A Plethora of AGN Among Lyman Alpha Galaxies at Low Redshift

Abstract

We investigate the fraction of z ~ 0.3 Lyman alpha emitting galaxies (LAEs) which host active galactic nucleus activity, which is typically from 1 - 5% at 2 < z < 6. Using optical spectroscopy of 23 LAEs at 0.2 < z < 0.45 selected with GALEX UV data, we probe for AGN with a variety of methods, including line widths, diagnostic line ratios, high-ionization emission, infrared activity and X-ray luminosity. We found that our sample of low-redshift LAEs has an AGN fraction of 43 ^{+18}{-26}%, significantly higher than at high redshift. While previous results have shown that low-redshift LAEs have a lower space density than their high-redshift analogs, these results show that star-forming LAEs at low-redshift are rarer still. Accounting for differences in available AGN classification methods, we conclude that rest-frame optical spectroscopy is necessary to identify low-luminosity AGNs in LAEs at high redshift, and that limits on the X-ray flux are necessary to determine the extent to which the AGN contaminates the Lyman alpha fluxes.

arXiv commentReplaced with ApJL accepted version, 5 pages, 2 figures

References in corpus (32)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Unified Schemes for Radio-Loud Active Galactic Nuclei
• The Host Galaxies of AGN
• Theoretical Modeling of Starburst Galaxies
• Rest-Frame Ultraviolet Spectra of z~3 Lyman Break Galaxies
• Mid-Infrared Selection of Active Galaxies
• Luminosity-dependent evolution of soft X-ray selected AGN: New Chandra and XMM-Newton surveys
• The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets
• The Chandra Deep Field South: Optical Spectroscopy I
• 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
• Hectospec, the MMT's 300 Optical Fiber-Fed Spectrograph
• Ly-alpha Emission-Line Galaxies at z = 3.1 in the Extended Chandra Deep Field South
• Ly Alpha-Emitting Galaxies at z=3.1: L* Progenitors Experiencing Rapid Star Formation
• High-z Lyman-alpha Emitters. I. A Blank-Field Search for Objects Near Redshift z=3.4 in and around the Hubble Deep Field and the Hawaii Deep Field SSA22
• Large Equivalent width Lyman-alpha line emission at z=4.5: young galaxies in a young universe
• First Results from the Large Area Lyman Alpha Survey
• The Discovery of Primeval Large-Scale Structures with Forming Clusters at Redshift 6
• AEGIS-X: The Chandra Deep Survey of the Extended Groth Strip
• The Physical Nature of Lyman Alpha Emitting Galaxies at z=3.1
• The Redshift Evolution of the 2-8 keV X-ray Luminosity Function
• Lyman Alpha Galaxies: Primitive, Dusty or Evolved Galaxies?
• Evolution in the properties of Lyman-alpha emitters from redshifts z ~ 3 to z ~ 2
• Optical to mid-IR observations of Lyman-alpha galaxies at redshift 5 in the HUDF: a young and low mass population
• Spectroscopic Properties of the z=4.5 Lyman-alpha Emitters
• A multi-wavelength study of z = 3.15 Lyman-alpha emitters in the GOODS South Field
• The Ages and Masses of Lyman Alpha Galaxies at Redshift $z\sim 4.5$
• Effects of Dust Geometry in Lyman Alpha Galaxies at z = 4.4
• Lyman alpha emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy
• X-ray nondetection of the Lyman-alpha Emitters at z ~ 4.5
• No X-ray Bright Type II Quasars Among the Lyman-alpha Emitters
• Gemini Near Infrared Spectrograph Observations of a Red Star Forming Galaxy at z=2.225: Evidence for Shock-Ionization due to a Galactic Wind
• Evolution of Lyman Alpha Galaxies: Stellar Populations at z ~ 0.3

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• A Comprehensive Study of Ly$\alpha$ Emission in the High-redshift Galaxy Population
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• X-ray properties of the z ~ 4.5 Lyman-alpha Emitters in the Chandra Deep Field South Region
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• Herschel FIR counterparts of selected Ly-alpha emitters at z~2.2. Fast evolution since z~3 or missed obscured AGNs?
• Lyman-alpha emitters as tracers of the transitioning Universe
• A Search for Lensed Lyman-Alpha Emitters within the Early HETDEX Data Set
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