binary quasars in the sloan digital sky survey joseph f. hennawi berkeley hubble symposium april 7,...
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Binary Quasars in the Sloan Binary Quasars in the Sloan Digital Sky SurveyDigital Sky Survey
Joseph F. HennawiBerkeley
Hubble SymposiumApril 7, 2005
Suspects
Naohisa Inada (Tokyo)
Masamune Oguri(Princeton)
Michael Strauss(Princeton)
Gordon Richards(Princeton)
ConclusionsConclusions
• New sample of 26 binary quasars with separations R < 50 kpc/h more than doubles the number known
• First measurement of quasar clustering on small scales 10 kpc/h < R < 400 kpc/h (proper)
• The quasar correlation function gets progressively steeper on sub-Mpc scales
• Factor of 10-30 excess clustering is detected on scales < 40 kpc/h over extrapolation of large scale power law
• Is excess clustering the hallmark of mergers and dissipative interactions which trigger quasar activity in rich environments?
An Old Problem: Excess Close PairsAn Old Problem: Excess Close Pairs
Djorgovski (1991)
• Djorgovski realized that 3 close pairs
in sample ~ 3000, implies a pair
probability P(R< 200 kpc/h) ~ 10-3
• Binary Quasar Lore– tides/mergers galaxy activated
– large R ~ 100 kpc/h no tides
– small R ~ 10 kpc/h tDF < tH
P(<
R)
Pro
bab
ilit
y of
Hav
ing
a C
omp
anio
n
R [kpc/h] Comoving Transverse Separation
• Could these be strong lenses?
– No corresponding radio population
– Requires dark/exotic mass concentration
– “We don’t expect splittings this large . . . .”
Small Scale Quasar ClusteringSmall Scale Quasar Clustering
• Fiber Collisions: Optical fibers can only be packed so tightly – For 2dF: No pairs with < 35”– For SDSS: No pairs with < 55”
• Shot Noise– Volume decreases faster than the
correlation function increases
Proper Mpc/h
0.4 101 4 40
Comoving Mpc/h
Solutions1. Wait for next generation all sky (i < 21)spectroscopic survey of ~ 106 quasars
– Several years of observing– Need $$ + huge consortium of people
n = 35 deg-2
2. Target only ~ 200 close pairs (i < 21)– Use LF to get mean density– Less than 20 nights of observing– Sucker in one graduate student
2dF: Croom et al. (2005)
Why Observe at Princeton?Why Observe at Princeton?
Apache Point Observatory (APO)
• SDSS spectroscopic survey– 4000 deg2
– 45,000 low -z quasars i < 19.1– 5,000 z > 3 quasars i < 20.2– Precise 5 band (u,g,r, i, z)
photometry
SDSS 2.5m
ARC 3.5m
• ARC 3.5m telescope– Plenty of time available in a
department full of theorists
– Remote operation from comfort of basement of Peyton Hall
– There was little else to do at night in Princeton
Jim Gunn
3.03.3
3.54.0
4.55.0
low-zqsos
A-stars
UVX
WD
2’55”
ExcludedArea
Finding Quasar PairsFinding Quasar Pairs = 14.7”
Keck Spectrum taken by Bob Becker & Michael Gregg
SDSS quasar @ z =2.17
Binary Quasars in the SDSSBinary Quasars in the SDSS
Statistical Clustering Sample – Subset of full sample with
quantifiable selection criteria– 38 binaries below fiber collision
limit ( < 55”; R< 400 kpc/h)
Full Binary Sample Statistical Clustering Sample
Pairs found from SDSS
Sparse sampling of this region
Dense sampling of this region
Fiber collision ( = 55”)
Barely Resolved ( = 3”)
Full Binary Sample– 26 new binaries with R < 50 kpc/h
( < 10”) – More than doubles the number of
such systems known!
Excess Small Scale ClusteringExcess Small Scale Clustering
• Factor ~ 10 excess for R < 40 kpc/h. Rises to ~ 30 for R ~ 10 kpc/h • Quasar correlation function progressively steepens for R < 1 Mpc/h• Is excess clustering the hallmark of mergers and dissipative
interactions? • High redshift galaxies (z = 1- 3) show no excess clustering, but
measurements don’t yet probe R < 100 kpc/hHennawi et al. (2005)
Projected Correlation Function
Extrapolation of larger scale 2dF clustering
Ratio of Observed/Extrapolated
Uncertain selectionfunction for smallest angles
FiberCollision
Future DirectionsFuture Directions
• Use photometric selection to measure clustering with better statistics
• Push to high redshift binary quasars at z > 4
• Deep imaging to study the environments of these systems. Proto-clusters at z ~ 2?
• Measure transverse small scale Ly forest correlations with quasar pairs with z > 2
Excess Galaxy Clustering?Excess Galaxy Clustering?
• Low-z galaxies lie on a single power law down to 10 kpc/h (comoving)
• High redshift (DEEP2, LBGs) clustering does not probe < 100 kpc/h
• Quasar-Galaxy correlations do not yet probe relevant scales or redshifts
SDSS Galaxies z ~ 0.1
Coil et al. (2004)
DEEP2 Galaxies z = 0.7-1.35
Masjedi et al. in prep
LBGs at z ~ 3
Adelberger (2003)
A B
C D
G1
Inada et al. (2003)Oguri et al. (2004)Inada et al. (2005)
z=1.734
The Widest Lensed QuasarThe Widest Lensed QuasarLargest Splitting
= 14.6”!
HST ACS HST NICMOS
• SDSS spectroscopic survey– 4000 deg2
– 45,000 low -z quasars i < 19.1– 5,000 z > 3 quasars i < 20.2– Precise 5 band (u,g,r, i, z)
photometry
SDSS Spectroscopic Quasars SDSS Photometric Quasars• Predict ~ 2 lenses with > 10” in
current (~ 4000 deg2) sample• Consistent with discovery of quad lens
SDSS 1004+4112
How Many Quasars Lensed by Clusters?How Many Quasars Lensed by Clusters?
• Predict ~ 8 lenses with > 10” in current (~ 7000 deg2) sample
• ~ 1 should have > 30”• ~ 1 will have zs ~ 4
Hennawi, Dalal, & Bode (2005)
From Ray Tracing Simulations through LCDM clusters