EELG1002: A Record-breaking [O iii ]+H β EW ∼ 3700 Å Galaxy at z ∼ 0.8—Analog of Early Galaxies?

Λεπτομέρειες βιβλιογραφικής εγγραφής
Τίτλος:	EELG1002: A Record-breaking [O iii ]+H β EW ∼ 3700 Å Galaxy at z ∼ 0.8—Analog of Early Galaxies?
Συγγραφείς:	Khostovan, Ali Ahmad, Kartaltepe, Jeyhan S., Brinch, Malte, Casey, Caitlin, Faisst, Andreas, Harish, Santosh, Gozaliasl, Ghassem, Onodera, Masato, Yabe, Kiyoto
Πηγή:	Astrophysical Journal; 2025, Vol. 994 Issue 1, p1-22, 22p
Θεματικοί όροι:	Emission-line galaxies, Star formation, Inflationary universe, Ionization (Atomic physics), Photon emission, Astronomical catalogs
Περίληψη:	Extreme emission line galaxies (EELGs) are powerful low- z analogs of high- z galaxies that can provide us valuable insights of early Universe conditions. We present a detailed analysis of EELG1002: a z = 0.8275 EELG identified within archival Gemini/GMOS spectroscopy as part of the ongoing COSMOS Spectroscopic Archive. We find EELG1002 is a low-mass (∼10⁸ M ⊙), compact (∼530 pc), bursty star-forming galaxy with a ∼15–35 Myr mass doubling timescale. EELG1002 has record-breaking rest-frame [O iii ]+H β EW ∼3100–3700 Å; ∼32–36× higher than typical z ∼ 0.8 [O iii ] emitters with similar stellar mass; and higher than typical z > 5 galaxies. We find no clear evidence of an active galactic nucleus suggesting the emission lines are star formation driven. EELG1002 is chemically unevolved (direct T e ; 12 + log 10 (O/H) ∼ 7.52 consistent with z > 5 galaxies at fixed stellar mass) and may be undergoing a first intense, bursty star formation phase analogous to conditions expected of galaxies in the early Universe. We find evidence for a highly energetic interstellar medium ([O iii ]/[O ii ] ∼ 9) and hard ionizing radiation field (elevated [Ne iii ]/[O ii ] at fixed [O iii ]/[O ii ]). Coupled with its compact, metal-poor, and actively star-forming nature, EELG1002 is found to efficiently produce ionizing photons (ξ ion ∼ 10^25.74 erg⁻¹ Hz) and may have ∼10%–20% Lyman Continuum (LyC) escape suggesting such sources may be important analogs of galaxies responsible for reionization. We find a dynamical mass of ∼10⁹ M ⊙ suggesting copious amounts of gas to support intense star formation as also suggested by identified Illustris-TNG analogs. EELG1002 may be an ideal low- z laboratory of galaxies in the early Universe and demonstrates how archival data sets can support high- z science and next-generation surveys planned with Euclid and Roman. [ABSTRACT FROM AUTHOR]
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