Carbon ionization states and the cosmic far-UV background with HeII absorption

Abstract

We constrain the spectrum of the cosmic ultraviolet background radiation by fitting the observed abundance ratios carbon ions at $z\sim 2–3$ with those expected from different models of the background radiation. We use the recently calculated modulation of the background radiation between 3 and 4 Ryd due to resonant line absorption by intergalactic HeII, and determine the ratios of CIII to CIV expected at these redshifts, as functions of metallicity, gas density and temperature. Our analysis of the observed ratios shows that 'delayed reionization' models, which assume a large fraction of HeII at $z\sim 3$, is not favored by data. Our results suggest that HeII reionization was inhomogeneous, consistent with the predictions from recent simulations.

30 pages, 5 figures, accepted in ApJ

References in corpus (7)

• An Observational Determination of the Bolometric Quasar Luminosity Function
• Time-Dependent Ionization in Radiatively Cooling Gas
• HeII Reionization and its Effect on the IGM
• Collisional Ionization Equilibrium for Optically Thin Plasmas. I. Updated Recombination Rate Coefficients for Bare though Sodium-like Ions
• Spectral shape of the UV ionizing background and HeII absorption at redshifts 1.8 < z < 2.9
• Numerical simulations of the Warm-Hot Intergalactic Medium
• The Implications of Gunn-Peterson Troughs in the HeII Lyman-alpha Forest

Cited by in corpus (5)

• Nonequilibrium ionization states and cooling rates of the photoionized enriched gas
• A chemical model for the interstellar medium in galaxies
• The impact of spatial fluctuations in the ultra-violet background on intergalactic carbon and silicon
• Reconstructing the intergalactic UV background with QSO absorption lines
• Thermal instability in the collisionally cooled gas