Low-mass and High-sSFR Hα Emitters at z ∼ 2 in the ZFOURGE-COSMOS Field

@misc{yun2026lowmass,
  title = {{Low-mass and High-sSFR H$α$ Emitters at $z \sim 2$ in the ZFOURGE-COSMOS Field}},
  author = {Jeung Yun and Kentaro Motohara and Kosuke Kushibiki and Nuo Chen and Masahiro Konishi and Hidenori Takahashi and Tomoya Yukino and Shuhei Koyama and Akiyoshi Tsujita and Ichi Tanaka and Hirofumi Okita and Tsuyoshi Terai},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.26788},
  eprint = {2610.26788},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.26788},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Low-mass and High-sSFR Hα Emitters at z ∼ 2 in the ZFOURGE-COSMOS Field
AU  - Jeung Yun
AU  - Kentaro Motohara
AU  - Kosuke Kushibiki
AU  - Nuo Chen
AU  - Masahiro Konishi
AU  - Hidenori Takahashi
AU  - Tomoya Yukino
AU  - Shuhei Koyama
AU  - Akiyoshi Tsujita
AU  - Ichi Tanaka
AU  - Hirofumi Okita
AU  - Tsuyoshi Terai
PY  - 2026
DA  - 2026/10/19
PB  - arXiv
DO  - 10.48550/arxiv.2610.26788
UR  - https://arxiv.org/abs/2610.26788
AB  - We present a near-infrared spectroscopic follow-up study of seven Hα emitter candidates at z∼2 in the ZFOURGE-COSMOS field, selected via the K_s-band flux excess method. Spectra obtained with Subaru/SWIMS confirm strong Hα emission line at z=2.06−2.49 for all the targets. Three galaxies are low-mass systems (log(M_⋆/M_⊙) < 9) with high specific SFRs, while four are high-mass systems (log(M_⋆/M_⊙) > 10) on the star-forming main sequence. The low-mass galaxies show consistent Hα flux measurements between the K_s-band flux excess method and the spectroscopy, whereas the high-mass galaxies show higher Hα flux inferred from the K_s-band flux excess than the spectroscopic measurement which may be attributed to their extended star formation distributions. The low-mass galaxies exhibit extreme [O III] λ5007 emission with high rest-frame equivalent widths (EW_rest) ranging from 480 to 1064 mathringA. They are characterized by high [O III]/Hβ ratios (>4) and weak [O II] and [N II] emission lines, indicating high ionization parameters and low metallicity. The line ratios are comparable to those of star-forming galaxies at z ≳ 6 and their local analogs. JWST/NIRCam imaging reveals a clear mass-dependent color gradient: the low-mass galaxies present positive F115W-F277W radial gradients with blue cores, while the high-mass galaxies exhibit negative gradients with red cores. These results suggest distinct assembly pathways for low- and high-mass galaxies during the cosmic noon epoch.
ER  -