The : showcasing the need for deep “whole-sky” HI-surveys

Renée C. Kraan-Korteweg ACGC (Astrophysics, Cosmology and Gravity Centre), UCT

Michelle Cluver, Tom Jarrett, Maciej Bilicki, Matthew Colless, Ahmed Elagali & Ed Elson

Ø Discovery of major supercluster hidden by ZOA Ø Implications Ø Whole sky-surveys and the ZOA

Ø A Vela SCL MeerKAT survey scenario (with Ed Elson)

8th PHISCC meeting Rutgers, March 2015 Suspicion of existence of massive overdensity in ZOA just beyond boundaries of current surveys 16-22000km/s

Follow-up observations of optically detected in ZOA in Vela (KK et al)

With 6dF instrument

à SALT & AAOmega proposals to consolidate & map extent of overdensity (with M Cluver, T Jarrett, M Bilicki, M Colless) à SALT & AAOmega observations of optically and 2M galaxies to map extent of overdensity (l,b) = 240° – 290°; ± (4°-10°)

SALT 10m & RSS: AT 4m & AAOmega: 8’ field: N~25 2° field; N ~400

2012-2103: 2014: 6 nights in February: à About a dozen fields of prospective cluster cores à Most confirmed as clusters at Vela à 4300 in 25 AAOmega fields: overdensity distance overdensity extends over vast region Preliminary results from 1 - 6 Feb 2014 AAOmega Observing run: 25 x 2-deg fields observed à N ~ 4300 redshifts

Massive overdensity: traced over ~ 20 o/o 25 observed fields

- Velocity histogram shows highly significant peak centred at ~18000km/s

- just beyond boundaries of current surveys 16-22000km/s

- Overdensity equally prominent above an below optical ZOA

- Numerous clusters at 18-20000km/s

- Embedded in broader wall-like structure (16-24000km/s) Preliminary results from 1 - 6 Feb 2014 AAOmega Observing run: 25 x 2-deg fields observed à N ~ 4300 redshifts

Massive overdensity: traced over ~ 20 o/o 25 observed fields

- Velocity histogram shows highly significant peak centred at ~18000km/s

- just beyond boundaries of current surveys 16-22000km/s

- Overdensity equally prominent above an below optical ZOA

- Numerous clusters at 18-20000km/s

- Embedded in broader wall-like structure (16-24000km/s) Preliminary results from 1 - 6 Feb 2014 AAOmega Observing run: 25 x 2-deg fields observed à N ~ 4300 redshifts

Numerous clusters at 18-20000km/s

Clusters embedded in great wall: à 13 massive clusters; 19 medium clusters/massive groups @ Vela z

Embedded in broader wall-like structure (16-24000km/s)

Redshift coding:

0 – 10000 km/s; 10-16000 km/s; 16-24000 km/s; 24-50000 km/s (black)

Massive overdensity traced over (Δl, Δb) ~ 20° x 20°

Assume continuityMass At 18-22000 km/s

à70 x 70 Mpc/h

Where extinction reaches ~AB = 2mag à hard to get redshifts, even for 2MASX galaxies à Area of ~|b| < ±5-7° unsampled Preliminary results from 1 - 6 Feb 2014 AAOmega Observing run: 25 x 2-deg fields observed à N ~ 4300 redshifts

Comparison to Concentration

- Massive overdensity traced over (Δl, Δb) >~ 20° x 20°

- Is on par with Shapley SSC (Proust et al 2006, N ~ 8600);

[also Horologium/Reticulum SCL (Fleenor et al 2006)]

- Despite f ~ 1.3 more distant à more extended on the sky:

12° x 30° ßà ~ 20° x 20° 30 x 75 ßà 70 x 70 Mpc/h

- Munoz & Loeb 2008: Based on X-ray of clusters in sky: SSC exerts about 9% acceleration on LG - ADD Vela SCL à Although very sparse data at higher redshifts, strong flow lines downwards from Shapley, then bending to left

Lepus????

Vela SCL

Tully et al 2014, Nature, Laniakea What does it all signify?

● Clear evidence for massive SCL in Vela;

● Vela SCL likely on par with SSC

● Forms Big Circle of SCL’s across the sky: Vela SCL à Shapley SCL à Ara/Triangulum?

● It’s impact on bulk flow is significant? – But difficult to assess properly with sparse sampling

● If it extends across the ZOA it will be even more massive

How much remains hidden behind ZOA? Does the Milky Way hide further surprises?

Only the forthcoming whole-sky HI-surveys WALLABY & WNSHS will provide full census MeerKAT Commissioning survey scenario à with Ed Elson

Ø “only” 25 AAOmega fields, with some other ZOA data à sparsely sampled

Ø AB = 2mag à hard to get optical redshifts àArea of ~|b| < ±5-7° unsampled 15 0 – 10000; 10-16000; 16-2400; black: 24-50000

10

5 Survey area of about

0 (l x b) = 20° x 12.5°

To trace Vela SCL across ZOA -5

-10

Goal:-15 Map all galaxies MHI > 9.5 M¤with 16-24000km/s 285 280 275 270 265 260 255 250 245 Galactic longitude MeerKAT Commissioning survey scenario à with Ed Elson

Updated MeerKAT Specifications:

2 Tsys = 22.4 K; Ae/Tsys ~ 430m /K; SS = 7.3 x JVLA

Simulations based on : Survey input parameters:

- Duffy et al 2012 simulations of - channel width Δv = 10 km/s stellar and HI-content of galaxies - Baseline 8km (à 15” resolution) (Wallaby & Dingo) - 5σ detection limit - of 4 million galaxies - within z < 0.44 à rms = 3.86 mJy - over FOV of 50 ☐° à 0.5 hr

2kTsys s = 1/2 Ae⌘(t⌫) Actual measurement on M63

Justin Jonas (March 2015) MeerKAT Commissioning survey scenario à with Ed Elson

Updated MeerKAT Specifications:

2 Tsys = 22.4 K; Ae/Tsys ~ 430m /K; SS = 7.3 x JVLA

Simulations based on : Survey input parameters:

- Duffy et al 2012 simulations of - channel width Δv = 10 km/s stellar and HI-content of galaxies - Baseline 8km (à 15” resolution) (ASKAP: Wallaby & Dingo) - 5σ detection limit: - of 4 million galaxies à rms = 3.86 mJy - within z < 0.44 à 0.5 hr - over FOV of 50 ☐° - FOV: 0.85☐° per pointing

2kTsys s = 1/2 Ae⌘(t⌫) Results: Predictions for MeerKAT survey scenario à with Ed Elson

For Vhel < 24000 km/s:

All > 5-σ lg MHI > 9.5

18360 2586 577

For 16000 < Vhel < 24000 km/s:

All > 5-σ lg MHI > 9.5

8681 527 247

MeerKAT FOV: 0.85 ☐° à to reach goal 250☐° à 106 hrs with M64 à 424 hrs with M32 Results: Predictions for MeerKAT survey scenario à with Ed Elson

For Vhel < 24000 km/s:

All > 5-σ lg MHI > 9.5

18360 2586 577 91800 12930 2885

For 16000 < Vhel < 24000 km/s:

All > 5-σ lg MHI > 9.5

8681 527 247 43405 2635 1235

MeerKAT FOV: 0.85 ☐° à to reach goal 250☐° à 106 hrs with M64 à 424 hrs with M32 Conclusions

● The case of the Vela SCL … and other new structures… showcase the importance of the forthcoming à “whole-sky” HI survey Wallaby & WNHSH (shallow) with ASKAP & AperTIF

● Deeper whole-sky surveys including ZOA are key in resolving the controversies around bulkflows § - what is amplitude of Bulk Flows on largest scales? § - what is their convergence radius? compatible with LCDM?

● MeerKAT in commissioning time can fill the ZOA gap the bisects the Vela SCL in reasonable time M64 à 106 hrs; M32 à 424 hrs