Telescope

The most interesting discovery desires the most advanced telescopes. We have the resources of several powerful telescopes from the radio to X-ray including VLA, ALMA, JWST, Keck, Subaru, DESI, and Chandra. With these resources, we can observe the extremely weak flux from the fascinating objects at the very early age of the Universe. This allow us to have the detailed understanding on the co-evolution between galaxies and their environment.

Science

How the galaxy form and evolve with time is still unclear. High redshift (the early Universe) is a good laboratory allowing us to study the details. Through imaging and spectroscopic studies (emission and absorption) with the most powerful instruments, we reveal the huge information lying in the high-z objects and dedicate to study the details of how galaxies co-evolve with the environment. Moreover, with the machine learning technique and the large spectroscopic survey, we could explore the Universe more thoroughly and efficiently.

Rencent Highlights

Inspiraling streams of enriched gas observed around a massive galaxy 11 billion years ago

Zhang S., Cai Z., et al. 2023, Science, 380, 494

Stars form in galaxies from gas that accreted from the intergalactic medium. Simulations have shown that recycling of gas ejected from a galaxy and then re-accreted could sustain star formation in the early Universe. We observe the gas surrounding a massive galaxy at z = 2.3 and detect emission lines from neutral hydrogen, helium and ionized carbon that extend 100 kiloparsecs from the galaxy. The kinematics of this circumgalactic gas is consistent with an inspiralling stream. The carbon abundance indicates that the gas had previously been enriched with elements heavier than helium, previously ejected from a galaxy. We interpret the results as evidence of gas recycling during high-redshift galaxy assembly.

[CII] 158 μm emitter associated with an OI absorber at the end of the reionization epoch

Wu Y., Cai Z., et al. 2022, NatAs, 5, 1110

The physical and chemical properties of the circumgalactic medium (CGM) at z>6 have been studied successfully through the absorption in the spectra of background Quasi-Stellar Objects (QSOs). One of the most crucial questions is to investigate the nature and location of the source galaxies that give rise to these early metal absorbers. Theoretical models suggest that momentum-driven outflows from typical star-forming galaxies can eject metals into the circumgalactic medium and the intergalactic medium at z=5-6. Deep, dedicated surveys have searched for Lya emission associated with strong CIV absorbers at , but only a few Lya emitter candidates have been detected. Interpreting these detections is moreover ambiguous because Ly is a resonant line, raising the need for complementary techniques for detecting absorbers' host galaxies. Here, we report a [CII] 155μm emitter detected using the Atacama Large Millimeter Array that is associated with a strong low-ionization absorber, OI, at z=5.978. The projected impact parameter between OI and [CII] emitter is 20.0 kpc. The measured [CII] luminosity is 7.0×107 solar luminosities. Further analysis indicates that strong OI absorbers may reside in the circumgalactic medium of massive halos one to two orders of magnitude more massive than expected values.