Strong lensing analysis of Abell 1689 from
deep Advanced Camera for Surveys imaging
Narciso Benitez
Instituto de
Astrofisica de
Andalucia (CSIC)
The ACS Science, Engineering, and IT Team
Principal Investigator
Deputy Principal Investigator
Project Scientist
Detector Scientist
T. Allen
JHU
K. Anderson JHU
D. Ardila
JHU
F. Bartko
Bartko Sci.
N. Benitez
IAA
J. Blakeslee JHU
R. Bouwens UCLick
T. Broadhurst Tel Aviv Univ.
R. Brown
STScI
C. Burrows
Seattle
E. Cheng Conceptual Analytics
D. Coe
JHU
N. Cross
JHU
P. Feldman
JHU
A. Framarini
M. Franx
B. Frye
D. Golimowski
T. Goto
C. Gronwall
N. Homier
L. Infante
M.-K. Jee
R. Kimble
J. Krist
A. Martel
D. Magee
W. McCann
ACS Technical Officer
Asst Tech Officer
ACS Program Manager
Systems Engineer
Systems Engineer
Ball Systems Engineer
P. Sullivan
D. Campbell
P. Volmer
J. Crocker
M. Rafal
R. Woodruff
H. Ford
G. Illingworth
G. Hartig
M. Clampin
JHU
U. Leiden
Princeton
JHU
JHU
PSU
JHU
PUC
JHU
GSFC
STScI
JHU
UCLick
JHU
JHU
UCLick
STScI
STScI
F. Menanteau
G. Meurer
G. Miley
V. Motta
R. Overzier
M. Postman
M. Sirianni
W. Sparks
H. Tran
Z. Tsvetanov
R. White
K. Zekser
A. Zirm
W. Zheng
GSFC
GSFC
Ball Aerospace
Lockheed Martin
NRAO
Boeing
JHU
JHU
Leiden U.
PUC/JHU
Leiden U.
STScI
JHU
STScI
Keck
JHU
STScI
JHU
Leiden U.
JHU
ACS: Goal >10x WFPC2
(2x area, 5x throughput)
4k × 4k, 0.05″ pixels
Over-coated Silver
1k × 1k, 0.025 ″ pixels
on the Mirrors
MgF2 + Al on the
Mirrors
ABELL 1689
•Discovered in 1958
by George Abell,
z=0.18
•Lens features first
noted in 1990 by
Tyson
•One of the most
massive galaxy
clusters in the
Universe
•The largest Einstein
ring in the sky (50”)
•One of the most
heavily studied and
observed galaxy
clusters
•Discrepancy
between X-ray and
lensing mass
ABELL 1689
Narciso Benitez (IAA)
Tom Broadhurst (TAU)
Dan Coe (JHU)
Keren Sharon (TAU)
Rick White (STScI)
Kerry Zekser (JHU)
Holland Ford (JHU)
Garth Illingworth(UC)
Broadhurst et al. 2004, ApJ,
in press astro-ph/0409132
Filter
Telescope
Seeing
Coverage ( sq ')
Exposure
Time ( sec)
g (S DS S )
AC S
0.11"
11.8
9,600
r (S DS S )
AC S
0.10"
11.8
9,600
i (S DS S )
AC S
0.10"
11.8
12,000
z (S DS S )
AC S
0.11"
11.8
16,800
U_Johnson
Du P ont Telescope @ Las C am panas
0.93"
72.3
900
B _NOT
Nordic Optical Telescope @ La P alm a
1.10"
41.0
1,200
V_LR IS
LR IS @ Keck II
0.81"
80.1
3,600
R _LR IS
LR IS @ Keck II
0.74"
93.1
3,142
I_LR IS
LR IS @ Keck II
0.69"
88.7
3,000
Z (NB 9148)
LR IS @ Keck II
0.91"
45.0
2,997
J_S OF I
S OF I @ ES O NTT
0.87"
50.4
14,400
H_Johnson
S OF I @ ES O NTT
0.99"
44.9
10,800
Ks_S OF I
S OF I @ ES O NTT
0.82"
50.4
15,600
Credits: U - Steve Landy; JHK - Lindsay King, Chris Clidman (reduction)
Redshifts
282 Keck/VLT spectra
58 secure redshifts
(Brenda Frye)
But only 4 arc systems
with spectroscopic
redshifts; photometric
redshifts essential
Method
Method
Starting mass model: MαL
Find obvious sets of images
(by eye)
Refine model
Find more images using
improved model
(minimization done in image plane)
Method
1. Starting point
Power-law profile is
assigned to each clustermember galaxy assuming
MαL.
Ö mass distribution is
smooth on the large scale
but with small scale
structure.
A smooth componant is
generated by fitting low
order cubic spline:
represents cluster darkmatter component
The residual image used to
represent the galaxy
perturbations
Multiple image identification
zsp = 4.86
87′′
Multiple image identification
“Paired Galaxies” with Very Different Redshifts
Method
Multiple image identification
Results:
Results
>100 images in
>30 systems
(and counting…)
Results
Demagnified images identified
in center (thanks to the model!)
Results
Final surface density accurately
determined
Final
Blue: critical density
Initial (MαL)
red: critical curve
Magnification
Results
Well defined
radial critical
curve, radial
arcs are
produced.
Interior to radial
critical curve
the images are
less magnified.
Radial mass profile & magnification
Results
Solid: NFW profile (C=8,
rs=300kpc/h) – good fit.
Dashed: Singular
Isothermal – too steep,
lacks a radial critical
curve.
Cosmology
Results
/d(z=3)
After iteration a tight
relation is formed
showing clearly the
expected behaviour
for standard
cosmologies
(Ω+Λ < ~1).
High Λ excluded.
Ω,Λ=(0.1,1.2)
Ω,Λ=(1,0)
Ω,Λ=(0.3,0.7)
Ω,Λ=(0.1,0)
Results
Comparison of Mass and Light
Light profile
steeper than mass
Mass profile
hardly affected by
galaxy
contribution (even
in center for
M/L<30).
M/L rises to
~400(M/L)~
Conclusions
Deep ACS imaging has provided >100 multiply
lensed images over full radius of A1689.
mass profile constructed in great detail.
Profile is considerably shallower than singular
isothermal and consistent with NFW profile with
large C~7-9, Rs~200-300 Kpc/h – (supported by
high velocity dispersion ~1700km/s).
High M/L: ~400(M/L)~
Cosmological curvature confirmed by purely
geometric bend-angle which increases with
distance, independently supports shallow profile.
Broadhurst et. al, ApJ, in press
What’s Next?
‰ ACS will observe 5 lensing clusters with z~0.180.4
‰ Second largest program within ACS GTO (~100
orbits)
‰ Targets
• ABELL 1689 (20 orbits g,r,i,z) 2002
• MS1358+6245 (20 orbits B,g,v,r,i,z) 2004
• ABELL 2218 (25 orbits B,g,v,r,i,z) 2004
• ABELL 1703 (20 orbits, B,g,v,r,i,z) 2004
• CL0024+16 (20 orbits B,g,v,r,i,z) 2004
Postscript: questions and answers
G. Soucail: How sensitive is your model to the
assumption of constant M/L for the individual
galaxies?
Answer: The “average” M/L is left to vary as a free
parameter. Allowing the M/L for individual
galaxies to change would probably improve the fit,
but at the cost of adding several dozens of
parameters to the model description, so this is an
option that we have not explored. In any case, one
does not expect great variations in the M/L ratio
for the cluster early types which form the bulk of
the lensing galaxies.
Postscript: questions and answers
M. López-Caniego: From our work on A1689, the existence of
radial arcs implies a soft core dark matter distribution. Does
your model reproduce these radial arcs? Can you exclude a
softened isothermal profile?
Answer: Our model does reproduce the radial arcs. The
softened isothermal profile is disfavored by the data, but
cannot be excluded at a high significance level.