A Search for High-Excitation Redshift Systems in the Absorption Spectra of Five Quasars
About: This article is published in The Astrophysical Journal.The article was published on 1973-08-01 and is currently open access. It has received 3 citation(s) till now. The article focuses on the topic(s): Redshift & Quasar.
Summary (1 min read)
- The authors used the method of analysis of rich absorption-line spectra developed by Bahcall (1968).
- At least two complete doublets among the three doublets (C iv, N v, O vi) must be present, also known as The rules were.
- By trial and error, the authors found that less stringent rules resulted in an undesirably large number of acceptable systems within random-number spectra having the same essential characteristics as the observed spectra .
- In other respects, their method of search was identical to that of previous analyses (see Bahcall and Joss 1973, and references therein).
III. RESULTS FOR FIVE QUASARS
- The authors have searched the observed spectra of five quasars for acceptable high-ionization redshift systems between z = 4.0 and a minimum redshift zmin, the value of which * Letters following the line strengths stand for diffuse (D), broad (B), and wide (W), as denoted by the observers.
- T Relative intrinsic strengths between the members of each doublet are given in parentheses.
- 59 was set equal to the minimum redshift for which two of the three doublets C iv, N v, and O vi fall within the observationally accessible portion of the spectrum.
- (If this doublet is discounted, the system is unacceptable.).
- Moreover, among these five previously identified lines, four were essential to the acceptability of low-ionization systems in which they were identified.
IV. RANDOM-NUMBER SPECTRA
- In order to estimate the probability that an acceptable high-ionization redshift system will occur by chance, the authors have generated and analyzed 20 random-number spectra corresponding to each quasar.
- These spectra were required to have the same essential characteristics as the observed spectra, e.g., the minimum separations between lines were the same as those imposed on the observed spectra by the spectroscopic techniques and observational conditions.
- This consideration is of limited value in the context of the present probability estimates, because high-ionization redshift systems have also not yet been reported in the absorption spectra of quasars.
60 J. BAHCALL, P. JOSS, AND J. COHEN
- This work was initiated while one of us (J. N. B.) was a visiting professor in the astronomy department of the University of California at Berkeley; J. N. B. wishes to express his gratitude for the hospitality and stimulation provided by the members of the Berkeley astronomy department.
- This work was supported in part by NSF grant 16147 A#1 and the Miller Institute for Basic Research.
- The purpose of the random-number spectra is to determine the statistical validity of the candidate redshifts that are found in the observed spectra.
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