A Proposed VLA Band 190 MHz Pathfinder Study
A Proposed VLA Band - 190 MHz Pathfinder Study for the EOR L. Greenhill (Cf. A) • Basic Goals – Detection of HI shells around “EOR quasars” – Exploration of line brightness fluctuations over ~10(°)2 • Explore noise-limited deep imaging • Befriend galactic foregrounds • Status – Funding approved by Smithsonian (October 1) • US$110 K • Leverages previous investments in the VLA – Now under peer review by NRAO – Technical/management review to begin Dec. 04 • Proposed tracks in late 2005, early 2007. • Permanent addition to the VLA. Legacy science.
Key VLA/VHF Science Questions • What are the shapes/sizes of the HII regions? – How anisotropic is the ionizing radiation? – When did the quasars form after recombination? • What is the nature of the IGM at z~6. 3? – When did Tspin exceed TCMB? • What is the reionization history? – Constrain the neutral fraction at z~ 6. 3 Pathfinder program w/r to foreground elimination and assessment of gross signal strength (case A/B). Co-Is: Blundell, Loeb, Zaldarriaga (Cf. A), Carilli, Perley (NRAO), Furlanetto (Cal. Tech)
Strong Signal Case and (more likely) Weak Signal Case
How Strong is Strong How Weak is Weak? 295 m. K (Wyithe & Loeb) • Initial target list: 3 SDSS quasars (z=6. 2 -6. 4) that show a “depth effect” to the Lya absorption (Fan et al. ). • The HI lines will lie at 192 -196 MHz.
The Sky at 408 MHz Haslam et al. 1982 Adapted by Emerson Tsky = 14 -16 K (408 MHz) => ~110 K (194 MHz)
Placement of Proposed VHF Receivers Although Ae(327 MHz) ~ 0. 40, Ae(VHF) ~ 0. 50 !
The proposed VHF system mized for sensitivity more existing 4 m and 0. 9 m sys Schematic Layout for VHF Rx of strong signal case echnical demo per source in 2005.
Radio Spectrum Allocation
RFI at the VLA Site Clear sky Lightning TV Carrier Monitoring continues. Winter observing
Timeline • • Oct. 04 - Observing proposal Jan. 05 - First prototype delivered Mar. 05 - Four prototypes deployed Jun. 05 - 14 Rx delivered Jul. 05 - 14 Rx delivered Late 05 - 1 st D-config. and 1 st “useful” data Early 07 - 2 nd D-config.
System Specifications • Dipole - parabolic dish hybrid – Eases calibration • • Bandwidth - 186 - 202 MHz (1. 6 m) Primary beam - 4. 3° Synthesized beam - 5 -15´ (D-config. ) Tsys ~ 180 K Ae ~ 0. 5 ( ~6600 m 2) Sensitivity ~ 10 m. K in 50 h Crossed dipole system l/3 from focus Invisibility
- Slides: 11