Selected Publications

Lyman-$\alpha$ emitters (LAEs) are a promising probe of the large-scale structure at high redshift, $z\gtrsim 2$. In particular, the Hobby-Eberly Telescope Dark Energy Experiment aims at observing LAEs at 1.9 $<z<$ 3.5 to measure the Baryon Acoustic Oscillation (BAO) scale and the Redshift-Space Distortion (RSD). However, (Zheng et al. 2011) pointed out that the complicated radiative transfer (RT) of the resonant Lyman-$\alpha$ emission line generates an anisotropic selection bias in the LAE clustering on large scales, $s\gtrsim 10\,{\rm Mpc}$. This effect could potentially induce a systematic error in the BAO and RSD measurements. Also, (Croft et al. 2016) claims an observational evidence of the effect in the Lyman-$\alpha$ intensity map, albeit statistically insignificant. We aim at quantifying the impact of the Lyman-$\alpha$ RT on the large-scale galaxy clustering in detail. For this purpose, we study the correlations between the large-scale environment and the ratio of an apparent Lyman-$\alpha$ luminosity to an intrinsic one, which we call the “observed fraction”, at $2<z<6$. We apply our Lyman-$\alpha$ RT code by post-processing the full Illustris simulations. We simply assume that the intrinsic luminosity of the Lyman-$\alpha$ emission is proportional to the star formation rate of galaxies in Illustris, yielding a sufficiently large sample of LAEs to measure the anisotropic selection bias. We find little correlations between large-scale environment and the observed fraction induced by the RT, and hence a smaller anisotropic selection bias than what was claimed by (Zheng et al. 2011). We argue that the anisotropy was overestimated in the previous work due to the insufficient spatial resolution: it is important to keep the resolution such that it resolves the high density region down to the scale of the interstellar medium, $\sim1$ physical kpc. We also find that the correlation can be further enhanced by assumptions in modeling intrinsic Lyman-$\alpha$ emission.
The impact of Lyman-α radiative transfer on large-scale clustering in the Illustris simulation, 2017.

Recent Publications

. Lya RT Real Space Clustering. The impact of Lyman-α radiative transfer on large-scale clustering in the Illustris simulation, 2017.

Preprint Project

. Viscosity, pressure, and support of the gas in simulations of merging cool-core clusters. Viscosity, pressure, and support of the gas in simulations of merging cool-core clusters, 2017.


Recent & Upcoming Talks

More Talks

Clustering Distortions from Lyman-alpha Radiative Transfer - A short introduction
Apr 13, 2018 10:20 AM
Cosmological radiative transfer simulations of Lyman-alpha emission: the impact on the galaxy clustering
Feb 5, 2018 6:10 PM
Radiative Transfer Simulations of Lyman Alpha Emitters on Cosmological Scales
Oct 4, 2017 3:00 PM

Recent Posts

Introduction Lyman-$\alpha$ emitters and their intensity map are powerful probes of the large-scale structure. Given typically very high optical depths, scatterings with neutral hydrogen have a non-negligible impact on the observed distribution of Lyman-$\alpha$ photons. To study this in detail, we run a suit of radiative transfer (RT) simulations on the Illustris simulation and investigate two possible distortion effects arising from RT in real space as well as in redshift space for the two-point correlation function.


The Haute Randonnée Pyrénéenne is an 800km hike from the Atlantic to the Mediterranean trying to cross the Pyrenees along the French-Spanish border at high altitude. This translates to a total elevation gain of 50km.1 There is no official trail, but a range of books and internet blogs giving outlines of a varying route (see Resources). I started becoming interested in hiking the HRP in early 2017 and luckily had 4 weeks of free time to complete it in August.