Finding Peas in the Early Universe with JWST

Abstract

The Early Release Observations (EROs) of JWST beautifully demonstrate the promise of JWST in characterizing the universe at cosmic dawn. We analyze the ERO spectra of three $z\sim 8$ galaxies to determine their metallicities, gas temperatures and ionization. These galaxies offer the first opportunity to understand the physical properties of epoch-of-reionization galaxies through detailed rest-optical emission line spectroscopy. We show that these objects have metal abundances $12+\log [O/H]\approx 6.9-8.2$, based on both the $T_e$ method and on a recent calibration of the $R_{23}$ metallicity indicator. Since the spectra are some of the earliest science data from JWST, we compare several line ratios with values expected from robust physics, to validate our measurement procedures. We compare the abundances and emission line ratios to a nearby sample of Green Pea galaxies -- a population of nearby emission line galaxies whose UV properties resemble epoch-of-reionization galaxies, and which often have large Lyman continuum escape fractions. The JWST data show striking further similarities between these high redshift galaxies and nearby Green Peas. The $z\sim 8$ galaxies span the metallicity range covered by Green Peas. They also show the compact morphology that is typical of emission line dominated galaxies at all redshifts. Based on these similarities with Green Peas, it is likely that these are the first rest-optical spectra of galaxies that are actively driving cosmological reionization

13 pages, 6 figures; Submitted to ApJ Letters

References in corpus (18)

• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
• Pōniuā'ena: A Luminous $z=7.5$ Quasar Hosting a 1.5 Billion Solar Mass Black Hole
• Conditions for Reionizing the Universe with A Low Galaxy Ionizing Photon Escape Fraction
• The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z~8
• The JWST Early Release Observations
• A Spectroscopic Redshift Measurement for a Luminous Lyman Break Galaxy at z=7.730 using Keck/MOSFIRE
• The Low-Redshift Lyman Continuum Survey I: New, Diverse Local Lyman-Continuum Emitters
• First look with JWST spectroscopy: $z\sim 8$ galaxies resemble local analogues
• The Low-Redshift Lyman Continuum Survey II: New Insights into LyC Diagnostics
• The flux ratio of the [OIII] 5007,4959 lines in AGN: Comparison with theoretical calculations
• A first look at the SMACS0723 JWST ERO: spectroscopic redshifts, stellar masses and star-formation histories
• Solar oxygen abundance
• Onset of Cosmic Reionization: Evidence of An Ionized Bubble Merely 680 Myrs after the Big Bang
• A Lyman-α protocluster at redshift 6.9
• Properties of the KISS Green Pea Galaxies
• The Atomic Gas Mass of Green Pea Galaxies
• A Green Pea starburst arising from a galaxy-galaxy merger

Cited by in corpus (34)

• A JWST/NIRCam Study of Key Contributors to Reionization: The Star-forming and Ionizing Properties of UV-faint $z\sim 7-8$ Galaxies
• JADES: Probing interstellar medium conditions at $z\sim 5.5-9.5$ with ultra-deep JWST/NIRSpec spectroscopy
• EIGER II. first spectroscopic characterisation of the young stars and ionised gas associated with strong H$\beta$ and [OIII] line-emission in galaxies at z=5-7 with JWST
• JWST NIRCam+NIRSpec: Interstellar medium and stellar populations of young galaxies with rising star formation and evolving gas reservoirs
• The Physical Conditions of Emission-Line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations
• The JWST-PRIMAL Legacy Survey. A JWST/NIRSpec reference sample for the physical properties and Lyman-$\alpha$ absorption and emission of $\sim 500$ galaxies at $z=5.5-13.4$
• A Magnified Compact Galaxy at Redshift 9.51 with Strong Nebular Emission Lines
• JADES: Detecting [OIII]$\lambda 4363$ Emitters and Testing Strong Line Calibrations in the High-$z$ Universe with Ultra-deep JWST/NIRSpec Spectroscopy up to $z\sim 9.5$
• First Sample of H$\alpha$+[O III] $\lambda$5007 Line Emitters at $z>6$ Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line Luminosity Functions
• Spatially Resolved Properties of High Redshift Galaxies in the SMACS0723 JWST ERO Field
• High-z galaxies with JWST and local analogues -- it is not only star formation
• An extremely metal poor star complex in the reionization era: Approaching Population III stars with JWST
• Evolution of the Mass-Metallicity Relation from Redshift $z\approx 8$ to the Local Universe
• The gas and stellar content of a metal-poor galaxy at $z=8.496$ as revealed by JWST and ALMA
• CLEAR: High-Ionization [Ne V] $\lambda$3426 Emission-line Galaxies at $1.4<z<2.3$
• CECILIA: The Faint Emission Line Spectrum of z~2-3 Star-forming Galaxies
• Ly-alpha emission in low-redshift most metal-deficient compact star-forming galaxies
• Early results from GLASS-JWST. XXVII. The mass-metallicity relation in lensed field galaxies at cosmic noon with NIRISS
• Uncovering the physical origin of the prominent Lyman-$\alpha$ emission and absorption in GS9422 at $z=5.943$
• Low-redshift Lyman Continuum Survey: Radio continuum properties of low-$z$ Lyman continuum emitters
• Lyman continuum leaker candidates among highly ionised, low-redshift dwarf galaxies selected from HeII
• Intermediate-Mass Black Holes in Green Pea Galaxies (IMBH-GP) I: a Candidate Sample from LAMOST and SDSS
• Blueberry galaxies up to 200 Mpc and their optical and infrared properties
• HI Imaging of a Blueberry Galaxy Suggests a Merger Origin
• Radio properties of Green Pea galaxies
• A MUSE/VLT spatially resolved study of the emission structure of Green Pea galaxies
• GA-NIFS: Dissecting the multiple sub-structures and probing their complex interactions in the \Lyalpha emitter galaxy CR7 at z = 6.6 with JWST/NIRSpec
• X-ray observations of Blueberry galaxies
• Discovery of Five Green Pea Galaxies with Double-peaked Narrow [OIII] Lines
• The Neon Gap: Probing Ionization with Dwarf Galaxies at z~1
• IFUM Integrated Field Spectroscopy of Ten M104 Satellite Galaxy Candidates
• Blueberry and Green Pea galaxies live in low density environments
• First joint absorption and T${}_e$-based metallicity measured in a GRB host galaxy at $z=4.28$ using JWST/NIRSpec
• Power-law Emission-line Wings and Radiation-Driven Superwinds in Local Lyman Continuum Emitters