![]() The characteristics of this absorption reflect the density distribution, ionization state and temperature of the intergalactic gas. The pattern of absorption lines imprinted on the spectra of distant objects by neutral hydrogen in the intergalactic medium (IGM), known as the ‘Lyα forest’, is one of the most fundamental probes of cosmic structure. Intergalactic medium, quasars: absorption lines, cosmology: observations, large-scale structure of Universe 1 INTRODUCTION This work also improves upon previous efforts using SDSS spectra by significantly reducing the level of systematic errors. Our results generally agree with the most careful measurements to date made from high-resolution data, but offer much greater precision and extend to higher redshifts. This trend is consistent with a gradual evolution of the ionization and thermal state of the intergalactic medium over 2 < z < 5. We find that F( z) evolves smoothly with redshift, with no evidence of a previously reported feature at z ≃ 3.2. at z ≤ 2.5, where continuum uncertainties are minimal. Absolute values for F( z) are found by scaling our relative values to measurements made from high-resolution data by Faucher-Giguère et al. The flux ratios of separate composites at the same rest wavelength are then used, without continuum fitting, to infer the mean transmitted flux, F( z), as a fraction of its value at z ∼ 2. The individual spectra are first combined into 26 composites with mean redshifts spanning 2.25 ≤ z comp ≤ 5.08. We exploit the general lack of evolution in the mean quasar continuum to avoid the bias introduced by continuum fitting over the Lyα forest at high redshifts, which has been the primary systematic uncertainty in previous measurements of the mean Lyα transmission. Offer much greater precision and extend to higher redshifts.We present new measurements of the mean transmitted flux in the Lyα forest over 2 < z < 5 made using 6065 quasar spectra from the Sloan Digital Sky Survey data release 7 (SDSS DR7). With the most careful measurements to date made from high-resolution data, but State of the intergalactic medium over 2 < z < 5. Trend is consistent with a gradual evolution of the ionization and thermal Redshift, with no evidence of a previously reported feature at z~3.2. (2008) at z < 2.5, whereĬontinuum uncertainties are minimal. High-resolution data by Faucher-Giguere et al. Absolute values forį(z) are found by scaling our relative values to measurements made from Transmitted flux, F(z), as a fraction of its value at z~2. Wavelength are then used, without continuum fitting, to infer the mean The flux ratios of separate composites at the same rest The individual spectraĪre first combined into twenty-six composites with mean redshifts spanning 2.25 Previous measurements of the mean Ly-alpha transmission. We exploit the general lack of evolution in the mean quasarĬontinuum to avoid the bias introduced by continuum fitting over the Ly-alphaįorest at high redshifts, which has been the primary systematic uncertainty in ![]() ![]() Flux meaning pdf#Xavier Prochaska (2) ((1) KICC/IoA, Cambridge, (2) UCO/Lick Observatory, University of California Santa Cruz) Download PDF Abstract: We present new measurements of the mean transmitted flux in the Ly-alphaįorest over 2 < z < 5 made using 6065 quasar spectra from the Sloan Digital Sky ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |