the cluster environments of high redshift radio galaxies
DESCRIPTION
MPIA Hauscolloquium 12 5 2006. The Cluster Environments of High Redshift Radio Galaxies. Jaron Kurk. MPIA Hauscolloquium 12 5 2006. Others: Chris Carilli, Wil van Breugel, Adam Stanford Steve Croft G. De Lucia T. Heckman H. Ford P. McCarthy. Other Leiden PhDs involved: - PowerPoint PPT PresentationTRANSCRIPT
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The Cluster Environments of High
Redshift Radio GalaxiesJaron Kurk
MPIA Hauscolloquium12 5 2006
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MPIA Hauscolloquium12 5 2006
Prof George Miley Dr Huub Röttgering
JKPhD May 2003
Bram VenemansPhD April 2005
Roderik OverzierPhD May 2006
Other Leiden PhDs involved: Laura PentericciCarlos De BreuckMichiel Reuland
Leiden students and postdocs: Andrew ZirmHuib Intema
Others:Chris Carilli,Wil van Breugel,Adam StanfordSteve CroftG. De LuciaT. HeckmanH. Ford
P. McCarthy
Leiden HzRGCluster Program
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Thesis defense: May 30
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Outline of Talk
• Introduction– Clusters– HzRGs– HzRG-Cluster Program
• Some examples– 1138 at z = 2.2– 1338 at z = 4.1
• Program Results– Line emitters– Distant clusters
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Importance of Distant Clusters
Distant clusters are of interest because• their presence constrains cosmological parameters (e.g. Eke et al. 1996)• their galaxies provide unique reservoir to investigate
galaxy evolution
– clusters at z ~ 0.5 contain more blue galaxies (Butcher & Oemler 1984)
– scatter in colour-magnitude relation constrains formation mode– central brightest cluster galaxies do not fit on LF
But difficult to find because of• contamination by foreground galaxies• cosmological surface brightness dimming of extended X-ray
emission
Most distant clusters found to date• at z = 1.11 by X-rays (Stanford et al. 2002)• at z = 1.26 by X-rays and NIR imaging (Rosati et al. 1999,
Stanford et al. 1997)
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Properties of HzRGs
Indirect evidence that HzRGs are located in (forming) clusters
• Radio galaxies observed in clusters or over-densities of galaxies
– Half of powerful RGs at z ~ 0.5 inhabit rich clusters (Hill & Lilly 1991, Yates et al. 1989), strong correlation with redshift as at z < 0.15 RGs avoid clusters (Prestage & Peacock 1989)
– Nearby example of Cygnus A (Owen et al. 1997)– Over-density of K band galaxies in 3CR fields (Best 2000, 2003)
and other z ~ 1 RG and QSO fields (Hall et al. 2001, Barr et al. 2004)– Over-density of EROs and sub-mm galaxies near 4C41.17 (Ivison et al. 2000)
• Radio galaxies observed in dense ambient gas
– High (> 1000 rad m-1) radio RMs (Carilli et al. 1997, Pentericci et al. 2000)
• Hosts of HzRGs resemble brightest cluster galaxies
• HzRGs are amongst the most massive galaxies up to z ~ 5 (De Breuck et al. 2002)
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Properties of HzRGs
De Breuck et al. (2002)HzRGs are amongst the most massive galaxies up to z ~ 5
K-z diagram
Powerful AGN massive black hole massive galaxy (Magorrian relation)
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Example HzRG: 1138-262 at z = 2.2
ACS/HST 20 orbits g+i
100 kpc
• Elements of both hierarchical and monolithic formation
• Morphological types that dominate the faint population in the UDF (chains, tadpoles and clump-clusters)
• Star formation in two modes: LBG-like (50%) and diffuse (50%)
Pentericci et al. (2002), Kurk (2003), Miley et al. (in prep.)
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Example HzRGs: emission line halos
1338 at z = 4.1VLT line emissionACS continuumZirm et al. (2005)
1138 at z = 2.2VLT line emissionRadio 8 GHz continuumKurk (2003)
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The Leiden HzRG Cluster Program
• Use HzRGs as beacons of forming clusters– HzRGs have properties of forming BCGs– Seem to live in dense environments at z ~ 1– Most massive galaxies at any z and therefore found in most massive DM halos
• Use Ly emitting galaxies as tracers of galaxy overdensities– Strongest (intrinsic) emission line– LAEs occupy faintest accesible part of LF– Spectroscopic confirmation relatively easy
• VLT Large Program– Eight radio galaxy fields at 2.2 < z < 5.2– Twenty nights with FORS/VLT (and twenty hours LRIS/Keck)
– Narrow band imaging of 33 Mpc2 fields and MOS spectroscopy
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Line emitting galaxies at high redshift
• Primordial galaxies should emit 3-6% of their bol. lum. in Ly, resulting in EW0 = 100-200 Å (Charlot & Fall 1993)
• Ly is resonant, so large extinction can occur: only 25% of LBGs have EW0 > 20 Å (Shapley et al. 2003)
• LAE surveys fashionable– Hu et al. (1998), Rhoads et al. (2000),
Stiavelli et al. (2001), Ouchi et al. (2002),Hu et al. (2004), Tapken et al. (2006),Steidel et al. (2000)
– Little evolution of UV continuum with z– Controversy about red colours and high
equivalent widths– Clustering observed in large fields
• LAEs are currently redshift record holders
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Intermezzo I - LAE at z = 6.5
• FORS2/VLT slitless spectroscopy combined with a medium band filter
• One LAE emitter found at z = 6.518 with flux of 210-17 erg s-1 cm-2
• Comparison of LFs at z = 5.7 and z = 6.5 shows little evolution and therefore reionization earlier than z = 6.5 (Malhotra & Rhoads 2004)
Kurk et al. (2004)
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The NB Imaging Technique
Kurk (2003)
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Individual HzRG Fields
• PKS 1138-262 at z = 2.16– Pilot VLT project (first VLT visitor observations, in 1999)
– Lowest redshift of sample– Indications of dense environment– Suitable redshift for H narrow band imaging– Chandra X-ray , NICMOS, MOIRCS observations– Main subject of my thesis my favourite object!
• TN J1338-1942 at z = 4.10– One of the brightest (in Ly line and radio continuum)
– Most overdense field (in terms of LAEs)– Drop-out imaging with ACS and Suprime-Cam
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1138 Imaging
Imaging: 0.5 hr B band, 4 hr narrow band- Fifty LAEs with EW0 > 20 A and F > 210-19 erg s-1 cm-2 A-1
Spectroscopy: 6, 5.5, 4 hr for each FORS1 mask- Fifteen confirmed (out of 27)
Kurk et
al. (2000)
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1138 Spectroscopy results
Spectroscopic confirmation of 15 LAEs- Single line rules out [OII],
[OIII], Hβ- One QSO: FWHM ~ 5800 km s-1, CIV emission
Pentericci et al. (2000)
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1138 Spectroscopy results
Spectroscopic confirmation of 15 LAEs- LAE redshifts centered on radio
galaxy- Probability redshifts drawn from random distr. < 0.4%- Redshifts seem to be distributed in two groups
Kurk et al. (2004)
σv = 385, 205 km s-1
σv = 900 km s-1
Actual redshift distribution
Monte Carlo Simulation
2
3
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• Two 2.5’2.5’ ISAAC fields– HAEs have 5 higher density within 0.66’ radius compared with outside 1.0’ radius
– No blank field HAE surveys deep enough to compare with
1138 H imaging
-Kurk et al.
(2004)
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1138 H spectroscopyTwo nights of ISAAC spectroscopy confirmed redshifts nine HAEs, including one QSO, v = 360 km s-1
-Kurk et al.
(2004)
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Intermezzo II - Wide field H survey
• Finally NIR detectors with large FoV available• WFCAM survey at z = 2.2 of 1.5 deg2 (on-going, P.I. Smail)• VISTA survey at z = 0.8 of 1.6 deg2 (proposed, P.I. Fynbo)• LF of H emitting galaxies, good estimate of (global) SFR at
z > 2• Comparison with HzRG fields (also other emission lines)
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• Chandra imaging (40 ksec) reveals– apart from RG 17 serendipitous sources in FORS field
– about 50% more soft sources with flux > 10-15 erg s-1 cm-2 than in CDF (1.5 significance)
– coincidence with 3 LAEs, 1 HAE, 1 ERO– optical/X-ray ratios indicate AGN– four X-ray sources and RG roughly aligned
1138 X-ray sources
-Pentericci et al. (2002),
Croft et al. (2005)
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1138 SCUBA companions
Field of 1138 is second densest in sample of seven HzRG fields (Stevens et al. 2003) with three companions, two of them aligned E-W
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1138 NICMOS CMD
RG Lya HaUDF/HDFN
Factor nine overdensity in red sequence galaxies (1.3 < J-H < 2.1) in six NICMOS fields near 1138
Zirm et al. (in preparation)
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1138 Subaru CMD
Red sequence Lya Ha
Red sequence galaxies (J-K > 2.3) in 4’7’ MOIRCS field (Kodama et al., in prep.)Subaru NIR MOS and VLT optical MOS proposed
(Vega)
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1338 ACS imaging
-Miley et al.
(2004)
ACS/HST FoV 3.4’3.4’gri imaging to detect g-
dropouts at z ~ 4Compare with cloned GOODS B-
dropoutsFactor 2.5 more g-dropouts than
expected, representing a 3 excess (i < 26)
More than 50% within 1 Mpc radius
Even stronger at i < 27Alternative of a cluster of z ~
0.5 Balmer break objects improbable
-g (4 orbits) r (4
orbits) i (5 orbits)
-LAE
-RG
-LAE
-LAE
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Suprime-Cam FoV 25’24’BRI imaging to detect LBGs at
3.5 < z < 4.5 (6% cont.)874 LBGs with IAB < 26.5
125 LBGs with IAB < 25.0
Correl length r0 = 3.7 / 4.6 h-1 Mpc
Largest overdensity at pos of 1338
Size of ~ 2 Mpc includes 104 LBGs
7 coincide with confirmed LAEs28-35 LBGs associated with RGOverdensity 5-7Spectroscopy needed to trace
web
1338 Subaru imaging
-Intema et al.
(submitted)
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Conclusions on Ly Emitters• In total ~ 300 LAEs of which ~ 150 confirmed
– spectroscopic confimation succes rate ~ 90%– AGN fraction < 10%, based on line widths (95% < 1000 km s-
1)• lines asymmetric, sometimes with absorption (M(HI) up to 5104 M)
– LLy < 1043 erg s-1, fainter than L* in UV continuum
– No evidence for zero metallicity (max EW0 < 240 A)
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– Continuum colours are blueer ( = -1.7) than for LBGs ( = -1.1)
– SFRs in the range 1 - 10 M yr-1 (LBGs typically > 10 M yr-1)
– Low dust content (blue UV and consistent Ly and UV SFR)• extinction correction on Ly SFR << 2
– Ages < 100 Myr, in 16% < 10 Myr (from UV continuum)– Half light radii (~ 1.0 kpc) smaller than for LBGs in GOODS (~ 2.3 kpc, Ferguson et al. 2004)
Conclusions on Ly Emitters
Venemans et al. (in prep)
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Large Program Results
Name of RG z IMG SPC
MRC 2048-272 2.06 10 3
MRC 1138-262 2.16 37 15
MRC 0052-241 2.86 57 37
MRC 0943-242 2.92 65 28
MRC 0316-257 3.13 77 31
TN J2009-3040 3.15 21 11
TN J1338-1942 4.10 54 37
TN J0924-2201 5.19 14 6
σv (km/s)N/A~900~980~715~640~515~265~305
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Conclusions on Distant Clusters
• At least six out of eight fields show overdensity– surface overdensity on the order of 3-5
• Confirmed emitters are clustered in redshift space– width of vel. distr. 2-5 smaller than NB
• Estimated protocluster masses 2-91014 M
– assuming bias parameter b = 3-6 and certain volume V (Steidel et al. 1999)M = <>V(1+m), 1 + bm = C(1+gal), C = 1 + f - f (1 + m)1/3
where <> is mean density of universe and C redshift space distortions
• Velocity dispersion decreases with redshift• FoV too small to give reliable estimate of sizes
– but from second field near 1338 radius of ~ 2 Mpc seems correct
Venemans et al. (in prep.)
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Conclusions on Distant Clusters
N-body modelling by G. De Lucia shows that– LAEs in protoclusters can
be identified with young (< 100 Myr) galaxies• luminosity or colour is
not enough– velocity distribution of
simulated clusters increases with decreasing redshift
– HAEs near 1138 lie within virialized core and may be older (as suggested by their brighter K-band continua)
Millenium simulation will improve results
Venemans et al. (in prep.)
RG proto-clustersSubgroupsSimulated clustersHubble Flow
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Conclusions on Distant Clusters
Theory of linear spherical collapse predicts critical density at which structure will collapse, almost indendent of cosmology L = 1.686 (Peacock 1999)
Compare evolution of linear matter overdensity of protoclusters with this critical density
gal M L L(z) in CDM (Carroll et al. 1992)
1338 collapses at z ~ 0.51138, 0316, 0924 at z ~ 0
Overzier et al. (in prep.)
1138
13380316
0924
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Intermezzo III - a QSO field at z = 6.3
• Overdensity of i-dropout galaxies in the field of QSO SDSS 1030+0524 at z = 6.28 (Pentericci et al., submitted)
• Follow-up spectroscopy (on-going, P.I. Walter)
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Empty slide
RG PKS 1138-262
EROs: extremely redLAEs: purple
BIK FORS/ISAAC
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Abbreviations used
• HzRGs: High Redshift Radio Galaxies• LAEs: Ly Emitters (Lyman- emitting galaxies)
• HAEs: H Emitters• EROs: Extremely Red Objects• ERGs: Extremely Red Galaxies (red distant galaxies)
• DRGs: Distant Red Galaxies (really red distant galaxies)
• LBGs: Lyman Break Galaxies (blue distant galaxies)