A survey of UV-excess AGNs in the South Galactic Pole - A sample for the analysis of the QSO clustering

Astronomy and Astrophysics Supplement Series, Jul 2018

Spectra, position, magnitudes and colors are presented for 485 faint () emission line objects selected with the ultraviolet-excess (UVX) criterion on a area of 24.6 deg2 in the South Galactic Pole. The objects were selected from the analysis of pixel-to-pixel stacking of COSMOS scans of UKST U J and R plates. The candidates were observed with the Meudon-ESO Fiber Optics System (MEFOS) at the ESO 3.6 m telescope. 429 type 1 AGNs have been identified (373 in the redshift range ). This sample has allowed the measure of a difference on the QSO clustering evolution in comparison with that found for galaxies [(La Franca et al. 1998)]. The region is part of the ESO Imaging Survey (EIS) and of the 2dF QSO redshift survey.

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A survey of UV-excess AGNs in the South Galactic Pole - A sample for the analysis of the QSO clustering

Astron. Astrophys. Suppl. Ser. A survey of UV-excess AGNs in the South Galactic Pole? F. La Franca 2 C. Lissandrini 1 S. Cristiani 0 1 L. Miller 4 M.R.S. Hawkins 3 H.T. McGillivray 3 0 Space Telescope-European Coordinating Facility, European Southern Observatory , Karl-Schwarzschild Str. 2, D-85748 Garching b. Mu ̈nchen , Germany 1 Dipartimento di Astronomia, Universita di Padova , Vicolo dell'Oservatorio 5, I-35122, Padova , Italy 2 Dipartimento di Fisica, Universita degli studi Roma Tre , Via della Vasca Navale 84, I-00146 Roma , Italy 3 Royal Observatory of Edinburgh , Blackford Hill, Edinburgh EH9 3HJ , UK 4 Department of Physics, Nuclear and Astrophysics Laboratory , Keble Road, Oxford OX1 3RH , UK Spectra, position, magnitudes and colors are QSO luminosity function evolution at z < 2:2 is well espresented for 485 faint (BJ < 20:5) emission line objects tablished (e.g. La Franca & Cristiani 1997; Goldschmidt selected with the ultraviolet-excess (UVX) criterion on a & Miller 1998). This kind of studies are mainly based area of 24.6 deg2 in the South Galactic Pole. The objects on the most statistically signi cant QSO samples such were selected from the analysis of pixel-to-pixel stacking us the Durham/AAT QSO sample (Boyle et al. 1990) at of COSMOS scans of UKST U J and R plates. The candi- faint magnitudes (B < 20:9), and the Bright QSO Survey dates were observed with the Meudon-ESO Fiber Optics (Schmidt & Green 1983), the Large Bright QSO Survey System (MEFOS) at the ESO 3.6 m telescope. 429 type (Hewett et al. 1995), the Edinburgh UVX QSO survey 1 AGNs have been identi ed (373 in the redshift range (Goldschmidt et al. 1992; Miller et al. in preparation), 0:3 < z 2:2). This sample has allowed the measure of a the Homogeneous Bright QSO Survey (HBQS, Cristiani di erence on the QSO clustering evolution in comparison et al. 1995) at bright magnitudes (B < 18:5). In total with that found for galaxies (La Franca et al. 1998). The these samples collect about a thousand of QSOs with region is part of the ESO Imaging Survey (EIS) and of the z < 2:2. But these samples are still not ideally suited to 2dF QSO redshift survey. study the QSO clustering and its evolution (see Andreani & Cristiani 1992). The best QSO samples for clustering - the WFI at the ESO 2.2 m telescope. Moreover about Table 1. UKST photographic plates 10 deg2 of the southern area of the region is included in the 2dF QSO redshift survey (Croom et al. 1998) . emulsion lter number date IIaO IIIaJ IIIaJ exp. time (min) 180 180 180 UG1 UG1 UG1 2. The construction of the catalogue Our survey is based on a set of UKST plates in the U , BJ and R bandpass (see Blair & Gilmore 1982 for a de nition of the various systems) . UKST plates subtend IIIaJ GG395 J 9764 1984-11-23 70 l6i:s4ted i6n: 4T.aDbleet1a.ilTshoef pthlaetepshhoatvoegrbaepehnicscpalnanteedminatMeraiaplpianrge IIIIIIIIIaaaJJJ GGGGGG333999555 JJJ 999777676605 111999888444---111111---222433 777000 and Imaging Mode on the COSMOS microdensitometer IIIaJ GG395 J 9771 1984-11-24 70 (MacGillivray & Stobie 1984). The mapping mode used a spot size of 16 m (FWHM), corresponding to 1 arc- 127-04 RG630 R 3498 1977-08-15 90 sec. For each band-pass the digitized Mapping Mode data IIIa-F RG630 R 4676 1978-12-02 90 have been added together in order to increase the signal IIIa-F RG630 R 9594 1984-09-22 90 to noise ratio. The reliability of the co-adding technique IIIa-F RG630 R 9672 1984-10-17 90 has been veri ed by many tests on UKST plates (Hawkins IIIa-F RG630 R 11331 1986-09-02 90 1991) . The resulting coadded digitized data has been analyzed by the COSMOS crowded- eld analysis software (Beard et al. 1990). The resulting tables contained the already known in the eld with BJ 20:5. The completeinstrumental magnitudes, the area above the threshold, ness becomes 89% if the \red" QSOS from Warren et al. the intensity weighted x and y positions, and other use- (1991a) are included in the comparison. ful parameters. We discriminated between point-like and extended sources using the COSMOS image parameters, that is, on morphological grounds. We de ned a plane in which stellar locus was well determined, and drew the separation line near the locus. For typically BJ < 19:5, we 3. The spectroscopic survey used the log(isophotal area) versus magnitude plane. At fainter magnitudes, where stellar peak surface brightness (Ipeak) are not saturated, the log(Ipeak − Isky)=Isky ver- We have used the 3.6 m ESO telescope, equipped with sus magnitude plane provided a better separation. The the Meudon-ESO Fiber Optic System MEFOS (Bellenger two separation lines produced the same star-galaxy ra- et al. 1991) , to obtain low-resolution spectra of the QSO tio at the overlap magnitude. Relative photometry, us- candidates in four observational campaigns between 1993 ing instrumental magnitudes, was produced by COSMOS. and 1995. MEFOS is a multi bre positioner which enCalibration was based on published sequences (Hawkins & ables the conventional use of the ESO Boller & Chivens Bessell 1988; Warren et al. 1991a) . Spectrograph to be extended to multiobject spectroscopy. The candidates were extracted from a rectangle in the The spectra of up to 29 objects inside the 1 eld of the sky centered at (1950): 00h 50m 34:3s and (1950): −28 prime focus of the 3.6 m telescope can be simultaneously 100 0800 with limits min = −2:170 , max = 2:715 , recorded. It consists of 29 remotely controlled arms, each min = −2:520 , max = 2:520 (i.e. the limits in right carrying two spectroscopic bers of 2.5 arcsec of diameter, ascension are the two lines distant from the merid- one for the object, and one for the sky sampling. We used ian at (1950): 00h 50m 34:3s; see Cristiani et al. (1995) , the ESO grating No. 13 (150 grooves/mm) with a resolutheir Table 1). All the objects inside a radius of 0.15 de- tion of 35 A in the wavelength range 3600 − 8400 A. The grees centered at (1950): 00h 50m 17:43s, and (1950): CCD was a 512 512 Tektronics with 27 m pixels (ESO −26 510 25:200 have been excluded from the catalogue as No. 32). Wavelength calibration was carried out by comthis region includes a crowded globular cluster. It results parison with exposures of He and Ar lamps. The campaign a total area of 24.55 deg2. dates with the number of pointings and the exposure time We have selected as candidates all the UVx \not ex- are listed in Table 2. The data reduction was performed tremely extended" objects with BJ 20:5, satisfying a under MIDAS and followed the optimized spectra extractype of modi ed Braccesi less-restricted two color crite- tion from ber spectrographs of Lissandrini et al. (1994). rion (La Franca et al. 1992; Cristiani et al. 1995) . The No absolute flux calibration has been applied. The speccompleteness of the selection has been tested against the tra have been flux calibrated in relative fluxes just for the QSOs already known in the eld with redshift in the range sake of facilitating the identi cation. Only the most evi0:3 < z 2:2. We have selected 92% of the 176 blue QSOs dent cosmic rays hits have been removed. 4. The catalogue Altogether 769 QSOs candidates have been identi ed (502 from the MEFOS campaign), 485 of which actually turned out to be emission line extragalactic objects. In Fig. 1 the spectra of all the newly identi ed objects are shown. The S/N of the spectra permitted to recognize emissionline objects without leaving much doubt of misidenti cation. Only 15 objects have a dubious redshift identi cation. In Table 3 the complete list of the 485 emission line objects and their spectroscopic identi cation is given. The identi cation classes are: QSO for broad emission line type 1 AGNs (QSOs and Seyfert 1 galaxies); NL for narrow emission line galaxies (such as Seyfert 2, LINERS, Star-burst or HII emissions). The uncertainty in the redshift estimation is of 0.001 rms. At magnitudes brighter than B < 18:7 the sample is complete and the QSOs are included in the catalogue of the Homogeneous Bright QSO Survey (HBQS, Cristiani et al. 1995) . A \d" in the comments identify the objects for which the redshift identi cation is dubious. A total of 429 type 1 AGNs have been identi ed, 373 in the redshift range 0:3 < z 2:2. The photometry has an uncertainty of about 0.1 mag, while the astrometry has an accuracy of 100 rms. MEFOS has been decommissioned by ESO in 1995, and consequently at magnitudes fainter than B = 18.7 a fraction of the QSO candidates has not been spectroscopically identi ed. The fainter sample is not useful for statistical applications aimed at measuring the evolution of the luminosity function of AGNs. However, the sample can be used for analysis of the clustering of QSOs by using the technique of scrambling the redshift distribution in the generation of the \random" data set used in the computation of the correlation function (see La Franca et al. 1998) . Acknowledgements. It is a pleasure to thank the enthusiastic support of the COSMOS and UKST sta . The work was partially supported by the Ministry for University and Research (MURST) under grant COFIN98-02-32. Andreani P. , Cristiani S. , 1992 , ApJ 298 , L13 Beard S.M., MacGillivray H.T. , Thanisch P.F. , 1990 , MNRAS 247 , 311 Bellenger R. , Dreux M. , Felenbok P. , et al., 1991 , The Messenger 65 , 54 Blair M. , Gilmore G. , 1982 , PASP 94 , 742 Boyle B.J. , Fong R. , Shanks T. , Peterson B.A. , 1990 , MNRAS 243 , 1 Campusano L.E. , 1991 , A &A 259 , 9 Cristiani S. , La Franca F., Andreani P. , et al., 1995 , A &AS 112 , 347 Croom S.M. , Shanks T. , Boyle B.J. , et al., 1998 , in Evolution of Large Scale Structure. Garching 1998 , astro-ph/9810127 da Costa L.N. , 1998 , in \Wide Field Surveys in Cosmology" , Colombi S. , Mellier Y . (eds.), astro-ph/9809209 Goldschmidt P., Miller L. , 1998 , MNRAS 293 , 107 Goldschmidt P. , Miller L. , La Franca F., Cristiani S. , 1992 , MNRAS 256 , 65 Hawkins M.R.S ., 1991 , IAU Comm. 9 - Newslett. 1 , 23 Hawkins M.R.S. , Bessell M.S. , 1988 , MNRAS 234 , 177 Hewett P.C., Foltz C.G. , Cha e F.H. , 1995 , AJ 109 , 1498 Hook I.M. , McMahon R.G. , Boyle B.J. , Irwin M.J. , 1994 , MNRAS 268 , 305 La Franca F. , Cristiani S. , 1997 , AJ 113 , 1517 La Franca F., Cristiani S. , Barbieri C. , 1992 , AJ 103 , 1062 La Franca F., Andreani P. , Cristiani S. , 1998 , ApJ 497 , 529 Lissandrini C. , Cristiani S. , La Franca F., 1994 , PASP 106 , 1157 Nonino M. , Bertin E. , Da Costa L., et al., 1999 , A &AS 137 , 43 MacGillivray H.T. , Stobie R.S. , 1984 , Vistas Astron . 27 , 433 Prandoni I. , Wichmann R ., da Costa L., et al., 1999 , A &A 345 , 448 Schmidt M. , Green R.G. , 1983 , ApJ 269 , 352 Veron-Cetty M.P. , Veron P. , 1998 , ESO Sci. Rep . 18 , 1 Warren S.J. , Hewett P.C. , Irwin M.J. , Osmer P.S. , 1991a, ApJS 76 , 1 Warren S.J. , Hewett P.C. , Osmer P.S. , 1991b, ApJS 76 , 23 Zaggia S., Hook I. , Mendez R. , et al., 1999 , A &AS 137 , 75


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F. La Franca, C. Lissandrini, S. Cristiani, L. Miller, M. R.S. Hawkins, H. T. McGillivray. A survey of UV-excess AGNs in the South Galactic Pole - A sample for the analysis of the QSO clustering, Astronomy and Astrophysics Supplement Series, 351-353, DOI: 10.1051/aas:1999523