arXiv subjects

Wooseok Kang

Publications and source records attributed to Wooseok Kang.

5 recordsLinked to original sources

arXiv2026

A New Window into the Baryon Cycle at Cosmic Noon with Line Intensity Mapping: Forecasts for auto- and cross-correlations in [CII]-158$μ$m, HI 21 cm, CO$_{J+1\rightarrow J}$, and H$α$ galaxies

Across the peak of cosmic star formation at $z\sim1-2$, inflow, processing, and feedback drive rapid changes in the spatial distribution and chemical composition of baryons in galaxies and surrounding reservoirs; this baryon cycle can be tomographically mapped by line intensity mapping (LIM) of atomic hydrogen, ionized carbon, and carbon monoxide. We present a simulation-based forecasting framework for detecting auto- and cross-power spectra between spectroscopic surveys of four such tracers at $z\sim0.5-1.7$ mapping the same deep field - TIM, EoRSpec/FYST, MeerKAT, & Euclid. We forward-model 3-D distributions for these tracers from magnetohydrodynamic simulations, directly capturing the two-halo, one-halo, and shot statistics without relying on analytical decompositions. We further detail a signal-to-noise formalism, tailored to LIM surveys with highly anisotropic geometries and Fourier-space coverage. We demonstrate that galaxy cross-correlations will be the dominant discovery channel for current-generation surveys. These instruments will detect the auto-spectra for CO and HI 21 cm and the CO $\times$ 21 cm cross-spectrum at modest S/N $\sim 1-10$, while placing upper limits on the [CII]-158$μ$m signals. [CII], CO, and HI LIM will be $\sim3-30\times$ ($0.5-1.5$ dex) more sensitive to cross-correlation with the Euclid survey, however, than their respective auto-correlations, constraining all three models of line emission at high significance (S/N $\sim 10-40$) within this decade. Finally, we formulate a staged instrumental trajectory with planned or reasonable improvements, including the as-proposed SKA-Mid. We forecast advancing the per-$k$-mode sensitivities of each auto-, galaxy-line, and line-line spectrum by several orders of magnitude, enabling new percent- and sub-percent level constraints on cosmology and the redshift evolution of star formation and the baryon cycle.

astro-ph.CO↗

arXiv2026

Forecasting the cross correlation of Terahertz Intensity Mapper [CII] line intensity maps with Euclid galaxies

We forecast that the Terahertz Intensity Mapper (TIM) cross-correlated with Euclid's Fornax deep field (EDF-F), TIM$\times$EDF-F, will detect the [CII]-galaxy cross-power spectrum at a median redshift of 1.1 with $\gtrsim 7 σ$ confidence. The Poisson component of the cross-power spectrum at $0.1 \leq k \leq 10$ hMpc$^{-1}$ (i.e. cross-shot noise) will be detected at $\gtrsim 3 σ$ in 4 bins spanning $0.5 < z< 1.7$. This measurement will constrain the mean [CII] specific intensity over half of cosmic history and assess the degree to which Euclid-selected galaxies account for the [CII] intensity observed by TIM. We find that TIM can detect the cross-power spectrum across a wide range of [CII] intensity models.

astro-ph.GA↗

arXiv2025

A Redshift Survey of the Coma Cluster (A1656): Understanding the Nature of Subhalos in the Weak-lensing Map

We study the physical properties of weak-lensing subhalos in the Coma cluster of galaxies using data from galaxy redshift surveys. The data include 12989 galaxies with measured spectroscopic redshifts (2184 from our MMT/Hectospec observation and 10807 from the literature). The $r$-band magnitude limit at which the differential spectroscopic completeness drops below 50% is 20.2 mag, which is spatially uniform in a region of 4.5 deg$^{2}$ where the weak-lensing map of Okabe et al. (2014) exists. We identify 1337 member galaxies in this field and use them to understand the nature of 32 subhalos detected in the weak-lensing analysis. We use Gaussian Mixture Modeling (GMM) in the line-of-sight velocity domain to measure the mean velocity, the velocity dispersion, and the number of subhalo galaxies by mitigating the contamination from the interloping galaxies. Using subhalo properties calculated with GMM, we find no significant difference in the redshift space distribution between the cluster member galaxies and subhalos. We find that the weak-lensing mass shows strong correlations with the number of subhalo member galaxies, velocity dispersion, and dynamical mass of subhalos with power-law slopes of $0.54^{+0.16}_{-0.15}$, $0.93^{+0.35}_{-0.32}$, and $0.50^{+0.31}_{-0.18}$, respectively. The slope of the mass--velocity dispersion relation of the weak-lensing subhalos appears shallower than that of the galaxy clusters, galaxy groups, and individual galaxies. These results suggest that the combination of redshift surveys with weak-lensing maps can be a powerful tool for better understanding the nature of subhalos in clusters.

astro-ph.GA↗

arXiv2025

Direct Evidence of a Major Merger in the Perseus Cluster

Although the Perseus cluster has often been regarded as an archetypical relaxed galaxy cluster, several lines of evidence including ancient, large-scale cold fronts, asymmetric plasma morphology, filamentary galaxy distribution, etc., provide a conflicting view of its dynamical state, suggesting that the cluster might have experienced a major merger. However, the absence of a clear merging companion identified to date hampers our understanding of the evolutionary track of the Perseus cluster consistent with these observational features. In this paper, through careful weak lensing analysis, we successfully identified the missing subcluster halo ($M_{200}=1.70^{+0.73}_{-0.59}\times10^{14}~M_{\odot}$) at the >5$σ$ level centered on NGC1264, which is located ~430 kpc west of the Perseus main cluster core. Moreover, a significant ($>3σ$) mass bridge, which is also traced by the cluster member galaxies, is detected between the Perseus main and sub clusters, which serves as direct evidence of gravitational interaction. With idealized numerical simulations, we demonstrate that a ~3:1 off-axis major merger can create the cold front observed ~700 kpc east of the main cluster core and also generate the observed mass bridge through multiple core crossings. This discovery resolves the long-standing puzzle of Perseus' dynamical state.

astro-ph.GA↗

arXiv2024

A Deep Redshift Survey of the Perseus Cluster: Spatial Distribution and Kinematics of Galaxies

We study the global kinematics of the Perseus galaxy cluster (Abell 426) at redshift z = 0.017 using a large sample of galaxies from our new MMT/Hectospec spectroscopic observation for this cluster. The sample includes 1447 galaxies with measured redshifts within 60' from the cluster center (1148 from this MMT/Hectospec program and 299 from the literature). The resulting spectroscopic completeness is 67% at r-band apparent magnitude $r_{\rm{Petro, 0}}\leq 18.0$ within 60' from the cluster center. To identify cluster member galaxies in this sample, we develop a new open-source Python package, CausticSNUpy. This code implements the algorithm of the caustic technique and yields 418 member galaxies within 60' of the cluster. We study the cluster using this sample of member galaxies. The cluster shows no significant signal of global rotation. A statistical test shows that the cluster does not have a noticeable substructure within 30'. We find two central regions where the X-ray emitting intracluster medium and galaxies show significant velocity differences ($>7σ$). On a large scale, however, the overall morphology and kinematics between the intracluster medium and galaxies agree well. Our results suggest that the Perseus cluster is a relaxed system and has not experienced a recent merger.

astro-ph.GA↗