The identification of two ztex2html_wrap_inline2963.8 QSOs
in a deep CCD survey

Ian Smail, Alastair C. Edge, Richard S. Ellis, PASA, 15 (3), 267
The html and gzipped postscript versions of this paper are in preprint form.
To access the final published version, download the pdf file

Next Section: Conclusions
Title/Abstract Page: The identification of two
Previous Section: Observations
Contents Page: Volume 15, Number 3

Analysis and Discussion

We identify strong, broad emission-lines associated with Lytex2html_wrap_inline332tex2html_wrap_inline5901216, Lytex2html_wrap_inline592tex2html_wrap_inline5901026, SiIVtex2html_wrap_inline5901397 and CIVtex2html_wrap_inline5901549 in the spectra of both QSOs (Fig. 3). Observed wavelengths, equivalent widths and FWHM of the lines were measured interactively with the IRAF task SPLOT, these are all listed in Table 2.  From the SiIV and CIV lines we estimate the redshifts of the two QSO as tex2html_wrap_inline600 and tex2html_wrap_inline602, for Q1332+5034 and Q1722+3211 respectively.


6 Q1332+5034


tex2html_wrap_inline590     z EWtex2html_wrap_inline608 (Å) FWHMtex2html_wrap_inline608 (Å) Comment


Table 2: Catalogue of Spectral Features.

Using the redshifts calculated above we estimate luminosities of tex2html_wrap_inline688 for Q1332+5034 and tex2html_wrap_inline690 for Q1722+3211. At these redshifts their modest apparent magnitudes, compared to other tex2html_wrap_inline692 QSOs, means that these two sources are roughly an order of magnitude less luminous than the median luminosity of known tex2html_wrap_inline692 QSOs. The observed X-ray flux of Q1322+5034 represents a luminosity of tex2html_wrap_inline696 erg stex2html_wrap_inline364 in the 0.5-11.6 keV band.

The spectrum of Q1332+5034 shows a number of strong absorption features shortward of Lyman-tex2html_wrap_inline332 emission in the QSO. These include at least three relatively strong features within 100Å (5000 km sectex2html_wrap_inline364) of the peak of the Lyman-tex2html_wrap_inline332 emission in the QSO. Similar `associated' absorbers are commonly seen in radio and X-ray bright QSOs. However, the more interesting absorbers are further to the blue, the first of these, DLA-1, is at 5398Å and we identify this as a damped Lyman-tex2html_wrap_inline332 absorber at z=3.439. This system completely obscures the background QSO at wavelengths below 912Å in its rest-frame and also produces detectable CIV and Ly-tex2html_wrap_inline592 absorption (Fig. 3).

Identifying the lower redshift absorption system in the spectrum of Q1332+5034 with Lyman-tex2html_wrap_inline332 absorption gives its redshift as tex2html_wrap_inline714. This feature is extremely strong, with a rest-frame equivalent width of 35Å, and if formed from a single absorption system would indicate a column density of around tex2html_wrap_inline716-22.0. Some support for this identification comes from the tentative detection of FeII tex2html_wrap_inline5902383 and FeII tex2html_wrap_inline5902374 at the extreme red-end of our spectrum, although these coincide with strong atmospheric emission. However, the absorption profile shows only marginal evidence for broad damping wings (Fig. 3) which should be easily visible for such a high column density. We suggest, therefore, that the feature most probably arises from a blend of a number of individual Lyman-tex2html_wrap_inline332 absorbers. The absorbers would need to be spread over a velocity range of tex2html_wrap_inline724 km sectex2html_wrap_inline364. This relatively broad velocity range implies that this system is unlikely to be a collapsed structure (c.f. Ortiz-Gil et al. 1997), but is more likely to be an over-dense region consisting of several high column density systems. For the observed velocity range at tex2html_wrap_inline728 these could be spread over a region as large as 10-15 Mpc.

Clusters of strong absorption systems similar to A-2 are relatively rarely seen, the system in PKS2000-330 (Carswell et al. 1987) being another, although that does not span as wide a velocity range as the system in Q1332+5034. Therefore, irrespective of its precise interpretation, A-2 is an intriguing system and hence worthy of more detailed study.

Next Section: Conclusions
Title/Abstract Page: The identification of two
Previous Section: Observations
Contents Page: Volume 15, Number 3

Welcome... About Electronic PASA... Instructions to Authors
ASA Home Page... CSIRO Publishing PASA
Browse Articles HOME Search Articles
© Copyright Astronomical Society of Australia 1997