Matthew Fleenor

Jim RoseWayne ChristiansenDick HunsteadClair MurrowoodMichael DrinkwaterWill Saunders

University of North Carolina University of North CarolinaUniversity of North CarolinaUniversity of SydneyUniversity of TasmaniaUniversity of QueenslandAnglo-Australian Observatory

Observations of the Horologium-Reticulum Supercluster

Melanie Johnston-HollittUniversity of Tasmania

• We are conducting multi-wavelength observations of 12 x 12 degrees centered on the HRS, this will comprise:

Optical:• 6dF over the whole area• 2dF over selected parts• 2.3m observations of bright cluster galaxies for AMP clusters

Radio:ATCA continuum imaging at 1.4, & 4.8 GHz over selected parts

X-ray: Chandra imaging of the central galaxies in the HRSExisting XMM data is available for some cluster members{consortium proposal for XMM observations along the major

cluster axis (PI Bohringer)}

Observations of the Horologium-Reticulum Supercluster

• To examine the dynamical state of the HRS outside of rich clusters

• To better understand and define the supercluster and compare it to similar mass concentrations like Shapley (define the extent of the supercluster, mass etc)

• To examining environmental affects and vice versa ie using tailed radio galaxies as a barometer for cluster weather

• To understand merging timescales of individual galaxy components

• To examine the velocity dispersion of large-scale filamentary structure…

Observations of the Horologium-Reticulum Supercluster: Rationale

Horologium-Reticulum Supercluster (HRS)

• “center” = 3h18m43s, = -50°01'40" (E94) • zavg = 0.0556, cz 19000 km s-1

• ~ 18-24 ACO member clusters (Z93, E94)

Covers (at least) 100 square degrees on the sky

‘Back of the Envelope’ Calculations (Ho=70 km s-1 Mpc-1, cz 18000 km s-1):

Dimensions:Distance = cz Ho -1 = 257 Mpc 1h 13 ° (58 Mpc),

15° (67 Mpc)

Kalinkov et al, MNRAS, 308(1998); Einasto et al, MNRAS, 269(1994); Zucca et al, ApJ, 407(1993)

• Goal: to produce a catalog of galaxies in the inter-cluster region

• Target Selection: complete catalog of galaxies down to Bj=17.5 in a 12 x 12 degree region was extracted from SuperCOSMOS excluding ~2 Abell radii around known clusters: 2848 a subset of 1500 targets was then chosen randomly from a weighted list (so as to preserve the natural overdensity).

• Observations: folded into the 6dFGS, taken in Oct/Nov 2002 with 580V/425R (5/8 nights ok)

6dF Observations of the Horologium-Reticulum Supercluster

Fleenor et al, 2005, AJ (submitted)

• Results: 95% of targets gave reliable redshifts

• 547 spectra obtained

(23% complete down to Bj=17.5)

This more than doubles the previous observations of the inter-cluster field galaxies.

6dF Observations of the Horologium-Reticulum Supercluster

Fleenor et al, 2005, AJ (submitted)

• Kinematic Extent of the HRS

Between 18 and 24 cluster members of which 17 ACO clusters lie in our region. We use these to define a “kinematic core” for the HRS being the FWHM of the observed z distribution of ACO clusters > 17,000 -22,500 km/s

-> find 48% of inter-cluster galaxies lie within this “kinematic core”

Observations of the Horologium-Reticulum Supercluster: First 6dF results

Fleenor et al, 2005, AJ (submitted)

• Overdensity for the Inter-cluster region:– from our redshift database we derived and overdensity of 2.4

(using the method of Drinkwater et al 2004)

• Large-scale redshift trend:– Careful examination of the 2D z-slices was used to further analyze

the large-scale structure, followed by a correlation analysis to define the principle axis of the inter-cluster galaxies. (Full details in Fleenor et al 2005).

– Discovered that the HRS is defined along an SE-NW axis of increasing z and that it is bimodal

Observations of the Horologium-Reticulum Supercluster: First 6dF results

• We have 4 main results that can be summarised thus:– The HRS spans the velocity range of at least 17,000 -22,500

km/s– The overdensity in this region is estimated to be 2.4– There is a systematic trend of increasing redshift along an

SE-NW axis– The HRS is bimodal in redshift with a separation of ~2500

km/s between the peaks of each component.

– The HRS appears to comprise of 2 components in redshift space, each exhibiting a similar spatical-redshift trend along a SE-NW axis

Observations of the Horologium-Reticulum Supercluster: First 6dF results

HRS RedshiftCatalog

Inner 122 deg

- 3000 Redshifts currently (4500)

- Detailed kinematic analysis of the A3128/A3125 region (multi-)

Work of Matthew Fleenor (PhD Thesis)

- 2dF study with 500 redshifts

-statistically defined many filaments and groupings that have undergone acceleration due to HRS potential

Rose et al. (2002) A3128/A3125

Dec.-R.A. plot for all galaxies in the sample

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2.93.13.33.53.73.94.1RA (hours)

Dec

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0.010<z<0.039

0.040<z<0.046

0.047<z<0.070

0.071<z<0.104

z=0.1 (Rose et al.2002) Chandra x-ray emission0.105<z<0.130(Mathams 89)

Honours project of Clair Murrowood, UTas

Honours project of Clair Murrowood, UTas

Decl.-R.A. plot for all galaxies in the sample

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3.23.33.43.53.6R.A. (hours)

Dec

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0.010<z<0.039

0.040<z<0.046

0.047<z<0.070

0.071<z<0.104

z=0.1 (Rose et al.2002) Cgabdra X-ray emission0.105<z<0.130(Mathams 89)"

Honours project of Clair Murrowood, UTas

R.A. vs. redshift for selected galaxies in the sample

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0.032<z<0.042

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A3125/A3128Removed

Dec. vs. redshift for selected galaxies in the sample

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A3125/A3128Removed

But wait there’s more….

• More 6dF observations were carried out over 6 nights in November 2004. This gave another ~1100 redshifts in the inter-cluster region

Fleenor et al, - new results from yesterday!

16 - 16.5 red15.5- 16 blue

17 - 17.5 red16.5- 17 blue

20 - 20.5 red19.5- 20 blue

21 - 21.5 red20.5- 21 blue

18 - 18.5 red17.5- 18 blue

19 - 19.5 red18.5- 19 blue

22 - 22.5 red21.5- 22 blue

23 - 23.5 red22.5- 23 blue

Now we have the fun job of quantifying structure!

Acknowledgements

• We thank the staff of the AAO and particular those involved in the 6dF galaxy survey, special thanks go to Fred Watson, Paul Cass and Will Saunders for supervising and conducting our observations.