Polarization of the \lya Halos Around Sources Before Cosmological Reionization

Abstract

In Loeb & Rybicki (1999; paper I) it was shown that before reionization, the scattering of \lya photons from a cosmological source might lead to a fairly compact ($\sim 15^{\prime \prime }$) \lya halo around the source. Observations of such halos could constrain the properties of the neutral intergalactic medium (IGM), and in particular yield the cosmological density parameters of baryons and matter on scales where the Hubble flow is unperturbed. Paper I did not treat the polarization of this scattered radiation, but did suggest that the degree of such polarization might be large. In this Letter we report on improved calculations for these \lya halos, now accounting for the polarization of the radiation field. The polarization is linear and is oriented tangentially to the projected displacement from the center of the source. The degree of polarization is found to be 14% at the core radius, where the intensity has fallen to half of the central value. It rises to 32% and 45% at the radii where the intensity has fallen to one-tenth and one-hundreth of the central intensity, respectively. At larger radii the degree of polarization rises further, asymptotically to 60%. Such high values of polarization should be easily observable and provide a clear signature of the phenomenon of \lya halos surrounding sources prior to reionization.

8 pages, 2 Postscript figures, accepted by Astrophysical Journal Letters; some typos corrected; added two paragraphs at the end of section 3 concerning detectability of Lyman alpha halos

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• Lyman Alpha Emitting Galaxies as a Probe of Reionization
• Lyman-alpha Cooling Emission from Galaxy Formation
• Scattered Lyman-alpha Radiation Around Sources Before Cosmological Reionization
• Line Transfer through Clumpy, Large-Scale Outflows: Lyman Alpha Absorption and Halos around Starforming Galaxies
• Central Powering of the Largest Lyman-alpha Nebula is Revealed by Polarized Radiation
• The Polarization of Scattered Lyman Alpha Radiation Around High-Redshift Galaxies
• Lyman-alpha blobs: polarization arising from cold accretion
• Nature of Lyman Alpha Blobs: Powered by Extreme Starbursts
• Deciphering Lyman $\alpha$ blob 1 with deep MUSE observations
• The Line Polarization Within a Giant Lyman-alpha Nebula
• Texas Spectroscopic Search for Ly$\alpha$ Emission at the End of Reionization II. The Deepest Near-Infrared Spectroscopic Observation at $z\gtrsim 7$
• Unlocking the Full Potential of Extragalactic Ly$\alpha$ through Its Polarization Properties
• Mapping the Morphology and Kinematics of a Lyman-alpha-selected Nebula at z=3.15 with MUSE
• Radiative Transfer in Lyα Nebulae: I. Modeling a Continuous or Clumpy Spherical Halo with a Central Source
• What Makes Ly$\alpha$ Nebulae Glow? Mapping the Polarization of LABd05
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• Ly-alpha Radiative Transfer: A Stokes Vector Approach to Ly-alpha Polarization
• Lyman-$\alpha$ Polarization Intensity Mapping
• MUSE-inspired view of the quasar Q2059-360, its Lyman alpha blob, and its neighborhood
• Mapping the Polarization of the Radio-Loud Ly$\alpha$ Nebula B3 J2330+3927
• On the formation of Lyman $\alpha$ emission from resonantly scattered continuum photons of GRB's afterglow