The University of Tokyo · Physics and Astronomy
Professor Yoshiaki Ono's research lab specializes in high-redshift galaxy evolution, focusing on the physical properties, stellar populations, and morphologies of distant galaxies observed in the early universe. Using deep multi-wavelength imaging and spectroscopy from Hubble and James Webb Space Telescopes, the lab investigates Lyman-alpha emitters and dropout galaxies at redshifts z ≈ 3–11 to understand early star formation, galaxy assembly, and reionization. The lab combines advanced photometric and spectroscopic techniques with detailed SED modeling and morphological analysis to probe the rest-frame UV to infrared properties of these primordial systems.
Figures are computed from collected data and may differ slightly.
We present the results of our ultra-deep Keck/DEIMOS spectroscopy of z-dropout galaxies in the SDF and GOODS-N. For 3 out of 11 objects, we detect an emission line at ~ 1um with a signal-to-noise ratio of ~ 10. The lines show asymmetric profiles with high weighted skewness values, consistent with being Lya, yielding redshifts of z=7.213, 6.965, and 6.844. Specifically, we confirm the z=7.213 object in two independent DEIMOS runs with different spectroscopic configurations. The z=6.965 object is
We investigate the stellar populations of Lyman alpha emitters (LAEs) at z=5.7 and 6.6 in a 0.65 deg^2 sky of the Subaru/XMM-Newton Deep Survey (SXDS) Field, using deep images taken with Subaru/Suprime-Cam, UKIRT/WFCAM, and Spitzer/IRAC. We produce stacked multiband images at each redshift from 165 (z=5.7) and 91 (z=6.6) IRAC-undetected objects, to derive typical spectral energy distributions (SEDs) of z~6-7 LAEs for the first time. The stacked LAEs have as blue UV continua as the HST/WFC3 z-dro
We investigate the stellar populations of Ly emitters (LAEs) at z = 3.1 and 3.7 in 0.65 deg 2 of the Subaru/XMM-Newton Deep Field, based on rest-frame ultraviolet-to-optical photometry obtained from the Subaru/XMM-Newton Deep Survey, the UKIRT Infrared Deep Sky Survey/ Ultra Deep Survey (UKIDSS/UDS), and the Spitzer legacy survey of the UKIDSS/UDS. Among a total of 302 LAEs (224 for z = 3.1 and 78 for z = 3.7), only 11 are detected in the K band, i.e. brighter than K(3 ) = 24.1 mag. Eight of the
Abstract We present morphologies of galaxies at z ≳ 9 resolved by JWST/NIRCam 2–5 μ m imaging. Our sample consists of 22 galaxy candidates identified by stringent dropout and photo- z criteria in GLASS, CEERS, SMACS J0723, and Stephan’s Quintet flanking fields, one of which has been spectroscopically identified at z = 11.44. We perform surface brightness (SB) profile fitting with GALFIT for six bright galaxies with a signal-to-noise ratio = 10–40 on an individual basis and for stacked faint gala
We analyze the redshift- and luminosity-dependent sizes of dropout galaxy candidates in the redshift range z â¼ 7-12 using deep images from the 2012 Hubble Ultra Deep Field (UDF12) campaign, which offers two advantages over that used in earlier work. First, we utilize the increased signal-to-noise ratio offered by the UDF12 imaging to provide improved measurements for known galaxies at z â 6.5-8 in the HUDF. Second, because the UDF12 data have allowed the construction of the first robust gala
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