Rest Equivalent Width Research Articles

THE LYMAN-ALPHA FOREST IN THE QUASAR B2 1225+317 FROM 3140 A TO 3940 A.

ABSTRACT The authors have obtained a spectrum of the quasar B2 1225+317 from 3140 Å to 3940 Å using the new "UV prime" spectrograph at the 3.6-m CFH telescope. A signal-to-noise ratio larger than 25 was achieved with an exposure of only 90 minutes using an RCA CCD. They produce a new line list of the Lyman-alpha forest that is complete to about 0.15 Å rest equivalent width. They confirm that the number density of the Lα lines increases steeply for rest equivalent widths smaller than 0.20 Å as suggested by previous workers. The new equipment is very suited for quick quasar survey and in particular for a Mg II search at z < 0.40.

The oxygen abundance in the clouds producing the Ly-alpha-Ly-beta absorption systems in the quasars 4C 5.34 (0805+046) and OQ 172 (1442+101)

view Abstract Citations (46) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The oxygen abundance in the clouds producing the Lyalpha-Lybeta absorption systems in the quasars 4C 5.34 (0805+046) and OQ 172 (1442+101). Norris, J. ; Hartwick, F. D. A. ; Peterson, B. A. Abstract A composite spectrum of the Lyα-Lyβ clouds seen in absorption in the spectra of the quasars 4C 5.34 (0805+046) and OQ 172 (1442+101) has been synthesized from the data of Chen et al. and Peterson et al. to enhance the available signal-to-noise ratio and to investigate the question of the metal abundance of the clouds. Apart from Lyα and Lyβ, we find no evidence for species other than O VI in the line absorption of the composite spectrum. We are forced to conclude that the identification of O VI has a 96% probability of being real. Assuming that the clouds are photoionized by the background quasar flux given by Sargent et a!., we derive metal abundances (or limits) for C, N, and 0. If the clouds are confined by a hotter intergalactic medium as suggested by Sargent et a!., we find [C/H] ≤ - 1.1, [N/H] ≤ -0.8, and [O/H] = -1.9. The oxygen result is relatively insensitive to the form of the quasar background flux and is consistent with Population II abundances, rather than with the clouds having primeval (i.e., zero heavy element) abundances. We note that the result can be understood in terms of Oort's hypothesis that the Lyα-Lyβ clouds are the remnants of material which formed superclusters, if the clouds have been enriched by matter driven out by winds from the clusters of galaxies which comprise the superclusters. The composite Lyα and Lyβ profiles of the redshift systems having rest equivalent widths W(Lyα) ≥ 1.0 Å are apparently inconsistent with the prediction of Fransson and Epstein that the Lyα lines should have double minima as the result of originating in material which has been driven from dwarf galaxies. Publication: The Astrophysical Journal Pub Date: October 1983 DOI: 10.1086/161383 Bibcode: 1983ApJ...273..450N Keywords: Abundance; Intergalactic Media; Lyman Alpha Radiation; Lyman Beta Radiation; Oxygen; Quasars; Absorption Spectra; Line Spectra; Radiation Spectra; Signal To Noise Ratios; Astrophysics full text sources ADS | data products SIMBAD (2) NED (2)

The distribution of Lyman-alpha absorption lines in the spectra of six QSOs - Evidence for an intergalactic origin

view Abstract Citations (589) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The distribution of Lyman-alpha absorption lines in the spectra of six QSOs: evidence for an intergalactic origin. Sargent, W. L. W. ; Young, P. J. ; Boksenberg, A. ; Tytler, D. Abstract The large Lyman-alpha samples in five QSOs with zem between 2.2 and 3.3 are used to test whether the absorbing gas is cosmologically distributed or ejected from the QSOs. It is shown that there is no significant variation in line density with redshift, nor in the rest equivalent width spectrum among the QSOs. In addition, the mean number density of lines in each object is found to be the same, that is, 60 lines per delta z=1 with W greater than or equal to 0.32 A. Publication: The Astrophysical Journal Supplement Series Pub Date: January 1980 DOI: 10.1086/190644 Bibcode: 1980ApJS...42...41S Keywords: Absorption Spectra; Galactic Evolution; Intergalactic Media; Lyman Spectra; Quasars; Astronomical Coordinates; Cosmology; Line Spectra; Red Shift; Tables (Data); Astrophysics full text sources ADS | data products NED (15) SIMBAD (6)