J/ApJ/457/102 Ly-Alpha Forest spectra simulation analysis. I. (Dobrzycki+ 1996)
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 1996ApJ...457..102D
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-)^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 1016cm-2 and =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 , 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:
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RA (2000) DE Designation(s)
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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
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File Summary:
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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
(End) [CDS] 05-Sep-1996