Active Galactic Nuclei Selected from GALEX Spectroscopy: The Ionizing Source Spectrum at z~1

Abstract

We use a complete sample of Lya emission-line selected AGNs obtained from nine deep blank fields observed with the grism spectrographs on the Galaxy Evolution Explorer (GALEX) satellite to measure the normalization and spectral shape of the AGN contribution to the ionizing background (rest-frame wavelengths 700-900 A) at z~1. Our sample consists of 139 sources selected in the redshift range z=0.65-1.25 in the near-ultraviolet (NUV; 2371 A central wavelength) channel. The area covered is 8.2 square degrees to a NUV magnitude of 20.5 (AB) and 0.92 square degrees at the faintest magnitude limit of 21.8. The GALEX AGN luminosity function agrees well with those obtained using optical and X-ray AGN samples, and the measured redshift evolution of the ionizing volume emissivity is similar to that previously obtained by measuring the GALEX far-ultraviolet (FUV; 1528 A central wavelength) magnitudes of an X-ray selected sample. For the first time we are able to construct the shape of the ionizing background at z~1 in a fully self-consistent way.

9 pages, in press at The Astrophysical Journal

References in corpus (10)

• An Observational Determination of the Bolometric Quasar Luminosity Function
• New Constraints on the Lyman Continuum Escape Fraction at z~1.3
• Lyman alpha emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy
• A Monte Carlo simulation of the intergalactic absorption and the detectability of the Lyman continuum from distant galaxies
• High-Redshift QSOs in the SWIRE Survey and the z~3 QSO Luminosity Function
• The Evolution of Lyman alpha Absorbers in the Redshift Range 0.5<z<1.9
• The OPTX Project I: The Flux and Redshift Catalogs for the CLANS, CLASXS, and CDF-N fields
• Continuous statistics of the Lyman-alpha forest at 0 < z < 1.6: the mean flux, flux distribution, and autocorrelation from HST FOS spectra
• Spectroscopic Analysis of H I Absorption Line Systems in 40 HIRES Quasars
• The UV background photoionization rate at 2.3 < z < 4.6 as measured from the Sloan Digital Sky Survey

Cited by in corpus (7)

• HST-COS Observations of AGN. II. Extended Survey of Ultraviolet Composite Spectra from 159 Active Galactic Nuclei
• Line driven winds and the UV turnover in AGN accretion discs
• Cold Accretion Disks and Lineless Quasars
• Ly alpha emitting galaxies as early stages in galaxy formation
• Super-Eddington QSO RX J0439.6-5311. II. Multi-wavelength Constraints on the Global Structure of the Accretion Flow
• A catalog of optical to X-ray spectral energy distributions of z~2 quasars observed with Swift. I: First results
• Statistical properties of the GALEX spectroscopic stellar sample