Kyungjin Ahn
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View article: Dust-UV offsets in high-redshift galaxies in the Cosmic Dawn III simulation
Dust-UV offsets in high-redshift galaxies in the Cosmic Dawn III simulation Open
Recent observations reveal puzzling spatial offsets between the ALMA dust continuum from bright galaxies at z = 5–7 and their UV emission seen by HST and JWST (e.g. ALPINE and REBELS surveys). We investigated this using Cosmic Dawn (‘CoDa’…
View article: Square Kilometre Array Science Data Challenge 3a: foreground removal for an EoR experiment
Square Kilometre Array Science Data Challenge 3a: foreground removal for an EoR experiment Open
We present and analyse the results of the Science Data Challenge 3a (SDC3a, https://sdc3.skao.int/challenges/foregrounds), an epoch of reionization (EoR) foreground-removal exercise organized by the Square Kilometre Array Observatory (SKAO…
View article: Predictions for dispersion measures of fast radio bursts through the epoch of reionization using CoDa II
Predictions for dispersion measures of fast radio bursts through the epoch of reionization using CoDa II Open
Dispersion measures (DM) of fast radio bursts (FRBs) probe the density of electrons in the intergalactic medium along their lines of sight, including the average density versus distance to the source and its variations in direction. While …
View article: The thermal Sunyaev–Zel’dovich effect from the epoch of reionization
The thermal Sunyaev–Zel’dovich effect from the epoch of reionization Open
The thermal Sunyaev–Zel’dovich (tSZ) effect arises from inverse Compton scattering of low energy photons on to thermal electrons, proportional to the integrated electron pressure, and is usually observed from galaxy clusters. We can expect…
View article: Line Intensity Mapping Prediction from the Cosmic Dawn (CoDa). III. Simulation for H<i>α</i> from Galaxies and the Intergalactic Medium During the Epoch of Reionization
Line Intensity Mapping Prediction from the Cosmic Dawn (CoDa). III. Simulation for H<i>α</i> from Galaxies and the Intergalactic Medium During the Epoch of Reionization Open
The evolution of large-scale structure, galaxies and the intergalactic medium (IGM) during the Epoch of Reionization can be probed by upcoming Line Intensity Mapping (LIM) experiments, which sample in redshift and direction without needing…
View article: Constraining Reionization with Ly<i>α</i> Damping-wing Absorption in Galaxy Spectra: A Machine Learning Model Based on Reionization Simulations
Constraining Reionization with Ly<i>α</i> Damping-wing Absorption in Galaxy Spectra: A Machine Learning Model Based on Reionization Simulations Open
Recently, NIRSpec PRISM/CLEAR observations by JWST have begun providing rest-frame UV continuum measurements of galaxies at z ≳ 7, revealing signatures of Ly α damping-wing (DW) absorption by the intergalactic medium (IGM). We develop a me…
View article: Kinematically induced dipole anisotropy in line-emitting galaxy number counts and line intensity maps
Kinematically induced dipole anisotropy in line-emitting galaxy number counts and line intensity maps Open
The motion of the solar system against an isotropic radiation background, such as the cosmic microwave background, induces a dipole anisotropy in the background due to the Doppler effect. Flux-limited observation of the continuum radiation…
View article: Dispersion Measures of Fast Radio Bursts through the Epoch of Reionization
Dispersion Measures of Fast Radio Bursts through the Epoch of Reionization Open
Dispersion measures (DM) of fast radio bursts (FRBs) probe the density of electrons in the intergalactic medium (IGM) along their lines-of-sight, including the average density versus distance to the source and its variations in direction. …
View article: Constraining Reionization with Lyα Damping-Wing Absorption in Galaxy Spectra: A Machine Learning Model Based on Reionization Simulations
Constraining Reionization with Lyα Damping-Wing Absorption in Galaxy Spectra: A Machine Learning Model Based on Reionization Simulations Open
Recently, NIRSpec PRISM/CLEAR observations by JWST have begun providing rest-frame UV continuum measurements of galaxies at $z\gtrsim7$, revealing signatures of Ly$α$ damping-wing (DW) absorption by the intergalactic medium (IGM). We devel…
View article: Dust-UV offsets in high-redshift galaxies in the Cosmic Dawn III simulation
Dust-UV offsets in high-redshift galaxies in the Cosmic Dawn III simulation Open
Recent observations have revealed puzzling spatial disparities between ALMA dust continuum and UV emission as seen by HST and JWST in galaxies at $z=5-7$ (e.g. ALPINE and REBELS surveys), compelling us to propose a physical interpretation …
View article: Probing the Global 21 cm Background by Velocity-induced Dipole and Quadrupole Anisotropies
Probing the Global 21 cm Background by Velocity-induced Dipole and Quadrupole Anisotropies Open
The motion of an observer in the rest frame of the cosmic 21 cm background induces an anisotropy in the observed background, even when the background is isotropic. The induced anisotropy includes a dipole and a quadrupole, in the order dec…
View article: Probing the Global 21-cm Signal via the Integrated Sachs-Wolfe Effect on the 21-cm Background
Probing the Global 21-cm Signal via the Integrated Sachs-Wolfe Effect on the 21-cm Background Open
We propose a novel method to probe the global 21-cm background. This background experiences the integrated Sachs-Wolfe effect (ISW) as the cosmic microwave background does. The 21-cm ISW is modulated by the spectral shape of the global 21-…
View article: Cosmic variance and the inhomogeneous UV luminosity function of galaxies during reionization
Cosmic variance and the inhomogeneous UV luminosity function of galaxies during reionization Open
When the first galaxies formed and starlight escaped into the intergalactic medium to reionize it, galaxy formation and reionization were both highly inhomogeneous in time and space, and fully coupled by mutual feedback. To show how this i…
View article: Probing the global 21-cm background by velocity-induced dipole and quadrupole anisotropies
Probing the global 21-cm background by velocity-induced dipole and quadrupole anisotropies Open
The motion of an observer in the rest frame of the cosmic 21-cm background induces an anisotropy in the observed background, even when the background is isotropic. The induced anisotropy includes a dipole and a quadrupole, in the order dec…
View article: Cosmic Variance and the Inhomogeneous UV Luminosity Function of Galaxies During Reionization
Cosmic Variance and the Inhomogeneous UV Luminosity Function of Galaxies During Reionization Open
When the first galaxies formed and starlight escaped into the intergalactic medium to reionize it, galaxy formation and reionization were both highly inhomogeneous in time and space, and fully-coupled by mutual feedback. To show how this i…
View article: The short ionizing photon mean free path at <i>z</i> = 6 in Cosmic Dawn III, a new fully coupled radiation-hydrodynamical simulation of the Epoch of Reionization
The short ionizing photon mean free path at <i>z</i> = 6 in Cosmic Dawn III, a new fully coupled radiation-hydrodynamical simulation of the Epoch of Reionization Open
Recent determinations of the mean free path of ionizing photons (mfp) in the intergalactic medium (IGM) at z = 6 are lower than many theoretical predictions. In order to gain insight, we investigate the evolution of the mfp in our new mass…
View article: Reionization time of the Local Group and Local-Group-like halo pairs
Reionization time of the Local Group and Local-Group-like halo pairs Open
Patchy cosmic reionization resulted in the ionizing UV background asynchronous rise across the Universe. The latter might have left imprints visible in present-day observations. Several numerical simulation-based studies show correlations …
View article: Reionization time of the Local Group and Local-Group-like halo pairs
Reionization time of the Local Group and Local-Group-like halo pairs Open
Patchy cosmic reionization resulted in the ionizing UV background asynchronous rise across the Universe. The latter might have left imprints visible in present day observations. Several numerical simulation-based studies show correlations …
View article: Probing the Early History of Cosmic Reionization by Future Cosmic Microwave Background Experiments
Probing the Early History of Cosmic Reionization by Future Cosmic Microwave Background Experiments Open
Cosmic reionization imprints its signature on the temperature and polarization anisotropies of the cosmic microwave background (CMB). Advances in CMB telescopes have already placed a significant constraint on the history of reionization. A…
View article: The short ionizing photon mean free path at z=6 in Cosmic Dawn III, a\n new fully-coupled radiation-hydrodynamical simulation of the Epoch of\n Reionization
The short ionizing photon mean free path at z=6 in Cosmic Dawn III, a\n new fully-coupled radiation-hydrodynamical simulation of the Epoch of\n Reionization Open
Recent determinations of the mean free path of ionising photons (mfp) in the\nintergalactic medium (IGM) at $\\rm z=6$ are lower than many theoretical\npredictions. To gain insight into this issue, we investigate the evolution of\nthe mfp …
View article: The short ionizing photon mean free path at z=6 in Cosmic Dawn III, a new fully-coupled radiation-hydrodynamical simulation of the Epoch of Reionization
The short ionizing photon mean free path at z=6 in Cosmic Dawn III, a new fully-coupled radiation-hydrodynamical simulation of the Epoch of Reionization Open
Recent determinations of the mean free path of ionising photons (mfp) in the intergalactic medium (IGM) at $\rm z=6$ are lower than many theoretical predictions. To gain insight into this issue, we investigate the evolution of the mfp in o…
View article: Pulmonary arterial hypertension due to antiphospholipid syndrome initially mimicking chronic thromboembolic pulmonary hypertension
Pulmonary arterial hypertension due to antiphospholipid syndrome initially mimicking chronic thromboembolic pulmonary hypertension Open
Pulmonary arterial hypertension (PAH) is the second most common lung complication in antiphospholipid syndrome (APS) patients. However, the concurrent development of APS-related nonthrombotic PAH is rarely reported. Lack of awareness for g…
View article: Crucial Factors for Lyα Transmission in the Reionizing Intergalactic Medium: Infall Motion, H ii Bubble Size, and Self-shielded Systems
Crucial Factors for Lyα Transmission in the Reionizing Intergalactic Medium: Infall Motion, H ii Bubble Size, and Self-shielded Systems Open
Using the CoDa II simulation, we study the Ly α transmissivity of the intergalactic medium (IGM) during reionization. At z > 6, a typical galaxy without an active galactic nucleus fails to form a proximity zone around itself due to the ove…
View article: Lyman-α transmission properties of the intergalactic medium in the CoDaII simulation
Lyman-α transmission properties of the intergalactic medium in the CoDaII simulation Open
The decline in abundance of Lyman-α (Lyα) emitting galaxies at z ≳ 6 is a powerful and commonly used probe to constrain the progress of cosmic reionization. We use the CoDaII simulation, which is a radiation hydrodynamic simulation featuri…
View article: Cosmic Reionization May Still Have Started Early and Ended Late: Confronting Early Onset with Cosmic Microwave Background Anisotropy and 21 cm Global Signals
Cosmic Reionization May Still Have Started Early and Ended Late: Confronting Early Onset with Cosmic Microwave Background Anisotropy and 21 cm Global Signals Open
The global history of reionization was shaped by the relative amounts of starlight released by three halo mass groups: the first two groups are atomic-cooling halos (ACHs) with virial temperatures T vir > 10 4 K, either (1) massive enough …
View article: Crucial Factors of Ly{\alpha} Transmission in the Reionizing Intergalactic Medium: Infall Motion, HII Bubble Size, and Self-shielded Systems
Crucial Factors of Ly{\alpha} Transmission in the Reionizing Intergalactic Medium: Infall Motion, HII Bubble Size, and Self-shielded Systems Open
Using the CoDaII simulation, we study the Ly$\alpha$ transmissivity of the intergalactic medium (IGM) during reionization. At $z>6$, a typical galaxy without an active galactic nuclei fails to form a proximity zone around itself due to the…
View article: The impact of inhomogeneous subgrid clumping on cosmic reionization – II. Modelling stochasticity
The impact of inhomogeneous subgrid clumping on cosmic reionization – II. Modelling stochasticity Open
Small-scale density fluctuations can significantly affect reionization, but are typically modelled quite crudely. Unresolved fluctuations in numerical simulations and analytical calculations are included using a gas clumping factor, typica…
View article: Abruptly-Switching MoS₂-Channel Atomic-Threshold-Switching Field-Effect Transistor With AgTi/HfO₂-Based Threshold Switching Device
Abruptly-Switching MoS₂-Channel Atomic-Threshold-Switching Field-Effect Transistor With AgTi/HfO₂-Based Threshold Switching Device Open
A two-dimension (2D) atomic-threshold-switching field-effect transistor (ATS-FET) was implemented, by connecting an AgTi/HfO2-based threshold-switching (TS) device in series to the drain electrode of the 2D baseline-FET with molybdenum dis…
View article: HIR4: cosmological signatures imprinted on the cross-correlation between a 21-cm map and galaxy clustering
HIR4: cosmological signatures imprinted on the cross-correlation between a 21-cm map and galaxy clustering Open
We explore the cosmological multitracer synergies between an emission-line galaxy distribution from the Dark Energy Spectroscopic Instrument and a Tianlai Project 21-cm intensity map. We use simulated maps generated from a particle simulat…
View article: First Structure Formation under the Influence of Gas–Dark Matter Streaming Velocity and Density: Impact of the “Baryons Trace Dark Matter” Approximation
First Structure Formation under the Influence of Gas–Dark Matter Streaming Velocity and Density: Impact of the “Baryons Trace Dark Matter” Approximation Open
The impact of streaming between baryons and dark matter on the first structures has been actively explored by recent studies. We investigate how the key results are affected by two popular approximations. One is to implement the streaming …