The Clowes-Campusano Large Quasar Group Survey

The Clowes-Campusano Large Quasar Group Survey

L. Haberzettl

G. Williger (UofL, USA)J.T. Lauroesch (UofL, USA)M. Graham (Caltech, USA)R. Davé (Steward Obs., USA)A. Koekemoer (STScI, USA)L. Campusano (Univ. de Chile, CL)

R. Clowes (Univ. Lancashire, UK)I. Soechting (Univ. Lancashire, UK)K. Harris (Univ. Lancashire, UK)C. Haines (Univ. Birmingham, UK)J. Loveday (Univ. Sussex, UK)D. Valls-Gabaud (Obs. de Paris, F)N. Nesvadba (Obs. de Paris, F)

The Clowes-Campusano LQG Survey

Outline

Background

- How to find them? - Significance of LQGs - History of the CCLQG

The CCLQG Survey

LBGs in the CCLQG

Future


discovered first by Webster 1982 →close triplet + one more distant QSO at z~0.37 scales ~75 h-1 Mpc

two other LQGs: Crampton et al. (87,89; 23 QSOs) at z~1.1 Clowes & Campusano (1991; 18 QSOs) z~1.3

large irregular shaped, filamentary structures on scales of 50-200 Mpc with concentrations of 5-20 QSO's

to large to be virialized, probable relics of large scale fluctuations

rare (4σ) structures, ~1/3 space density of super-clusters

Background: LQGs


duration of QSO phase ~107 yr ⇒ much shorter than timescale for quiescent evolution of AGN and age of Universe

at any time only small number of galaxies in QSO phase ⇩

QSOs should be randomly distributed

comparing real QSO distributions to catalogs of random object distributions using spatial correlation functions

ξ(r) = (<DD(r)>nr2/<RR(r)>n2) - 1

⇩

search for Large Scale Structures

How to find them?


Barrow et al. 1985

2Zwicky Galaxy Catalog 2Random Sample

1091 galaxies in the North Galactic Cap with Pmag ≤ 14 mag and δ≥0 and b≥40°

1091 galaxies over the same sky area


Minimal Spanning Tree(e.g. Barrow et al. 1985)

generalization of the nearest-neighbor or friend-of-friend method

connecting points with unique path distribution in tree length:

1D: w1(l) = 1/l

0 exp(-l/l

0)

with <l> = l0

2D: w2(l) = 2l/l

02 exp(-l2/l

02)

with <l> = √(2π)/2 l0

⇩minimal tree if sum of length of segments is minimal

MST can be used to identify under- and over-dense regions


defining thresholds for max. (over-dense) and min. (under-dense) length of branches l

t and the min. number of objects in a domain M

⇒ 3D: density of clusters with l ≥ lt is higher than minimum density

ρt ≡<ρ><l3>/lt3

⇧

strongly depends on the choice of lt,M and determining the

statistical significance


Finding Structures(Barrow et al. 1985)

two reduction methods to find structures

a) pruning: remove all branches with k≤p

b) separating: remove edges who exceed cut-off length


MSTpruned to level 10 (branches k≤ 10 removed)

mean edge length:<lz> = 0.0215 rad (1.232°) and <l

r> = 0.0267 (1.530°)


MST pruned and separated

cut-offs: 2<lz> and 1.6<l

r> ⇒ 0.043 rad (3.142˚) separation in both cases


Barrow et al. 1985

2Zwicky Galaxy Catalog 2Random Sample

1091 galaxies in the North Galactic Cap with Pmag ≤ 14 mag and δ≥0 and b≥40°

1091 galaxies over the same sky area


3D-MST pruned and separated

cut-offs: 3<lCfA

> and 1.8<lr> ⇒ 10.2 Mpc separation in both cases

only branches with ≥10 edges are shown


frequency distribution of MST(Zwicky)shows excess of large and small l

z

frequency distribution of MST (random) follows Gauss distributioncentered on <l

r>


Statistical Significance of LQGs

first known LQGs: Webster et al. (1982) – triplet at z~0.37 and one more distant QSO on scales ~75 h-1 Mpc

Crampton et al. (1987) – CCH LQG 18 QSOs at z~1.1 (BJ ≤ 20.0 mag)

on scales ~60 h-1 Mpc

Clowes & Campusano (1991) – CCLQG 18 QSOs at z~1.3 (BJ ≤ 20 mag)

on scales ~120x240 h-2 Mpc2 elongated overall and clumpy inner structure

Komberg et al. (1996) 10 LQGs from nearest neighbor method 10 – 25 QSOs with M

B< -23 mag

z ~ 0.6 – 2.1 and 40 – 160 h-1 Mpc scales


Pilipenko (2007) ⇨extended QSO clusters search in 2dF+SDSS QSO catalogs (> 100,000 QSOs)

18 new LQG identified by MST + 2 LQG confirmed

6 – 16 QSOs on scales ~40 – 155 h-1 Mpc

two groups of LQGs

14 LQGs with 6 – 8 members on scales ~60 h-1 Mpc spatial overdensity l

03/<l3> ≈ 10

6 LQGs with 15 – 19 members on scales ~140 h-1 Mpc (Jumbo LQGs) spatial overdensity l

03/<l3> ≈ 4

space density: <ρ> ≃ 7 h3 Gpc3 ⇨~500 – 1000 “Jumbo” LQGs

morphologies: <ε> = 0.8 ⇨walls+blobs (ε = Ltrunk

/Ltree

<1) rather than filaments (ε~1)


History of the Clowes-Campusano LQG

automated search on UKST objective-prism plate (~25.3 deg2) UJ5846P ESO/SERC field 927

α = 10:40:00 δ=+05:30:00

61 QSOs (29 S-band + 32 W-band) with 0.14<z<2.8 10 QSOs with 1.2≤z≤1.4

<z> = 1.267selection effect by the objective-prismLy-α emission shifted in the blue at z>1.8

cover 2.5° x 5° on the sky

banana like structure

8 additional QSOs from spectr. follow-up (Clowes et al. 1999)


2D MST

Power Spectrum Analysis

clustering scale ~1° (~35 h-1 Mpc) power spectrum analysis

Q=1 no clustering


CCLQG z~1.3 LQG z~0.8

3 x MgII-absorber overdensity 2 x MgII-absorber overdensitydiscovery of 2nd foreground LQG

Williger et al. 2002


Haines et al. 2004

CTIO BTC 4m V,I data ~0.25 deg2 subfield31 x 27 h-2 Mpc2 at z ~ 1.2

3 x overdensity in red galaxies

2 x overdensity in red galaxies

dashed contour ≙ 1.65 gal. arcmin-2


Clowes-Campusano Large Quasar Group Survey

~2 deg2 imaging and spectroscopy survey from UV – NIR


2 x 1.2˚ GALEX FUV+NUV m

lim~24 mag

SDSS u,g,r,i,z~1.6˚ Bok g ⇒ m

lim ~ 26 mag

2 x 1˚CFHT r+z ⇒ mlim

~ 26 mag m

lim ~ 24 mag

~1.2˚KPNO 2.1m FLAMINGOS NIR J+Ks

~600 Magellan IMACS spectra

Existing Data Set:

2

additional GALEX observations as part of the Deep Imaging Survey


Telescope Band Size expos. Time Status

GALEX FUV,NUV 1.2 deg analyzed

2.1m KPNO J, Ks N: 7200s (J); 9600 (Ks) 75% reduced ~20 (J)

2.3m Bok g N: 16800s reduced ~26.5

CFHT r,z analyzed

6.5 Magellan 4500-9000 A N: 12600s 25% reduced

3s detect. limit (Abmag)

N: 22902s (FUV); 38623s (NUV) S: 20827s (FUV); 33021s (NUV)

~25 (FUV), ~25 (NUV) ~25 (FUV), ~25 (NUV)

1.6x1.6 deg2

1.2x1.2 deg2

1 deg2 N: 15800s (r); 3720s (z) S: 6120s (r); 3400s (z)

N: ~27.5 (r), ~25.5 (z) S: ~27 (r), ~25.5 (z)

0.6x0.7deg2

Survey Summary

N

S

FUV NUV


completeness of GALEX data

IRAF+Galfit:

- GALEX background- IRAF artificial galaxy catalog - Galfit photometry- SExtractor search

80-90% complete down to mFUV,NUV

= 24 mag ~70% complete down to m

NUV = 24.5 mag


Survey Aim

galaxy populations in LQGs

Lyman Break Galaxies (LBGs)

red galaxy population

environmental effects on galaxy evolution

red sequence/blue cloud at z~1 in dense environment

QSO/AGN feedback mechanism

Large Scale Structure (LSS) formation and evolution


Lyman Break 912 Åat z~1

search for LBGs at z~1 using FUV-dropout technique

FUV

NUV

FUV-dropout examples:

FUV NUV SDSS

Lyman Break Galaxies (LBGs)


LBG search + selection criteria

GALEX NUV selected sample: ~15,800 objects

SDSS DR5 cross-correlation: ~13,800 primary counter parts

selection criteria for LBGs from Burgarella et al. (2006):

mNUV

≤ 24.5 mag + FUV – NUV ≥ 2

additional selection criteria: SDSS photo type = “GALAXY”

resulting sample of 1,023 LBG candidates


photometric redshifts: Hyperz (Bolzonella et al. 2000)

7 band photometry – FUV,NUV+5 SDSS bands

compared to SDSS spectroscopy & MegaZ catalogz

SDSS = 0.06 for z≤0.4

zMegaZ

= 0.08 for 0.4≤z≤0.8


photometric redshift distribution

LBG candidates

LQG@z~0.8

CCLQG@z~1.3

z = 0.05


Arnouts et al. (2005)

selecting redshift+luminosity limited subsample

2 redshift bins in front of the LQGs LQG@z~0.8

CCLQG@z~1.3

bright: MNUV

≤ M*NUV

faint: MNUV

> M*NUV


SFHs of averaged LBG SEDs

2-fit of averaged and normalized LBG SEDs to library of PÈGASE models

LQG@z~0.8 ⇒ 3 Gyr ≤ tbest

≤ 7 Gyr

CCLQG@z~1.3 ⇒ 3 Gyr ≤ t

best ≤ 7 Gyr

although fits with 250 ≤ t

youngest ≤ 800

are acceptable


results for best fitting ages show significant older t

best

than Burgarella et al. 2007 (250≤t

best≤500 Myr)

Burgarella sample include fainter LBGs ⇒ younger star bursts ⇒ younger averaged SEDs?

Role of dust?

~500 Myr

~250 Myr


LBG concentrations + filamentsLBGs in proximity to QSOs ⇒ QSO feedback mechanism?


red galaxies tend to avoid QSOs

formation of large filaments



Future Plans

immediate future:

- Bok+90prime observations g in southern field medium band imaging (N,S)

- CFHT queue observation r+z extend existing field ~5 deg2


next projects:

- stellar masses of LQG galaxies (LBG+red)- spatial correlation analysis- color evolution at z~1-1.5?- global SFRs at z~1?- LSB galaxies

- AGN contribution in the LQGs- search for more “jumbo” LQGs- morphologies of LQG galaxies






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The Clowes-Campusano Large Quasar Group Survey