Post on 11-Jan-2016
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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?
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
MSTpruned to level 10 (branches k≤ 10 removed)
mean edge length:<lz> = 0.0215 rad (1.232°) and <l
r> = 0.0267 (1.530°)
The Clowes-Campusano LQG Survey
MST pruned and separated
cut-offs: 2<lz> and 1.6<l
r> ⇒ 0.043 rad (3.142˚) separation in both cases
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
frequency distribution of MST(Zwicky)shows excess of large and small l
z
frequency distribution of MST (random) follows Gauss distributioncentered on <l
r>
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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)
The Clowes-Campusano LQG Survey
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)
The Clowes-Campusano LQG Survey
2D MST
Power Spectrum Analysis
clustering scale ~1° (~35 h-1 Mpc) power spectrum analysis
Q=1 no clustering
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
Clowes-Campusano Large Quasar Group Survey
~2 deg2 imaging and spectroscopy survey from UV – NIR
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG 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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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)
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
photometric redshift distribution
LBG candidates
LQG@z~0.8
CCLQG@z~1.3
z = 0.05
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
LBG concentrations + filamentsLBGs in proximity to QSOs ⇒ QSO feedback mechanism?
The Clowes-Campusano LQG Survey
red galaxies tend to avoid QSOs
formation of large filaments
The Clowes-Campusano LQG Survey
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
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
The Clowes-Campusano LQG Survey
The Clowes-Campusano LQG Survey
The Clowes-Campusano LQG Survey
The Clowes-Campusano LQG Survey
The Clowes-Campusano LQG Survey