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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
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 1016cm-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
ReadMe 80 . This file q1206119.dat 131 150 Line list for Q1206+119 q1225017.dat 131 109 Line list for Q1225-017 q1315472.dat 131 104 Line list for Q1315+472 q1607183.dat 131 118 Line list for Q1607+183 q1623268.dat 131 105 Line list for Q1623+268 q1700643.dat 131 133 Line list for Q1700+643 q1946770.dat 131 119 Line list for Q1946+770 table2.tex 94 936 AASTeX version of line lists for all quasars
Byte-by-byte Description of file: q*
Bytes Format Units Label Explanations
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
Origin: AAS CD-ROM series, Volume 6, 1996 Lee Brotzman [ADS] 22-Apr-96
(End) [CDS] 05-Sep-1996
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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