charting cosmic flows into the zone of avoidance: the overdensity in vela
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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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
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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
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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
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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.
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Vela Overdensity
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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)
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SALT Observations
RSS-MOS: 10 masks targeted
40% Data Acquired to Date
Huge Thanks to:Alexei Kniazev, Petri Vaisanen & David Gilbank
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SALT Observations
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SALT ObservationsOne Target Field (Block): Exposure: 375 sec
Visits: 2
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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
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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)
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Beware !
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SALT ObservationsYellow == (skewed) sky lines; blue == desired sky line locations
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Deflection (Angstrom) versus Wavelength
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SALT ObservationsYellow == (skewed) sky lines; blue == desired sky line locations
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SALT Results
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SALT Results4 MOS Fields -- ~ 40 target galaxies
3 emission lines detected21 absorption line systems
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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.