Yuxiang Qin
A5076969945- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Cosmology and Gravitation Theories
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Scientific Research and Discoveries
- Antenna Design and Optimization
- Gyrotron and Vacuum Electronics Research
- Superconducting and THz Device Technology
- Adaptive optics and wavefront sensing
- Particle Accelerators and Free-Electron Lasers
- Geophysics and Gravity Measurements
- Microwave Engineering and Waveguides
- Dark Matter and Cosmic Phenomena
- Gaussian Processes and Bayesian Inference
- Immunotherapy and Immune Responses
- Pulsed Power Technology Applications
- Computational Fluid Dynamics and Aerodynamics
- Millimeter-Wave Propagation and Modeling
- Educational Tools and Methods
The University of Melbourne
2016-2025
Australian National University
2025
ARC Centre of Excellence for All-sky Astrophysics
2018-2024
ASTRO-3D
2018-2024
Scuola Normale Superiore
2019-2024
Institute of Electronics
2021
Parks Victoria
2018
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 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 We present the JWST cycle 1 53.8 h medium program FRESCO, short for ‘First Reionization Epoch Spectroscopically Complete Observations’. FRESCO covers 62 arcmin2 in each of two GOODS/CANDELS fields a total area 124 exploiting JWST’s powerful new grism spectroscopic capabilities at near-infrared wavelengths. By obtaining ∼2 deep NIRCam/grism observations with F444W filter, yields unprecedented spectra R ∼ 1600 covering 3.8–5.0 µm most galaxies NIRCam field view. This setup enables...
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 > 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 ${M_{\small UV}}\lesssim -16$...
Abstract The variations in Ly α forest opacity observed at z > 5.3 between lines of sight to different background quasars are too strong be caused by fluctuations the density field alone. leading hypothesis for cause this excess variance is a late, ongoing reionization process redshifts below six. Another model proposes ionizing coupled short, spatially varying mean free path photons, without explicitly invoking incomplete reionization. With recent observations suggesting short ∼ 6, and...
ABSTRACT The transmission of Lyman α (Ly α) in the spectra distant quasars depends on density, temperature, and ionization state intergalactic medium. Therefore, high-redshift (z > 5) Ly forests could be invaluable studying late stages epoch reionization (EoR), as well properties sources that drive it. Indeed, high-quality quasar have now firmly established existence large-scale opacity fluctuations at z 5, whose physical origins are still debated. Here, we introduce a Bayesian...
This brief code paper presents a new Python-wrapped version of the popular 21cm cosmology simulator, 21cmFAST. The version, v3+, maintains same core functionality previous versions 21cmFAST, but features simple and intuitive interface, great deal more flexibility. evolution represents work formalized collaboration, available publicly on GitHub, provides single point-of-reference for all future upgrades community-added features. In this paper, we describe usage some its features, provide...
Abstract We present a new investigation of the intergalactic medium near reionization using dark gaps in Ly β forest. With its lower optical depth, offers potentially more sensitive probe to any remaining neutral gas compared commonly used α line. identify forest spectra 42 QSOs at z em > 5.5, including data from XQR-30 VLT Large Programme. Approximately 40% these QSO exhibit longer than 10 h −1 Mpc ≃ 5.8. By comparing results predictions simulations, we find that are broadly consistent...
Abstract We present a new investigation of the intergalactic medium (IGM) near end reionization using “dark gaps” in Ly α forest. Using spectra 55 QSOs at z em > 5.5, including data from XQR-30 VLT Large Programme, we identify gaps forest where transmission averaged over 1 comoving h −1 Mpc bins falls below 5%. Nine ultralong ( L 80 Mpc) dark are identified < 6. In addition, quantify fraction QSO exhibiting longer than 30 Mpc, F , as function redshift. measure ≃ 0.9, 0.6, and 0.15 =...
Abstract The mean free path of ionizing photons, λ mfp , is a critical parameter for modeling the intergalactic medium (IGM) both during and after reionization. We present direct measurements from QSO spectra over redshift range 5 < z 6, including first at ≃ 5.3 5.6. Our sample includes data XQR-30 VLT large program, as well new Keck/ESI observations QSOs near ∼ 5.5, which we also acquire [C ii ] 158 μ m redshifts with ALMA. By measuring Lyman continuum transmission profile in stacked...
Recent quasar absorption line observations suggest that reionization may end as late $z \approx 5.3$. As a means to search for large neutral hydrogen islands at $z<6$, we revisit long dark gaps in the Ly$\beta$ forest VLT/X-Shooter and Keck/ESI spectra. We stack Ly$\alpha$ corresponding both edges of these identify damping wing-like extended profile. The average redshift stacked is $z=5.8$. By comparing with simulations, infer such feature can be naturally explained if are least partially...
Abstract The redshifted 21cm signal from the Cosmic Dawn is expected to provide unprecedented insights into early Universe astrophysics and cosmology. Here we explore how dark matter can heat intergalactic medium before first galaxies, leaving a distinctive imprint in power spectrum. We dedicated Fisher matrix forecasts on sensitivity of Hydrogen Epoch Reionization Array (HERA) telescope decays. show that with 1000 hours observation, HERA has potential improve current cosmological...
Abstract We implemented Population III (Pop. III) star formation in mini-halos within the meraxes semi-analytic galaxy and reionisation model, run on top of a N-body simulation with L = 10h−1 cMpc 20483 particles resolving all dark matter halos down to (∼105M⊙). Our modelling includes chemical evolution IGM, metals released through supernova-driven bubbles that expand according Sedov-Taylor model. found SN-driven metal are generally small, radii typically 150 ckpc at z 6. Hence, majority...
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...
Motivated by recent measurements of the number density faint AGN at high redshift, we investigate contribution quasars to reionization tracking growth central supermassive black holes in an update Meraxes semi-analytic model. The model is calibrated against observed stellar mass function $z\sim0.6-7$, hole $z\lesssim0.5$, global ionizing emissivity $z\sim2-5$ and Thomson scattering optical depth. reproduces a Magorrian relation agreement with observations $z<0.5$ predicts decreasing towards...
ABSTRACT The very first galaxies that started the cosmic dawn likely resided in so-called ‘minihaloes’, with masses of ∼105–$10^8{\, {\rm M}_\odot }$, accreting their gas from intergalactic medium through H2 cooling. Such molecularly cooled (MCGs) mostly formed pristine environments, hosted massive, metal-free stars, and were eventually sterilized by build-up a disassociating (Lyman–Werner; LW) background. Therefore, properties might be different we see later Universe. Although MCGs are...
ABSTRACT Before the end of Epoch Reionization, Hydrogen in Universe was predominantly neutral. This leads to a strong attenuation Ly α lines z ≳ 6 galaxies intergalactic medium. Nevertheless, has been detected up very high redshifts (z ∼ 9) for several especially UV luminous galaxies. Here, we test what extent galaxy’s local environment might impact transmission such sources. We present an analysis dedicated Hubble Space Telescope (HST) imaging CANDELS/EGS field search fainter neighbours...
ABSTRACT Using a semi-analytic galaxy formation model, we study analogues of eight z ≳ 12 galaxies recently discovered by James Webb Space Telescope (JWST). We select from cosmological simulation with (311 cMpc)3 volume and an effective particle number 1012 enabling the resolution every atomic-cooling at ≤ 20. vary model parameters to reproduce observed ultraviolet (UV) luminosity function 5 &lt; 13, aiming for statistically representative high-redshift mock catalogue. forward-modelled...
ABSTRACT The attenuation of Lyα photons by neutral hydrogen in the intergalactic medium (IGM) at z ≳ 5 continues to be a powerful probe for studying epoch reionization. Given framework estimate intrinsic (true) emission high-z sources, one can infer ionization state IGM during In this work, we use enlarged XQR-30 sample 42 high-resolution and high signal-to-noise quasar spectra between $5.8\lesssim \, z\lesssim 6.6$ obtained with VLT/X-shooter place constraints on fraction. This is achieved...
Over the past decade, existence of a substantial population optically invisible, massive galaxies at $z\gtrsim3$ has been implied from mid-infrared to millimeter observations. With unprecedented sensitivity JWST, such extremely galaxy candidates have immediately identified even $z>7$, in much larger numbers than expected. These discoveries raised hot debate. If confirmed, early, high-mass challenge current models formation. However, lack spectroscopic confirmations leads uncertain stellar...
Abstract The precise characterization and mitigation of systematic effects is one the biggest roadblocks impeding detection fluctuations cosmological 21 cm signals. Missing data in radio experiments, often due to frequency interference (RFI), pose a particular challenge power spectrum analysis as this could lead ringing bright foreground modes Fourier space, heavily contaminating Here we show that problem missing becomes even more arduous presence effects. Using realistic numerical...