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