Small-scale Intensity Mapping: Extended Halos as a Probe of the Ionizing Escape Fraction and Faint Galaxy Populations during Reionization

Mas-Ribas, Lluís; Dijkstra, Mark; Davies, Frederick B.; Stern, Jonathan; Rix, Hans─Walter

doi:10.3847/1538-4357/aa8328

Cited by 26 publications

(36 citation statements)

References 67 publications

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“…This could significantly impact the local UV background and therefore the HI structures in the nearby CGM of galaxies (e.g. Mas-Ribas et al 2017;Sadoun et al 2017), particularly for star-forming galaxies that are still in a local neutral bubble. Naively, one would expect that galaxies that reside in such a significantly more neutral environment have flatter Lyα SB profiles and observed Lyα lines with higher velocity shift (due to an increased importance of resonant scattering and the IGM damping wing), compared to post-re-ionisation LAEs (e.g.…”

Section: Discussionmentioning

confidence: 99%

Resolved Lyman-α properties of a luminous Lyman-break galaxy in a large ionized bubble at z = 6.53

Matthee

Sobral

Grönke

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The observed properties of the Lyman-α (Lyα) emission line are a powerful probe of neutral gas in and around galaxies. We present spatially resolved Lyα spectroscopy with VLT/MUSE targeting VR7, a UV-luminous galaxy at z = 6.532 with moderate Lyα equivalent width (EW 0 = 38Å). These data are combined with deep resolved [CII] 158µm spectroscopy obtained with ALMA and UV imaging from HST. Lyα emission is clearly detected with S/N ≈ 40 and FWHM of 370 km s −1 . We also detect UV continuum with MUSE. Lyα and [CII] are similarly extended beyond the UV, with effective radius r eff = 2.1±0.2 kpc for a single component or r eff,Lyα,halo = 3.45 +1.08 −0.87 kpc when measured jointly with the UV continuum. The Lyα profile is broader and redshifted with respect to the [CII] line (by 220 km s −1 ), but there are spatial variations that are qualitatively similar in both lines and coincide with resolved UV components. This suggests that the emission originates from two components, while spatially varying HI column densities are also present. We place VR7 in the context of other galaxies at similar and lower redshift. The Lyα halo scale length is similar at different redshifts and velocity shifts with respect to the systemic are typically smaller. Overall, we find little indications of a more neutral vicinity at higher redshift. This means that the local (∼ 10 kpc) neutral gas conditions that determine the observed Lyα properties in VR7 resemble the conditions in post-re-ionisation galaxies.

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Section: Discussionmentioning

confidence: 99%

Resolved Lyman-α properties of a luminous Lyman-break galaxy in a large ionized bubble at z = 6.53

Matthee

Sobral

Grönke

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The galactic escape fraction can be inferred from the diffuse Hα emission from the CGM of a galaxy (Bland-Hawthorn & Maloney 1999;Mas-Ribas et al 2017). This approach has been applied to the two local dwarf galaxies, the Small Magellanic Cloud (SMC) and LMC, of the Milky Way by Barger et al (2013).…”

Section: Scale Of Lyc Leakage: Observational Test With the Magellanic Systems And Local Blue Compact Dwarfsmentioning

confidence: 99%

Radiation Hydrodynamics of Turbulent H ii Regions in Molecular Clouds: A Physical Origin of LyC Leakage and the Associated Lyα Spectra

Kakiichi

Grönke

2021

ApJ

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We examine Lyman continuum (LyC) leakage through H II regions regulated by turbulence and radiative feedback in a giant molecular cloud in the context of fully coupled radiation hydrodynamics (RHD). The physical relations of the LyC escape with H I covering fraction, kinematics, ionizing photon production efficiency, and emergent Lyα line profiles are studied using a series of RHD turbulence simulations performed with RAMSES-RT. The turbulenceregulated mechanism allows ionizing photons to leak out at early times before the onset of supernova feedback. The LyC photons escape through turbulence-generated low column density channels that are evacuated efficiently by radiative feedback via photoheating-induced shocks across the D-type ionization fronts. The Lyα photons funnel through the photoionized channels along the paths of LyC escape, resulting in a diverse Lyα spectral morphology including narrow double-peaked profiles. The Lyα peak separation is controlled by the residual H I column density of the channels, and the line asymmetry correlates with the porosity and multiphase structure of the H II region. This mechanism through the turbulent H II regions can naturally reproduce the observed Lyα spectral characteristics of some of the LyC-leaking galaxies. This RHD turbulence origin provides an appealing hypothesis to explain high LyC leakage from very young (∼3 Myr) star-forming galaxies found in the local universe without need of extreme galactic outflows or supernova feedback. We discuss the implications of the turbulent H II regions on other nebular emission lines and a possible observational test with the Magellanic System and local blue compact dwarf galaxies as analogs of reionization-era systems.

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“…Steidel et al 2011;Matsuda et al 2012;Borisova et al 2016;Wisotzki et al 2018), the ISM and continuum-undetected galaxy populations (e.g. Zheng et al 2011;Mas-Ribas et al 2017). Leclercq et al (2017) report no correlations between the halo scale lengths and any observed galaxy properties nor redshift at z ≈ 3 − 5.…”

Section: Introductionmentioning

confidence: 99%

The nature of CR7 revealed with MUSE: a young starburst powering extended Ly α emission at z = 6.6

Matthee

Pezzulli

Mackenzie

et al. 2020

Monthly Notices of the Royal Astronomical Society

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CR7 is among the most luminous Lyman-α emitters (LAEs) known at z = 6.6 and consists of at least three UV components that are surrounded by Lyman-α (Lyα) emission. Previous studies have suggested that it may host an extreme ionising source. Here, we present deep integral field spectroscopy of CR7 with VLT/MUSE. We measure extended emission with a similar halo scale length as typical LAEs at z ≈ 5. CR7’s Lyα halo is clearly elongated along the direction connecting the multiple components, likely tracing the underlying gas distribution. The Lyα emission originates almost exclusively from the brightest UV component, but we also identify a faint kinematically distinct Lyα emitting region nearby a fainter component. Combined with new near-infrared data, the MUSE data show that the rest-frame Lyα equivalent width (EW) is ≈100 Å. This is a factor four higher than the EW measured in low-redshift analogues with carefully matched Lyα profiles (and thus arguably HI column density), but this EW can plausibly be explained by star formation. Alternative scenarios requiring AGN powering are also disfavoured by the narrower and steeper Lyα spectrum and much smaller IR to UV ratio compared to obscured AGN in other Lyα blobs. CR7’s Lyα emission, while extremely luminous, resembles the emission in more common LAEs at lower redshifts very well and is likely powered by a young metal poor starburst.

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Small-scale Intensity Mapping: Extended Halos as a Probe of the Ionizing Escape Fraction and Faint Galaxy Populations during Reionization

Cited by 26 publications

References 67 publications

Resolved Lyman-α properties of a luminous Lyman-break galaxy in a large ionized bubble at z = 6.53

Resolved Lyman-α properties of a luminous Lyman-break galaxy in a large ionized bubble at z = 6.53

Radiation Hydrodynamics of Turbulent H ii Regions in Molecular Clouds: A Physical Origin of LyC Leakage and the Associated Lyα Spectra

The nature of CR7 revealed with MUSE: a young starburst powering extended Ly α emission at z = 6.6

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