Unveiled large-scale structures in the ZOA and their effects on local flow fields Renée C. Kraan-Korteweg University of Cape Town
Ø First encounters with Ofer & joint ZOA projects Ø From the smallest to larger structures Ø A ’nearby’ hidden supercluster in Vela Ø Summary of Vela SCL results Ø Comparisons with reconstructions (CF2 & CF3) Ø Future Plans: MeerKAT & Taipan
Ofer Fest 8 - 10 Apr 2019 “Formal Introduction” in December 1990 at the Durham Meeting on “Observational Tests of Cosmological Inflation” By our respective former PhD advisors
”HI-observation of galaxies in the ZOA in Puppis”, RKK & Huchtmeier 1992, A&A
Scharf, Hoffman, Lahav & Lynden-Bell, 1992, MN 256, 229 “Formal Introduction” in December 1990 at the Durham Meeting on “Observational Tests of Cosmological Inflation” By our respective former PhD advisors
”HI-observation of galaxies in the ZOA in Puppis”, RKK & Huchtmeier 1992, A&A
Scharf, Hoffman, Lahav & Lynden-Bell, 1992, MN 256, 229 SAAO Sutherland
DLB’s next plan: conceptualised during an SAAO observing run 1991
The Dwingeloo Obscured Galaxy Survey (DOGS)
DLB à day to day interactions to Ofer the 25m Dwingeloo radio telescope (1956) àsearch for nearby (v < 4000 km/s) àmassive HI-rich galaxies àrms = 40 mJy à in the northern ZOA ( |b| < 5○)
à The first systematic blind (ZOA) HI survey Discovery of Dwingeloo 1 1994Natur.372...77K Kraan-Korteweg, Loan, Burton, Lahav, Ferguson, Henning, Lynden-Bell Visit of Ofer to the 64m Parkes radio telescopes while we were observing highly obscured galaxies at the heart of the Great Attractor
The first ZOA conference in Paris in 1994
A number of other joint ZOA papers followed, including - 1998SciAm.279d..28K Kraan-Korteweg & Lahav - 2000A&ARv..10..211K Kraan-Korteweg &Lahav Visit of Ofer to the 64m Parkes radio telescopes while we were observing highly obscured galaxies at the heart of the Great Attractor
The first ZOA conference in Paris in 1994
A number of other joint ZOA papers followed, including - 1998SciAm.279d..28K Kraan-Korteweg & Lahav - 2000A&ARv..10..211K Kraan-Korteweg &Lahav The uncovered ZOA structures got larger and larger …. Dwingeloo Puppis the GA and Norma cluster Dekel+ 2014
Discovery of the Vela SCL hidden by ZOA
Kraan-Korteweg+ 2017, MNL Sparsely sampled along Galactic Equator: Over ZOA region of (l,b) = 245° – 285°; ± 10° (4°-10°)
Redshift coding: 0 – 8000 km/s; 8 - 16000 km/s; 16 – 20000 km/s 20 - 24000 km/s; 24 – 32000 km/s 32 - 40000 km/s
Massive overdensity At 18000 km/s traced overMass 25° and 20° degrees on either side of the GP
4756 redshifts from AAOmega + SALT +6dF + Optopus + 1.9m SAAO & Literature ~ 95% unpublished data Where AB > 2-3mag à hard to get redshifts, even for 2MASX galaxies Vela Supercluster (VSCL) in ZOA: |b| < 10 Kraan-Korteweg+ 2017, MNL
4756 redshifts from AAOmega + SALT +6dF + Optopus + 1.9m SAAO & Literature ~ 95% unpublished data Above GP: 0° < b < +10°
Led a
2nd Wall
Main Wall Below GP: -10° < b < 0° What was found – what does it signify?
Clear evidence for a galaxy supercluster in Vela: à possibly a supercluster in formation - not many X-ray clusters (but overdense in X-ray clusters) - clusters are young, have many star forming galaxies - two merging wall of extent of 80 x 65 h-1 Mpc
Despite sparse sampling à Vela SCL is significantly overdense - in 2M galaxy counts and - in volume defined by the overdensity What was found – what does it signify?
2M galaxy counts:
Vela survey area limited to 6° < b < 10°; 260° < l < 285°
99% complete for AK < 0.3mag and K < 13.8 à K0 ~13.5mag
3 comparison samples: ZOA: 110° < l < 260° SGC: b < -60° Full: 2MASX for |b| > 15°
à Enhancement in counts f = 1.2 What was found – what does it signify?
Volume overdensity in shells:
Based on photometric redshifts (2MPZ; Bilicki et al 2014)
Caution: large errors in phot-z à dilution of overdensity
Overdensity in shells 0.055 < z < 0.065
à Overdensity δVela ~ 0.60 What was found – what does it signify?
Clear evidence for a galaxy supercluster in Vela The Vela SCL is significantly overdense - in 2M galaxy counts - in volume defined by the overdensity
Simple linear perturbation theory à VLG ~ 50 km/s
à δSSC ~ 1.4; however if subjected to same completeness limit and biases, this would be reduced by f ~ 2.3 à making overdensity similar to Shapley
Independent evidence for Vela SCL? à Comparison to reconstructions based on - CF2 (CLUES) - CF3 (watershed …) Use CLUES method to predict hidden ZOA structures
Sorce, Colless, Kraan-Korteweg, Gottloeber 2017 MN (arXiv:1707:04267) Data set: Cosmic Flows 2 (CF-2) (Tully et al 2013) à 8315 pec vel out to ~30000km/s
200 constrained realisations - interpreting the sums - not average - various test about robustness of recovery of structures à remarkable agreement for known nearer ZOA structures (GA,PuP) à good agreement with 2MRS 2006 reconstructions (Erdogdu+ 2016)
à both Walls of Vela SCL recovered (18000 & 21000 km/s) in the Constrained Realisation Using the Watershed Analysis CF2 à CF3
Stepping back
Results from Lanikea paper Tully+ 2014
Based on CF2
Although very sparse data at higher redshifts, à strong flow lines downwards from Shapley, à then bending to left Using the Watershed Analysis on CF3 à The Vela Antlia Basin
Preliminary Results Based on CF3
CF3: N= 18000 vpec
Mostly: - Spitzer TF: 2257 - 6dF: 8885
Some further - TRGB - SNIa
Courtois, Hoffman, Kraan-Korteweg, Pomarède, in prep What was found – what does it signify?
Clear evidence for a galaxy supercluster in Vela The Vela SCL is significantly overdense - in 2M galaxy counts - in volume defined by the overdensity
à δSSC ~ 1.4; however if subjected to same completeness limit and Biases this would be reduced by f ~ 2.3 à making overdensity similar to Shapley
à Simple linear perturbation theory à VLG ~ 50 km/s à Independent evidence from reconstructions
How much remains hidden behind ZOA? Does the Milky Way hide further surprises? Taipan observations à in Science Verification …….
Taipan survey - multi-object spectroscopic instrument à galaxy survey - will cover the whole southern sky - spectra for over 1 million galaxies in the local Universe (z<0.3) over 4 years.
TAIPAN instrument: - on 1.2m UK Schmidt Telescope (Siding Springs) - innovative starbugs optical fibre positioner
à 150 objects per 6-deg field à reasonably complete redshifts, as faint as r =17.5 mag in 15 min integration
ZOA (|b| < 10°) not part of the Taipan survey But selected for the Taipan Science Verification Taipan Vela Survey
Ø Minimal Survey Area over Vela area with intermediate extinction
Redshift coding: 0 – 8000 km/s; 8 - 16000 km/s; 16 – 20000 km/s 20 - 24000 km/s; 24 – 32000 km/s 32 - 40000 km/s MeerKAT
64 dishes over 8 km baseline 13.5-m with Gregorian offset single pixel receiver (0.9-1.7 GHz) Compact core, extended baseline
MeerKAT roll-out: - AR1 (M16) : mid-July 2016 (fully operational – verification concluded) - AR2 (M32) : mid March 2017 (early science verification started snd concluded) - AR3 (M64) : end 2018 (science ready)
Time allocation (goal): 70% for Large-Survey Projects; 30% open time MeerKAT 64 Survey Scenario
Presented at MeerKat Science Workshop 2016 Kraan-Korteweg, R. C. et al. 2017arXiv170803587
Redshift coding: 0 – 8000 km/s; 8 - 16000 km/s; 16 – 20000 km/s 20 - 24000 km/s; 24 – 32000 km/s MeerKAT HI- Survey 32 - 40000 km/s of inner ZOA F(HI) = 0.2 Jy km/s à trace Vela SCL across ZOA requires: rms = 1mJy/beam in 10 km/s channel à integrations: M16 : 120 min
à Map all galaxies log MHI > 9.5 M¤with 16-24000km/s M64 : 7.5 min per field MeerKAT M16: Early Open Science observations Allocated early May 2018
6 contiguous VSCL fields observed:
AB = 1.0 1.5 2.0 2.5 mag 0.15
0.10 MK16-detections
0.15 N ~ 70 detections0.15 (~240 optical v < 22’000 in this area) 0.10
N = 51 clear N = 14 marginal -7 000
0.100.10 0.10 0.10 2250022500 N = 5 marg à dodgy
2000020000
300 1750017500 Position of VC04
0.100.10
0.150.15 prominent cluster -8 000 1500015000 1 Abell radius
0.100.10 1250012500
0.25 0.25
0.200.20 300 Velocity (km/s) Velocity (km/s) Galactic Latitude Galactic Latitude 1000010000 With X-ray emission 75007500 -9 000 Similar to Virgo
X-ray 50005000
30 300 25002500
0.100.10
273 000 272 300 0000 271 3000 000000 270270 303000 Galactic Longitude 0.15
0.10 MK16-detections
0.15 N ~ 70 detections0.15 (~240 optical v < 22’000 in this area) 0.10
V04 IR/Opt counterpart no z z sources N = 51 clear N = 14 marginal -7 000
0.100.10 0.10 0.10 2250022500 N = 5 marg à dodgy 2000020000 Only 23 of HI-det. 300
1750017500 have opt/NIR ctrp
0.100.10 à green crosses
0.150.15 -8 000 1500015000 Of 240 redshifts 0.100.10 1250012500
0.250.25 0.25 (left part of panel) 0.200.20 300 Velocity (km/s) Velocity (km/s) Velocity (km/s) Galactic Latitude Galactic Latitude Galactic Latitude 1000010000 à 16 detected in HI à 2 at VSCL redshift 75007500 -9 000 none in VC04 core
X-ray 50005000 àGood for stacking 30 300 25002500 0.10 0.10 àWall is well traced 273 000 272 300 0000 271 3000 000000 270270 303000 by HI-detections Galactic Longitude Steps towards a full census of the Vela SCL ... to determine its extent, richness and mass overdensity à and contribution to bulk flow
Ø Early Science Survey with MeerKAT (M64) to cover optically obscured part of Vela SCL (|b| < 6 )
Ø First simulation show that this is feasible (60-70 hrs with M64) Ø First observations with MK16 confirm survey strategy to be realistic Ø With M64: extend survey, and include 2nd hidden part of Big Circle towards TriAu clusters
Ø Taipan survey in science verification mode (end of 2019)
Ø Follow-up VSCL cluster observations (IRSF, WISE, SALT)
Ø (K-band LF, mass - possibly peculiar velocities using WISE TF over the MeerKAT HI survey area)
Ø Further/SALT observations of new potential clusters and deeper surveyed IRSF cluster
Ø Full-sky HI mapping (SKA Pathfinders) Early meeting announcement
2016 Vietnam on Large Scale Structure and Galaxy Flows 2013 Marseille on Cosmic Flows: Observations and Simulations ……..
Large Surveys, Cosmic Flows & Visualisation Cape Town, 2020
Provisional date: 17 – 21 February 2020 STIAS Conference Centre, Stellenbosch
Email me: [email protected]