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Matthew Fleenor Jim Rose Wayne Christiansen Dick Hunstead Clair Murrowood Michael Drinkwater

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Observations of the Horologium-Reticulum Supercluster. Melanie Johnston-Hollitt University of Tasmania. Matthew Fleenor Jim Rose Wayne Christiansen Dick Hunstead Clair Murrowood Michael Drinkwater Will Saunders. University of North Carolina University of North Carolina

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slide1

Observations of the Horologium-Reticulum Supercluster

Melanie Johnston-Hollitt

University of Tasmania

Matthew Fleenor

Jim Rose

Wayne Christiansen

Dick Hunstead

Clair Murrowood

Michael Drinkwater

Will Saunders

University of North Carolina

University of North Carolina

University of North Carolina

University of Sydney

University of Tasmania

University of Queensland

Anglo-Australian Observatory

slide2

Observations of the Horologium-Reticulum Supercluster

  • 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 HRS

Existing XMM data is available for some cluster members

{consortium proposal for XMM observations along the major cluster axis (PI Bohringer)}

slide3

Observations of the Horologium-Reticulum Supercluster: Rationale

  • 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…
slide4

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

Da1h13°(58 Mpc),

Dd15°(67 Mpc)

Kalinkov et al, MNRAS, 308(1998);

Einasto et al, MNRAS, 269(1994);

Zucca et al, ApJ, 407(1993)

slide5

6dF Observations of the Horologium-Reticulum Supercluster

  • 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)
slide7

6dF Observations of the Horologium-Reticulum Supercluster

  • 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.

slide9

Observations of the Horologium-Reticulum Supercluster:

First 6dF results

  • 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”

slide11

Observations of the Horologium-Reticulum Supercluster:

First 6dF results

  • 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
slide12

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
slide13

HRS Redshift

Catalog

Inner 122 deg

  • 3000 Redshifts
  • currently (4500)
  • Detailed kinematic
  • analysis of the
  • A3128/A3125
  • region (multi-l)

Work of Matthew Fleenor (PhD Thesis)

slide14

Rose et al. (2002) A3128/A3125

- 2dF study with 500

redshifts

-statistically defined many filaments

and groupings that have undergone

acceleration due to HRS potential

but wait there s more
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
slide22

16 - 16.5 red

15.5- 16 blue

17 - 17.5 red

16.5- 17 blue

20 - 20.5 red

19.5- 20 blue

21 - 21.5 red

20.5- 21 blue

18 - 18.5 red

17.5- 18 blue

19 - 19.5 red

18.5- 19 blue

22 - 22.5 red

21.5- 22 blue

23 - 23.5 red

22.5- 23 blue

Fleenor et al, - new results from yesterday!

Now we have the fun job of quantifying structure!

acknowledgements
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.
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