The University of Tokyo · 물리·천문학
히로야 우메다 교수의 연구실은 우주의 재이온화 시대를 탐구하는 데 초점을 맞추고 있으며, 특히 제임스 웹 우주망원경(JWST)을 활용한 고감도 스펙트럼 관측을 통해 초기 은하의 중성수소 분율과 이온화 구역의 크기를 정량적으로 측정합니다. 또한 극도로 금속 농도가 낮은 은하에서 관측되는 강한 이온화 헬륨 선을 분석하여 비열역학적 원천의 존재 가능성을 탐색하고, 빛의 붉은 점(_LRDS_)과 같은 이상한 활성은하핵의 물리적 메커니즘을 규명하는 데에도 기여하고 있습니다. 이 연구들은 초기 은하의 형성과 블랙홀 성장, 그리고 초기 우주의 환경을 이해하는 데 핵심적인 정보를 제공합니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
Abstract We present volume-averaged neutral hydrogen fractions x H I and ionized bubble radii R b measured with Ly α damping wing absorption of galaxies at the epoch of reionization. We combine JWST/NIRSpec spectra taken by the CEERS, GO-1433, DDT-2750, and JADES programs and obtain a sample containing 27 bright UV-continuum ( M UV < −18.5 mag) galaxies at 7 < z < 12. We construct four composite spectra binned by redshift and find the clear evolution of the softening break toward high r
Abstract Strong high-ionization lines such as He ii of young galaxies are puzzling at high and low redshift. Although recent studies suggest the existence of nonthermal sources, whether their ionizing spectra can consistently explain multiple major emission lines remains a question. Here we derive the general shapes of the ionizing spectra for three local extremely metal-poor galaxies (EMPGs) that show strong He ii λ 4686. We parameterize the ionizing spectra composed of a blackbody and power-la
We present volume-averaged neutral hydrogen fractions $x_{\rm \HI}$ and ionized bubble radii $R_{\rm b}$ measured with Ly$α$ damping wing absorption of galaxies at the epoch of reionization. We combine JWST/NIRSpec spectra taken by CEERS, GO-1433, DDT-2750, and JADES programs, and obtain a sample containing 27 bright UV-continuum ($M_{\rm UV}<-18.5~{\rm mag}$) galaxies at $7
Abstract We present luminosity functions (LFs) and angular correlation functions (ACFs) derived from 18,960 Ly α emitters (LAEs) at z = 2.2−7.3 over a wide survey area of ≲24 deg 2 that are identified in the narrowband data of the HSC-SSP and CHORUS surveys. Confirming the large sample with 241 spectroscopically identified LAEs, we determine Ly α LFs and ACFs in the brighter luminosity range down to 0.5 L ⋆ , and confirm that our measurements are consistent with previous studies but offer signif
Abstract Little Red Dots (LRDs) newly discovered with JWST are active galactic nuclei (AGNs) that may represent black hole (BH) growth at the earliest cosmic epochs. These sources show puzzling features unlike typical AGNs, including red optical continua, weak hot-dust emission, and a lack of detectable X-rays. Previously, LRDs have often been interpreted as dust-reddened AGNs, leading to severe inconsistencies with the luminosity and BH mass densities inferred for previously known AGNs over 0 &
