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Astron. Astrophys. 332, 514-522 (1998)


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Spectroscopy of the extended emission associated with two high-z quasars *

M.D. Lehnert 1, 2 and R.H. Becker 2, 3

1 Sterrewacht Leiden, P.O. Box 9513, 2300 RA, Leiden, The Netherlands
2 Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, 7000 East Ave., L-413, Livermore, CA 94550, USA
3 Department of Physics and Astronomy, University of California Davis, USA

Received 23 June 1997 / Accepted 5 November 1997

Abstract

We present spectra taken with the Low Resolution Imaging Spectrograph on the Keck 10m telescope of spatially-resolved structures (`fuzz') around the high-redshift radio-loud quasars PKS 0445+097 (z=2.108) and PKS 2338+042 (z=2.589). For PKS 0445+097 we oriented the slit such that it passed through the quasar nucleus and through an object identified on an HST exposure 1.8" to the southeast of the nucleus. We find that this object has strong [OII] [FORMULA] 3727 emission and weaker emission due to [NeV] [FORMULA] 3426 and [NeIII] [FORMULA] 3869, at a redshift of z=0.8384. This redshift is very close ([FORMULA] v=200 km s-1) to that of a MgII absorption line identified in the spectrum of PKS 0445+097. The line ratios and narrowness of the lines indicate that this galaxy probably has a Seyfert 2 nucleus. Moreover, we find that there is faint extended HeII [FORMULA] 1640 and CIII] [FORMULA] 1909 from the quasar host galaxy. Both of the lines are broad ([FORMULA] =1000 [FORMULA] 200 km s-1 and FWHM=2200 [FORMULA] 600 kms-1). The limits on the fluxes, the large line widths, and the line ratio HeII/CIII] are similar to that observed for high redshift radio galaxies.

From the spectrum of PKS 2338+042, we find extended Ly [FORMULA] emission on scales about 10" which is strongly one sided (on the side of the stronger, closer to the nucleus, more distorted radio lobe). The extended Ly [FORMULA] line is broad with widths of over 1000 km s-1. The extended emission shows no evidence for a strong velocity shear. We also find weak extended CIV and HeII emission which has similar characteristics (line widths, line fluxes, and line ratios) to that of high redshift radio galaxies. In addition, we serendipitously discovered what appears to be a Ly [FORMULA] emitting galaxy about 29" to the southeast of the quasar at z=2.665. The single line identified in the spectrum has a measure equivalent width of 2100Å and a full width at half maximum of 2150 km s-1. The high equivalent width and large velocity width of the putative Ly [FORMULA] line suggest that this galaxy must be a high redshift AGN, although we note that the upper limits on the CIV and HeII line ratios are mildly inconsistent with this galaxy harboring an AGN. An approximate calculation shows the quasar nucleus is not exciting the Ly [FORMULA] emission from this galaxy.

Key words: quasars: individual: PKS 0445+097 – quasars: individual: PKS 2338+042 – galaxies: evolution – radio continuum: galaxies

* Based on observations taken at the W. M. Keck Observatory

Send offprint requests to: M. Lehnert

© European Southern Observatory (ESO) 1998

Online publication: March 23, 1998
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