Lyman-Alpha Escape from Low-Mass, Compact, High-Redshift Galaxies

Abstract

We investigate the effects of stellar populations and sizes on Ly$\alpha$ escape in 27 spectroscopically confirmed and 35 photometric Lyman-Alpha Emitters (LAEs) at z $\approx$ 2.65 in seven fields of the Boötes region of the NOAO Deep Wide-Field Survey. We use deep $HST$/WFC3 imaging to supplement ground-based observations and infer key galaxy properties. Compared to typical star-forming galaxies (SFGs) at similar redshifts, the LAEs are less massive ($M_{\star }\approx 10^7-10^9{M}_{\odot }$), younger (ages $\lesssim$ 1 Gyr), smaller ($r_e<$ 1 kpc), less dust-attenuated (E(B$-$V) $\le$ 0.26 mag), but have comparable star-formation-rates (SFRs $\approx 1-100M_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$). Some of the LAEs in the sample may be very young galaxies having low nebular metallicities (${\mathrm{Z}}_{\mathrm{neb}}\lesssim 0.2{\mathrm{Z}}_{\odot }$) and/or high ionization parameters ($\log (\mathrm{U})\gtrsim -2.4$). Motivated by previous studies, we examine the effects of the concentration of star formation and gravitational potential on Ly$\alpha$ escape, by computing star-formation-rate surface density, ${\Sigma }_{\mathrm{SFR}}$ and specific star-formation-rate surface density, ${\Sigma }_{\mathrm{sSFR}}$. For a given ${\Sigma }_{\mathrm{SFR}}$, the Ly$\alpha$ escape fraction is higher for LAEs with lower stellar masses. LAEs have higher ${\Sigma }_{\mathrm{sSFR}}$ on average compared to SFGs. Our results suggest that compact star formation in a low gravitational potential yields conditions amenable to the escape of Ly$\alpha$ photons. These results have important implications for the physics of Ly$\alpha$ radiative transfer and for the type of galaxies that may contribute significantly to cosmic reionization.

36 pages, 15 figures; Accepted for publication in The Astronomical Journal

References in corpus (34)

• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Constraining the Low-Mass Slope of the Star Formation Sequence at 0.5<z<2.5
• The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
• The MOSFIRE Deep Evolution Field (MOSDEF) Survey: Rest-Frame Optical Spectroscopy for ~1500 H-Selected Galaxies at 1.37 < z < 3.8
• Star formation in AEGIS field galaxies since z=1.1 . Staged galaxy formation, and a model of mass-dependent gas exhaustion
• The MUSE Hubble Ultra Deep Field Survey: I. Survey description, data reduction and source detection
• Lyman-alpha spectral properties of five newly discovered Lyman continuum emitters
• Deriving model-based T${}_e$-consistent chemical abundances in ionised gaseous nebulae
• Observations of the Lyman-$\alpha$ Universe
• A Local Clue to the Reionization of the Universe
• Diffuse Lyman-alpha Halos around Galaxies at z=2.2-6.6: Implications for Galaxy Formation and Cosmic Reionization
• TiNy Titans: The Role of Dwarf-Dwarf Interactions in the Evolution of Low Mass Galaxies
• The MOSDEF Survey: the Variation of the Dust Attenuation Curve with Metallicity
• Understanding the escape of LyC and Ly$\alpha$ photons from turbulent clouds
• The CALYMHA survey: Lya luminosity function and global escape fraction of Lya photons at z=2.23
• Spatially resolved star formation and fuelling in galaxy interactions
• The HETDEX Pilot Survey V: The Physical Origin of Lyman-alpha Emitters Probed by Near-infrared Spectroscopy
• A VLT/FORS2 view at $z\sim 6$: Lyman-$\alpha$ emitter fraction and galaxy physical properties at the edge of the epoch of cosmic reionization
• The physical properties of Lyalpha emitting galaxies: not just primeval galaxies?
• The Overdense Environment of a Large Lyman-alpha Nebula at z~2.7
• Physical properties of z~4 LBGs: differences between galaxies with and without Ly-alpha emission
• A Comprehensive Study of Ly$\alpha$ Emission in the High-redshift Galaxy Population
• The MOSDEF-LRIS Survey: The Connection Between Massive Stars and Ionized Gas in Individual Galaxies at $z\sim 2$
• Spectral Energy Distribution Fitting of HETDEX Pilot Survey Lyman-alpha Emitters in COSMOS and GOODS-N
• The evolution of rest-frame UV properties, Lya EWs and the SFR-Stellar mass relation at z~2-6 for SC4K LAEs
• Direct evidence for Ly$\alpha$ depletion in the protocluster core
• The Stellar Mass, Star Formation Rate and Dark Matter Halo Properties of LAEs at $z\sim 2$
• How Do Galaxies trace a large scale structure?: A case study around a massive protocluster at $z=3.13$
• Constraining Lyman-alpha spatial offsets at $3<z<5.5$ from VANDELS slit spectroscopy
• Connections between galaxy mergers and Starburst: evidence from local Universe
• Physics of Prodigious Lyman Continuum Leakers
• A detailed study of massive galaxies in a protocluster at z=3.13
• Differences and similarities of stellar populations in LAEs and LBGs at $z\sim$ 3.4 - 6.8
• The MUSE-Wide survey: Three-dimensional clustering analysis of Lyman-$\alpha$ emitters at $3.3<z<6$

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