HeII emission in Lyman-alpha nebulae: AGN or cooling radiation?

Abstract

We present a study of an extended Lyman-alpha (Lya) nebula located in a known overdensity at z~2.38. The data include multiwavelength photometry covering the rest-frame spectral range from 0.1 to 250um, and deep optical spectra of the sources associated with the extended emission. Two galaxies are associated with the Lya nebula. One of them is a dust enshrouded AGN, while the other is a powerful starburst, forming stars at >~600 Msol/yr. We detect the HeII emission line at 1640A in the spectrum of the obscured AGN, but detect no emission from other highly ionized metals (CIV or NV) as is expected from an AGN. One scenario that simultaneously reproduces the width of the detected emission lines, the lack of CIV emission, and the geometry of the emitting gas, is that the HeII and the Lya emission are the result of cooling gas that is being accreted on the dark matter halo of the two galaxies, Ly1 and Ly2. Given the complexity of the environment associated with our Lya nebula it is possible that various mechanisms of excitation are at work simultaneously.

Accepted for publication on the Astrophysical Journal

References in corpus (19)

• The MAPPINGS III Library of Fast Radiative Shock Models
• Mid-Infrared Spectral Diagnosis of Submillimeter Galaxies
• Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars
• Population III stars: hidden or disappeared ?
• Unveiling obscured accretion in the Chandra Deep Field South
• Gravitational Quenching in Massive Galaxies and Clusters by Clumpy Accretion
• Chandra and Spitzer unveil heavily obscured quasars in the SWIRE/Chandra Survey
• Spitzer Mid-to-Far-Infrared Flux Densities of Distant Galaxies
• The Chandra Deep Protocluster Survey: Ly-alpha Blobs are powered by heating, not cooling
• The nature of faint Spitzer-selected dust-obscured galaxies
• Significant primordial star formation at redshifts z ~ 3-4
• Deep spectroscopy of the FUV-optical emission lines from a sample of radio galaxies at z~2.5: metallicity and ionization
• Evidence for Cold Accretion onto a Massive Galaxy at High Redshift?
• The Overdense Environment of a Large Lyman-alpha Nebula at z~2.7
• The Discovery of a Large Lyman-alpha+HeII Nebula at z~1.67: A Candidate Low Metallicity Region?
• Ly-alpha excess in high redshift radio galaxies: a signature of star formation
• Infrared and millimetre-wavelength evidence for cold accretion within a z = 2.83 Lyman-alpha blob
• Redshift Distribution of Extragalactic 24 micron Sources
• Submillimeter observations of the J2142-4423 Lya protocluster at z = 2.38

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