Lunch Talk: Koki Kakiichi (UCSB)
The art of cosmography, i.e. map-making of the Universe, is essential for progress in astronomy. In this talk, I present a new technique to map the large-scale structure of the intergalactic medium (IGM) using ultra-deep Subaru/HSC narrow-band imaging. This so-called “photometric IGM tomography” detects faint Lyman-alpha forest transmission along all background galaxies photometrically, allowing us to reconstruct the tomographic map of HI at high redshifts from z~4 to 6. Using the publicly available HSC data, I demonstrate the proof-of-concept and present the first co-spatial, large-scale map of the cosmic web of both galaxies and the IGM at z~5 in the COSMOS field. By analyzing the IGM tomographic map with theory/numerical simulations, I discuss the physical implications on the sources of reionization, the escape fractions of galaxies, and the growth of supermassive black holes. I conclude by discussing how this technique could be improved further by using the data from JWST and Subaru/PFS.
Summary
The art of cosmography, i.e. map-making of the Universe, is essential for progress in astronomy. In this talk, I present a new technique to map the large-scale structure of the intergalactic medium (IGM) using ultra-deep Subaru/HSC narrow-band imaging. This so-called “photometric IGM tomography” detects faint Lyman-alpha forest transmission along all background galaxies photometrically, allowing us to reconstruct the tomographic map of HI at high redshifts from z~4 to 6. Using the publicly available HSC data, I demonstrate the proof-of-concept and present the first co-spatial, large-scale map of the cosmic web of both galaxies and the IGM at z~5 in the COSMOS field. By analyzing the IGM tomographic map with theory/numerical simulations, I discuss the physical implications on the sources of reionization, the escape fractions of galaxies, and the growth of supermassive black holes. I conclude by discussing how this technique could be improved further by using the data from JWST and Subaru/PFS.