A5007837596- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Superconducting and THz Device Technology
- Dark Matter and Cosmic Phenomena
- Radio Wave Propagation Studies
- Fiber-reinforced polymer composites
- Gamma-ray bursts and supernovae
- Antenna Design and Optimization
- Pulsars and Gravitational Waves Research
- History and Developments in Astronomy
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Material Properties and Applications
- Electromagnetic Compatibility and Measurements
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Carbon Nanotubes in Composites
- Soil Moisture and Remote Sensing
- Graphite, nuclear technology, radiation studies
- Computational Physics and Python Applications
- Graphene research and applications
University of Cambridge
2019-2025
Institute of Astronomy
2024-2025
University College London
2023
Center for Astrophysics Harvard & Smithsonian
2016-2022
University of Sussex
2019-2022
The University of Tokyo
2019
Sussex County Community College
2019
Princeton University
2018
Harvard University
2016-2018
Centre National de la Recherche Scientifique
2013-2016
We present a theoretical analysis of some unexplored aspects relaxed Bose–Einstein condensate dark matter (BECDM) haloes. This type ultralight bosonic scalar field is viable alternative to the standard cold (CDM) paradigm, as it makes same large-scale predictions CDM and potentially overcomes CDM's small-scale problems via galaxy-scale de Broglie wavelength. simulate BECDM halo formation through mergers, evolved under Schrödinger–Poisson equations. The formed haloes consist soliton core...
The recent tentative detection by the EDGES Low-Band antenna of hydrogen 21-cm line from cosmic dawn, if confirmed, is first ever signature observed epoch primordial star formation. However, magnitude and shape this signal are incompatible with standard astrophysical predictions, requiring either colder than expected gas, or an excess radio background above Cosmic Microwave Background (CMB) radiation. In paper we explore latter option, investigating possible signals in models a...
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...
The early star-forming Universe is still poorly constrained, with the properties of high-redshift stars, first heating sources, and reionization highly uncertain. This leaves observers planning 21-cm experiments little theoretical guidance. In this work we explore possible range parameters including star formation efficiency minimal mass halos; efficiency, spectral energy distribution, redshift evolution X-ray sources; history reionization. These are only weakly constrained by available...
The recent detection of an anomalously strong 21-cm signal neutral hydrogen from cosmic dawn by the EDGES low-band radio experiment can be explained if cold dark matter particles scattered off baryons draining excess energy gas. In this Letter we explore expanded range that is opened up interaction, varying astrophysical parameters as well properties in widest possible range. We identify models consistent with current data comparing to both region and upper limits high-band antenna. find...
The Large-aperture Experiment to Detect the Dark Age (LEDA) was designed detect predicted O(100) mK sky-averaged absorption of cosmic microwave background by hydrogen in neutral pre- and intergalactic medium just after cosmological Age. spectral signature would be associated with emergence a diffuse Lyα from starlight during 'Cosmic Dawn'. Recently, Bowman et al. have reported detection this feature, an unexpectedly large amplitude 530 mK, centred at 78 MHz. Verification result independent...
Recently the initial supersonic relative velocity between dark matter and baryons was shown to have an important effect on galaxy formation at high redshift. We study impact of this motion distribution star-forming halos redshift very first star. include a new aspect found in recent simulations by fitting their results obtain spatially-varying minimum halo mass needed for molecular cooling. Thus, velocities three separate effects: suppression abundance, gas content within each halo, boosting...
In hierarchical models of structure formation, the first galaxies form in low-mass dark matter potential wells, probing behavior on kiloparsec scales. Even though these objects are below detection threshold current telescopes, future missions will open an observational window into this emergent world. Letter, we investigate how assembled a "fuzzy" (FDM) cosmology where is ultralight ∼10^{-22} eV boson and primordial stars expected to along dense filaments. Using first-of-its-kind...
The formation of the first stars is an exciting frontier area in astronomy. Early redshifts z ~ 20 have become observationally promising as a result recently recognized effect supersonic relative velocity between dark matter and gas. This produces prominent structure on 100 comoving Mpc scales, which makes it much more feasible to detect 21-cm fluctuations from epoch heating. We use semi-numerical hybrid methods follow for time joint evolution X-ray Lyman-Werner radiative backgrounds,...
The Schr\"odinger-Poisson equations describe the behavior of a superfluid Bose-Einstein condensate under self-gravity with 3D wave function. As $\ensuremath{\hbar}/m\ensuremath{\rightarrow}0$, $m$ being boson mass, have been postulated to approximate collisionless Vlasov-Poisson also known as Boltzmann-Poisson equations. latter matter 6D classical distribution We investigate nature this correspondence suite numerical test problems in 1D, 2D, and along analytic treatments when possible....
Concerted effort is currently ongoing to open up the Epoch of Reionization (z ∼15-6) for studies with IR and radio telescopes.Whereas detections have been made sources (Lyman-α emitters, quasars drop-outs) in this redshift regime relatively small fields view, no direct detection neutral hydrogen, via redshifted 21-cm line, has yet established.Such a expected coming years, surveys, could entire universe from z ∼6-200 astrophysical cosmological studies, opening not only Reionization, but also...
Spectral distortions in the cosmic microwave background over 40--200~MHz band are imprinted by neutral hydrogen intergalactic medium prior to end of reionization. This signal, produced redshift range $z = 6-34$ at rest frame wavelength 21 cm, has not been detected yet; and poor understanding high astrophysics results a large uncertainty expected spectrum. The SARAS~2 radiometer was purposely designed detect sky-averaged 21-cm signal. instrument, deployed Timbaktu Collective (Southern India)...
ABSTRACT Bose–Einstein condensate dark matter (BECDM, also known as fuzzy matter) is motivated by fundamental physics and has recently received significant attention a serious alternative to the established cold (CDM) model. We perform cosmological simulations of BECDM gravitationally coupled baryons investigate structure formation at high redshifts (z ≳ 5) for boson mass m = 2.5 × 10−22 eV, exploring dynamical effects its wavelike nature on cosmic web first galaxies. Our are directly...
ABSTRACT The ARCADE2 and LWA1 experiments have claimed an excess over the cosmic microwave background (CMB) at low radio frequencies. If cosmological high-redshift contribution to this is between 0.1 per cent 22 of CMB 1.42 GHz, it could explain tentative EDGES low-band detection anomalously deep absorption in 21-cm signal neutral hydrogen. We use upper limit on from Epoch Reionization (z = 9.1) based 141 h observations with LOFAR evaluate Universe detected background. Marginalizing...
We investigate cosmological structure formation in Fuzzy Dark Matter (FDM) with an attractive self-interaction (SI) numerical simulations. Such a SI would arise if the FDM boson were ultra-light axion, which has strong CP symmetry-breaking scale (decay constant). Although weak, may be enough to counteract quantum 'pressure' and alter formation. find our simulations that can enhance small-scale formation, soliton cores above critical mass undergo phase transition, transforming from dilute...
ABSTRACT The recent reported discovery of a low-mass z = 5.2 and an intermediate-mass 7.3 quenched galaxy with JWST/NIRSpec is the first evidence halted star formation above ≈ 5. Here, we show how bursty at 4–8 gives rise to temporarily quenched, or mini-quenched galaxies in mass range M⋆ 107–109 M⊙ using four models formation: periodic box simulation IllustrisTNG, zoom-in simulations vela FirstLight empirical halo model. main causes for mini-quenching are stellar feedback, lack gas...
We explore the complete history of 21 cm signal in redshift range z = 7–40. This includes various epochs cosmic evolution related to primordial star formation, and should be accessible existing or planned low-frequency radio telescopes. use semi-numerical computational methods fluctuation over wavenumbers between 0.03 1 Mpc−1, accounting for inhomogeneous backgrounds Lyα, X-ray, Lyman–Werner ionizing radiation. focus on recently noted expectation heating dominated by a hard X-ray spectrum...
Long wavelength spectral distortions in the Cosmic Microwave Background arising from 21-cm transition neutral Hydrogen are a key probe of Dawn and Epoch Reionization. These features may reveal nature first stars ultra-faint galaxies that transformed spin temperature ionization state primordial gas. SARAS~2 is radiometer purposely designed for precision measurement these monopole or all-sky global distortions. We use 63~hr night time observing radio background frequency band 110-200~MHz with...
The Herschel Multi-tiered Extragalactic Survey (HerMES) has identified large numbers of dusty star-forming galaxies (DSFGs) over a wide range in redshift. A detailed understanding these DSFGs is hampered by the limited spatial resolution Herschel. We present 870 μm 045 imaging obtained with Atacama Large Millimeter/submillimeter Array (ALMA) sample 29 HerMES that have far-infrared (FIR) flux densities lie between brightest sources found and fainter via ground-based surveys submillimeter...
Abstract We present new constraints on parameters of cosmic dawn and the epoch reionization derived from EDGES High-Band spectrum (90–190 MHz). The are probed by evaluating global 21 cm signals generated with recently developed Global21cm tool. This tool uses neural networks trained tested ∼30,000 spectra produced semi-numerical simulations that assume standard thermal evolution microwave background intergalactic medium. From our analysis, we constrain at 68% (1) minimum virial circular...
ABSTRACT Radio sources are expected to have formed at high redshifts, producing an excess radiation background above the cosmic microwave (CMB) low frequencies. Their effect on redshifted 21-cm signal of neutral hydrogen is usually neglected, as it assumed that associated small. Recently, radio has been proposed a possible explanation for unusually strong reported by EDGES. As result, implications smooth and extremely both sky-averaged its fluctuations considered. Here, we take into account...