Pushing the limits with spectroscopy: High-redshift overdensities - PowerPoint PPT Presentation

Pushing the limits with spectroscopy: 
 High-redshift overdensities at 2<z<6 in zCOSMOS and MUSE-Wide Catrina Diener + Simon Lilly (ETH Zurich), the zCOSMOS team 
 Lutz Wisotzki (AIP Potsdam), the MUSE-Wide team

We can’t find proto-clusters using spectroscopy

Go low redshift - in approach • Using spectroscopic redshifts • Friends-of-friends type algorithm 
 Look for proto-groups/cluster rather than groups/clusters

Go low redshift - in approach • Using spectroscopic redshifts Better contrast! • Friends-of-friends type algorithm 
 Look for proto-groups/cluster rather than groups/clusters

Go low redshift - in approach • Using spectroscopic redshifts Better contrast! • Friends-of-friends type algorithm 
 Look for proto-groups/cluster rather than groups/clusters Can probe less “extreme” system But: It is expensive to cover large enough areas

Go low redshift - in approach • Using spectroscopic redshifts Better contrast! • Friends-of-friends type algorithm 
 Look for proto-groups/cluster rather than groups/clusters Can probe less “extreme” system But: It is expensive to cover large enough areas Proof of principle: • zCOSMOS-deep: 2<z<3 with 3500 galaxies • MUSE-Wide: 3<z<6 with ~1000 Lya-emitters at completion

Why find proto-clusters in first place? Galaxies in massive haloes at z=high will be in massive haloes at z=0 15 15 15 15 log M, z=6.2 log M, z=4.9 log M, z=3.9 log M, z=3.1 13 13 13 13 11 11 11 11 12 14 16 12 14 16 12 14 16 12 14 16 log M, z=0 log M, z=0 log M, z=0 log M, z=0 16 16 16 log M, z=2.1 log M, z=1.1 log M, z=0.5 14 14 14 12 12 12 12 14 16 12 14 16 12 14 16 log M, z=0 log M, z=0 log M, z=0

Bad news: the reverse is not true… Galaxies in z=0 massive group and cluster haloes 
 live not necessarily in massive haloes at higher z 16 16 16 16 log M, z=6.2 log M, z=4.9 log M, z=3.9 log M, z=3.1 14 14 14 14 12 12 12 12 10 10 10 10 8 8 8 8 13 14 15 16 13 14 15 16 13 14 15 16 13 14 15 16 log M, z=0 log M, z=0 log M, z=0 log M, z=0 16 16 16 log M, z=2.1 log M, z=1.1 log M, z=0.5 14 14 14 12 12 12 10 10 10 8 8 8 13 14 15 16 13 14 15 16 13 14 15 16 log M, z=0 log M, z=0 log M, z=0

We are missing most progenitors of todays clusters… 1 0.9 descendants 0.8 0.7 0.6 0.5 F 0.4 0.3 0.2 0.1 progenitors 0 0 1 2 3 4 5 6 7 redshift

We are missing most progenitors of todays clusters… 1 0.9 descendants 0.8 0.7 0.6 0.5 F 0.4 0.3 0.2 0.1 progenitors 0 0 1 2 3 4 5 6 7 redshift This is not helped by focussing on over-densities 
 around high-density tracers (like radio-galaxies)

The zCOSMOS-deep survey • Part of the zCOSMOS Large Programme 
 of 600hr at VLT/VIMOS 80 • BzK and ugr selected + magnitude cut in 
 70 B and K band (star-forming galaxies at z>1) 60 50 number • 70% sampled area covering 0.6x0.62deg 
 40 (From full area of 0.92x0.91deg) 30 20 • 3502 objects with reliable redshifts in 
 10 the range 1.8<z<3 0 1.8 2 2.2 2.4 2.6 2.8 3 z spec • ~50% overall sampling and dv=300km/s 
 cf. zCOSMOS-bright, 120km/s, 18 ’ 000 objects tp z ~ 1, about 500 groups wi ti N>2 ( Li lm y et al. 2009, Knobel et al. 2012 )

Combined approach: Simulations and observations Using the Millennium simulation and its publicly available mocks to: • Calibrate the group-finding parameters • Use mock counterparts of the identified 
 structures to make predictions on DM 
 halo distribution and evolution • Carefully tune these mock catalogues to 
 observations: i.e. match number densities, 
 redshift errors, selection criteria...

Combined approach: Simulations and observations Using the Millennium simulation and its publicly available mocks to: • Calibrate the group-finding parameters • Use mock counterparts of the identified 
 structures to make predictions on DM 
 halo distribution and evolution • Carefully tune these mock catalogues to 
 observations: i.e. match number densities, 
 redshift errors, selection criteria... Obvious caveat: 
 Only valid as long as simulations indeed reflect the observations

Finding proto-groups applied to zCOSMOS 2.6 • Automated group-finder using 
 the friends-of-friends method 2.4 • Calibrated with mocks DEC 2.2 • Linking lengths: 
 dr = 500kpc and 
 2 dv = 700km/s • Requiring N>2 1.8 150.6 150.4 150.2 150 149.8 RA Yields a catalogue of 42 candidate proto-groups


 What does our group-finder detect? • At redshift of detection: mostly centrals (>90%) • 93% will fully or partially assemble by present epoch (z=0) 
 700 1 1 not assembled 0.9 0.9 600 0.8 0.8 <fraction of groups (N=3)> fraction of proto − groups 500 0.7 0.7 0.6 0.6 r rms [kpc] partially 400 0.5 0.5 300 0.4 0.4 0.3 0.3 200 fully 0.2 0.2 100 0.1 0.1 0 0 0 200 400 600 800 3 2.5 2 1.5 1 0.5 0 v rms [km/s] redshift Assembly process “Success” almost independent 
 of transverse size…

Evolution to z=0: Typically group-type haloes none bright enough too dispersed detectable too few 
 bright 
 enough detected Fraction of a given halo with respect to 
 all haloes at this mass: Cataloguing a good fraction of todays cluster z=0 halo mass

Evolution to z=0: Typically group-type haloes General halo mass function none bright enough too dispersed detectable too few 
 bright 
 enough detected Fraction of a given halo with respect to 
 Halo mass distribution at z=0 
 all haloes at this mass: of structures identified at z~2 Cataloguing a good fraction of todays cluster z=0 halo mass

Side note: z=2.45 proto-cluster with 11 members • Discovered in a FORS2 run targeting 
 known proto-groups • 11 spectroscopically confirmed members 
 within dr=1.4Mpc and dv=700km/s • Overdensity: ~10

− − − − − − − − Side note: z=2.45 proto-cluster with 11 members − − − − • Discovered in a FORS2 run targeting 
 known proto-groups • 11 spectroscopically confirmed members 
 within dr=1.4Mpc and dv=700km/s • Overdensity: ~10 − − − − − 0.2 − − − M z=0 =10 14.9 M sun /h • Corresponding z=0 cluster has several 0.2 thousands progenitor galaxies at z~2.5 0.1 • Most too faint for FORS2-type spectroscopy, 0 but within dv=700km/s − 0.1 • Diameter of progenitor region is 3-20Mpc, − much bigger than identified proto-cluster − 0.2 − 0.2 − 0.1 0 0.1 0.2

Work in progress Proceed with caution…

MUSE-Wide: 1000 Lya-emitters at 3<z<6 MUSE-Wide (PI L. Wisotzki): Part of MUSE GTO time • Covering representative area of sky in with MUSE (1’x1’ FOV) • Observing legacy fields (mainly CDFS and COSMOS fields) Final survey will: • Observe ~100 fields at 1h depth • Detect several 1000 emission-line 
 objects from 0<z<6 • Exploit the multi-wavelength data 
 to derive galaxy properties

MUSE-Wide: 1000 Lya-emitters at 3<z<6 MUSE-Wide (PI L. Wisotzki): Part of MUSE GTO time • Covering representative area of sky in with MUSE (1’x1’ FOV) • Observing legacy fields (mainly CDFS and COSMOS fields) Final survey will: • Observe ~100 fields at 1h depth • Detect several 1000 emission-line 
 objects from 0<z<6 • Exploit the multi-wavelength data 
 to derive galaxy properties Current status: • About 75 fields observed & reduced • Catalogue for first 24 fields 
 (22.2arcmin 2 ) • Including 237 Lya-emitters

Proto-groups in MUSE-Wide Preliminary: 
 Using similar parameters for the FoF algorithm as in zCOSMOS 30 • 13 associations with 3-6 members • Most prominently a z=4.50 structure 
 20 with 6 members N LAE • Simulation suggest that ~70% of 
 10 these galaxies end in >10 13 M sun haloes 
 (30% even in >10 14 M sun ) 0 3 3.5 4 4.5 5 5.5 6 z spec Many properties yet to come, but: 
 Tentatively higher Lya-fluxes (and continuum fluxes) for proto-group galaxies

Proto-groups in MUSE-Wide Preliminary: 
 Using similar parameters for the FoF algorithm as in zCOSMOS 30 • 13 associations with 3-6 members • Most prominently a z=4.50 structure 
 20 with 6 members N LAE • Simulation suggest that ~70% of 
 10 these galaxies end in >10 13 M sun haloes 
 (30% even in >10 14 M sun ) 0 3 3.5 4 4.5 5 5.5 6 z spec The future is bright: • Quadruple the sample • Calibrate FoF parameters • Derived galaxy properties

Summary 1 0.9 descendants 0.8 0.7 Even if finding proto-clusters we only ever sample a small 
 0.6 0.5 F fraction of today’s cluster progenitor galaxies 0.4 0.3 0.2 0.1 progenitors 0 0 1 2 3 4 5 6 7 redshift 1 0.9 Application of an automated 
 0.8 <fraction of groups (N=3)> 0.7 group-finder to zCOSMOS 
 Discovery of z=2.45 
 0.6 0.5 yielding 42 overdensities; 
 proto-cluster 
 0.4 0.3 these are mostly proto-groups 0.2 0.1 3 2.5 2 1.5 1 0.5 0 redshift 30 20 With the advent of MUSE spectroscopic proto-group N LAE detection can be extended out to z~6 10 0 3 3.5 4 4.5 5 5.5 6 z spec