Computer Science – Numerical Analysis
Scientific paper
Feb 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...440l..53z&link_type=abstract
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 440, no. 2, p. L53-L56
Computer Science
Numerical Analysis
23
Absorption Spectra, Diffuse Radiation, Helium Ions, Intergalactic Media, Quasars, Red Shift, Astronomical Models, Line Shape, Numerical Analysis, Ultraviolet Radiation
Scientific paper
The Gunn-Peterson effect predicts that an absorption trough should be associated with any resonance line arising in the intergalactic medium (IGM), extending blueward of the line in the QSO's rest frame. We show that such an absorption trough will not generally have a sharp edge at the QSO's redshift but should develop gradually toward shorter wavelengths. This proximity profile of the Gunn-Peterson trough arises because diffuse intergalactic gas in the vicinity of the QSO is more highly ionized than the general IGM. We consider the case of a uniform IGM in approximate photoionization equilibrium with a metagalactic UV background and investigate the proximity profile of He II lambda 304, which might be observable in QSOs with ZQ approximately 3. Assuming the QSO continuum extends beyond the He II ionization edge, the proximity profile has a characteristic width of delta zp = delta lambda/304 is approximately 0.1 f is the QSO Lyman limit luminosity in units of 1031 ergs/s/Hz averaged over the past approximately 107 yr, omegaI is the IGM density near (is less than or equal to 10 Mpc) the QSO, omegab is the normalized baryon density predicted by standard big band necleosynthesis, and f is a factor of order unity which depends weakly on several other factors. Application of this result to the reported detection of the He II Gunn-Peterson effect in Q0302-003 (Jakobsen et al. 1994) suggests that omegaI is approximately equal to omegab, some three orders of magnitude larger than the minimum density that may be inferred from application of the ordinary Gunn-Peterson effect to this QSO. Future observations of the He II proximity profile at higher resolution and signal-to-noise ratio in serveral ASOs should provide the means to measure the IGM density accurately.
Davidsen Arthur
Zheng Wei
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