Environments of Strong Gravitational Lenses · Which strong lenses? Observer Quasar Lens galaxy z ~...
Transcript of Environments of Strong Gravitational Lenses · Which strong lenses? Observer Quasar Lens galaxy z ~...
Environments of Strong Gravitational Lenses
( An Inconvenient Truth )
Ivelina Momcheva(University of Arizona)
In collaboration with: Ann Zabludoff (Arizona), Kurtis Willams (Texas), Chuck Keeton (Rutgers), Catherine Grant (MIT), Christy Tremonty (Arizona)
Which strong lenses?
Observer
Quasar
Lens galaxy
z ~ 15
z ~ 0.10.8
I1
I2
''... I made some calculations which show that extragalactic
nebulae offer a much better chance than stars for the observation
of gravitational lens effects.''F. Zwicky, 1937, in ''Nebulae as Gravitational Lenses''
Lens equation: β=θα(θ)
θα
β
Motivation• Sample increases (SDSS
– 17 (100 expected), LSST – 1500 expected)
• Masses and shapes of DM halos
• Time delays and H0• Microlensing,
substructure and flux anomalies
Inada 2005, 2006; Oguri 2004Koopmans et al., 2006Fohlmeister et al., 2006Fohlmeister et al, 2006B2045, McKean et al., 2006
• What are the environments in which lens galaxies reside?• Lenses not isolated, > 23% in dense environments
(Keeton, Christlein & Zabludoff 2000)field ~77%groups ~20%clusters ~3%
• Biases and uncertainties (Keeton & Zabludoff, 2004)
• Both convergence κ and shear γ need to be included
But …
With shear With convergence Group included
Importance of lineofsight structures• Lineofsight structures produce large convergence κ and shear
γ (≥ 0.05 in green and yellow)
• κ adds as scalar but γ adds in quadrature, so κ rises faster.PG1115, zl = 0.31, zs = 1.7 (Momcheva et al. 2005)
Redshift offset Δ z = z_lens – z_perturber
Impa
ct p
aram
eter
b [“
]
Survey I
• 69 CASTLES lenses• Most 0.04<z<0.9• ~17 sq. deg.• 2 bands• I > 24 mag• 30 (2image) + 21 (4
image) + 10 (Ring) + 8 (other)
• 14 timedelay lenses
0.5 deg. HST12531
Survey II
• 28 lenses followed up spectroscopically
• 0.11<z<0.84• ~17,000 spectra• 32 groups confirmed• 12 (2image) + 8 (4
image) + 3 (Ring) + 5 (other)
• 8 timedelay lenses
Lens Environments
• Doubles
• Quads
• Others
B1152z=0.44
CASTLES Survey (Kochanek et al.)
Lens Environments
• Doubles
• Quads
• Others
B1152z=0.44
CASTLES Survey (Kochanek et al.)
FBQ0951z=0.24
BRI0952z=0.41
SBS1520z=0.72
B1600z=0.41
HE2149z=0.5
B1152z=0.44
B0712z=0.41
PG1115z=0.31
H1413z=0.?
B1422z=0.34
B1608z=0.63
HST14113z=0.46
B0751z=0.35
2R
MG1131z=0.8
2R
MG1654z=0.25
R
PMN2004z=?2R
B2114z=0.34
2+2
MG1549z=0.11
R
FBQ0951z=0.24
BRI0952z=0.41
SBS1520z=0.72
B1600z=0.41
HE2149z=0.5
B1152z=0.44
B0712z=0.41
PG1115z=0.31
H1413z=0.?
B1422z=0.34
B1608z=0.63
HST14113z=0.46
B0751z=0.35
2R
MG1131z=0.8
2R
MG1654z=0.25
R
PMN2004z=?2R
B2114z=0.34
2+2
MG1549z=0.11
R
Lens Environments
κgrp, γgrp > 0.05
κgrp, γgrp > 0.05
κgrp, γgrp > 0.05
Redshift z
Num
ber o
f gal
axies
Momcheva et al., 2006
Lens Environments – PG1115
κgrp, γgrp > 0.05
Redshift
Num
ber
of
gala
xies
Momcheva et al., 2006Williams et al., 2006
Lens Environments – HST14113
κgrp, γgrp > 0.05
Num
ber
of
gala
xies
Redshift
Momcheva et al., in prepWilliams et al., in prep.
Momcheva et al., 2006
κgrp, γgrp > 0.5
Redshift
Num
ber
of g
alax
iesInterloping Structures
k eff/κ
=γef
f/γ
Num
ber
of
gala
xies
Interloping structures – FBQ0951
κgrp, γgrp > 0.05
Redshift Momcheva et al., in prepWilliams et al., 2006
I mag
Results
• Characterized lens environments• 4image lenses problematic more often• ~50% of lenses in groups which affect lens
potential• ~50% along dense lines of sight• ~10 % interlopers affect lens potential
Golden Lenses?• Exclude/account for interlopers and environment
Convergence Convergence
Num
ber o
f len
ses
Num
ber o
f len
ses
The KitchenSink Model
• Include group galaxies and group halo
RA offset (arcsec)
Dec
offs
et (a
rcse
c)
PG1115, Cangi et al., in prep.
Group Evolution
• Few z>0.1 groups• Simple environments• Mergers, tidal interactions dominant• Preprocessing of cluster galaxies
E. GrebelMulchaey & Zabludoff
Observing Group Evolution Directly• z=0.25 – 0.5• Span a range of σ• BGG is early type • BGG is not the lens in all
but two cases.• There are evolved groups
but not all
RA offset (arcsec)
Dec
offs
et (a
rcse
c)
Velocity dispersion
BGG
offs
et (k
pc)
Group evolution – future work
Conclusions
• Characterized lens environments• ~50% of lenses in groups which affect lens
potential• ~10 % interlopers affect lens potential• Can we find a golden (unperturbed) lens?• Or can we guild (model) it?• New sample of intermediatez groups