In total, 169 candidates were observed spectroscopically. During two runs in October 1998 and May 1999, 157 objects were observed at the ESO 3.6 m, La Silla, Chile using the EFOSC spectrograph. For both runs the detector used was "ccd40'', a Loral CCD with pixels, binned . For the 1999 May observations grism #12 was used, covering the spectral range 5800 Å-9500 Å with a dispersion of 4.23 Å per binned pixel. For the 1998 October observations grisms #4 and #5 were used covering the ranges 3420-7460 Å and 6000-10 000 Å respectively with dispersions of 4.08 and 4.27 Å per binned pixel. The slit width was chosen to match the seeing, typically 1.2-1.5 arcsec. For the 1998 October observations a sky PA of was used, and for the 1999 May observations the slit was at the paralactic angle. Approximate relative flux calibration was obtained using observations of spectrophotometric standards from Hamuy et al. (1994). Twelve sources were observed at AAT using the RGO spectrograph in October 1996.
26 sources remain to be observed, of which 24 are in the North Galactic Cap (NGC) and 2 are in the South Galactic Cap (SGC) region.
|Number of candidates||Number confirmed|
|with z data||3.5<z<4.0||4.0<z<4.5||z>4.5|
The data were reduced using standard procedures with the IRAF software environment.
Table 1 summarises the current survey status and in Table 2 we give redshifts, optical magnitudes and radio flux densities for the objects which were identified as new high-redshift quasars. The spectra are shown in Fig. 5, and finding charts, with J2000 coordinates, are given in Fig. 7. Two of the z>4 QSOs are discussed in more detail below.
this is now the most distant radio-selected quasar. The object is blank on the UKST B-band plate, detected in R, and very bright in I(17.3). Near-IR magnitudes from the 2MASS survey are , , .
The optical spectrum (Fig. 5) shows strong lines of SiIV/OIV and CIV from which we estimate a redshift of 4.763. However the absorption of the CIV and Ly- line make redshift determination uncertain. A 4800 s IR spectrum was obtained using SOFI at the 3.5 m NTT, La Silla on 31 May 1999. The spectrum shows strong, broad emission lines of CIII and MgII at a redshift of 4.764 and approximately 4.78 respectively (the MgII line has a complex shape, see Fig. 6). We adopt a redshift of 4.763 for this QSO.
The NVSS map (see Fig. 8) shows a source at the optical
position of the QSO, and a second NVSS source about 4 arcmin away. The
PMN position appears to lie between the two, although much closer to the
first position (that of the QSO). It is possible that the PMN flux
density is overestimated because of a contribution from the second
|Figure 4: Colour-magnitude and colour-colour plots for the APM identifications within 3'' of the NVSS radio position. Solid symbols represent objects classified as stellar, open symbols represent objects classified as galaxies by the APM. Arrows are used to represent limits on the colours when objects are not detected in one or more of the three passbands.|
This source has been confirmed as an X-ray source with ROSAT HRI and its X-ray properties are the subject of another paper (Fabian et al. 2001).
|Name||RA||DEC||z||R||B||I||Place & Date||comments|
|PMN J0022-0759||00 22 00.246||-07 59 16.03||3.896||19.47||21.26||>19.25||54||-0.18||ESO 10/98|
|PMN J0214-0518||02 14 29.295||-05 17 44.55||3.986||18.42||20.54||18.75||93||0.61||ESO 11/00|
|PMN J0235-1805||02 34 55.143||-18 06 08.49||4.314||18.79||22.00||-||49||-0.16||ESO 11/00||mJy (confused; see NVSS)|
|PMN J0324-2918||03 24 44.280||-29 18 21.10||4.630||18.66||22.18||-||354||0.30||ESO 11/00|
|PMN J0326-3253||03 27 00.407||-32 54 18.65||3.463||19.40||21.15||-||78||-0.01||ESO 11/00|
|PMN J0525-3343||05 25 06.166||-33 43 05.34||4.413||18.50||21.47||-||210||0.06||AAT 10/96||X-ray source, Fabian et al. (2001)|
|PMN J1043-2140||10 43 11.963||-21 40 47.97||3.774||20.66||>22.39||>18.99||59||-0.07||ESO 05/99|
|PMN J1108-1804||11 08 48.035||-18 04 50.85||3.433||20.00||21.48||19.18||48||-0.31||ESO 05/99||mJy|
|PMN J1429-1616||14 29 31.410||-16 15 40.44||3.842||19.76||21.26||19.42||50||0.34||ESO 05/99|
|PMN J1451-1512||14 51 47.052||-15 12 19.99||4.763||19.14||>22.60||17.25||90||0.89||ESO 05/99||confused; see NVSS|
|PMN J2042-2223||20 42 57.278||-22 23 26.69||3.630||19.70||21.52||-||184||0.23||ESO 10/98|
|PMN J2134-0419||21 34 12.006||-04 19 09.87||4.346||19.98||>22.80||19.73||221||-0.23||ESO 10/98|
|PMN J2219-2719||22 19 35.304||-27 19 02.76||3.634||19.72||21.61||-||221||-0.27||ESO 11/00|
|PMN J2220-3336||22 20 26.957||-33 36 59.44||3.691||21.08||22.73||-||123||0.67||ESO 11/00||confused; see NVSS|
|PMN J2314+0201||23 14 48.722||+02 01 50.86||4.110||19.87||>22.18||>19.28||97||-0.22||ESO 10/98||X-ray source, Boller et al. (1997)|
|Previously known QSOs contained in the sample||Reference|
|PMN J1028-0844||4.276||18.84||20.72||18.37||159||-0.43||Zickgraf et al. (1997), X-ray source 0.3' away|
|PMN J1230-1139||3.528||19.45||21.95||-||374||-0.19||Drinkwater et al. (1997)|
|PMN J2003-3251||3.78||17.60||19.31||-||1248||0.77||Peterson et al. (1982)|
|Name||Ly peak||SiIV/OIV||CIV||CIII||mean z|
Péroux et al. measure z=4.388 for this QSO (when using the above rest wavelengths) based on a higher-quality spectrum.
Line measured from IR spectrum.
Copyright ESO 2002