Optically-Thin Spatially-Resolved Mg II Emission Maps the Escape of Ionizing Photons

Abstract

Early star-forming galaxies produced copious ionizing photons. A fraction of these photons escaped gas within galaxies to reionize the entire Universe. This escape fraction is crucial for determining how the Universe became reionized, but the neutral intergalactic medium precludes direct measurement of the escape fraction at high-redshifts. Indirect estimates of the escape fraction must describe how the Universe was reionized. Here, we present new Keck Cosmic Web Imager spatially-resolved spectroscopy of the resonant Mg II 2800 doublet from a redshift 0.36 galaxy, J1503+3644, with a previously observed escape fraction of 6%. The Mg II emission has a similar spatial extent as the stellar continuum, and each of the Mg II doublet lines are well-fit by single Gaussians. The Mg II is optically thin. The intrinsic flux ratio of the red and blue Mg II emission line doublet, $R=F_{2796}/F_{2803}$, is set by atomic physics to be two, but Mg${}^{+}$ gas along the line of sight decreases $R$ proportional to the Mg II optical depth. Combined with the metallicity, $R$ estimates the neutral gas column density. The observed $R$ ranges across the galaxy from 0.8-2.7, implying a factor of 2 spatial variation of the relative escape fraction. All of the ionizing photons that escape J1503+3644 pass through regions of high $R$. We combine the Mg II emission and dust attenuation to accurately estimate the absolute escape fractions for ten local Lyman Continuum emitting galaxies and suggest that Mg II can predict escape fraction within the Epoch of Reionization.

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References in corpus (27)

• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: I. Galaxy Mergers & Quasar Activity
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Ubiquitous outflows in DEEP2 spectra of star-forming galaxies at z=1.4
• 3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line profile morphologies
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• The Discovery of 1000 km/s Outflows in Massive Post-starburst Galaxies at z=0.6
• Conditions for Reionizing the Universe with A Low Galaxy Ionizing Photon Escape Fraction
• Faint AGNs at z>4 in the CANDELS GOODS-S field: looking for contributors to the reionization of the Universe
• Using Lyman-alpha to detect galaxies that leak Lyman continuum
• Lyman-alpha spectral properties of five newly discovered Lyman continuum emitters
• A Local Clue to the Reionization of the Universe
• High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
• Q1549-C25: A Clean Source of Lyman-Continuum Emission at $z=3.15$
• The Lyman-alpha Reference Sample: I. Survey outline and first results for Markarian 259
• Evolution of the Cool Gas in the Circumgalactic Medium (CGM) of Massive Halos -- A Keck Cosmic Web Imager (KCWI) Survey of Ly$\alpha$ Emission around QSOs at $z\approx 2$
• The origin of the escape of Lyman alpha and ionizing photons in Lyman Continuum Emitters
• A 100-kiloparsec wind feeding the circumgalactic medium of a massive compact galaxy
• Intense CIV and HeII Emission in z~0 Galaxies: Probing High-Energy Ionizing Photons
• Constraining the UV emissivity of AGN throughout cosmic time via X-ray surveys
• A Semi-Analytical Line Transfer (SALT) model to interpret the spectra of galaxy outflows
• Minor Contribution of Quasars to Ionizing Photon Budget at z~6: Update on Quasar Luminosity Function at the Faint-end with Subaru/Suprime-Cam
• The Lyman Alpha Reference Sample: III. Properties of the Neutral ISM from GBT and VLA Observations
• Neutral Gas Properties and Ly$\alpha$ Escape in Extreme Green Pea Galaxies
• The MUSE Hubble Ultra Deep Field Survey: VII. FeII* Emission in Star-Forming Galaxies
• Properties of five z~0.3-0.4 confirmed LyC leakers: VLT/XShooter observations
• An IFU investigation of possible Lyman continuum escape from Mrk 71/NGC 2366

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