Kei Ito

Diverse Metallicities in Protoclusters at $z \sim 3.4$ detected by Deep Learning

Yoshihiro Takeda, Nobunari Kashikawa, Kei Ito +12

We present spectroscopic follow-up observations with Subaru/MOIRCS of four protocluster candidate regions identified by the deep-learning model PCFNet. In three candidate regions,…

Probing Spatial Variations in IGM Transmission: Higher Ly $α$ Visibility in an H $α$ -Selected Galaxy Overdensity at $z ≃ 6.2$

Shunta Shimizu, Nobunari Kashikawa, Junya Arita +13

The visibility of Ly $α$ emission during the epoch of reionization depends on both galaxy properties and the transmission of Ly $α$ photons through the intergalactic medium (IGM). Us…

H I Absorbers as Beacons of Hidden Structure at $z \sim 3$ : Multi-Component, Metal-Rich Absorption System near a Protocluster

Kentaro Koretomo, Nobunari Kashikawa, Toru Misawa +12

H I gas traces the large-scale structure and provides the primary fuel for star formation. High- $z$ protoclusters are ideal laboratories to study how H I gas is accreted and consum…

Subaru meets JWST: A Direct Measurement of Ly $α$ Escape Fraction at $z ≃ 6.2$ with Dual Narrow-Band Imaging

Shunta Shimizu, Nobunari Kashikawa, Ryo Emori +15

We present a direct measurement of the Ly $α$ escape fraction, $f_{esc}^{Ly α}$ , for H $α$ emitters (HAEs) at $z ≃ 6.2$ in the JWST CEERS field by combining JWST/NIRCam F47…

Predicting Ly $α$ Emission from Distant Galaxies with Neural Network Architecture

Takehiro Yoshioka, Nobunari Kashikawa, Yoshihiro Takeda +7

The Ly $α$ emission line is a characteristic feature found in high- $z$ galaxies, serving as a probe of cosmic reionization. While previous works present various correlations between…

astro-ph.GA2024★ 3 cited

Hidden in Pixels. I. Discovery of dual "little red dots" indicates excess clustering on kilo-parsec scales

Takumi S. Tanaka, John D. Silverman, Kazuhiro Shimasaku +56

``Little Red Dots'' (LRDs) are an abundant high-redshift population newly discovered by the James Webb Space Telescope (JWST) and considered to be an early growth phase of supermas…

astro-ph.GA2024★ 10 cited

Mining for Protoclusters at $z \sim 4$ from Photometric Datasets with Deep Learning

Yoshihiro Takeda, Nobunari Kashikawa, Kei Ito +9

Protoclusters are high- $z$ overdense regions that will evolve into clusters of galaxies by $z = 0$ , making them ideal for studying galaxy evolution expected to be accelerated by envi…

JWST/NIRSpec spectroscopy of intermediate-mass quiescent galaxies at $z \sim 3 - 4$

Riku A. Sato, Akio K. Inoue, Yuichi Harikane +9

We present the analysis of three intermediate-mass quiescent galaxies (QGs) with stellar masses of $\sim 1 0^{10} M_{⊙}$ at redshifts $z \sim 3 - 4$ using NIRSpec low-resolutio…

astro-ph.GA2024★ 2 cited

A Post-Starburst Pathway for the Formation of Massive Galaxies and Black Holes at z>6

Masafusa Onoue, Xuheng Ding, John D. Silverman +45

Understanding the rapid formation of supermassive black holes (SMBHs) in the early universe requires insight into stellar mass growth in host galaxies. Here, we present NIRSpec res…

Galaxy properties from the outskirts to the core of a protocluster at z=3.699

Jun Toshikawa, Stijn Wuyts, Nobunari Kashikawa +6

We present follow-up spectroscopy on a protocluster candidate selected from the wide-field imaging of the Hyper SuprimeCam Subaru Strategic Programme. The target protocluster candi…

Cosmic Himalayas: The Highest Quasar Density Peak Identified in a 10,000 deg $^{2}$ Sky with Spatial Discrepancies between Galaxies, Quasars, and IGM HI

Yongming Liang, Masami Ouchi, Dongsheng Sun +27

We report the identification of a quasar overdensity in the BOSSJ0210 field, dubbed Cosmic Himalayas, consisting of 11 quasars at $z = 2.16 - 2.20$ , the densest overdensity of quasars…

astro-ph.GA2023★ 1 cited

A proto-cluster of massive quiescent galaxies at z=4

Masayuki Tanaka, Masato Onodera, Rhythm Shimakawa +7

We report on discovery of a concentration of massive quiescent galaxies located at z=4. The concentration is first identified using high-quality photometric redshifts based on deep…

Remarkably Compact Quiescent Candidates at $3 < z < 5$ in JWST-CEERS

Lillian Wright, Katherine E. Whitaker, John R. Weaver +9

In this letter, we measure the rest-frame optical and near-infrared sizes of ten quiescent candidates at $3 < z < 5$ , first reported by Carnall et al. (2023a). We use James Webb Space…

An enhanced abundance of bright galaxies in protocluster candidates at z~3-5

Jun Toshikawa, Stijn Wuyts, Nobunari Kashikawa +11

We present a protocluster search covering $z \sim 3$ to $z \sim 5$ based on the combination of the Hyper SuprimeCam Subaru Strategic Programme and the CFHT Large Area $U$ -band Deep Sur…

GALAXY CRUISE: Deep Insights into Interacting Galaxies in the Local Universe

Masayuki Tanaka, Michitaro Koike, Sei'ichiro Naito +15

We present the first results from GALAXY CRUISE, a community (or citizen) science project based on data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The current p…

astro-ph.GA2023★ 1 cited

A massive quiescent galaxy in a group environment at $z = 4.53$

Takumi Kakimoto, Masayuki Tanaka, Masato Onodera +10

We report on the spectroscopic confirmation of a massive quiescent galaxy at $z_{spec} = 4.53$ in the COSMOS field. The object was first identified as a galaxy with suppressed…

HINOTORI I: The Nature of Rejuvenation Galaxies

Takumi S. Tanaka, Kazuhiro Shimasaku, Sandro Tacchella +4

We present the HINOTORI (star formation History INvestigatiOn TO find RejuvenatIon) project to reveal the nature of rejuvenation galaxies (RGs), which are galaxies that restarted t…