its application redshift evolution 'Lya fraction', i.e. fraction color-selected galaxies with detectable emission line. We use tiered approach, which combines large-scale semi-numeric simulations reionization moderate-scale hydrodynamic ionized IGM. This allows us simultaneously account for in both: (i)...
By depleting the ionizing photon budget available to expand cosmic HII regions, recombining systems (or Lyman limit systems) can have a large impact during (and following) reionization. Unfortunately, directly resolving such structures in large-scale reionization simulations is computationally impractical. Instead, here we implement sub-grid prescription for tracking inhomogeneous recombinations intergalactic medium. Building on previous work parameterizing photo-heating feedback...
We quantify the presence of Ly\alpha\ damping wing absorption from a partially-neutral intergalactic medium (IGM) in spectrum $z=7.08$ QSO, ULASJ1120+0641. Using Bayesian framework, we simultaneously account for uncertainties in: (i) intrinsic QSO emission spectrum; and (ii) distribution cosmic HI patches during epoch reionisation (EoR). For use new line reconstruction method (Greig et al.), sampling covariance matrix properties built large database moderate-$z$ QSOs. (ii), Evolution 21-cm...
The nature of the seeds high-redshift supermassive black holes (SMBHs) is a key question in cosmology. Direct collapse (DCBH) that form pristine, atomic-line cooling halos, illuminated by Lyman-Werner (LW) UV flux exceeding critical threshold J_crit, represent an attractive possibility. We investigate when and where these conditions are met during cosmic evolution. For LW intensity, J_LW, we account for departures from background value close proximity to star forming galaxies. pristine halo...
We study the visibility of Lyα emission line during epoch reionization. Combining galactic outflow models with large-scale seminumeric simulations reionization, we quantify probability distribution function fraction photons transmitted through intergalactic medium (IGM), . Our focuses on galaxies populating dark matter haloes masses Mhalo= 1010 M⊙ at z= 8.6, which is inspired by recent reported discovery a galaxy 8.6 strong emission. For reasonable assumptions, find that combination winds...
The spectra of several high-redshift (z > 6) quasars have shown indications for a Gunn–Peterson (GP) damping wing, suggesting substantial mean neutral hydrogen fraction (|$\bar{x}_{\rm H\,{\scriptscriptstyle I}}^{\rm IGM}\gtrsim 0.03$|) in the z ≈ 6 intergalactic medium (IGM). However, previous analyses assumed that IGM was uniformly ionized outside quasar's H ii region. Here we relax this assumption and model patchy reionization scenarios range quasar parameters. Compared to uniform...
The cosmological 21 cm signal is a physics-rich probe of the early Universe, encoding information about both ionization and thermal history intergalactic medium (IGM). latter likely governed by X-rays from star formation processes inside very high redshift (z ≳ 15) galaxies. Due to strong dependence mean free path on photon energy, X-ray spectral energy distribution (SED) can have significant impact interferometric cosmic dawn. Recent Chandra observations nearby, star-forming galaxies show...