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arXiv:0708.0828v2 [astro-ph] 30 Oct 2007
Draft version February 1, 2008
Preprint typeset using L
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THE SLOAN DIGITAL SKY SURVEY QUASAR LENS SEARCH. II.
STATISTICAL LENS SAMPLE FROM THE THIRD DATA RELEASE
Naohisa Inada,1,2 Masamune Oguri,3,4 Robert H. Becker,5,6 Min-Su Shin,4Gordon T. Richards,7
Joseph F. Hennawi,8Richard L. White,9Bartosz Pindor,10 Michael A. Strauss,4
Christopher S. Kochanek,11 David E. Johnston,12,13 Michael D. Gregg,5 ,6 Issha Kayo,14
Daniel Eisenstein,15 Patrick B. Hall,16 Francisco J. Castander,17 Alejandro Clocchiatti,18
Scott F. Anderson,19 Donald P. Schneider,20 Donald G. York,21 ,22 Robert Lupton,4
Kuenley Chiu,23 Yozo Kawano,14 Ryan Scranton,24 Joshua A. Frieman,22,25,26 Charles R. Keeton,27
Tomoki Morokuma,28 Hans-Walter Rix,29 Edwin L. Turner,4Scott Burles,30,31
Robert J. Brunner,32 Erin Scott Sheldon,33 Neta A. Bahcall,4and Masataka Fukugita34
Draft version February 1, 2008
ABSTRACT
We report the first results of our systematic search for strongly lensed quasars using the spectro-
scopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from
the SDSS Data Release 3 (∼4188 deg2), we select a subsample of 22,683 quasars that are located at
redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction corrected i-band mag-
nitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct
extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to
construct a complete lensed quasar sample at image separations between 1′′ and 20′′ and flux ratios
of faint to bright lensed images larger than 10−0.5. We construct a statistical sample of 11 lensed
quasars. Ten of these are galaxy-scale lenses with small image separations (∼1′′ −2′′ ) and one is a
large separation (15′′ ) system which is produced by a massive cluster of galaxies, representing the first
statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release
3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample.
Subject headings: gravitational lensing — quasars: general — cosmology: observations
1Cosmic Radiation Laboratory, RIKEN (The Physical and
Chemical Research Organization), 2-1 Hirosawa, Wako, Saitama
351-0198, Japan.
2Institute of Astronomy, Faculty of Science, University of Tokyo,
2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan.
3Kavli Institute for Particle Astrophysics and Cosmology, Stan-
ford University, 2575 Sand Hill Road, Menlo Park, CA 94025.
4Princeton University Observatory, Peyton Hall, Princeton, NJ
08544.
5IGPP-LLNL, L-413, 7000 East Avenue, Livermore, CA 94550.
6Department of Physics, University of California at Davis, 1
Shields Avenue, Davis, CA 95616.
7Department of Physics, Drexel University, 3141 Chestnut
Street, Philadelphia, PA 19104.
8Department of Astronomy, University of California at Berke-
ley, 601 Campbell Hall, Berkeley, CA 94720-3411.
9Space Telescope Science Institute, 3700 San Martin Drive, Bal-
timore, MD 21218.
10 Space Research Centre, University of Leicester.
11 Department of Astronomy, The Ohio State University, Colum-
bus, OH 43210.
12 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena
CA, 91109.
13 California Institute of Technology, 1200 East California Blvd,
Pasadena, CA 91125.
14 Department of Physics and Astrophysics, Nagoya University,
Chikusa-ku, Nagoya 464-8062, Japan.
15 Steward Observatory, University of Arizona, 933 North
Cherry Avenue, Tucson, AZ 85721.
16 Department of Physics and Astronomy, York University, 4700
Keele Street, Toronto, Ontario, M3J 1P3, Canada.
17 Institut d’Estudis Espacials de Catalunya/CSIC, Gran Capita
2-4, 08034 Barcelona, Spain.
18 Departamento de Astronom´ıa y Astrof´ısica, Pontificia Univer-
sidad Cat´olica de Chile, Casilla 306, Santiago 22, Chile.
19 Astronomy Department, Box 351580, University of Washing-
ton, Seattle, WA 98195.
20 Department of Astronomy and Astrophysics, The Pennsylva-
nia State University, 525 Davey Laboratory, University Park, PA
16802.
1. INTRODUCTION
Large systematic surveys of gravitationally lensed
quasars are essential for various scientific applications,
as shown in a recent review by Kochanek (2006). For
example, lensing probabilities from large homogeneous
surveys, which can be estimated from the number of
lenses in a statistically well-defined sample of quasars,
offer a probe of cosmological parameters. The largest ex-
21 Department of Astronomy and Astrophysics, The University
of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637.
22 Enrico Fermi Institute, The University of Chicago, 5640 South
Ellis Avenue, Chicago, IL 60637.
23 School of Physics, University of Exeter, Stocker Road, Exeter
EX4 4QL, UK.
24 University of Pittsburgh, Department of Physics and Astron-
omy, 3941 O’Hara Street, Pittsburgh, PA 15260.
25 Center for Particle Astrophysics, Fermilab, P.O. Box 500,
Batavia, IL 60510.
26 Kavli Institute for Cosmological Physics, University of
Chicago, Chicago, IL 60637.
27 Department of Physics and Astronomy, Rutgers University,
Piscataway, NJ 08854.
28 National Astronomical Observatory, 2-21-1 Osawa, Mitaka,
Tokyo 181-8588, Japan.
29 Max Planck Institute for Astronomy, Koenigsstuhl 17, 69117
Heidelberg, Germany.
30 Department of Physics, Massachusetts Institute of Technol-
ogy, 77 Massachusetts Avenue, Cambridge, MA 02139.
31 Kavli Institute for Astrophysics and Space Research, Mas-
sachusetts Institute of Technology, Cambridge, MA 02139.
32 Department of Astronomy, University of Illinois, 1002 West
Green Street, Urbana, IL 61801.
33 Center for Cosmology and Particle Physics, Department of
Physics, New York University, 4 Washington Place, New York, NY
10003.
34 Institute for Cosmic Ray Research, University of Tokyo, 5-1-5
Kashiwa, Kashiwa, Chiba 277-8582, Japan.
2 INADA ET AL.
isting survey, the Cosmic-Lens All Sky Survey (CLASS;
Myers et al. 2003; Browne et al. 2003) contains a total
of 22 lenses discovered from high-resolution imaging of
over 16,000 flat spectrum radio sources. A subset of 13
lenses from 8,958 radio sources constitutes a statistically
well-defined lens sample which has been used to study
cosmological parameters as well as the structure of lens
galaxies (e.g., Rusin & Tegmark 2001; Chae et al. 2002;
Chen 2004; Chae et al. 2006; Mitchell et al. 2005). How-
ever, a drawback of radio lens surveys like CLASS is that
the redshift distribution of the source population, which
is a key component for statistical analyses, is poorly con-
strained (e.g., Mu˜noz et al. 2003). Thus we will bene-
fit from complementary optical lens samples for which
source populations are better understood, although the
effects of absorption and emission by the lensing galaxies
are larger in the optical than the radio (e.g., Falco et al.
1999). The largest existing statistical sample of optical
lensed quasars is the Hubble Space Telescope snapshot
survey (Maoz et al. 1993). It contains only five lenses se-
lected from 502 bright high-redshift quasars, indicating
the need for much larger optical lens samples.
Larger statistical lens samples will also allow the study
of the formation of structure. Quasars can be lensed
by structures on scales from individual galaxies, through
groups, to clusters, and therefore the image separation
distribution of strongly lensed quasars from small to large
separations directly reflects the hierarchical structure
formation and the effects of cooling the baryons (e.g.,
Kochanek & White 2001; Oguri 2006). Unfortunately,
the probability of quasars strongly lensed by clusters is
1–2 orders of magnitudes smaller than that by galaxies,
so we need large homogeneous surveys to study the full
image separation distribution. Indeed, despite searching
for them explicitly, no cluster-scale lens was discovered
in the CLASS (Phillips et al. 2001).
The main purpose of the Sloan Digital Sky Survey
Quasar Lens Search (SQLS; Oguri et al. 2006, hereafter
Paper I) is to construct a large sample of lensed quasars
in the optical. It is made possible by the large spectro-
scopic quasar catalog obtained from the data of the Sloan
Digital Sky Survey (SDSS; York et al. 2000). Lens can-
didates are selected morphologically among the spectro-
scopically confirmed SDSS quasars. Additional lens can-
didates are selected by looking for companion objects to
the SDSS quasars that have similar colors. Our selection
algorithms have been tested against simulated SDSS im-
ages; this allows accurate quantification of the selection
function (see Paper I). A number of previous strong lens
discoveries (Inada et al. 2007a, and references therein)
indicate the effectiveness of our candidate selection algo-
rithm.
In this paper, we present the statistical sample of
strongly lensed quasars, constructed from the SDSS Data
Release 3 (DR3; Abaza jian et al. 2005) spectroscopic
quasar catalog (Schneider et al. 2005). Lens candidates
are selected according to the algorithms presented in Pa-
per I. We conduct extensive follow-up observations for
these candidates with various facilities in order to test
the hypothesis that they are lensed, and to make a com-
plete lens sample. Cosmological constraints from this
statistical sample will be reported in Paper III of this
series (Oguri et al. 2007a).
The structure of this paper is as follows. We describe
the construction of the source quasar sample in §2, and
the selection of lens candidates in §3. Results of our
follow-up observations for the candidates are summarized
in §4. Section 5 lists lensed quasars in the statistical
quasar subsample as well as those included in the DR3
quasar catalog. Finally we summarize our results in §6.
2. SOURCE QUASAR SAMPLE
The SDSS is a combination of photometric and
spectroscopic surveys of a quarter of the entire sky
(York et al. 2000). It uses a dedicated wide-field (3◦
field of view) 2.5-m telescope (Gunn et al. 2006) at the
Apache Point Observatory in New Mexico, USA. Pho-
tometric observations (Gunn et al. 1998; Tucker et al.
2006) consist of imaging in five broad band filters
(Fukugita et al. 1996). The data are processed and
analyzed automatically by the photometric pipeline
(Lupton et al. 2001; Lupton 2007). Targets for spec-
troscopy are selected according to selection algorithms
applied to the imaging data (see Richards et al. (2002)
for the quasar target selection algorithm). Spectra of
these targets are obtained with a multi-fiber spectro-
graph (wavelength range between 3800 ˚
A and 9200 ˚
A at a
resolution of R∼1800). The astrometric accuracy of the
imaging data is better than about 0.
′′1 rms per coordi-
nate (Pier et al. 2003) and photometric zeropoint errors
are less than about 0.03 magnitude over the entire survey
area (Hogg et al. 2001; Smith et al. 2002; Ivezi´c et al.
2004; Padmanabhan et al. 2007). The data release pa-
pers (Stoughton et al. 2002; Abazajian et al. 2003, 2004,
2005; Adelman-McCarthy et al. 2006, 2007) describe the
contents of the SDSS data releases.
We start with a sample of 46,420 spectroscopically
confirmed quasars in the SDSS DR3 quasar catalog
(Schneider et al. 2005). The area covered by the spec-
troscopy is 4188 deg2. The sample contains quasars from
z= 0.08 to 5.41 with a median redshift of 1.47. This
is not a well-defined quasar sample for lens surveys, as
it includes objects selected with a wide variety of tech-
niques. For example, when high redshift quasar candi-
dates (z > 2.2) are targeted for SDSS spectroscopy, they
are required to be point sources, leading to a strong bias
against selecting small separation lenses. We focus on
the low redshift (z < 2.2) and bright (icor <19.1; here
icor is the Point Spread Function magnitude corrected
for Galactic extinction from the maps of Schlegel et al.
(1998)) quasars of the main quasar sample, which are
known to have high completeness regardless of whether
they are resolved or unresolved (Vanden Berk et al. 2005;
Richards et al. 2006). Thus the quasars with z < 2.2 and
icor <19.1 should have no explicit biases against gravi-
tational lenses. We further restrict the redshift range to
0.6< z < 2.2 to eliminate lower redshift, intrinsically ex-
tended quasars, and exclude quasars with SDSS images
of poor seeing (PSF WIDTH>1.
′′8) in which the identifica-
tion of close lens pairs is difficult. Paper I discusses the
selection of the source quasars in greater detail. These
criteria produce a subsample of 22,683 quasars35 suit-
able for lens statistics. From this quasar subsample, we
construct a statistical sample of lensed quasars.
35 This includes one quasar (SDSS J094222.89+102025.3),
which we missed in Paper I. See
http://www-utap.phys.s.u-tokyo.ac.jp∼sdss/sqls/ for the red-
shift and icor distributions of our quasar subsample.
SDSS QUASAR LENS SEARCH. II. 3
Fig. 1.— Flowchart of the candidate selection procedure of the SQLS. First we construct a statistical subsample of quasars (source QSOs)
from the SDSS spectroscopic quasar catalog. The specific selection criteria (M1–M3, C1–C2, and S1) are given in Paper I. The details of
the additional selection criteria are described in §3. Table 1 presents the numbers of the source quasars, parent candidates, objects rejected
at each step, and final follow-up candidates.
3. LENS CANDIDATE SELECTION
We illustrate the SQLS candidate selection procedure
in Figure 1. As discussed in Paper I, we use two different
selection methods (morphological and color selection), in
order to identify both galaxy- and cluster-scale lens can-
didates. For candidates selected by each approach, we
apply several additional selection criteria to construct
a final lens candidate sample appropriate for detailed
follow-up on other facilities. We explain these additional
criteria for morphological candidates in §3.1 and those
for color candidates in §3.2. These two selection algo-
rithms are not exclusive with each other, since the (de-
blended) quasar component of a color candidate could be
a morphological candidate. The numbers of candidates
selected/removed by each approach are summarized in
Table 1. We finally identify 220 lensed quasar candidates
for follow-up from the 22,683 source quasars.
3.1. Morphological Selection
The morphological selection algorithm is intended to
discover galaxy-scale (θ.2.
′′5) lensed quasars that the
4 INADA ET AL.
TABLE 1
NUMBERS OF CANDIDATES
Number
Source quasars 22,683
Parent morphological candidates 649
Rejected by GALFIT fitting −552
Rejected by visual inspection −7
Final morphological candidates for follow-up 90
Parent color candidates 227
Rejected by FIRST image check −16
Rejected by visual inspection −16
Rejected by searching for possible lensing objects −63
Final color candidates for follow-up 132
Final total candidates for follow-up 220
Note. — Two candidates are selected by both the morpho-
logical and color selection algorithms.
SDSS photometric pipeline did not deblend into multiple
components. In Paper I, we showed that such lens can-
didates can be identified by searching for quasars that
are not well fit by the PSF in each SDSS field. Thus
we select the galaxy-scale lens candidates based on the
goodness of fit of a quasar image to the PSF model in
each field (star L). Different criteria of star L are used
according to the ob ject classification (objc type), which
is set by the difference between the PSF and model mag-
nitudes in the SDSS data. The specific criteria (M1, M2,
or M3) are given in Paper I. These “morphological selec-
tion” criteria identify 649 quasars (∼3% of the source
quasars) as lens candidates.
As discussed in Paper I, a significant fraction of the
candidates selected by the algorithm are single quasars.
In addition, the candidates contain superpositions of
quasars with foreground galaxies or stars. Therefore, we
use two additional criteria described below in order to
exclude most of these false positives before performing
any subsequent observations. In the first criterion, we fit
the SDSS u- and i-band images of each candidate with
two PSFs using the GALFIT software (Peng et al. 2002).
When a single quasar is fitted with two PSFs, the result
tends to be unusual in the sense that the fitted two PSFs
have a very small separation (≪1′′ ) and similar magni-
tudes, or a moderate separation (&1′′) and very differ-
ent magnitudes. In addition, when a single quasar plus
star/galaxy system is fitted with two PSFs, the results
from the SDSS u- and i-band images tend to be very
different because a quasar at 0.6< z < 2.2 is usually
much bluer than either a star or a galaxy. In particular,
such quasar plus star/galaxy systems may result in very
large u-band flux ratios since the galaxy/star component
tends to be very faint in u-band. Thus we can eliminate
a significant fraction of these false positives by making
cuts to the fitted separations and flux ratios (see Paper
I for selection criterion S1). This procedure (“GALFIT
fitting”) successfully removes ∼85% of the candidates.
Most of the rejections are single isolated quasars, but
as expected, they also include several quasar-star and
quasar-galaxy pairs.
For the second criterion, we inspect the SDSS images
of the remaining candidates and eliminate those which
appear to be chance superpositions of a quasar and a
galaxy (“visual inspection”). This visual inspection elim-
inates about 10% of the candidates left after the GAL-
FIT modeling and yields 90 morphological (galaxy-scale)
candidates that require further investigation.
3.2. Color Selection
Larger separation (θ&2.
′′5) lenses created by groups
or clusters of galaxies are accurately deblended by the
SDSS photometric pipeline, and therefore can be se-
lected by comparing the colors of each quasar to those
of nearby objects (“color selection”). The idea is similar
to the Hennawi et al. (2006) approach for finding binary
quasars in the SDSS, but we modify the color selection
criteria to allow for differential extinction between lensed
images. These criteria are discussed in detail in Paper I,
but we have slightly broadened the limits to include im-
age separations of θ < 20.
′′1 and i-band magnitude differ-
ences of ∆i < 1.3, considering the typical uncertainties
in the quasar positions (0.
′′1) and magnitudes (0.05) in
the SDSS data. We identified 227 quasar pairs based on
the criteria.
We first test the lensing hypothesis for these candidates
by comparing the radio flux ratios from the Faint Images
of the Radio Sky at Twenty centimeters survey (FIRST;
Becker et al. 1995) with the optical flux ratios (“FIRST
image check”). We eliminate 10% of the candidates with
separations larger than 6′′ (set by the ∼5′′ resolution of
the FIRST) in which one component is radio loud with a
flux well above the FIRST survey limits and the other is
not. Such pairs are either binary quasars or quasar-star
pairs (Kochanek et al. 1999).
Next we check the SDSS images of the candidates (“vi-
sual inspection”). Since we select both point sources and
extended sources as the nearby objects in the color se-
lection stage, quasar plus galaxy systems are sometimes
selected as candidates. The purpose of visual inspection
in the color selection algorithm is to eliminate the can-
didates whose companion objects to the SDSS quasars
clearly appear to be galaxies. At this step an additional
∼10% of the candidates are excluded.
In addition, for low-redshift candidates we can search
for possible lensing galaxies in the SDSS images (“search-
ing for possible lensing objects”). To determine the crite-
ria, we compute the expected magnitudes of the lensing
objects using the halo model of Oguri (2006). Specifi-
cally, we define the magnitude limit of the lensing galaxy
(or the central galaxy of the lensing cluster for a cluster-
scale lens candidate) such that 99% of simulations have
a lensing galaxy brighter than that magnitude limit, and
compute the magnitude limit as a function of the image
separation and source (quasar) redshift. In the model,
halos are linked to galaxies by adopting a universal scal-
ing relation (with scatter) between masses of halos and
luminosities of galaxies. We ignore the redshift evo-
lution of the mass-luminosity relation, which provides
conservative estimates of the minimum luminosity since
standard passive evolution predicts that galaxies were
brighter in the past. The luminosity is converted to
observed magnitude using the K-correction for ellipti-
cal galaxies in Fukugita et al. (1995). Figure 2 shows
the magnitude limit as a function of image separations
and quasar redshifts. We check for a lensing galaxy in
the SDSS image when its expected magnitude is brighter
than i= 20.5 (corresponding to ∼0.5L∗for a typical lens
redshift); given the magnitude limit of the SDSS images,
ilim ∼21.5, the choice should be very conservative. In
SDSS QUASAR LENS SEARCH. II. 5
Fig. 2.— The i-band magnitude limit of the lensing ob jects
(defined such that 99% of simulated lenses are caused by galaxies
brighter than the limit) in the zs-θplane, where zsdenotes the
source (quasar) redshift. The limit is computed using the halo
model of Oguri (2006). The dotted line indicates the limits of
the source redshift and image separation (eq. [1]): For candidates
which lie in the region of eq. [1], we search for possible lensing
galaxies in the SDSS i-band images and reject the candidates if no
galaxy is seen among the components. See text for more details.
practice, we examine candidates with low redshifts and
large separations defined by the region shown in Fig-
ure 2:
zs<1.1 for 7′′ < θ < 12′′ ,
zs<1.2 for 12′′ < θ < 17′′,
zs<1.3 for 17′′ < θ, (1)
where zsis the redshift of the source quasar. The candi-
date which lies in the region and lacks a possible lensing
object in the SDSS image is rejected. Roughly 30% of
the candidates fail this test, leaving 132 color (larger-
separation) candidates. These 132 objects constitute
the final color candidates for additional investigation.
Among these, two candidates were also selected by the
morphological algorithm, which is consistent with our
simulation that predicts ∼10% of objects with image
separations of 1.
′′5.θ.3.
′′0 are selected by both algo-
rithms (see Paper I). Thus the total number of candidates
for follow-up is 220.
4. FOLLOW-UP OBSERVATIONS
The final morphological and color candidates and the
summary of their observations are shown in Tables 2 and
3, respectively. In this section we describe the follow-up
observations and how we decide on the lens nature of
each candidate. We also note several interesting objects
discovered in the course of our lens search.
4.1. Basic Strategy
Before conducting any subsequent observations, we
first check if the candidates have been studied before with
the NASA/IPAC Extragalactic Database (NED). Three
of the 220 candidates are previously known gravitational
lens systems for which no follow-up observations were
necessary. One system, SDSS J133945.37+000946.1,
turns out to be a quasar pair at different redshifts
(Croom et al. 2004).
The rest of the candidates are investigated to test their
lensing hypotheses. These observations consist of optical
spectroscopy, optical imaging, and near-infrared imag-
ing, conducted at the following facilities: the University
of Hawaii 2.2-meter telescope (UH88), the Astrophysi-
cal Research Consortium 3.5-meter telescope (ARC 3.5-
m), the Keck I and II telescopes, the United Kingdom
Infra-Red Telescope (UKIRT), the Subaru telescope, the
Magellan Consortium’s Walter Baade 6.5-m telescope
(WB 6.5-m), the Hubble Space Telescope (HST), the
MDM 2.4-meter telescope (MDM 2.4-m), the MMT Ob-
servatory, the European Southern Observatory 3.6-meter
telescope (ESO 3.6-m), the New Technology Telescope
(NTT), and the WIYN telescope.
The SDSS images have moderate observing conditions
(typically ∼1.
′′3 seeing) and a short exposure time (about
55 sec), making it difficult in many cases to determine
whether a lensing galaxy is present. Therefore, for small
separation lens candidates we usually start with acquir-
ing deeper optical (ior I) or infrared (Hor K) images
under good seeing conditions (∼0.
′′5−1.
′′0). Some of the
candidates turn out to be single quasars or quasar-galaxy
pairs, and therefore they are rejected rather easily. If the
candidates consist of two (or more) stellar components,
we take optical and/or infrared images that are deep
enough to locate lensing galaxies. The typical magnitude
limits for extended objects are I∼23.0, H∼18.5, and
K∼20.0. Additional images with bluer filters may be
taken in order to better separate multiple components.
Candidates that do not exhibit any residuals after sub-
tracting stellar components are rejected based on the ab-
sence of the lensing object. Some of our candidates are
rejected simply by the fact that the separation of the two
stellar components is smaller than 1′′ , since we set the
minimum image separation of our complete lens sample
to be 1′′ (i.e., some of the “rejected” candidates with
θ < 1′′ could in fact be gravitational lenses; see §4.2.).
If the data reveal stellar components with similar colors
and a possible lensing galaxy, we try to obtain spectra
of the multiple stellar components to determine whether
their spectral energy distributions (SEDs) are similar.
We detect possible lensing objects only for 9 candidates
out of 81 morphological candidates with deep images.
Seven of them turn out to be new lenses from the SDSS
(see §5 and Tables 2), and the other two are confirmed
to be binary quasars (SDSS J084710.40−001302.6 and
SDSS J100859.55+035104.4; see §4.2). We note that
in addition to the candidates with possible lensing ob-
jects we conduct spectroscopic observations for any can-
didates which have stellar components with very simi-
lar colors in imaging data (including the SDSS images)
even if they are rejected based on the absence of lens-
ing objects. We perform this spectroscopic observation
in order to test the validity of the rejection criterion.
This includes SDSS J093207.15+072251.3 (see §4.2) and
SDSS J112012.11+671116.0 (Pindor et al. 2006) that are
confirmed to be binary quasar pairs with indistinguish-
able redshifts.
Our strategy for follow-up of large separation lens
candidates is similar to the above process. We ei-
ther acquire spectra of the two components to check
their SEDs or deep optical/infrared images to search
for any possible lensing galaxies or clusters. Rejection
based upon spectroscopic observations is straightforward
6 INADA ET AL.
when the candidates are quasar-star pairs or quasar-
quasar pairs at different redshifts. Some of the can-
didates turn out to be binary quasars, as reported in
Hennawi et al. (2006). In some cases candidates turn
out to be quasar pairs at quite similar redshifts. For
these sources we use deep optical/infrared follow-up im-
ages to search for any signature of a lensing galaxy or a
lensing cluster. As well as the small separation lens can-
didates, we perform spectroscopic observations regard-
less of the existences of the lensing objects particularly
when the colors of the two components are very simi-
lar. Most of them are quasar-quasar pairs at different
redshifts. Two of them, SDSS J090955.54+580143.2 and
SDSS J211102.60+105038.3, turn out to be quasar pairs
with indistinguishable redshifts, but are rejected based
on the differences of the SEDs (see §4.2).
To summarize, we identify a candidate as a lens sys-
tem when the following three conditions are met: (i) the
stellar components have the same redshifts within the
measurement uncertainty; (ii) their SEDs are reasonably
similar; (iii) a galaxy or a cluster/group of galaxies is
detected between the stellar components. When candi-
dates have four stellar images, we do not always require
conditions (i) and (ii), because the object’s lensing na-
ture is obvious from its characteristic image configura-
tion. The fact that we use the existence of the lensing
object for the judgment suggests that our selection may
be against hypothetical dark lenses (e.g., Rusin 2002)
that have anomalously high mass-to-light ratios. How-
ever, since our candidates with very similar colors tend to
be rejected spectroscopically (see above and §4.2) rather
than the absence of lensing objects alone, we believe that
our follow-up strategy is reasonably effective in locating
such dark lenses as well.
4.2. Notes on Individual Objects
Below we note several interesting candidates which
have not been discussed elsewhere in the literature. In
addition to the objects discussed below, at least 30 ob-
jects out of our 220 candidates are confirmed to be pairs
of quasars; 9 out of the 30 pairs have already been
reported in Hennawi et al. (2006). Furthermore, there
are 9 candidates whose image separations turned out
to be θ < 1′′ in the follow-up studies. They include
the known lensed quasar FBQ1633+3134 (Morgan et al.
2001). These systems are not included in the statisti-
cal lens sample and therefore we did not perform any
further spectroscopy or deeper imaging. Although our
current follow-up images do not show any possible lens-
ing objects for any of the candidates, lensing galaxies
of subarcsecond lenses are expected and observed to be
faint. Very deep and high resolution images are neces-
sary to conclude whether they are lensed quasars or not.
See Tables 2 and 3 for more details of these objects.
SDSS J0847−0013: This is a small separation (θ=
1.
′′0) lens candidate discovered by the morphological se-
lection criterion. Spectroscopic observations conducted
with LRIS at Keck revealed that this is a quasar pair
with similar redshifts of z= 0.626 and z= 0.627. The
spectra of the two quasar components, however, have
different Mg II emission line shapes (upper left panel of
Figure 3), supporting the binary interpretation of this
system. The image taken with Tek2k at UH88 shows
extended emission in the vicinity of the brighter compo-
nent. The spectrum of this emission taken with LRIS
at Keck indicates that this emission is due to the host
galaxy of the quasar (Gregg et al. 2007).
SDSS J0909+5801: The spectroscopic observation
at ARC 3.5-m revealed that both the components sep-
arated by θ= 8.
′′1 are quasars at same redshifts (z=
1.712). However, we see a broad absorption line feature
only in the C IV emission line of the brighter compo-
nent (upper right panel of Figure 3). Together with the
absence of the lensing object in deep i-band image, we
conclude that the system is a binary quasar rather than
a lens.
SDSS J0932+0722: A morphological candidate with
an image separation of θ= 1.
′′4 found to be a pair of
quasars at z= 1.994 in Keck ESI observations. None
of the deep optical and near-infrared images show any
lensing galaxy between the two components, and the flux
ratio of the two quasars in the optical are significantly
different from that in the near-infrared (0.12 in I-band
and 0.02 in H-band). Thus we regard this system as a
binary quasar.
SDSS J1008+0351: We detected possible extended
emission between the stellar components in both deep
optical and infrared images. However, spectra of this
small separation (θ= 1.
′′1) candidate taken with FOCAS
at Subaru suggest that this is a binary quasar, because
of the slightly different redshifts (z= 1.745 and 1.740)
and the different overall shapes of the spectra, as shown
in the lower left panel of Figure 3. One interpretation is
that the extended emission is due to the host galaxy of
one of (or both of ) the quasars.
SDSS J2111+1050: This is a large separation (θ=
9.
′′7) lens candidate from the color selected sample. From
ARC 3.5-m spectroscopy, the redshifts of the two stellar
components are quite similar with z= 1.897. However,
the SEDs (in particular, the shapes of the C IV emission
lines; see the lower right panel of Figure 3) are different,
and a deep I-band image does not show a lensing galaxy
between the two components. We conclude that this is a
binary quasar rather than a lens.
5. LENSED QUASARS
After completing the observations, we have a statis-
tical sample of 11 lensed quasars with image separa-
tions of 1′′ < θ < 20′′ and i-band flux ratios (for two-
image systems) of faint to bright lensed images larger
than 10−0.5. Nine of them are newly discovered lensed
quasars in the SQLS (e.g., Inada et al. 2005), and two of
them, SDSS J0913+5259 (SBS 0909+523; Oscoz et al.
1997) and SDSS 1001+5553 (Q0957+561; Walsh et al.
1979), are previously known lensed quasars. The statis-
tical sample is drawn from a subsample (22,683 quasars
with 0.6< z < 2.2 and icor >19.1) of the 46,420 DR3
quasars, and therefore some of lenses outside the SDSS
DR3 (e.g., Inada et al. 2006a,b) are not included. Table
4 summarizes the DR3 statistical lensed quasar sample
and Figure 4 shows a histogram of the maximum image
separations of each system. The number of the lenses
decreases from θ= 1′′ as the image separation increases,
consistent with previous observations (e.g., Browne et al.
2003). The statistical sample contains 9 double lenses
and 2 quadruple lenses, and ranges from θ= 1.
′′0 to
θ= 14.
′′6, covering both galaxy- and cluster-scale lenses.
There are two lensed quasars listed in Table 2 or
SDSS QUASAR LENS SEARCH. II. 7
4200 4400 4600 4800 5000
J0847–0013
MgII
arbitrary
wavelength (angstroms) 4000 4200 4400
J0909+5801
CIV
arbitrary
wavelength (angstroms)
4800 5000 5200 5400 5600
J1008+0351
CIII]
arbitrary
wavelength (angstroms) 4000 4500 5000
J2111+1050
CIV
arbitrary
wavelength (angstroms)
Fig. 3.— Upper Left: The Mg II emission lines of the two quasar components of SDSS J0847−0013 taken at the Keck telescope (spectral
resolution of R∼1000). The different shapes support the binary interpretation of this system. Upper Right: The C IV emission lines of
the two quasar components of SDSS J0909+5801 taken at the ARC 3.5-m telescope (R∼500). The broad absorption line feature is seen
only in the spectrum of the brighter component, which suggests that this is a binary quasar rather than a lens. Lower Left: The C III]
emission lines of the two quasar components of SDSS J1008+0351 from the observation at the Subaru telescope (R∼500). In addition to
the different overall shapes, they show slightly different redshifts. Lower Right: The C IV emission lines of the two quasar components of
SDSS J2111+1050 observed at the ARC 3.5-m telescope (R∼500). The different strengths of the emission lines, together with the absence
of any lensing objects in the deep I-band image, support the binary interpretation.
Table 3 that are not part of our statistical sample
in Table 4. SDSS J0832+0404 (Oguri et al. 2007b)
is a color-selected SDSS lens but it is not included
in the statistical sample because its I-band flux ratio
is too extreme. The previously known lensed quasar
SDSS J1633+3134 (FBQ 1633+3134; Morgan et al.
2001) is a morphologically-selected lens, but its image
separation of θ= 0.
′′66 is too small to be included in the
statistical sample. These two lenses are listed in Table 5,
which contains additional DR3 lensed quasars outside the
statistical sample.
We also applied our selection algorithms to the DR3
spectroscopic quasars outside the subsample of 22,683
quasars. For the higher redshift quasars (z > 2.2),
we used the star Lcriteria for the griz bands rather
than for the ugri bands of the lower redshift lens
selection. We found 4 SDSS lenses, SDSS J0903+5028
(Johnston et al. 2003), SDSS J1138+0314 (Burles et al.
2007), SDSS J1155+6346 (Pindor et al. 2004), and
SDSS J1406+6126 (Inada et al. 2007a), and recovered
2 known lenses, SDSS J0145−0945 (Q0142−100;
Reimers et al. 2002) and SDSS J0911+0550
(RX J0911+0551; Surdej et al. 1987). Note that
SDSS J0903+5028 was first identified through its
compound nature (quasar plus luminous red galaxy)
of the SDSS spectrum (Johnston et al. 2003) and
SDSS J1138+0314 was first identified in a WB 6.5-m
snapshot survey of ∼1000 SDSS quasars (Burles et al.
2007).
There are three lenses in the DR3 area which we did
not recover as final follow-up candidate. In two cases,
SDSS J0813+2545 (HS 0810+2554; Reimers et al. 2002)
and SDSS J1650+4251 (Morgan et al. 2003), the ob-
jects are selected in the first stage of our morphologi-
cal selection process and then eliminated by the GAL-
FIT criteria which are designed to select lenses with
θ > 1′′ and i-band flux ratios of faint to bright lensed im-
ages larger than 10−0.5(see Paper I). SDSS J0813+2545
(HS 0810+2554) has a small image separation (<1′′)
and SDSS J1650+4251 has a small flux ratio (<10−0.5),
that is why they did not pass the GALFIT fitting.
The subarcsecond (0.
′′68) radio lens (PMN J0134-0931;
Winn et al. 2002; Gregg et al. 2002) was never flagged at
any stage of our survey because of its small image sepa-
ration. These 3 lenses would not be part of our statistical
lens sample in any case. It does illustrate, however, that
our survey is incomplete outside of our selection limits.
8 INADA ET AL.
Fig. 4.— Image separation distribution of the SQLS DR3 sta-
tistical sample i n bins of ∆ l og θ= 0.2. The statistical sample is
constructed in the range 1′′ < θ < 20′′ as indicated by the dotted
lines. The individual lenses are listed in Table 4.
6. SUMMARY AND DISCUSSIONS
We have presented a complete sample of gravitation-
ally lensed quasars which can be used for various statis-
tical studies. The sample is based on the 46,420 spectro-
scopic quasars in the SDSS DR3. We focused on a sub-
sample of 22,683 quasars with 0.6< z < 2.2 and Galac-
tic extinction-corrected i-band PSF magnitudes brighter
than 19.1. Lens candidates were identified using the al-
gorithms described here and in paper I, and verified by
extensive follow-up observations in the optical and near-
IR. The resulting 11 lensed quasars constitute a statisti-
cal sample with image separation of 1′′ < θ < 20′′ and
flux ratios (for two-image systems) of fi>10−0.5that
should have very high completeness based on our tests in
paper I. The DR3 spectroscopic quasar catalog contains
an additional 11 lensed quasars that do not satisfy the
criteria for our complete sample. Thus we identified a
total of 22 lenses, 7 of which were discovered in earlier
lens searches other than the SDSS.
The lens fraction in our statistical sample, ∼0.05%,
appears to be lower than in previous studies, but this
is largely explained by our tight criterion on the image
separations and flux ratios and the fact that our sam-
ple uses relatively low-redshift faint quasars. For exam-
ple, the CLASS survey found a lens fraction of ∼0.14%
(Browne et al. 2003), but ∼30% of the lenses have sep-
arations smaller than 1′′ and ∼50% of the double im-
age lenses have flux ratios of faint to bright lensed im-
ages smaller than 10−0.5. The HST Snapshot Survey
(Maoz et al. 1993) found that ∼1% of bright quasars
were lensed, but the magnification bias for bright quasars
is significantly larger than for our fainter quasar sample.
This is the first statistical lensed quasar sample that
contains both galaxy-scale (θ.3′′) lenses and cluster-
scale (θ&10′′) lenses. The maximum image sepa-
ration in our DR3 statistical sample is 14.
′′62 (SDSS
J1004+4112), much larger than the maximum image sep-
aration in the CLASS, 4.
′′56. The distribution of image
separations across the wide mass range from galaxies to
clusters will be valuable in studying the structure for-
mation. We note that such distributions of splitting an-
gles are obtained from surveys of lensed galaxies as well.
For instance, Cabanac et al. (2007) presented 40 strongly
lensed galaxy candidates, with separations ranging from
2′′ to 15′′. The simple point-like nature of source quasars,
however, makes it much easier to quantify various selec-
tion effects than in surveys of lensed galaxies. In addi-
tion, our statistical sample has an advantage over lensed
galaxies (or radio lenses) in well-understood redshift dis-
tribution of the source population. As an application of
the statistical sample, we study cosmological constraints
from the galaxy-scale lenses of the DR3 statistical lens
sample in Paper III.
The DR3 spectroscopic quasar sample consists of less
than half of the full SDSS data. Our lens sample
will increase significantly in the future. Assembly of
a complete lens sample from the DR5 quasar catalog
(Schneider et al. 2007) is in progress.
N. I. acknowledges support from the Special Postdoc-
toral Researcher Program of RIKEN and the Japan So-
ciety for the Promotion of Science. This work was sup-
ported in part by Department of Energy contract DE-
AC02-76SF00515. A portion of this work was also per-
formed under the auspices of the U.S. Department of
Energy, National Nuclear Security Administration by
the University of California, Lawrence Livermore Na-
tional Laboratory under contract No. W-7405-Eng-48.
M. A. S. acknowledges support from NSF grant AST
03-07409. I. K. acknowledges supports from Ministry
of Education, Culture, Sports, Science, and Technol-
ogy, Grant-in-Aid for Encouragement of Young Scientists
(No. 17740139), and Grant-in-Aid for Scientific Research
on Priority Areas No. 467 “Probing the Dark Energy
through an Extremely Wide & Deep Survey with the
Subaru Telescope”. A. C. acknowledges the support of
CONICYT, Chile, under grant FONDECYT 1051061.
Use of the UH 2.2-m telescope and the UKIRT 3.8-
m telescope for the observations is supported by the
National Astronomical Observatory of Japan (NAOJ).
Based in part on observations obtained with the Apache
Point Observatory 3.5-meter telescope, which is owned
and operated by the Astrophysical Research Consor-
tium. Based in part on data collected at Subaru Tele-
scope (some of data obtained from the Subaru Telescope
Sciences Archive System [SMOKA]), which is operated
by NAOJ. Some of the data presented herein were ob-
tained at the W.M. Keck Observatory, which is operated
as a scientific partnership among the California Insti-
tute of Technology, the University of California and the
National Aeronautics and Space Administration. The
Keck Observatory was made possible by the generous
financial support of the W.M. Keck Foundation. The
WIYN Observatory is a joint facility of the University
of Wisconsin-Madison, Indiana University, Yale Univer-
sity, and the National Optical Astronomy Observatories.
This work is also based in part on observations obtained
with the MDM 2.4m Hiltner telescope, which is owned
and operated by a consortium consisting of Columbia
University, Dartmouth College, the University of Michi-
gan, the Ohio State University and Ohio University. The
WB 6.5-m telescope is the first telescope of the Magel-
lan Project; a collaboration between the Observatories
of the Carnegie Institution of Washington, University of
Arizona, Harvard University, University of Michigan, and
Massachusetts Institute of Technology to construct two
6.5 Meter optical telescopes in the southern hemisphere.
Based in part on observations made with the NASA/ESA
SDSS QUASAR LENS SEARCH. II. 9
Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Inc., under
NASA contract NAS 5-26555. These observations are
associated with HST program GO-9744. Based in part
on observations made with telescopes (ESO 3.6-m and
NTT) at the European Southern Observatories La Silla
in Chile. Some observations reported here were obtained
at the MMT Observatory, a joint facility of the Univer-
sity of Arizona and the Smithsonian Institution.
Funding for the SDSS and SDSS-II has been pro-
vided by the Alfred P. Sloan Foundation, the Partic-
ipating Institutions, the National Science Foundation,
the U.S. Department of Energy, the National Aeronau-
tics and Space Administration, the Japanese Monbuka-
gakusho, the Max Planck Society, and the Higher Educa-
tion Funding Council for England. The SDSS Web Site
is http://www.sdss.org/.
The SDSS is managed by the Astrophysical Research
Consortium for the Participating Institutions. The Par-
ticipating Institutions are the American Museum of Nat-
ural History, Astrophysical Institute Potsdam, Univer-
sity of Basel, Cambridge University, Case Western Re-
serve University, University of Chicago, Drexel Univer-
sity, Fermilab, the Institute for Advanced Study, the
Japan Participation Group, Johns Hopkins University,
the Joint Institute for Nuclear Astrophysics, the Kavli
Institute for Particle Astrophysics and Cosmology, the
Korean Scientist Group, the Chinese Academy of Sci-
ences (LAMOST), Los Alamos National Laboratory, the
Max-Planck-Institute for Astronomy (MPIA), the Max-
Planck-Institute for Astrophysics (MPA), New Mexico
State University, Ohio State University, University of
Pittsburgh, University of Portsmouth, Princeton Uni-
versity, the United States Naval Observatory, and the
University of Washington.
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TABLE 2
MORPHOLOGICAL CANDIDATES
Object zaicor bθSDSSc∆icimagedspecdcomment Ref.
SDSS J001125.75−105710.4 0.641 18.95 0.48 0.70 UF(K)· · · single QSO · · ·
SDSS J004242.00+135450.0 1.622 16.72 0.56 0.81 UF(K)· · · single QSO · · ·
SDSS J011229.41+151213.9 1.957 18.86 1.12 0.30 WF(i)· · · QSO+galaxy · · ·
SDSS J012259.49+151147.2 1.276 18.17 0.45 0.36 UF(K)· · · single QSO · · ·
SDSS J020707.59−100541.6 0.662 18.78 0.48 0.10 UF(K)· · · single QSO · · ·
SDSS J021249.59+003448.7 1.222 18.86 1.69 0.73 8k(I),WF(i) WF QSO+galaxy · · ·
SDSS J021645.80−010204.8 1.087 18.55 0.53 1.35 UF(K)· · · single QSO · · ·
SDSS J024634.09−082536.1 1.685 17.77 1.03 1.10 AC(V,I),Ma(i),NR(K′),NM(H) ES SDSS Lens 1
SDSS J034601.93−070024.2 0.630 19.09 0.74 1.37 UF(K)· · · extended single QSO · · ·
SDSS J034801.20−070416.9 1.959 18.10 1.54 1.54 UF(K)· · · no lensing object · · ·
SDSS J041254.86−062049.8 1.266 18.96 0.48 0.58 UF(K)· · · single QSO · · ·
SDSS J072843.03+370834.9 1.404 18.97 1.34 0.08 WF(i)· · · no lensing object · · ·
SDSS J073406.75+273355.6 1.916 16.87 2.48 0.27 ··· DA QSO+star · · ·
SDSS J074352.62+245743.6 2.166 19.01 1.02 1.14 WF(i)· · · no lensing object · · ·
SDSS J080002.76+405927.1 1.624 19.00 0.80 1.27 8k(V)· · · single QSO · · ·
SDSS J083530.89+054240.7 1.696 18.50 0.99 0.18 RE(r),WF(i),QU(H)· · · no lensing object · · ·
SDSS J083956.19+410950.9 0.629 19.08 0.73 1.96 WF(i)· · · single QSO · · ·
SDSS J084512.74+543421.5 1.285 18.53 1.50 0.82 ··· MS QSO+star 2
SDSS J084710.40−001302.6 0.627 18.60 0.95 0.43 Te(I) LR QSO pair (z= 0.626,0.627) · · ·
SDSS J084856.08+011540.0 0.646 18.86 1.37 0.53 Ma(i) ES QSO+galaxy+star · · ·
SDSS J085122.37+472249.0 0.894 18.80 1.47 0.03 WF(i)· · · no lensing object · · ·
SDSS J085643.71+413444.8 0.756 17.75 0.55 0.59 8k(V)· · · single QSO · · ·
SDSS J091301.03+525928.9 1.377 16.17 1.12 0.42 · · · · · · known lens (SBS 0909) 3
SDSS J092455.79+021924.9 1.523 18.12 1.34 0.64 Ma(u, g, r, i) ES SDSS Lens 4
SDSS J092528.68+071442.7 1.630 18.13 0.55 0.68 8k(V)· · · single QSO · · ·
SDSS J093207.15+072251.3 1.993 18.96 1.42 1.95 RE(r),8k(I),UF(K),QU(H) ES QSO pair (z= 1.994,1.994) · · ·
SDSS J094945.68+632622.9 0.650 17.72 0.41 1.26 Te(I)· · · single QSO · · ·
SDSS J095324.39+570319.5 0.619 18.81 2.57 0.14 8k(V),Te(I)·· · no lensing object · · ·
SDSS J100229.46+444942.7 2.052 18.39 0.72 0.25 RE(r),Te(I),NR(K′),QU(H)·· · θ=0.
′′8· · ·
SDSS J100327.37+595804.0 1.138 17.71 1.19 0.09 FO(V, I )· · · no multiple point sources · · ·
SDSS J100859.55+035104.4 1.746 19.09 0.98 1.18 RE(r),Te(I),UF(K),QU(H) FO QSO pair (z= 1.745,1.740) · · ·
SDSS J102111.02+491330.3 1.720 18.97 1.03 0.55 8k(I),NR(K′) MS SDSS Lens 2
SDSS J103244.09+084022.5 0.604 19.05 0.87 2.05 SC(V, R)· · · single QSO · · ·
SDSS J104716.39+055159.5 0.891 18.51 0.54 1.50 Op(I)· · · θ=0.
′′4· · ·
SDSS J105337.63+074257.0 0.635 18.96 2.19 1.08 Op(I)· · · single QSO · · ·
SDSS J111348.65+494522.4 0.659 19.03 0.68 0.14 Op(I)· · · extended single QSO · · ·
SDSS J111557.64+040224.3 0.668 18.23 0.61 1.79 Op(I)· · · single QSO · · ·
SDSS J112012.11+671116.0 1.494 18.46 1.71 1.40 8k(I),AR(H) MS QSO pair (z= 1.494,1.494) 2,5
SDSS J112241.58+641601.2 1.433 18.31 1.40 0.19 8k(V),Op(I)· · · no lensing object · · ·
SDSS J113236.06+030335.1 1.766 18.42 3.81 1.18 QU(H)· · · no lensing object · · ·
SDSS J113352.61+035300.5 1.780 16.90 0.41 0.92 Op(I)· · · single QSO · · ·
SDSS J113613.37+033840.9 1.188 18.50 1.65 0.24 ··· MS QSO+star 2
SDSS J115244.06+571202.1 1.603 17.92 0.41 1.24 8k(V)· · · single QSO · · ·
SDSS J121244.33+091208.1 1.686 18.63 2.04 1.37 QU(H) EF QSO pair (z= 1.686,1.600) · · ·
SDSS J122558.45−005226.2 0.963 18.84 0.46 2.04 8k(V)· · · single QSO · · ·
SDSS J122608.02−000602.2 1.125 18.23 1.21 0.80 Ma(g, i),AC(V,I),NM(H) DW SDSS Lens 6
SDSS J123020.41+452047.6 2.112 18.20 0.55 1.42 8k(V)· · · single QSO · · ·
SDSS J123844.79+105622.2 1.305 18.54 0.97 0.92 Op(I)· · · QSO+galaxy · · ·
SDSS J123846.69+644836.5 1.558 17.66 1.30 1.09 8k(V),Te(I)·· · QSO+galaxy · · ·
SDSS J124803.09+611628.1 1.585 18.76 0.63 1.57 8k(V)· · · single QSO · · ·
SDSS J125141.90+031140.9 1.223 18.69 1.73 1.02 ··· MS QSO+star 2
SDSS J125617.97+584550.0 1.205 17.88 1.19 0.83 8k(V),Op(I)· · · no lensing object · · ·
SDSS J125758.84+623834.2 2.136 18.50 0.72 1.47 8k(V)· · · θ=0.
′′4· · ·
SDSS J130337.87+505824.5 2.104 18.68 1.89 1.39 8k(I)· · · QSO+galaxy · · ·
SDSS J131815.12+012450.6 0.688 18.04 0.41 1.15 8k(V)· · · single QSO · · ·
SDSS J133222.62+034739.9 1.438 17.89 0.99 0.82 SC(i),QU(H) FO SDSS Lens 7
SDSS J133512.10+052732.4 1.958 18.98 0.79 0.32 8k(V),Op(I)· · · θ=0.
′′8· · ·
SDSS J133534.79+011805.5 1.571 17.53 1.59 1.16 SC(i),NR(K′) EM SDSS Lens 8
SDSS J133632.95+631425.0 1.799 17.21 0.58 1.98 8k(I)· · · single QSO · · ·
SDSS J140159.74+414156.2 1.702 17.91 1.43 2.19 QU(H)· · · QSO+galaxy+galaxy · · ·
SDSS J140622.44−011230.7 1.154 18.84 1.15 1.18 8k(V),Op(I)· · · no lensing object · · ·
SDSS J141647.60+630251.4 2.034 18.97 0.70 1.10 Op(I)· · · single QSO · · ·
SDSS J142011.60+003711.9 0.727 18.10 0.46 0.83 8k(I)· · · single QSO · · ·
SDSS J142931.58+012123.5 1.518 18.99 2.13 1.67 SC(R)· · · QSO+galaxy · · ·
SDSS J143239.09+510431.6 1.193 18.94 0.68 1.59 8k(V),Op(I)· · · θ=0.
′′6· · ·
SDSS J143826.72+642859.8 1.218 18.08 1.19 1.01 8k(I)· · · QSO+galaxy · · ·
SDSS J144135.56+511023.1 1.556 18.98 1.44 1.39 8k(I)· · · QSO+galaxy · · ·
SDSS J144654.77+610248.7 1.760 17.72 0.50 0.92 8k(V)· · · single QSO · · ·
SDSS J145240.53+544345.1 1.520 18.39 1.35 1.58 8k(V),Te(I)·· · QSO+galaxy · · ·
SDSS J145356.57−025151.8 1.740 16.40 0.41 1.71 8k(V)· · · single QSO · · ·
SDSS J150835.59+503820.8 0.668 18.85 0.40 1.33 8k(V)· · · single QSO · · ·
SDSS J151236.95+553901.0 1.361 18.92 1.96 0.89 ··· MS QSO+star 2
SDSS J151304.35+021603.8 0.637 18.42 0.57 2.09 8k(V)· · · single QSO · · ·
SDSS J152445.63+440949.6 1.210 18.76 1.13 0.78 Op(V, R, I ) FO SDSS Lens 9
SDSS J154120.15+542500.6 1.654 18.40 0.70 2.15 8k(V)· · · single QSO · · ·
SDSS QUASAR LENS SEARCH. II. 11
TABLE 2 — Continued
Object zaicor bθSDSSc∆icimagedspecdcomment Ref.
SDSS J162935.01−010538.6 1.053 16.99 0.44 1.25 8k(V)· · · single QSO · · ·
SDSS J163348.98+313411.8 1.519 16.89 0.71 1.86 · · · · · · known lens (FBQ 1633) 10
SDSS J170339.54+325957.1 1.375 17.95 1.41 2.04 8k(V),Te(I)·· · QSO+galaxy · · ·
SDSS J171101.70+292950.9 1.329 17.84 2.18 0.71 8k(I)· · · no lensing object · · ·
SDSS J171117.66+584123.8 0.616 18.35 0.55 0.99 8k(V)· · · single QSO · · ·
SDSS J171925.07+271338.0 1.912 18.55 1.53 0.03 MM(z)· · · no lensing object · · ·
SDSS J172308.15+524455.5 1.818 17.14 1.02 0.88 ··· MS QSO+star 2
SDSS J211108.95+110642.3 1.003 19.00 0.62 0.03 8k(V),UF(K)· · · θ=0.
′′6· · ·
SDSS J212243.01−002653.6 1.971 18.64 0.75 0.75 8k(V),UF(K)· · · θ=0.
′′3· · ·
SDSS J213552.95−081048.1 0.637 19.10 0.54 0.35 8k(V)· · · single QSO · · ·
SDSS J213932.17−011405.7 1.232 19.03 0.49 1.05 WF(i)· · · single QSO · · ·
SDSS J221110.98−000953.3 0.666 18.63 0.81 1.15 UF(K)· · · θ=0.
′′7· · ·
SDSS J221729.41−081154.9 1.010 18.99 0.61 2.18 UF(K)· · · single QSO · · ·
SDSS J231116.97−103849.7 1.540 18.79 1.81 1.43 · · · · · · QSO+star 2
SDSS J233713.66+005610.8 0.708 18.65 1.38 1.31 WF(i) WF QSO+galaxy · · ·
References. — (1) Inada et al. 2005; (2) Pindor et al. 2006; (3) Oscoz et al. 1997; (4) Inada et al. 2003a; (5) Hennawi et al. 2006; (6)
Inada et al. 2007b; (7) Morokuma et al. 2007; (8) Oguri et al. 2004b; (9) Oguri et al. 2007b; (10) Morgan et al. 2001.
aRedshifts from the SDSS DR3 quasar catalogbi-band PSF magnitudes with Galactic extinction corrections from the SDSS DR3 quasar
catalogcImage separations (θSDSS) in units of arcsec and magnitude differences (∆i) between the expected two components, derived from
fitting the SDSS i-band image with two PSFs using GALFIT.dInstruments (and filters) used for the follow-up observations. 8k: UH8k
at UH88, QU: QUIRC at UH88, Op: Optic at UH88, WF: WFGS2 at UH88, Te: Tek2048 at UH88, DA: DIS III at ARC 3.5m, ES: ESI
at Keck, LR: LRIS at Keck, NR: NIRC at Keck, UF: UFTI at UKIRT, FO: FOCAS at Subaru, SC: Suprime-Cam at Subaru, Ma: MagIC
at WB 6.5m, DW: Double Imaging Spectrograph at WB 6.5m, AC: ACS at HST, NM: NICMOS at HST, RE: RETROCAM at MDM
2.4m, MS: MMT spectrograph, AR: ARIES at MMT, EF: EFOSC2 at ESO 3.6m, EM: EMMI at NTT, MM: MiniMo at WIYN.
TABLE 3
COLOR CANDIDATES
Object zaicor bθSDSScimagedspecdcomment Ref.
SDSS J004757.25+144741.9 1.612 18.67
SDSS J004757.87+144744.7 (2.790) 18.72 9.42 · · · DA QSO pair · · ·
SDSS J021649.25−003723.5 1.542 18.55
SDSS J021649.15−003711.5 ··· 19.57 12.15 · · · DA QSO+star · · ·
SDSS J023205.09+010640.2 1.259 17.28
SDSS J023205.18+010634.2 ··· 17.90 6.20 · · · DA QSO+star · · ·
SDSS J025804.27−001059.9 1.551 18.93
SDSS J025803.81−001118.1 ··· 20.05 19.43 · · · DA different SED · · ·
SDSS J073118.72+371100.6 1.468 18.96
SDSS J073119.02+371115.4 ··· 18.75 15.21 · · · DA QSO+star · · ·
SDSS J074013.44+292648.4 0.980 18.42
SDSS J074013.42+292645.8 (0.978) 19.68 2.64 · · · · · · QSO pair 1
SDSS J074357.07+300742.6 2.177 18.82
SDSS J074355.82+300731.1 ··· 18.59 19.88 · · · DA QSO+star · · ·
SDSS J075011.23+430419.0 1.265 18.87
SDSS J075011.66+430413.3 ··· 18.87 7.37 · · · DA QSO+star · · ·
SDSS J075310.75+292110.4 1.937 18.84
SDSS J075311.03+292055.0 ··· 19.60 15.77 · · · DA QSO+star · · ·
SDSS J080435.00+314311.4 2.141 19.05
SDSS J080435.23+314328.7 ··· 19.74 17.53 · · · DA different SED · · ·
SDSS J080658.22+273448.0 1.243 18.63
SDSS J080658.17+273450.1 ··· 19.91 2.26 WF(i)··· no lensing object · · ·
SDSS J081502.51+262804.2 1.286 18.56
SDSS J081502.28+262804.7 ··· 19.53 3.11 · · · DA different SED · · ·
SDSS J081617.73+293639.6 0.768 18.24
SDSS J081618.06+293643.7 ··· 19.51 5.92 UF(K)··· no lensing object · · ·
SDSS J081624.72+324928.9 1.259 18.59
SDSS J081624.08+324931.0 ··· 18.39 8.44 · · · DA QSO+star · · ·
SDSS J081812.94+511923.4 2.098 18.98
SDSS J081813.02+511917.5 ··· 19.80 6.05 · · · DA different SED · · ·
SDSS J081904.56+035455.6 0.886 18.44
SDSS J081904.40+035455.8 ··· 19.66 2.41 WF(i)··· no lensing object · · ·
SDSS J082046.24+035742.1 1.574 18.57
SDSS J082046.67+035740.9 (1.870) 19.13 6.44 · · · DA QSO pair · · ·
SDSS J083216.99+040405.2 1.115 18.89
SDSS J083217.11+040403.8 (1.115) 19.97 2.23 Te(V, I ),UF(K) EF SDSS Lens 2
SDSS J083349.46+440952.7 2.011 19.03
SDSS J083349.19+440954.0 ··· 19.89 3.17 UF(K)··· no lensing object · · ·
SDSS J083557.50+341455.4 1.328 18.91
SDSS J083556.32+341504.2 (1.505) 19.44 17.08 UF(K) DA QSO pair · · ·
12 INADA ET AL.
TABLE 3 — Continued
Object zaicor bθSDSScimagedspecdcomment Ref.
SDSS J083649.55+484154.0 1.710 18.04
SDSS J083649.45+484150.0 (0.657) 19.09 4.10 · · · · · · QSO pair 1
SDSS J084137.51+032830.0 1.585 19.00
SDSS J084137.75+032837.1 ··· 19.88 7.93 · · · DA QSO+star · · ·
SDSS J090809.13+444138.9 1.722 17.78
SDSS J090809.45+444158.6 ··· 18.70 20.03 · · · DA QSO+star · · ·
SDSS J090955.54+580143.2 1.712 18.97
SDSS J090956.50+580140.5 (1.712) 20.18 8.07 WF(i) DA QSO pair, no lensing ob ject · · ·
SDSS J092024.21+030636.0 1.363 18.86
SDSS J092024.01+030650.9 (1.450) 19.56 15.20 · · · DA QSO pair · · ·
SDSS J092151.55+524559.7 1.991 18.98
SDSS J092153.00+524551.4 ··· 20.17 15.59 · · · DA different SED · · ·
SDSS J092248.35+515611.8 1.825 18.49
SDSS J092246.22+515614.5 ··· 18.23 19.82 · · · DA QSO+star · · ·
SDSS J093336.57+620521.8 2.145 19.10
SDSS J093336.59+620509.3 ··· 19.52 12.55 · · · DA QSO+star · · ·
SDSS J094309.66+103400.6 1.239 18.62
SDSS J094309.36+103401.3 (1.430) 19.60 4.57 · · · EF QSO pair · · ·
SDSS J094510.75+472448.8 1.952 18.90
SDSS J094510.88+472435.9 (0.560) 20.02 12.92 · · · DA QSO pair · · ·
SDSS J095224.84+064732.0 2.186 18.08
SDSS J095225.25+064742.8 ··· 18.50 12.41 · · · DA QSO+star · · ·
SDSS J095711.08+640548.6 1.338 18.62
SDSS J095711.22+640602.7 (1.288) 19.86 14.11 · · · DA QSO pair · · ·
SDSS J095841.15+385629.9 1.639 18.94
SDSS J095839.67+385621.9 ··· 18.99 18.98 · · · DA different SED · · ·
SDSS J100034.17+540628.6 1.212 18.64
SDSS J100034.86+540641.4 (1.220) 19.14 14.19 Te(I) DA QSO pair, no lensing object · · ·
SDSS J100120.84+555349.5 1.413 16.67
SDSS J100120.69+555355.6 (1.405) 16.81 6.16 · · · · · · known lens (Q0957) 4
SDSS J100128.61+502756.8 1.839 17.31
SDSS J100128.35+502758.4 (1.838) 17.68 2.93 8k(V, R, I ),SP(z) DA SDSS Lens 3
SDSS J100304.55+444335.9 1.630 18.80
SDSS J100304.61+444338.8 ··· 19.93 2.95 8k(V, I )··· no lensing object · · ·
SDSS J100434.91+411242.8 1.740 18.84
SDSS J100434.80+411239.2 (1.734) 18.41 3.76 SC(g, r, i, z),SP(r) DA,LR SDSS Lens (component A) 5,6
SDSS J100433.82+411234.8 (1.734) 19.34 14.71 SC(g , r, i, z),SP(r) DA,LR SDSS Lens (component C) 5,6
SDSS J101930.41+522411.7 1.961 18.24
SDSS J101930.17+522413.2 ··· 19.47 2.70 8k(V),Op(I)··· no lensing object · · ·
SDSS J103423.11+623340.3 1.406 18.76
SDSS J103423.16+623343.3 ··· 19.86 3.03 8k(V),Op(I)··· no lensing object · · ·
SDSS J103519.36+075258.0 1.215 19.03
SDSS J103519.22+075256.3 (1.218) 20.11 2.66 8k(I),QU(H)··· QSO pair, no lensing object 1
SDSS J103716.94+014126.3 1.576 19.05
SDSS J103717.79+014121.0 ··· 18.68 13.95 · · · DA QSO+star · · ·
SDSS J103724.73+580513.0 1.517 17.39
SDSS J103724.20+580514.1 ··· 17.99 4.36 · · · DA QSO+star · · ·
SDSS J103950.00+593511.6 1.560 18.92
SDSS J103949.51+593505.9 ··· 19.72 6.81 · · · DA different SED · · ·
SDSS J104213.61+061942.0 1.559 18.67
SDSS J104214.22+061959.1 (1.620) 19.60 19.41 · · · DA QSO pair · · ·
SDSS J104658.02+471726.9 1.532 18.58
SDSS J104657.05+471737.4 (2.060) 19.24 14.43 · · · DA QSO pair · · ·
SDSS J110536.22+031952.4 0.922 18.15
SDSS J110536.29+031955.3 ··· 18.92 3.06 · · · DA different SED · · ·
SDSS J110932.13+531635.7 0.982 18.72
SDSS J110932.49+531635.5 (1.350) 19.00 3.25 · · · DA QSO pair · · ·
SDSS J112456.26+090848.8 1.649 19.03
SDSS J112455.65+090849.7 ··· 19.43 9.16 Op(I)··· no lensing object · · ·
SDSS J113813.76+024548.4 1.639 18.85
SDSS J113814.17+024556.3 ··· 17.64 10.10 · · · DA QSO+star · · ·
SDSS J114306.19+025402.1 1.605 19.02
SDSS J114305.85+025413.1 ··· 19.89 12.14 Op(I)··· no lensing object · · ·
SDSS J114546.22+032251.9 2.008 19.01
SDSS J114546.54+032236.7 (1.773) 19.94 15.93 · · · · · · QSO pair 1
SDSS J115940.79−003203.5 2.033 17.62
SDSS J115940.40−003213.9 ··· 18.68 11.83 · · · DA different SED · · ·
SDSS J120457.12+043241.0 1.187 18.28
SDSS J120456.64+043245.7 ··· 19.50 8.55 Op(I)··· no lensing object · · ·
SDSS J120523.68−033618.2 1.495 18.80
SDSS J120522.75−033614.6 ··· 17.54 14.32 · · · DA QSO+star · · ·
SDSS J121002.47+495312.7 1.618 18.96
SDSS J121002.28+495253.1 (1.554) 20.06 19.74 Op(I) DA QSO pair, no lensing object · · ·
SDSS J121636.02+543159.2 1.894 19.01
SDSS J121637.35+543158.2 (1.780) 20.03 11.57 · · · DA QSO pair · · ·
SDSS QUASAR LENS SEARCH. II. 13
TABLE 3 — Continued
Object zaicor bθSDSScimagedspecdcomment Ref.
SDSS J121647.22+495720.4 1.200 18.34
SDSS J121647.62+495710.6 (1.195) 19.55 10.53 Op(I) DA QSO pair, no lensing object · · ·
SDSS J122126.47+572414.0 1.959 18.99
SDSS J122126.69+572416.6 ··· 20.27 3.12 8k(V),Op(I)··· no lensing object · · ·
SDSS J123504.17+020743.7 2.169 18.77
SDSS J123505.16+020734.8 ··· 19.51 17.31 · · · DA QSO+star · · ·
SDSS J123558.55−023503.3 2.064 18.36
SDSS J123558.36−023503.6 ··· 17.69 2.80 · · · DA QSO+star · · ·
SDSS J124315.47−012120.8 1.864 18.70
SDSS J124314.68−012135.5 ··· 18.83 18.88 Op(I) DA QSO+star · · ·
SDSS J125029.25+025747.9 0.610 18.25
SDSS J125028.62+025745.1 ··· 17.11 9.86 · · · DA QSO+star · · ·
SDSS J125422.00+610421.6 2.055 18.91
SDSS J125420.54+610435.6 (2.041) 19.27 17.61 · · · · · · QSO pair 1
SDSS J131008.97+660350.3 1.747 18.90
SDSS J131008.54+660349.6 ··· 20.04 2.74 8k(I)··· no lensing object · · ·
SDSS J131505.88+590157.5 1.933 17.50
SDSS J131507.15+590150.7 ··· 17.59 11.89 · · · DA QSO+star · · ·
SDSS J132732.66−031645.7 1.274 19.06
SDSS J132733.00−031644.3 ··· 19.85 5.31 · · · DA different SED · · ·
SDSS J133303.35+000451.3 1.511 19.05
SDSS J133302.65+000437.8 ··· 18.07 17.14 · · · DA QSO+star · · ·
SDSS J133945.37+000946.1 1.872 18.85
SDSS J133945.06+001004.4 (0.978) 19.85 18.85 · · · · · · QSO pair, from 2dF data 7
SDSS J134702.84+032233.4 1.710 18.96
SDSS J134703.70+032238.4 ··· 18.87 13.80 WF(i)··· no lensing object · · ·
SDSS J134918.53−015734.8 1.586 19.09
SDSS J134919.32−015736.9 ··· 19.31 12.01 Op(I)··· no lensing object · · ·
SDSS J135418.26+585935.9 0.791 19.00
SDSS J135418.10+585951.7 ··· 19.14 15.82 · · · DA different SED · · ·
SDSS J135752.15+051544.7 1.595 18.92
SDSS J135751.03+051545.5 ··· 20.13 16.78 · · · DA different SED · · ·
SDSS J140016.87+542131.7 1.479 18.99
SDSS J140016.19+542136.6 (1.810) 19.84 7.72 Op(I) DA QSO pair · · ·
SDSS J140326.90+561307.3 1.075 17.09
SDSS J140326.97+561305.5 ··· 18.26 1.95 8k(I)··· QSO+galaxy+galaxy · · ·
SDSS J142327.05+591819.8 1.672 19.06
SDSS J142326.24+591833.5 ··· 18.25 15.08 · · · DA QSO+star · · ·
SDSS J142359.48+545250.8 1.409 18.31
SDSS J142400.00+545248.7 (0.610) 19.56 4.94 · · · DA QSO pair · · ·
SDSS J142541.12+021018.7 1.665 19.04
SDSS J142542.27+021010.1 ··· 19.77 19.27 Op(I)··· no lensing object · · ·
SDSS J142944.25+042202.6 1.148 18.86
SDSS J142944.18+042205.6 ··· 19.69 3.20 Op(I),8k(I)··· no lensing object · · ·
SDSS J143433.45+613752.7 1.818 19.04
SDSS J143432.68+613737.0 (0.427) 19.21 16.59 WF(i) DA QSO pair · · ·
SDSS J143735.94+033334.3 2.122 18.63
SDSS J143736.44+033326.9 ··· 19.13 10.55 · · · DA different SED · · ·
SDSS J143817.62+031908.6 1.483 19.01
SDSS J143817.02+031901.9 ··· 20.27 11.24 · · · DA QSO+star · · ·
SDSS J144104.91+044348.4 1.112 18.42
SDSS J144104.58+044350.8 ··· 18.69 5.48 WF(i)··· no lensing object · · ·
SDSS J144145.09+023743.0 1.160 19.07
SDSS J144145.09+023744.8 ··· 19.46 1.75 · · · MS QSO+star · · ·
SDSS J145455.89+420306.0 1.598 19.01
SDSS J145455.73+420256.1 ··· 19.60 10.04 WF(i) DA QSO+star · · ·
SDSS J150319.42+475206.8 0.757 17.92
SDSS J150319.46+475209.7 ··· 18.74 2.84 8k(I)··· no lensing object · · ·
SDSS J150503.46−022324.4 2.097 18.61
SDSS J150503.70−022308.6 ··· 19.21 16.23 · · · DA QSO+star · · ·
SDSS J150533.86+013201.8 1.512 18.67
SDSS J150534.19+013145.7 ··· 18.07 16.84 · · · DA QSO+star · · ·
SDSS J151519.40−001103.4 1.564 19.01
SDSS J151519.94−001049.3 ··· 19.45 16.36 SC(I)··· no lensing object · · ·
SDSS J152130.70+023915.1 2.127 18.71
SDSS J152129.83+023917.9 ··· 19.08 13.33 · · · DA QSO+star · · ·
SDSS J152510.00+602828.1 1.337 19.03
SDSS J152510.45+602833.3 ··· 19.25 6.19 Op(I)··· no lensing object · · ·
SDSS J153518.78+582912.2 1.527 19.06
SDSS J153518.86+582925.9 ··· 19.62 13.70 Op(I) DA QSO+star · · ·
SDSS J153559.97+430819.0 1.620 18.67
SDSS J153559.26+430833.1 ··· 18.57 16.01 · · · DA QSO+star · · ·
SDSS J154107.47−003716.0 0.755 17.57
SDSS J154107.21−003711.8 ··· 18.07 5.65 · · · MS QSO+star 8
SDSS J154148.81+523051.9 2.054 19.01
14 INADA ET AL.
TABLE 3 — Continued
Object zaicor bθSDSScimagedspecdcomment Ref.
SDSS J154148.93+523053.6 ··· 19.59 1.94 8k(I)··· no lensing object · · ·
SDSS J155723.93+492607.5 2.195 18.42
SDSS J155723.79+492551.1 ··· 19.69 16.46 · · · DA different SED · · ·
SDSS J160305.94+272100.9 1.620 18.14
SDSS J160307.00+272059.3 ··· 18.43 14.21 · · · DA QSO+star · · ·
SDSS J160547.59+511330.2 1.785 19.09
SDSS J160546.66+511322.6 (1.844) 18.46 11.63 · · · · · · QSO pair 1
SDSS J160914.86+380728.1 1.126 18.64
SDSS J160914.85+380730.0 ··· 18.68 1.93 8k(I)··· no lensing object · · ·
SDSS J161953.24+351321.8 1.901 18.64
SDSS J161953.45+351323.5 ··· 19.50 3.13 8k(I)··· no lensing object · · ·
SDSS J161952.82+351315.4 ··· 19.89 8.20 8k(I)··· no lensing object · · ·
SDSS J162602.40+334030.0 1.541 18.77
SDSS J162603.61+334025.9 ··· 19.97 15.65 WF(i)··· no lensing object · · ·
SDSS J162902.59+372430.8 0.926 19.03
SDSS J162902.63+372435.1 (0.906) 19.37 4.35 NR(K′)··· QSO pair, no lensing object 1
SDSS J165248.93+352134.1 1.498 18.33
SDSS J165250.29+352141.6 ··· 19.20 18.26 WF(i)··· no lensing object · · ·
SDSS J165459.71+305208.3 1.971 19.08
SDSS J165459.12+305158.5 ··· 19.41 12.36 · · · DA QSO+star · · ·
SDSS J171334.41+553050.3 1.276 18.54
SDSS J171335.03+553047.9 ··· 18.59 5.84 · · · DA QSO+star · · ·
SDSS J172633.52+530300.4 0.654 19.00
SDSS J172633.44+530302.0 ··· 19.07 1.70 8k(I)··· no lensing object · · ·
SDSS J172806.78+582039.2 2.011 19.06
SDSS J172808.74+582040.0 ··· 20.17 15.46 WF(i) DA QSO+star · · ·
SDSS J203845.35+005532.1 1.903 18.53
SDSS J203846.08+005541.4 ··· 19.47 14.32 WF(i) DA no lensing object, different SED · · ·
SDSS J203955.67−054102.8 1.460 18.90
SDSS J203955.63−054044.7 ··· 19.80 18.08 WF(i)··· no lensing object · · ·
SDSS J204030.52−003015.9 1.549 18.84
SDSS J204030.71−003010.5 ··· 18.33 6.04 WF(i)··· no lensing object · · ·
SDSS J204113.41−060158.5 1.432 18.63
SDSS J204114.12−060149.0 0.830 19.56 14.19 Op(I) DA QSO pair · · ·
SDSS J210706.22−062506.7 1.577 18.91
SDSS J210706.31−062503.2 ··· 19.56 3.71 WF(i)··· no lensing object · · ·
SDSS J210946.73+105601.0 1.628 18.57
SDSS J210946.23+105559.5 ··· 18.39 7.53 · · · DA QSO+star · · ·
SDSS J211102.60+105038.3 1.897 18.87
SDSS J211102.41+105047.5 (1.897) 19.02 9.67 Te(I) DA QSO pair (different SED) · · ·
SDSS J211230.33−063332.1 1.554 18.94
SDSS J211229.31−063331.4 (0.551) 19.71 15.21 · · · · · · QSO pair 1
SDSS J211610.83+111429.0 1.076 18.46
SDSS J211610.58+111423.2 ··· 19.23 6.83 · · · DA different SED · · ·
SDSS J212429.83−004727.0 1.614 18.96
SDSS J212430.90−004725.2 ··· 19.11 16.26 · · · DA different SED · · ·
SDSS J212906.23−071613.3 1.213 18.57
SDSS J212906.32−071612.1 ··· 17.81 1.79 · · · · · · QSO+star 8
SDSS J212956.44−005150.4 1.112 18.98
SDSS J212956.56−005152.4 ··· 20.04 2.68 WF(i)··· no lensing object · · ·
SDSS J213414.01−004533.1 1.535 18.77
SDSS J213414.17−004514.6 ··· 18.44 18.59 · · · DA different SED · · ·
SDSS J213639.11+114731.8 1.518 19.04
SDSS J213640.40+114736.9 ··· 18.13 19.47 · · · DA different SED · · ·
SDSS J220256.32−092556.7 0.723 18.31
SDSS J220257.01−092602.3 ··· 18.80 11.71 · · · DA different SED · · ·
SDSS J222504.14+123814.5 1.549 19.04
SDSS J222503.32+123815.1 ··· 18.15 12.08 · · · DA QSO+star · · ·
SDSS J222822.17−005943.5 2.172 18.62
SDSS J222822.18−005949.3 ··· 19.14 5.82 · · · DA QSO+star · · ·
SDSS J223219.23+140017.0 0.725 18.87
SDSS J223219.42+140012.6 ··· 19.06 5.16 · · · DA QSO+star · · ·
SDSS J230250.85+143203.2 0.654 18.99
SDSS J230250.90+143158.5 ··· 20.17 4.71 · · · DA different SED · · ·
SDSS J230951.18−094016.3 1.572 19.07
SDSS J230950.59−093958.3 ··· 20.32 20.04 · · · DA different SED · · ·
SDSS J231152.83+145455.0 1.261 18.98
SDSS J231152.38+145507.5 ··· 19.88 14.17 · · · · · · QSO+star 1
SDSS J235108.66+134322.6 1.218 18.81
SDSS J235108.70+134320.8 ··· 19.92 1.86 WF(i)··· no lensing object · · ·
SDSS J235924.73+152541.6 1.574 19.01
SDSS J235924.84+152544.3 ··· 19.98 3.09 WF(i)··· no lensing object · · ·
SDSS QUASAR LENS SEARCH. II. 15
TABLE 3 — Continued
Object zaicor bθSDSScimagedspecdcomment Ref.
References. — (1) Hennawi et al. 2006; (2) Oguri et al. 2007b; (3) Oguri et al. 2005; (4) Walsh et al. 1979; (5) Inada et al. 2003b;
(6) Oguri et al. 2004a; (7) Croom et al. 2004; (8) Pindor et al. 2006.
Note. — Two candidates that are identified by the morphological selection algorithm as well, SDSS J073406.75+273355.6 and
SDSS J133534.79+011805.5, are listed in Table 2.
aRedshifts from the SDSS DR3 quasar catalog and the follow-up observations (in parentheses) bi-band PSF magnitudes with the
Galactic extinction correction from the SDSS DR3 quasar catalogcImage separations in units of arcsec between two components from
the SDSS imaging data.dInstruments (and filters) used for the follow-up observations. 8k: UH8k at UH88, QU: QUIRC at UH88, Op:
Optic at UH88, WF: WFGS2 at UH88, Te: Tek2048 at UH88, DA: DIS III at ARC 3.5m, SP: SPIcam at ARC 3.5m, LR: LRIS at Keck,
NR: NIRC at Keck, UF: UFTI at UKIRT, SC: Suprime-Cam at Subaru, MS: MMT spectrograph, EF: EFOSC2 at ESO 3.6m.
TABLE 4
LENSED QUASARS FROM THE SDSS DR3: STATISTICAL SAMPLE
Object Nimg zaθmax bfior fIcComment Ref.
SDSS J0246−0825 2 1.682 1.04 0.34 SDSS lens 1
SDSS J0913+5259 2 1.377 1.14 0.70 known lens SBS 0909+523 2, 3
SDSS J0924+0219 4 1.524 1.78 0.43 SDSS lens 4
SDSS J1001+5027 2 1.838 2.86 0.72 SDSS lens 5
SDSS J1001+5553 2 1.405 6.17 0.94 known lens Q0957+561 3, 6
SDSS J1004+4112 5 1.732 14.62 0.23 SDSS lens 7, 8
SDSS J1021+4913 2 1.720 1.14 0.40 SDSS lens 9
SDSS J1226−0006 2 1.121 1.24 0.45 SDSS lens 10
SDSS J1332+0347 2 1.445 1.14 0.70 SDSS lens 11
SDSS J1335+0118 2 1.570 1.56 0.37 SDSS lens 12
SDSS J1524+4409 2 1.210 1.67 0.56 SDSS lens 13
References. — (1) Inada et al. 2005; (2) Oscoz et al. 1997; (3) CASTLES webpage (C. S. Kochanek et al.,
http://cfa-www.harvard.edu/castles/.); (4) Inada et al. 2003a; (5) Oguri et al. 2005; (6) Walsh et al. 1979; (7) Inada et al. 2003b; (8)
Oguri et al. 2004a; (9) Pindor et al. 2006; (10) Inada et al. 2007b; (11) Morokuma et al. 2007; (12) Oguri et al. (2004b); (13) Oguri et al.
2007b.
aRedshifts from the follow-up observationsbMaximum image separations in units of arcsec.cFlux ratios between the brightest lensed
image and the farthest lensed image from the brightest image, in the I- or i-band images.
TABLE 5
ADDITIONAL LENSED QUASARS IN THE SDSS DR3 QUASAR
CATALOG
Object Nimg zaθbfior fIcComment RejectdRef.
SDSS J0134−0931 5 2.216 0.68 0.03 known lens PMN J0134−0931 too small θ1, 2, 3
SDSS J0145−0945 2 2.719 2.23 0.15 known lens Q0142−100 z > 2.2, fI<10−0.53, 4
SDSS J0813+2545 4 1.500 0.91 0.06 known lens HS 0810+2554 by GALFIT fitting 3, 5
SDSS J0832+0404 2 1.115 1.98 0.22 SDSS lens fI<10−0.56
SDSS J0903+5028 2 3.584 2.80 0.46 SDSS lens z > 2.2 7
SDSS J0911+0550 4 2.800 3.26 0.41 known lens RX J0911+0551 z > 2.2 3, 8
SDSS J1138+0314 4 2.442 1.44 0.35 SDSS lens z > 2.2 3, 9
SDSS J1155+6346 2 2.890 1.83 0.50 SDSS lens z > 2.2 3, 10
SDSS J1406+6126 2 2.126 1.98 0.58 SDSS lens icor >19.1 11
SDSS J1633+3134 2 1.511 0.66 0.30 known lens FBQ 1633+3134 θ < 1′′,fI<10−0.512
SDSS J1650+4251 2 1.547 1.20 0.17 SDSS lens by GALFIT fitting 13
References. — (1) Winn et al. 2002; (2) Gregg et al. 2002; (3) CASTLES webpage (C. S. Kochanek et al.,
http://cfa-www.harvard.edu/castles/.); (4) Surdej et al. 1987; (5) Reimers et al. 2002; (6) Oguri et al. 2007b; (7) Johnston et al. 2003;
(8) Bade et al. 1997; (9) Burles et al. 2007; (10) Pindor et al. 2004; (11) Inada et al. 2007a; (12) Morgan et al. 2001; (13) Morgan et al.
2003.
Note. — See text for the selection of each lensed quasar.
aRedshifts from follow-up observations.bMaximum image separations in units of arcsec.cFlux ratios between the brightest lensed image
and the farthest lensed image from the brightest image, in the I- or i-band images.dThe reason that each lens is excluded from the
statistical sample.
