CDROM/AJ/V106/P0848
Mg II Lines in Quasars (Drinkwater+ 1993)
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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
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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
--DESign 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.
below shows the first five records in the file.
The example
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
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(End)
Lee Brotzman [ADS] 17Mar-1995