Spectroscopy of lensing galaxies in the GTC era

0.14 MB·English

by  Vyacheslav N. Shalyapin

To appear in “Fourth Science with the GTC (2011)” RevMexAA(SC)
SPECTROSCOPY OF LENSING GALAXIES IN THE GTC ERA
1 2
Vyacheslav N. Shalyapin and Luis J. Goicoechea
RESUMEN
Estamos usando OSIRIS para obtener espectros de galaxias d´ebiles y pr´oximas a cu´asares mu´ltiples, e inicial-
2 mente nos hemos concentrado en los campos de HE 1413+117 (Hoja de Tr´ebol) y SDSS 1116+4118. En esta
1 contribuci´on, presentamos observaciones de dos galaxias cercanas a la Hoja de Tr´ebol, mostrando que una de
0 ellas no contribuye a la cizalla externa del sistema lente gravitatoria. Tambi´en analizamosy discutimos espec-
2
tros de la galaxia candidata a lente principal en SDSS 1116+4118. Si SDSS 1116+4118 es un sistema lente,

n nuestros espectros indican que la lente principal no puede estar formada por una u´nica galaxia dominante.
a
J
ABSTRACT

9
We are using OSIRISto obtain spectra of faint galaxiesclose to multiply imagedquasars. We initially focused
1
on the fields of HE 1413+117 (Cloverleaf quasar) and SDSS 1116+4118. In this contribution, we present

] long-slit spectroscopy of two galaxies in the southwest of the Cloverleaf, and show that one of them makes
A
a negligible contribution to the external shear of the gravitational lens system. Spectra of the main lensing
G
galaxy candidate in SDSS 1116+4118 are also analysed and discused. If gravitational lensing is causing the
. quasar image splitting, our spectra reveal that the main lens can not consist of only one dominant galaxy.
h
p Key Words: Galaxies: general — Gravitational lensing: strong — Techniques: spectroscopic
-
o
r 1. FIRST TARGETS AND GOALS these targets to the external shear on the Clover-
t leaf. We have also taken long-slit spectra of the
s Time delays between multiple images of lensed
a galaxybetweenthepairofquasarsSDSS1116+4118
quasars can be used in lensing mass reconstructions
[ and the determination of cosmological parameters at redshift z ∼ 3. Both quasars are separated
′′
1 by 13.7, so we want to check if the galaxy pro-
(e.g., Oguri 2007). However, a spectroscopic follow-
v duces an image splitting ∆θ ∼ 14′′ for a source at
up of lensing galaxies is essential to use time delays
5 z ∼ 3 (Sa´nchez Alvaro & Rodriguez Calonge 2007;
1 to constraint lensing mass distributions or cosmol-
Ellison et al. 2007).
1 ogy (for a recent review see Schneider et al. 2006).
4 Here,wepresentthefirstobservationsofourspectro-
. 2. RESULTS AND DISCUSSION
1 scopic programme with OSIRIS on the GTC, which
0 are part of an ambitious project with the new 10.4 2.1. HE 1413+117 (Cloverleaf quasar)
2 mtelescope(Ull´an & Goicoechea2003). These2011
This year we have performed seven 2 ksec spec-
1
data of faintgalaxiesat relativelylargeangularsep-
: troscopic observations of the galaxies 1 and 2 in the
v arations from lensed quasars have been obtained in
southwest of the Cloverleaf quasar, using the low-
i average seeing conditions or even worse.
X resolution grism R300R (λ/∆λ = 348) and placing
We haverecentlymeasuredthe threetime delays
r the slit along the line joining both galaxies (e.g.,
a of the quadruple quasar HE 1413+117 (Cloverleaf
MacLeod et al. 2009). From the first five datasets
quasar; Goicoechea & Shalyapin 2010). The exter-
of each galaxy corresponding to March 31 and June
nal shear strength in this lens system is γ ∼ 0.1, 6 (mean seeing of ∼ 1′.′5), we infer the combined
and the shear direction points towards the three
spectra that appear in Figure 1. The galaxy No. 2
field galaxies 1, 2, and H2 (MacLeod et al. 2009;
(R ∼ 24 mag) has a noisy spectrum that only in-
Goicoechea & Shalyapin 2010). Thus, we have ob- cludes one strong emission line in the 5000–8000 ˚A
tained OSIRIS/GTC spectra of the galaxies 1 and
region. Fortunately, the spectrum of the galaxy No.
2, which allow us to discuss the contribution of
1(R∼23mag)showstwostrongemissionlinesthat
1Institute for Radiophysics and Electronics, National we identify with the OII(λ3727) and OIII(λ4959,
Academy of Sciences of Ukraine, 12 Proskura St., 61085 5007), leading to z = 0.57 ± 0.01.
Kharkov,Ukraine([email protected]). Emission line galaxies at z ∼ 0.5–0.6 have an
2Departamento de F´ısica Moderna, Universidad de −1
Cantabria,Avda. deLosCastross/n,39005Santander,Spain average rotation velocity of 175 km s . This Vrot
([email protected]). is also measured in some relatively bright (R ∼ 21
1
2 SHALYAPIN & GOICOECHEA
Fig.1. Spectraofthegalaxies1and2aroundtheClover- Fig. 2. Spectra of the candidatefor main lensing galaxy
leafquasar. Verticaldashedanddottedlinescorrespond of SDSS 1116+4118. The darkest line represents the
to emission and absorption lines at z = 0.57, respec- spectrum along the major axis of the galaxy, while the
tively. The threegray highlighted regions are associated other line describes the spectrum along its minor axis.
with prominent atmospheric and night sky features. The gray highlighted regions have the same meaning as
in Fig. 1,and thevertical markscorrespond toemission
mag) galaxies at z ∼ 0.5–0.6 (e.g., Bamford et al. and absorption lines at z = 0.195.
2005). Therefore, we consider a singular isother-
mal sphere (SIS) model and an upper limit Vrot ≤ age splitting is ∆θ ∼ 6′′. This extreme value is less
−1 than half of the angular separationbetween the two
175 km s to describe the halo mass of the
distant quasars.
galaxy No. 1. If the main lens redshift was z
Basedonobservationsmade with the GranTele-
= 0.57, then the shear from this galaxy would be
scopio Canarias (GTC), instaled in the Spanish Ob-
less than 0.02. However, the main lens redshift is
servatorio del Roque de los Muchachos of the Insti-
likely about 2 (Goicoechea & Shalyapin 2010), and
tuto de Astrofsica de Canarias, in the island of La
thus, the effective shear should be less than 0.002
Palma.
(Momcheva et al. 2006). This shear strength is sig-
nificantlylowerthantheexternalshearinthesystem REFERENCES
(γ ∼ 0.1).
Bamford, S. P., Milvang-Jensen, B., Arag´on-Salamanca,
A., & Simard, L. 2005, MNRAS,361, 109
2.2. SDSS 1116+4118
Ellison, S.L.,Hennawi,J.F.,Martin,C.L.,&Sommer-
We have observed the lens system candidate on Larsen, J. 2007, MNRAS,378, 801
March 31 and April 7, 2011. The low-resolution Giovanelli,R.,Haynes,M.P.,Rubin,V.C.,&KentFord,
spectraalongthemajorandminoraxesofthegalaxy W. 1986, ApJ,301, L7
between the pair of quasars at z ∼ 3 are displayed Goicoechea, L. J., & Shalyapin, V. N. 2010, ApJ, 708,
in Figure 2. The exposure times/seeing values are 995
′′ ′′ MacLeod,C.L.,Kochanek,C.S.,&Agol,E.2009,ApJ,
2.0 ksec/2.00 (major axis) and 1.2 ksec/2.35 (mi-
699, 1578
nor axis), and both spectra are consistent with each
Momcheva,I.,Williams,K.,Keeton,C.,&Zabludoff,A.
other. From the Kinney-Calzetti templates, we con-
2006, ApJ, 641, 169
clude that the candidate for main lensing galaxy
Oguri, M. 2007, ApJ, 660, 1
(R∼ 19 mag; Sa´nchez Alvaro & Rodriguez Calonge
Rigopoulou,D.,Franceschini,A.,Aussel,H.,Genzel,R.,
2007) is a spiral (Sb?) at z = 0.195 ± 0.002. Thatte, N., & Cesarsky, C. J. 2002, ApJ, 580, 789
Assuming a SIS model and a standard rotation S´anchez Alvaro, E., & Rodriguez Calonge, F. J. 2007,
velocity(Vrot ≤300kms−1),thelensinggalaxycan- astro-ph/0701537
didatecanonlygenerateanimagesplitting ∆θ ≤2′′ Schneider,P.,Kochanek,C.S.,&Wambsganss, J.2006,
for a source at z ∼ 3. This is well below the ob- In: Gravitational Lensing: Strong, Weak & Micro.
servedseparationbetweenthe pair of quasars. Even Eds. G. Meylan, P. Jetzer, & P. North. (Berlin:
for an extremely massive spiral with Vrot ∼ 500 km Springer-Verlag)
−1 Ull´an,A.,&Goicoechea,L.J.2003,RevistaMexicanade
s ,e.g.,UGC12591(Giovanelli et al.1986)orISO-
Astronom´ıa y Astrof´ısica Conference Series, 16, 317
HDFS27(Rigopoulou et al.2002),thepredictedim-