Dark Energy BAO Intensity Mapping
T. Chang, UP, J. Peterson, P. McDonaldPRL 100, 091303 (March 5, 2008)
UP, L. Staveley-Smith, J. Peterson, T. Chang arXiv:0802.3239
Baryon Acoustic Oscillations – Dark Energy Probe
• CMB acoustic oscillations: imprinted standard ruler, 100 Mpc.
• Present in current matter distribution
WMAP5 and other, Nolta et al (2008)
Present LSS BAO Detections
• Percival et al 2007
Percival et al 2007Eisenstein et al 2005
Mapping Large Scale Structure
• Measure individual galaxy redshifts – SDSS(3), SKA, ADEPT, WFMOS (radio/optical), etc.
• OR measure collective emission from galaxies without resolving individual objects. Hundreds of galaxies in each BAO pixel!
• Prototype observations and analysis in progress – CMU cylinder, GBT, VLBA, ATA, Parkes, GMRT. (Bandura, Staveley-Smith, Briggs)
Radio Mapping Experiments
• Redshifted 21cm Hydrogen transition: 300MHz-1.4 GHz, radio maps
• Large area survey, large field of view, low surface brightness: like CMB. Signal ~ 50 µK
• Foregrounds large -- ~K, but smooth (spatially and spectrally).
First Intensity Mapping Detection
• Archival analysis of Parkes HIPASS data• 21cm Survey of 68% of the sky, at dec<22 deg• z<0.04, median detected galaxy z=0.01• Cross correlate with 6dF
Pen et al 2008
Prospects with existing telescopes
• Cross correlation detected with µK noise.• CMB-like scan strategy for extended source mapping.• Parkes multibeam: perfect for all sky z<0.13 (receiver
limit). Redo SDSS volume, fill in zone of avoidance (?). Strengthen low z BAO signal.
• GBT: pencil beam surveys to z=2.5, in progress (April 23-May 1, 2008). May detect BAO at z=1.5 with major campaign.
• ATA (used as single dishes): northern sky, z<0.2.
Dedicated Survey Experiment
• Low frequency technology cheap, modest collecting area
• Large field of view: receiver arrays• High surface brightness sensitivity: compact
arrays• Stable, reliable: no moving parts• Technologies: aperture arrays (Wyithe, Loeb,
Geil 2008), cylinders (Peterson et al)
Existing cylinders
MOLONGLO
OOTY
Molonglo
AUSTRALIABrisbane
Darwin
PerthCanberra
Hobart
AdelaideMelbourne
Sydney
+
NORTHERN CROSS
Cambridge
CMU cylinder under construction: U. Seljak, J. Peterson, K. Bandura.
Mapping LSS
Cosmic Variance Limited Hubble SurveysChang, UP, Peterson, McDonald, PRL 100, 091303, March 5, 2008
Conclusions
• Baryon Acoustic Oscillations – geometric measure of the universe and dark energy
• First detections reported – 2dF, SDSS• Intensity Mapping: unresolved galaxies.• First detection of IM through cross correlation
in archival HIPASS data.• Prototypes and observations under way.
Cylinder telescopes a promising technology.
Top Related