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 and 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

One 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) epochs 4.Improve wavelength calibration using skylines and cubic fit 5.Extract 1-D spectrum: collapse spatial info, remove local sky 6.Determine redshift

SALT Reductions LACosmic – python script based on Pieter van Dokkum's L.A.Cosmic algorithmPieter 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 Observations Yellow == (skewed) sky lines; blue == desired sky line locations

Deflection (Angstrom) versus Wavelength

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

SALT Results

4 MOS Fields -- ~ 40 target galaxies 3 emission lines detected 21 absorption line systems

SALT Results Even 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- 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.