Lyman "bump" galaxies - I. Spectral energy distribution of galaxies with an escape of nebular Lyman continuum

Abstract

It is essential to know galactic emissivity and spectrum of Lyman continuum (LyC) in order to understand the cosmic reionization. Here we consider an escape of nebular LyC from galaxies and examine the consequent spectral energy distribution. It is usually assumed that hydrogen nebular LyC mostly produced by bound-free transitions is consumed within photo-ionized nebulae (so-called "on-the-spot" approximation). However, an escape of the continuum should be taken into account if stellar LyC escapes from galaxies through "matter-bounded" nebulae. We show that the escaping hydrogen bound-free LyC makes a strong bump just below the Lyman limit. Such a galaxy would be observed as a Lyman "bump" galaxy. This bump results from the radiation energy re-distribution of stellar LyC by nebulae. The strength of the bump depends on electron temperature in nebulae, escape fraction of stellar and nebular LyC, hardness of stellar LyC (i.e. metallicity, initial mass function, age and star formation history), and IGM attenuation. We can use the bump to find very young ($\sim 1$ Myr), massive ($\sim 100$ $M_{\odot }$), and extremely metal-poor (or metal-free) stellar populations at $z<4$. Because of the bump, 900 Å-to-1500 Åluminosity density ratio (per Hz) becomes maximum (2--3 times larger than the stellar intrinsic ratio) when about 40% of the stellar LyC is absorbed by nebulae. The total number of escaping LyC photons increases due to the escape of nebular LyC but does not exceed the stellar intrinsic one. The radiation energy re-distribution by nebulae reduces the mean energy of escaping LyC only by $\approx 10$% relative to that of stellar LyC. Therefore, the effect of the escape of nebular LyC on the reionization process may be small.

MNRAS in press

References in corpus (12)

• Observational constraints on Cosmic Reionization
• The End of the Reionization Epoch Probed by Ly-alpha Emitters at z=6.5 in the Subaru Deep Field
• The Direct Detection of Lyman-Continuum Emission from Star-forming Galaxies at z~3
• A galaxy at a redshift z = 6.96
• The impact of nebular emission on the ages of z~6 galaxies
• New Constraints on the Lyman Continuum Escape Fraction at z~1.3
• Feedback in the local LBG Analog Haro 11 as probed by far-UV and X-ray observations
• A Monte Carlo simulation of the intergalactic absorption and the detectability of the Lyman continuum from distant galaxies
• Escape fraction of ionizing photons from galaxies at z=0--6
• The impact of nebular emission on the broadband fluxes of high-redshift galaxies
• The escape of ionizing photons from supernova-dominated primordial galaxies
• Modeling Lyman continuum emission from young galaxies

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