CDROM/AJ/V106/P0848 Mg II Lines in Quasars (Drinkwater+ 1993) ================================================================================ On the Nature of Mg II Absorption Line Systems in Quasars M. J. Drinkwater, R. L. Webster, & P. A. Thomas <1993, AJ, 106, 848> =1993AJ....106..848D ================================================================================ Abstract: The results of a large R-band imaging survey of 71 bright (m(V) < 18) quasars are presented. The quasars were chosen from published samples which have intermediate resolution optical spectroscopy available, so the presence of low redshift Mg II absorption lines can be determined. We have searched our data for galaxies close to the line-of-sight to the quasars, which we might be able to identify with the absorption systems. We find a high coincidence between galaxies very near the line-of-sight and quasars showing absorption systems in their spectra, a result consistent with other studies. These galaxies have a mean luminosity of 0.5 L(star) (assuming they lie at the absorption redshift). The distribution of impact parameters between the galaxies and the quasars extends with a flat distribution to large radii (> 30 h^-1 kpc). This suggests that the absorption systems may not be gravitationally bound to the observed galaxies, but may be part of larger extended systems. We also find a significant number of galaxies near the line-of-sight to the quasar where no absorption is seen in the quasar spectrum. The selection of our quasars is unbiased with respect to galaxies near the line-of-sight, so we can compare the observed number of absorption systems to that predicted by a simple model with a constant covering factor in Mg II absorbing gas within a maximum radius of each detected galaxy. The model is consistent with a covering factor of unity, but allowing for incompleteness in the detection of galaxies, the covering factor is less than unity. The redshifts of the galaxies are required to confirm this result. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table1.dat 118 71 Quasars observed table3.dat 58 540 Catalogue of quasar companions -------------------------------------------------------------------------------- Comments for file: table1.dat -------------------------------------------------------------------------------- Table 1 contains data for the quasars selected for observation from the published samples of quasars with intermediate (~5 A) resolution spectra that followed the follwing criteria: 1) z(q) < 2.5, where z(q) is the quasar redshift. 2) z(1) < 0.5, where z(1) is the minimum redshift at which Mg II absorption could be detected in the published spectrum. 3) Constraints on right ascension and declination imposed by the allocated observing time and the location of the observatory (latitude +45.46 deg so declination > -10 deg). Broadband R CCD images taken with the 1.6 m telescope at the Observatoire de Mont Megantic, Quebec, Canada, and an RCA CCD having a scale of 0.48 arcsec per pixel giving a field of 2.6 by 4.1 arcmin. For each object, the total exposure time was up to 2400 s in R, in three separate exposures. The three exposures were combined using a sigma-clipping algorithm to remove spurious signals due to cosmic rays. The effective resolution of the final image (atmosphere seeing convolved with tracking errors) was measured by fitting Gaussians to about eight stars in the field and taking the mean value of the corresponding full width at half-maximum (FWHM). Any images with FWHM greater than 3 arcsec for stellar images were discarded. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- QSO Quasar name 9 1X --- --- Blank 10-12 A3 --- Type *Detection technique 13 1X --- --- Blank 14-15 F2.0 h RAh Right ascension (1950.0) 16 1X --- --- Separator, ':' 17-18 F2.0 min RAm R.A. 19 1X --- --- Separator, ':' 20-24 F5.2 s RAs R.A. 25 1X --- --- Blank 26 A1 --- DE- Sign of Declination, '-' or blank 27-28 F2.0 deg DEd Declination (1950.0) 29 1X --- --- Separator, ':' 30-31 F2.0 arcmin DEm Dec. 32 1X --- --- Separator, ':' 33-36 F4.1 arcsec DEs Dec. 37-42 F6.2 mag mV Quasar V magnitude 43-48 F6.3 --- zqso *Quasar redshift 49-53 F5.2 --- z1 Minimum z at which Mg II might be observed 54-58 F5.2 --- z2 Maximum z at which Mg II might be observed 59-65 F7.4 --- zab1 []? Redshift of any Mg II absorption systems 66-72 F7.4 --- zab2 []? Redshift of any Mg II absorption systems 73 1X --- --- Blank 74-82 A9 --- Ref *Reference for the published spectra 83 1X --- --- Blank 84-91 A8 --- Date Date observed (UT) (dd/mm/yy) 92-96 I5 s Exp Exposure time 97-101 F5.2 arcsec FWHM FWHM seeing 102-107 F6.2 mag mR Quasar R magnitude 108 1X --- --- Blank 109-110 A2 --- Phot *Photometry flag 111-113 3X --- --- Blank 114-118 F5.2 --- mLim *Limiting R magnitude of image -------------------------------------------------------------------------------- Notes for file: table1.dat -------------------------------------------------------------------------------- Type: Detection technique (C, color; O, spectral survey; R, radio; X, X-ray) zqso: Quasar redshift (Data in bytes 1-48 taken from Hewitt & Burbidge 1987, ApJS, 63, 1, and Hewitt & Burbidge 1989, ApJS, 69, 1) Ref: Reference for the published spectra, parentheses signifying a non-detection ---------------------------- Number W(rest) Reference Angstroms ---------------------------- 1 ~ 0.5 Weyman, et al. 1979, ApJ, 234, 33 1a ~ 0.8 Weyman, et al. 1979, ApJ, 234, 33 2 0.6 Young, et al. 1982, ApJS, 48, 455 3 0.5 Foltz, et al. 1986, ApJ, 307, 504 4 Boulade, et al. 1987, in High Redshift and Primeval Galaxies, edited by J. Bergeron et al. (Editions Frontieres, France), p. 349 5 Miller, et al. 1987, AJ, 94, 633 6 ~ 0.4 Tytler, et al. 1987, ApJS, 64, 667 7 0.3 Sargent, et al. 1988, AJ, 334, 22 8 ~ 0.5 Bergeron & Boisse 1991, A&A, 243, 344 9 0.3 Steidel & Sargent 1992, ApJS, 80, 1 10 0.3 Bechtold & Ellingson 1992, ApJ, 396, 20 10a 0.6 Bechtold & Ellingson 1992, ApJ, 396, 20 Phot: Photometry flag (blank, photometric; X, not photometric; D, double image with magnitude from small DAOPHOT; e, no small DAOPHOT fitting was possible) mLim: Limiting R magnitude of image (the magnitude of the faintest object for which the formal error in the magnitude was less than 0.2 mag) -------------------------------------------------------------------------------- Comments for file: table3.dat -------------------------------------------------------------------------------- Table 3 contains all objects detected above the magnitude limit and within 30 arcsec of each quasar. For each quasar, the overall format of the table is as follows: 1) A header record giving the quasar name, redshift, seeing, and magnitude limit; 2) followed by one record for each of the detected objects, 3) followed by a blank record. This format is not amenable to conversion to FITS format. The example below shows the first five records in the file. Example: # QSO 0710+118 z=0.768 seeing=2.0" magnitude limit=21.53 -25.5 -13.3 28.7 g 19.23 0.02 242.42 -21.9 10.0 24.0 s 19.59 0.03 294.50 -15.6 22.2 27.2 fg 21.49 0.17 324.96 -4.8 -10.7 11.8 s 18.80 0.02 204.22 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat, Header record -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 6X --- --- The string '# QSO ' 7-14 A8 --- QSO Quasar name 15-18 4X --- --- The string ' z=' 19-23 F5.3 --- z Quasar redshift 24-32 9X --- --- The string ' seeing=' 33-35 F3.1 arcsec See Seeing 36-53 18X --- --- The string '" magnitude limit=' 54-58 F5.2 mag MagLim Magnitude limit -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat, Detected object records -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 F5.1 arcsec RA R.A. offset from the quasar 6-11 F6.1 arcsec DE Dec. offset from the quasar 12-13 2X --- --- Blank 14-17 F4.1 arcsec Dist Distance from the quasar 18 1X --- --- Blank 19-20 A2 --- Class Classification (f: faint, g: galaxy, s: star) 21-26 F6.2 mag mR Apparent R magnitude, m(R) 27-31 F5.2 mag e_mR Formal photometry error in the magnitude 32-38 F7.2 deg PA *Position angle of the object wrt the quasar -------------------------------------------------------------------------------- Notes for file: table3.dat, Detected object records -------------------------------------------------------------------------------- PA: Position angle of the object with respect to the quasar, measured anti-clockwise from North -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 17-Mar-1995