Charting Cosmic Flows into the Zone of Avoidance: The Overdensity in Vela

R. Kraan-Korteweg, T. Jarrett, M. Cluver, M. Bilicki, H. Jones, M.

Colless

The Local Universe

Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. The image is derived from the 2MASS Extended Source Catalog (XSC)--more than 1.5 million galaxies, and the Point Source Catalog (PSC)--nearly 0.5 billion Milky Way stars. The map is projected with an equal area Aitoff in the Galactic system (Milky Way at center). Jarrett 2004

The Local Universe

Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. The image is derived from the 2MASS Extended Source Catalog (XSC)--more than 1.5 million galaxies, and the Point Source Catalog (PSC)--nearly 0.5 billion Milky Way stars. The map is projected with an equal area Aitoff in the Galactic system (Milky Way at center). Jarrett 2004

Vela Overdensity

Galaxies observed behind the Hydra-Antlia-Vela region of the Milky Way, projected in Galactic coordinates. The cyan dots are the on-sky

distribution of galaxies with known redshifts between 16000 and 22000 km/s from the 6dFGS . The blue stars indicate where two CIZA galaxy

clusters are found.

Vela Overdensity

Observations/Strategy

AAT: AAOMEGA SALT: RSS-MOS --- target high extinction

regions where the AAT lacks the mojo 2MRS: J. Huchra Legacy: Lucas Macri (UT A/M)

Spectra

Spectro-Imaging (multi-lambda) WISE & VISTA (photozs) Pathfinders (WALLABY)

SALT Observations

RSS-MOS: 10 masks targeted

40% Data Acquired to Date

Huge Thanks to:Alexei Kniazev, Petri Vaisanen & David Gilbank

SALT Observations

SALT ObservationsOne Target Field (Block): Exposure: 375 sec

Visits: 2

SALT Reductions

RSS-MOS Data Reduction:0. inputs: “mbxgp” 2-D spectral cubes (2 in total),

wavelength calibration “arc” -- Argon,RSMT file (target coords)

1. Python Script (D. Gilbank): apply wavelength calibration, extract slit-lits, create indiv. fits files

2. Clean cosmic rays (python script, see next page)3. combine (2) epochs4. Improve wavelength calibration using skylines

and cubic fit5. Extract 1-D spectrum: collapse spatial info,

remove local sky6. Determine redshift

SALT Reductions

LACosmic – python script based on Pieter van Dokkum's L.A.Cosmic algorithm

c = cosmics.cosmicsimage(array, gain=2.2, readnoise=10.0, sigclip = 4.0, sigfrac = 0.3, objlim = 3.0)

Beware !

SALT ObservationsYellow == (skewed) sky lines; blue == desired sky line locations

Deflection (Angstrom) versus Wavelength

SALT ObservationsYellow == (skewed) sky lines; blue == desired sky line locations

SALT Results

SALT Results4 MOS Fields -- ~ 40 target galaxies

3 emission lines detected21 absorption line systems

SALT ResultsEven this tiny amount of data indicates that the SALT redshift results are very encouraging – targeted galaxies appear to belong to the overdensities painted by our multi-l datasets, bridging the ZoA.

This suggests that the Local Universe great attractors might be connected on an unprecedented scale – in the form of an enormous ring/shell of galaxies/filaments/clusters/superclusters. This poten- tially massive overdensity might provide the missing clue in the unsettled dipole results.