1. A Proposed VLA Band - 190 MHz Pathfinder Study for the EOR L
A Proposed VLA Band MHz Pathfinder Study for the EOR L. Greenhill (CfA)
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$110K
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.

2. 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 (CfA), Carilli, Perley (NRAO), Furlanetto (CalTech)

3. (more likely) Weak Signal Case
Strong Signal Case and
(more likely) Weak Signal Case

4. How Strong is Strong - How Weak is Weak? 295 mK
(Wyithe & Loeb)
Initial target list: 3 SDSS quasars (z= ) that show a “depth effect” to the Lya absorption (Fan et al.).
The HI lines will lie at MHz.

5. The Sky at 408 MHz Tsky = 14-16 K (408 MHz) => ~110 K (194 MHz)
Haslam et al. 1982
Adapted by Emerson
Tsky = K (408 MHz) => ~110 K (194 MHz)

6. Placement of Proposed VHF Receivers
Although Ae(327 MHz) ~ 0.40, Ae(VHF) ~ 0.50 !

7. Schematic Layout for VHF Rx
Test of strong signal case
and technical demo
50h per source in 2005.
The proposed VHF system is opti-mized for sensitivity more so than existing 4m and 0.9 m systems.

8. Radio Spectrum Allocation

9. RFI at the VLA Site Clear sky TV Carrier Lightning
Monitoring continues. Winter observing

10. Timeline Oct. 04 - Observing proposal
Jan First prototype delivered
Mar Four prototypes deployed
Jun Rx delivered
Jul Rx delivered
Late st D-config. and 1st “useful” data
Early nd D-config.

11. System Specifications
Dipole - parabolic dish hybrid
Eases calibration
Bandwidth MHz (1.6 m)
Primary beam - 4.3°
Synthesized beam ´ (D-config.)
Tsys ~ 180 K
Ae ~ 0.5 ( ~6600 m2)
Sensitivity ~ 10 mK in 50h
Crossed dipole system l/3 from focus
Invisibility