A machine-learning approach to measuring the escape of ionizing radiation from galaxies in the reionization epoch

Abstract

Recent observations of galaxies at $z\gtrsim 7$, along with the low value of the electron scattering optical depth measured by the Planck mission, make galaxies plausible as dominant sources of ionizing photons during the epoch of reionization. However, scenarios of galaxy-driven reionization hinge on the assumption that the average escape fraction of ionizing photons is significantly higher for galaxies in the reionization epoch than in the local Universe. The NIRSpec instrument on the James Webb Space Telescope (JWST) will enable spectroscopic observations of large samples of reionization-epoch galaxies. While the leakage of ionizing photons will not be directly measurable from these spectra, the leakage is predicted to have an indirect effect on the spectral slope and the strength of nebular emission lines in the rest-frame ultraviolet and optical. Here, we apply a machine learning technique known as lasso regression on mock JWST/NIRSpec observations of simulated $z=7$ galaxies in order to obtain a model that can predict the escape fraction from JWST/NIRSpec data. Barring systematic biases in the simulated spectra, our method is able to retrieve the escape fraction with a mean absolute error of $\Delta f_{\mathrm{esc}}\approx 0.12$ for spectra with $S/N\approx 5$ at a rest-frame wavelength of 1500 Å for our fiducial simulation. This prediction accuracy represents a significant improvement over previous similar approaches.

13 pages, 11 figures. Accepted for publication in ApJ

References in corpus (10)

• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars
• Lyman continuum leaking from the compact star-forming dwarf galaxy J0925+1403
• The First Billion Years Project: The escape fraction of ionizing photons in the epoch of reionization
• Cosmic Reionization On Computers I. Design and Calibration of Simulations
• Cosmic Reionization On Computers II. Reionization History and Its Back Reaction on Early Galaxies
• The Efficiency of Stellar Reionization: Effects of Rotation, Metallicity, and Initial Mass Function
• A Comprehensive Comparative Test of Seven Widely-Used Spectral Synthesis Models Against Multi-Band Photometry of Young Massive Star Clusters
• The Lyman-continuum photon production efficiency in the high-redshift Universe

Cited by in corpus (8)

• Fundamental Physics with the Square Kilometre Array
• Analysing the 21cm signal from the Epoch of Reionization with artificial neural networks
• The spectral evolution of the first Galaxies. III. Simulated James Webb Space Telescope spectra of reionization-epoch galaxies with Lyman continuum leakage
• Simulation-Based Inference of Reionization Parameters From 3D Tomographic 21 cm Lightcone Images
• Inferring physical properties of galaxies from their emission line spectra
• Testing an indirect method for identifying galaxies with high levels of Lyman continuum leakage
• Identifying reionization-epoch galaxies with extreme levels of Lyman continuum leakage in James Webb Space Telescope surveys
• Lyman continuum leakage versus quenching with the James Webb Space Telescope: The spectral signatures of quenched star formation activity in reionization-epoch galaxies