Anisotropic Lyman-alpha Emission

Abstract

As a result of resonant scatterings off hydrogen atoms, Lyman-alpha (Lya) emission from star-forming galaxies provides a probe of the (hardly isotropic) neutral gas environment around them. We study the effect of the environmental anisotropy on the observed Lya emission by performing radiative transfer calculations for models of neutral hydrogen clouds with prescriptions of spatial and kinematic anisotropies. The environmental anisotropy leads to corresponding anisotropy in the Lya flux and spectral properties and induces correlations among them. The Lya flux (or observed luminosity) depends on the viewing angle and shows an approximate correlation with the initial Lya optical depth in the viewing direction relative to those in all other directions. The distribution of Lya flux from a set of randomly oriented clouds is skewed to high values, providing a natural contribution to the Lya equivalent width (EW) distribution seen in observation. A narrower EW distribution is found at a larger peak offset of the Lya line, similar to the trend suggested in observation. The peak offset appears to correlate with the line shape (full width at half maximum and asymmetry), pointing to a possibility of using Lya line features alone to determine the systemic redshifts of galaxies. The study suggests that anisotropies in the spatial and kinematic distributions of neutral hydrogen can be an important ingredient in shaping the observed properties of Lya emission from star-forming galaxies. We discuss the implications of using Lya emission to probe the circumgalactic and intergalactic environments of galaxies.

14 pages, 13 figures, ApJ in press

References in corpus (13)

• Cold streams in early massive hot haloes as the main mode of galaxy formation
• Ubiquitous outflows in DEEP2 spectra of star-forming galaxies at z=1.4
• The Subaru/XMM-Newton Deep Survey (SXDS). IV. Evolution of Lya Emitters from z=3.1 to 5.7 in the 1 deg^2 Field: Luminosity Functions and AGN
• 3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line profile morphologies
• The Impact of The IGM on High-Redshift Lyman Alpha Emission Lines
• Lyman-alpha emission properties of simulated galaxies: interstellar medium structure and inclination effects
• Gas Motion Study of Lya Emitters at z~2 Using UV and Optical Spectral Lines
• On the (non-)enhancement of the Lyman α equivalent width by a multiphase interstellar medium
• Beamed Lyman Alpha Emission through Outflow-Driven Cavities
• Directional Lya equivalent boosting I. Spherically symmetric distributions of clumps
• Effects of Lyman alpha scattering in the IGM on clustering statistics of Lyman alpha emitters
• [OIII] Emission and Gas Kinematics in a Lyman-alpha Blob at z ~ 3.1
• A WENO algorithm for radiative transfer with resonant scattering: the time scale of the Wouthuysen-Field Coupling

Cited by in corpus (48)

• Extended Lyman alpha haloes around individual high-redshift galaxies revealed by MUSE
• Ly$\alpha$ emission from Green Peas: the role of circumgalactic gas density, covering, and kinematics
• "Big Three Dragons": a z = 7.15 Lyman BreakGalaxy Detected in [OIII] 88 $\mu$m, [CII] 158 $\mu$m, and Dust Continuum with ALMA
• Observations of the Lyman-$\alpha$ Universe
• The Spectroscopic Properties of Lyα-Emitters at z $\approx$ 2.7: Escaping Gas and Photons from Faint Galaxies
• Recovering the systemic redshift of galaxies from their Lyman-alpha line profile
• The physics of Lyman-alpha escape from high-redshift galaxies
• A Close Comparison between Observed and Modeled Lyα Lines for z ~ 2.2 Lyman Alpha Emitters
• The BOSS Emission-Line Lens Survey. IV. : Smooth Lens Models for the BELLS GALLERY Sample
• Ly$\alpha$ Spectra from Multiphase Outflows, and their Connection to Shell Models
• Magnifying the early episodes of star formation: super star clusters at cosmological distances
• A Close Relationship between Lyman Alpha and Mg II in Green Pea Galaxies
• The Mean Ultraviolet Spectrum of a Representative Sample of Faint z~3 Lyman Alpha Emitters
• The MUSE Hubble Ultra Deep Field Survey X. Ly$\alpha$ Equivalent Widths at $2.9<z<6.6$
• Puzzling Lyman-alpha line profiles in green pea galaxies
• The X-SHOOTER Lyman-$\alpha$ survey at z=2 (XLS-z2) I: What makes a galaxy a Lyman-$\alpha$ emitter?
• (Re)Solving Reionization with Lyα: How Bright Lyα Emitters account for the $z\approx 2-8$ Cosmic Ionizing Background
• Morphologies of ~190,000 Galaxies at z=0-10 Revealed with HST Legacy Data. III. Continuum Profile and Size Evolution of Lya Emitters
• Large-scale clustering of Lyman-alpha emission intensity from SDSS/BOSS
• Modelling the observed luminosity function and clustering evolution of Lyman-$\alpha$ emitters: growing evidence for late reionization
• The physics of Lyman-alpha escape from disc-like galaxies
• On the Diffuse Lyman-alpha Halo Around Lyman-alpha Emitting Galaxies
• SILVERRUSH. II. First Catalogs and Properties of ~2,000 Lya Emitters and Blobs at z~6-7 Identified over the 14-21 deg2 Sky
• Lyman-alpha radiation hydrodynamics of galactic winds before cosmic reionization
• Evidence for a direct collapse black hole in the Lyman-alpha source CR7
• Inclination Dependence of Lyman-Alpha Properties in a Turbulent Disk Galaxy
• The ALPINE-ALMA [CII] survey: Small Lya-[CII] velocity offsets in main-sequence galaxies at 4.4 < z < 6
• Discovery of a z = 7.452 High Equivalent Width Lyman-α Emitter from the Hubble Space Telescope Faint Infrared Grism Survey
• On the decreasing fraction of Strong Ly$\alpha$ Emitters around $z$ $\sim$ $6$-$7$
• Ly$\alpha$ Emitters with Very Large Ly$\alpha$ Equivalent Widths, EW${}_0$(Ly$\alpha$) $\simeq 200-400$ Å, at $z\sim 2$
• Radiative effects during the assembly of direct collapse black holes
• Lyman-alpha radiative transfer: Modeling spectrum and surface brightness profile of Lyman-alpha emitting galaxies at z=3-6
• Lyα emitters in a cosmological volume I: the impact of radiative transfer
• Rest-frame UV Properties of Luminous Strong Gravitationally Lensed Ly$\alpha$ Emitters from the BELLS GALLERY Survey
• Radiative Transfer Distortions of Lyman-$\alpha$ Emitters: a New Fingers-of-God Damping in the Clustering in Redshift Space
• Lyman-$\alpha$ feedback prevails at Cosmic Dawn: Implications for the first galaxies, stars, and star clusters
• Scrutiny of a very young, metal-poor star-forming Lyα-emitter at z ~ 3.7
• Probing delayed-end reionization histories with the 21cm-LAE cross-power spectrum
• Stellar feedback in a clumpy galaxy at $z\sim$ 3.4
• Revealing the Nature of a Lyman-$\alpha$ Halo in a Strongly Lensed Interacting System at $z=2.92$
• Crossing walls and windows: the curious escape of Lyman-$\alpha$ photons through ionised channels
• Can galaxy evolution mimic cosmic reionization?
• C IV and He II Line Emission of Lyman Alpha Blobs: Powered by Shock Heated Gas
• Lyman alpha Properties of Simulated Galaxies in Overdense Regions: Effects of Galactic Winds at z > 6
• A public grid of radiative transfer simulations for Lyman-alpha and metal lines in idealised galactic outflows
• Evidence for Infalling Gas in a Lyman-$\alpha$ Blob
• Lyman-alpha resonant-line radiative transfer in expanding media
• Influence of turbulence on Lyman-alpha scattering