Xiaojing Lin

I am currently a third-year graduate student at Department of Astronomy, Tsinghua University, advised by Prof. Zheng Cai. I am now an exchange student in Steward Observatory working with Prof. Xiaohui Fan. Before coming to Tsinghua, I got my Bachelor degree at Peking University in Sep. 2021.

I have broad interests in galaxy evolution and galactic ecosystem in the early Universe. In particular, my research is focused on How galaxies evolve with their intrinsic and environmental properties, from both cosmological-scale and galatic-scale views, with multi-band observations and large surveys, e.g., SDSS, DESI, MUSE, JWST etc.

Contact Me
linxj21@mails.tsinghua.edu.cn
linxiaojing@pku.edu.cn

Research

Quantifying the escape of LyA at z=5-6: a census of Lyα escape fraction with Hα emitting galaxies spectroscopically confirmed by JWST and VLT/MUSE ADS

JWST provides an unprecedented opportunity for unbiased surveys of Hα-emitting galaxies at z>4 with the NIRCam wide-field slitless spectroscopy (WFSS). In this work, we present a census of Lyα escape fraction (fesc,Lyα) of 165 star-forming galaxies at z=4.9−6.3 using their Hα emission directly measured from FRESCO NIRCam/WFSS data. We search for Lyα emission of each Hα-emitting galaxy in VLT/MUSE data. The overall fesc,Lyα measured by stacking is fesc,Lyα is 0.090±0.006. We find that fesc,Lyα displays a strong dependence on the observed UV slope (βobs) and E(B-V), such that the bluest galaxies (βobs∼−2.5) have the largest escape fractions (fesc,Lyα≈0.6), indicative of the crucial role of dust and gas in modulating the escape of Lyα photons. fesc,Lyα is less well related to other parameters, including the UV luminosity and stellar mass, and the variation in fesc,Lyα with them can be explained by their underlying coupling with E(B-V) or βobs. Our results suggest a tentative decline in fesc,Lyα at z≳5, implying increasing intergalactic medium attenuation towards higher redshift. Furthermore, the dependence of fesc,Lyα on βobs is proportional to that of the ionizing photon escape fraction (fesc,LyC), indicating the escape of Lyα and ionizing photon may be regulated by similar physical processes. With fesc,Lyα as a proxy to fesc,LyC, we infer that UV-faint (MUV>−16) galaxies contribute >70% of the total ionizing emissivity at z=5−6. If these relations hold during the epoch of reionization, UV-faint galaxies can contribute the majority of UV photon budget to reionize the Universe.

Metal-Enriched Neutral Gas Reservoir in a low-mass metal-poor galaxies ADS POSTER
Direct observations of low-mass, low-metallicity galaxies at z≳4 provide an indispensable opportunity for detailed inspection of the ionization radiation, gas flow, and metal enrichment in sources similar to those that reionized the Universe. Combining the James Webb Space Telescope (JWST), VLT/MUSE, and ALMA, we present detailed observations of a strongly lensed, low-mass galaxy at z = 3.98, which owns an associated DLA with super-solar metallicity but a metal-poor HII region. This implies that, low-mass galaxies at high redshifts could be surrounded by a high covering fraction of the metal-enriched, neutral-gaseous clouds, and the metal enrichment of low-mass galaxies is highly efficient.

Probe Diffuse Lyman-alpha emission on cosmological scales ADS POSTER
The filamentary structure of the cosmic web is predicted to be a rich reservoir of nearly pristine gas and full of extended Lyα emission. However, direct imaging of the IGM Lyα emission is challenging because of its low surface brightness. In this work, we detected the large-scale structure of Lyα emission in the universe at redshifts z = 2-3.5 by cross-correlating quasar positions and Lyα emission imprinted in the residual spectra of luminous red galaxies, using the most-updated SDSS-DR16. Our analytical model shows that the bulk of the Lyα photons in the Universe originate from star-forming galaxies, including contributions from that concentrated around the galaxy centers and that in diffuse Lyα-emitting halos.

Quasar-CMB Lensing Cross-correlation ADS
Damped Lyα systems (DLAs) are a class of absorbers along the QSO sightlines with high neutral hydrogen column densities of logNHI>20.3. Over the last three decades, a number of attempts have been made to discover the nature of DLAs, but statistical studies of the DLA hosts also remain unclear and controversial. In this work we study the cross-correlation of damped Lyα systems (DLAs) and their background quasars, using the most updated DLA catalog and the Planck 2018 CMB lensing convergence field. Our measurement suggests that the DLA bias is smaller than 3.1, corresponding to log(M/M⊙h−1)⩽12.3 at a confidence of 90%.

Publication

All papers on ADS

First author papers
[4] Lin,X., Cai, Z., Wu, Y., et al. 2022, arXiv:2401.09532 Quantifying the escape of LyA at z=5-6: a census of Lyα escape fraction with Hα emitting galaxies spectroscopically confirmed by JWST and VLT/MUSE
[3] Lin, X., Cai, Z., Zou, S., et al. 2022, ApJL, 944, 59 Metal-Enriched Neutral Gas Reservoir around a Strongly-lensed, Low-mass Galaxy at z=4 Identified by JWST/NIRISS and VLT/MUSE
[2] Lin, X., Zheng, Z., & Cai, Z. 2022, ApJS, 262, 38. Probing the Diffuse Lyα Emission on Cosmological Scales: Lyα Emission Intensity Mapping Using the Complete SDSS-IV eBOSS
[1] Lin, X., Cai, Z., Li, Y., et al. 2020, ApJ, 905, 176. Constraining the Halo Mass of Damped Lyman alpha Absorption Systems (DLAs) at z = 2-3.5 Using the Quasar-CMB Lensing Cross-correlation