Building Ancient Cosmic CitiesGalaxy Protoclusters are large overdense structures in the early Universe from which galaxy clusters gravitationally collapse. They represent an unique interface between the subjects of galaxy formation and cosmology, and a key laboratory to study both in their extreme conditions. A major part of my work has been pioneering the numerical modeling, observations, and physical inferences of protoclusters and their relations to both large and small scale astrophysics.
Dissecting The 3D UniverseExtragalactic Background Light in Broadband Intensity Mapping. Most of the photons ever recorded by astronomical instruments are in the form of images—or broadband intensity maps. Usually a large fraction of these photons are in the diffuse field, or pixels outside individual objects. They are often discarded during the process of background removal (with e.g., SExtractor), together with potentially valuable information. I develop an angular cross correlation technique to recover the redshift of the diffuse extragalactic background light (EBL). Pushing it one step further, I introduce a "spectral tagging" technique to statistically assign frequency information to EBL photons using these redshift-dependent clustering measurements. This has potential to recover the spectrum of the universe with a spectral resolution much higher than the original bandwidth. Such a time- and frequency-dependent assessment of the background light will provide a critical summary statistic of cosmological galaxy formation.
Clustering Redshift Estimation is a data-driven technique to obtain distances, or redshift distributions of extragalactic objects using information in their angular fluctuations on the sky. The technique has potential to outperform some photometric redshift algorithms especially in the regime of wide and deep cosmology or galaxy evolution surveys for faint objects.
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