Surface Brightness Profile of Lyman-α Halos out to 320 kpc in HETDEX
Maja Lujan Niemeyer, Eiichiro Komatsu, Chris Byrohl, Dustin Davis, Maximilian Fabricius, Karl Gebhardt, Gary J. Hill, L. Wisotzki, W. Paul Bowman, Robin Ciardullo, Daniel J. Farrow, Steven L. Finkelstein, Eric Gawiser, C. Gronwall, Donghui Jeong, Martin Landriau, Chenxu Liu, Erin Mentuch Cooper, Masami Ouchi, Donald P. Schneider, Gregory R. Zeimann
Abstract
Abstract We present the median-stacked Lyman -α ( Ly α ) surface brightness profiles of 968 spectroscopically selected Ly α emitting galaxies (LAEs) at redshifts 1.9 < z < 3.5 in the early data of the Hobby-Eberly Telescope Dark Energy Experiment. The selected LAEs are high-confidence Ly α detections with high signal-to-noise ratios observed with good seeing conditions (point-spread function FWHM <1.″4), excluding active galactic nuclei. The Ly α luminosities of the LAEs are 10 42.4 –10 43 erg s −1 . We detect faint emission in the median-stacked radial profiles at the level of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:mn>3.6</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.3</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>20</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:mi>erg</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>arcsec</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> from the surrounding Ly α halos out to r ≃ 160 kpc (physical). The shape of the median-stacked radial profile is consistent at r < 80 kpc with that of much fainter LAEs at 3 < z < 4 observed with the Multi Unit Spectroscopic Explorer (MUSE), indicating that the median-stacked Ly α profiles have similar shapes at redshifts 2 < z < 4 and across a factor of 10 in Ly α luminosity. While we agree with the results from the MUSE sample at r < 80 kpc, we extend the profile over a factor of two in radius. At r > 80 kpc, our profile is flatter than the MUSE model. The measured profile agrees at most radii with that of galaxies in the Byrohl et al. cosmological radiative transfer simulation at z = 3. This suggests that the surface brightness of a Ly α halo at r ≲ 100 kpc is dominated by resonant scattering of Ly α photons from star-forming regions in the central galaxy, whereas at r > 100 kpc, it is dominated by photons from galaxies in surrounding dark matter halos.