Deciphering Lyman-$\alpha$ Emission Deep into the Epoch of Reionisation

Abstract

During the epoch of reionisation the first galaxies were enshrouded in pristine neutral gas, with one of the brightest emission lines in star-forming galaxies, Lyman-$\alpha$ (Ly$\alpha$), expected to remain undetected until the Universe became ionised. Providing an explanation for the surprising detection of Ly$\alpha$ in these early galaxies is a major challenge for extra-galactic studies. Recent JWST observations have reignited the debate on whether residence in an overdensity of galaxies is a it sufficient and necessary condition for Ly$\alpha$ to escape. Here, we take unique advantage of both high-resolution and high-sensitivity images from the JWST instrument NIRCam to reveal that all galaxies in a sample of z>7 Ly$\alpha$ emitters have close companions. We exploit novel on-the-fly radiative transfer magnetohydrodynamical simulations with cosmic ray feedback to show that galaxies with frequent mergers have very bursty star formation which drives episodes of high intrinsic Ly$\alpha$ emission and facilitates the escape of Ly$\alpha$ photons along channels cleared of neutral gas. We conclude that the rapid build up of stellar mass through mergers presents a compelling solution to the long-standing puzzle of the detection of Ly$\alpha$ emission deep into the epoch of reionisation.

Published in Nature Astronomy. 45 pages, 9 figures, 2 tables

References in corpus (52)

• 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
• The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope I. Overview of the instrument and its capabilities
• A Comprehensive Study on Galaxies at z~9-16 Found in the Early JWST Data: UV Luminosity Functions and Cosmic Star-Formation History at the Pre-Reionization Epoch
• CEERS Key Paper I: An Early Look into the First 500 Myr of Galaxy Formation with JWST
• JADES NIRSpec Spectroscopy of GN-z11: Lyman-$\alpha$ emission and possible enhanced nitrogen abundance in a $z=10.60$ luminous galaxy
• NIRCam Performance on JWST In Flight
• A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z > 6 Quasars
• Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars
• Lyman Alpha Emitting Galaxies as a Probe of Reionization
• CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results
• Building Merger Trees from Cosmological N-body Simulations
• Confirmation and refutation of very luminous galaxies in the early universe
• A scheme for radiation pressure and photon diffusion with the M1 closure in RAMSES-RT
• JADES Imaging of GN-z11: Revealing the Morphology and Environment of a Luminous Galaxy 430 Myr After the Big Bang
• UV Luminosity Density Results at z>8 from the First JWST/NIRCam Fields: Limitations of Early Data Sets and the Need for Spectroscopy
• The GREATS H$\beta$+[OIII] Luminosity Function and Galaxy Properties at $\mathbf{z}\sim 8$: Walking the Way of JWST
• Kinematic Dynamos using Constrained Transport with High Order Godunov Schemes and Adaptive Mesh Refinement
• Early results from GLASS-JWST. XIV: A spectroscopically confirmed protocluster 650 million years after the Big Bang
• A spectroscopic search for AGN activity in the reionization era
• Overview of the JWST Advanced Deep Extragalactic Survey (JADES)
• LyC escape from SPHINX galaxies in the Epoch of Reionization
• A Magnified Compact Galaxy at Redshift 9.51 with Strong Nebular Emission Lines
• Onset of Cosmic Reionization: Evidence of An Ionized Bubble Merely 680 Myrs after the Big Bang
• First Sample of H$\alpha$+[O III] $\lambda$5007 Line Emitters at $z>6$ Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line Luminosity Functions
• 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
• Probing Cosmic Dawn : Ages and Star Formation Histories of Candidate $z\ge$9 Galaxies
• The Lyman-alpha signature of the first galaxies
• Mapping Neutral Hydrogen During Reionization with the Ly-alpha Emission from Quasar Ionization Fronts
• Inferring the IGM Neutral Fraction at z ~ 6-8 with Low-Luminosity Lyman Break Galaxies
• JADES: Discovery of extremely high equivalent width Lyman-alpha emission from a faint galaxy within an ionized bubble at z=7.3
• Lyman-$\alpha$ as a tracer of cosmic reionisation in the SPHINX radiation-hydrodynamics cosmological simulation
• Modelling the observed luminosity function and clustering evolution of Lyman-$\alpha$ emitters: growing evidence for late reionization
• How primordial magnetic fields shrink galaxies
• Lyman Alpha Driven Outflows Around Star Forming Galaxies
• AGN-driven outflows and the formation of Ly$\alpha$ nebulae around high-z quasars
• Simulating the diversity of shapes of the Lyman-$\alpha$ line
• The ALMA REBELS Survey: Efficient Ly$\alpha$ Transmission of UV-Bright z$\simeq$7 Galaxies from Large Velocity Offsets and Broad Line Widths
• Radiation-MagnetoHydrodynamics simulations of cosmic ray feedback in disc galaxies
• A lensed protocluster candidate at $z=7.66$ identified in JWST observations of the galaxy cluster SMACS0723-7327
• The Prevalence of Galaxy Overdensities Around UV-Luminous Lyman $\alpha$ Emitters in the Epoch of Reionization
• On the sizes of ionized bubbles around the highest redshift galaxies. Spectral shapes of the Lyman-alpha emission from galaxies
• The Pandora project. I: the impact of radiation and cosmic rays on baryonic and dark matter properties of dwarf galaxies
• JWST catches the assembly of a $z\sim 5$ ultra-low-mass galaxy
• CEERS: Diversity of Lyman-Alpha Emitters during the Epoch of Reionization
• Resolving Ambiguities in the Inferred Star Formation Histories of Intense [O III] Emitters in the Reionisation Era
• Nature and Nurture? Comparing Ly$\alpha$ Detections in UV-Bright and Fainter [O III]+H$\beta$ Emitters at $z\sim 8$ With Keck/MOSFIRE
• Evidence for a low Lyman Continuum Escape fraction in three Massive, UV-bright galaxies at z > 7
• JWST observations of galaxy damping wings during reionization interpreted with cosmological simulations
• Inside the bubble: exploring the environments of reionisation-era Lyman-$\alpha$ emitting galaxies with JADES and FRESCO
• GA-NIFS: JWST discovers an offset AGN 740 million years after the Big Bang
• PRISM: A Non-Equilibrium, Multiphase Interstellar Medium Model for Radiation Hydrodynamics Simulations of Galaxies

Cited by in corpus (20)

• The JWST-PRIMAL Legacy Survey. A JWST/NIRSpec reference sample for the physical properties and Lyman-$\alpha$ absorption and emission of $\sim 500$ galaxies at $z=5.5-13.4$
• GN-z11: The environment of an AGN at $z=$10.603
• JADES: Primaeval Lyman-$\alpha$ emitting galaxies reveal early sites of reionisation out to redshift $z\sim 9$
• The THESAN-ZOOM project: Burst, quench, repeat -- unveiling the evolution of high-redshift galaxies along the star-forming main sequence
• The density-bounded twilight of starbursts in the early Universe
• The THESAN-ZOOM project: central starbursts and inside-out quenching govern galaxy sizes in the early Universe
• Constraints on the state of the IGM at $z\sim 8-10$ using redshifted 21-cm observations with LOFAR
• Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe
• Mapping reionization bubbles in the JWST era II: inferring the position and characteristic size of individual bubbles
• HI Imaging of a Blueberry Galaxy Suggests a Merger Origin
• The Lyman-alpha and Continuum Origins Survey. I. Survey description and Ly$\alpha$ imaging
• The leakage of Lyman-continuum photons from a major merger at $z\sim 1$
• The Lyman-alpha and Continuum Origins Survey II: the connection between the escape of ionizing radiation and Lyman-alpha halos in star-forming galaxies
• Influence of mergers on LyC escape of high redshift galaxies
• GA-NIFS: Dissecting the multiple sub-structures and probing their complex interactions in the \Lyalpha emitter galaxy CR7 at z = 6.6 with JWST/NIRSpec
• Ly$\alpha$ Emission from [OIII] Emitters Near Reionization: The role of environment in galaxy Ly$\alpha$ detection
• The Lyman Alpha Reference Sample. XVI. Global 21cm HI properties of Lyman-$\alpha$ emitting galaxies
• The metal-poorest tail of the Galactic halo: hypothesis on its origin from precise spectral analysis
• The universality of the relation between magnetic fields and star formation in galaxies
• Deep JWST spectroscopy of galaxies in a candidate ionized bubble at $z=8.7$: probing reionization at pMpc scales with Ly$\alpha$ emission