Lyman-alpha absorption in the spectrum of the Z = 4.5 QSO BR 1033-0327

Details Lyman-alpha absorption in the spectrum of the Z = 4.5 QSO BR 1033-0327 Lyman-alpha absorption in the spectrum of the Z = 4.5 QSO BR 1033-0327

Jun 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...428..574w&link_type=abstract

The Astrophysical Journal, vol. 428, no. 2, pt. 1, p. 574-590

Astronomy and Astrophysics

Astrophysics

86

Absorption Spectra, Density Distribution, Doppler Effect, H I Regions, Heavy Ions, Lyman Alpha Radiation, Quasars, Red Shift, Cameras, Charge Coupled Devices, Echelle Gratings, Spectrometers, Telescopes, Voigt Effect

Scientific paper

We present the results of echelle spectroscopy of the Lyalpha forest region in the spectrum of the bright (mR = 18.5) optically selected z = 4.5 QSO BR 1033-0327. These results, which extend Lyalpha forest absorption line studies up to a redshift of z= 4.5 at a resolution of 12 km/sec, represent the first high-resolution study of Lyalpha forest systems at such high redshifts. We compare the properties of the Lyalpha forest systems in the redshift range 3.7 less than z less than 4.3 with those inferred from similar observations at 1.86 less than z less than 3.27 and find some clear indications of redshift dependence in these. First, the ionizing flux from the quasar appears to affect the Lyalpha line density further from the QSO than at lower redshifts, implying that the Lyman limit background flux at redshift z approximately 4.2 is Jnu approximately 1 to 3 x 10-22 ergs/cm2/sec/Hz/sr. This is about a factor of 10 lower than estimates at z approximately 2.5. Second, the Doppler parameter distribution for systems where the effect of the QSO ionizing flux is small (3.7 less than z less than 4.3) has an excess at values approximately 20 km/sec, compared with lower redshifts; we suggest this may be due to the lower ionizing flux at z approximately 4.2, which would reduce the heating of the gas. Finally, while there is no evidence that the shape of the H I column density distribution changes significantly, the redshift dependence of the total number of systems is stronger t han that found at lower redshifts, with the number of systems per unit redshift approximately (1+ z) 4.6. Also, over the entire redshift range there is no significant correlation between Doppler parameter and H I column density and no signal in the two-point correlation function down to velocity separations of Delta v approximately 100 km/sec. There is no evidence for continuously distributed HI absorption (the Gunn-Peterson effect) at these redshifts.

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