A Proposed VLA Band - 190 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.

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)

Strong Signal Case and (more likely) Weak Signal Case

295 mK

(Wyithe & Loeb)

How Strong is Strong - How Weak is Weak?

• Initial target list: 3 SDSS quasars (z=6.2-6.4) that show a “depth effect” to the Ly absorption (Fan et al.). • The HI lines will lie at 192-196 MHz.

The Sky at 408 MHz

Haslam et al. 1982Adapted 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 !

Schematic Layout for VHF Rx

The proposed VHF system is opti-mized for sensitivity more so than existing 4m and 0.9 m systems.

Test of strong signal caseand technical demo 50h per source in 2005.

Radio Spectrum Allocation

RFI at the VLA Site

Clearsky

LightningTV 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 - 1st D-config. and 1st “useful” data

• Early 07 - 2nd 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 m2)• Sensitivity ~ 10 mK in 50h • Crossed dipole system /3 from focus• Invisibility