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J/ApJ/457/102  Ly-Alpha Forest spectra simulation analysis. I. (Dobrzycki+ 1996)
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Simulation analysis of Ly-Alpha forest spectra. I. Empirical description at z~3
     Dobrzycki A., Bechtold J.
    <Astrophys. J. 457, 102 (1996)>
    =1996ApJ...457..102D
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ADC_Keywords: QSOs ; Spectroscopy
Keywords: cosmology: observations - intergalactic medium -
          quasars: absorption lines

Abstract:
    We present moderate-resolution (~50km/s FWHM) spectra of the Ly-alpha
    forest for seven quasars with redshifts ranging from 2.53 to 3.13,
    obtained with the Blue Spectrograph and photon-counting Reticon at the
    Multiple Mirror Telescope. Combined with spectra of 10 other quasars
    presented elsewhere, we have characterized the distribution of cloud
    properties in a way which was designed to minimize any subjective part
    of the analysis.
    We used artificial absorption spectra, with the same resolution,
    sampling and signal-to-noise ratio as a function of wavelength as the
    actual data. Distributions of the physical parameters of the Ly-alpha
    clouds, namely, the neutral hydrogen column density (N) and Doppler
    parameter (b), were approximated with d"N"/dN proportional to
    N^(-beta) and d"N"/db proportional to exp[-(b-<b>)^2/(2 sigma_b^2)],
    respectively. We constructed a grid of simulated spectra with
    different input parameters. Comparison of properties of the simulated
    spectra with the observed spectra yielded acceptable ranges of
    parameters. Our technique differs from previous similar work in that
    we use the information contained in the distribution of the strength
    of the absorption in each resolution element and the distribution of
    separations between absorption complexes. We derive beta =1.4+/-0.1
    for N ranging from 10^13 to 10^16cm^-2 and <b>=30+/-15km/s.
    Most previous studies based on line lists indicated beta=1.7-1.9. We
    attribute this difference to flattening of the column density
    distribution for low N, recently confirmed by higher resolution
    observations. Our result for <b>, though consistent with values quoted
    in the literature, is of lower significance, since it is less than the
    resolution of our spectra. We conclude by commenting on the importance
    of line blending in data sets of this kind.

Objects:
    --------------------------------------------------------------------
       RA  (2000)  DE      Designation(s)
    --------------------------------------------------------------------
    12 09 18   +11 38 31   QSO 1206+119
    12 27 59   -02 03 03   QSO 1225-017
    13 18 02   +47 06 30   QSO 1315+472 = QSO 1315+4722 = PC 1315+4722
    16 10 05   +18 11 45   QSO 1607+183 = QSO 1607+1819
    16 25      +26 42      QSO 1623+268
    17 01 00   +64 12 09   QSO 1700+643 = QSO 1700+6414 = QSO 1700+642
    19 44 55   +77 05 52   QSO 1946+770 = QSO 1946+7658 = QSO 1946+769
    --------------------------------------------------------------------

File Summary:
--------------------------------------------------------------------------------
 FileName    Lrecl    Records   Explanations
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ReadMe          80          .   This file
q1206119.dat   111        150   Line list for Q1206+119
q1225017.dat    90        109   Line list for Q1225-017
q1315472.dat   129        104   Line list for Q1315+472
q1607183.dat   110        118   Line list for Q1607+183
q1623268.dat   129        105   Line list for Q1623+268
q1700643.dat   110        133   Line list for Q1700+643
q1946770.dat    90        119   Line list for Q1946+770
table2.tex      94        936   AASTeX version of line lists for all quasars
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Byte-by-byte Description of file: q*
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   Bytes Format  Units   Label     Explanations
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   1-  3  I3     ---     Num       Line number
   5- 12  F8.2   0.1nm   Lambda    Wavelength
  14- 20  F7.3   0.1nm   EW        Equivalent width
  22- 27  F6.3   0.1nm e_EW        Equivalent width error
  30- 89  A60    ---     Ident     Line identification
  92-131  A40    ---     Poss      Possible line identification
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Origin: AAS CD-ROM series, Volume 6, 1996           Lee Brotzman [ADS] 22-Apr-96
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(End)                                                         [CDS]  05-Sep-1996