PEGASUS (Pfs Emission-line GAlaxy SUrvey with Subaru): II. Metal Poor AGNs in High Equivalent-Width Narrow-Band Emitters

@misc{uchiyama2026pegasus,
  title = {{PEGASUS (Pfs Emission-line GAlaxy SUrvey with Subaru): II. Metal Poor AGNs in High Equivalent-Width Narrow-Band Emitters}},
  author = {Hisakazu Uchiyama and Tohru Nagao and Mariko Kubo and Tadayuki Kodama and Rhythm Shimakawa and Akio Inoue and Masayuki Tanaka and Jialai Wang and Ronaldo Laishram and Yuma Sugahara and Masato Onodera and Kazuki Daikuhara and Ko Ishida and Ryo Albert Sutanto and Haruka Kusakabe and Yoshiki Matsuoka and Alberto Rodriguez-Ardila and Yuta Suzuki and Yoshiki Toba and Xinfeng Xu and Yongquan Xue and Yongming Liang},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.34150},
  eprint = {2609.34150},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.34150},
}

TY  - UNPB
TI  - PEGASUS (Pfs Emission-line GAlaxy SUrvey with Subaru): II. Metal Poor AGNs in High Equivalent-Width Narrow-Band Emitters
AU  - Hisakazu Uchiyama
AU  - Tohru Nagao
AU  - Mariko Kubo
AU  - Tadayuki Kodama
AU  - Rhythm Shimakawa
AU  - Akio Inoue
AU  - Masayuki Tanaka
AU  - Jialai Wang
AU  - Ronaldo Laishram
AU  - Yuma Sugahara
AU  - Masato Onodera
AU  - Kazuki Daikuhara
AU  - Ko Ishida
AU  - Ryo Albert Sutanto
AU  - Haruka Kusakabe
AU  - Yoshiki Matsuoka
AU  - Alberto Rodriguez-Ardila
AU  - Yuta Suzuki
AU  - Yoshiki Toba
AU  - Xinfeng Xu
AU  - Yongquan Xue
AU  - Yongming Liang
PY  - 2026
DA  - 2026/09/28
PB  - arXiv
DO  - 10.48550/arxiv.2609.34150
UR  - https://arxiv.org/abs/2609.34150
AB  - We present Subaru 'Ōnohi'ula Prime Focus Spectrograph (PFS) optical--NIR spectroscopic follow-up of high-equivalent-width (EW) narrow-band (NB) emission-line galaxies selected from Hyper Suprime-Cam Subaru Strategic Program, to assess whether high-EW sources preferentially host low-metallicity AGNs. PFS spectroscopy yielded secure identifications for 583 targets, including 581 sources with reliable PFS redshift solutions and two manually identified z∼4 interlopers. We construct BPT diagnostics for the 70 objects with significant detections in all four BPT lines. Among them, ∼34% are located in the AGN region of the BPT diagram, suggesting that AGNs constitute a significant fraction of the sample. A non-negligible fraction does not populate the classical AGN branch; instead, it lies in the intermediate ``valley'' between the star-forming and AGN sequences. Comparison to Cloudy models suggests that the valley population is consistent with sub-solar metallicities. Three He II/[Ne V]-detected sources are also found in the star-forming region of the BPT diagram and extend to lower-metallicity solutions, consistent with Z/Z_⊙≈0.25−0.5 (12+log(O/H)≈8.1−8.4). One object shows a clear broad Hα component; a multi-component fit yields M_BH≈8.8×10^6 M_⊙ and λ_Edd≈0.035, consistent with near-solar narrow-line region metallicity. The fraction of point-like sources in the parent target sample (22%±2%) is intermediate between those of star-forming galaxies (12%±5%) and AGN (33%±10%), consistent with a contribution from compact components. Stacked [O III] line profiles show no clear evidence for strong outflows. Our findings suggest that high-EW NB selection efficiently identifies candidates for metal-poor AGNs.
ER  -