Zone of Avoidance (ZOA)P. Henning, UNM

• Obscuration due to dust and high stellar density in our Galaxy blocks ~20% of optical extragalactic universe, less in the IR

• Need all-sky map of surrounding mass inhomogeneity to understand LG’s motion, dynamical evolution

• HI surveys can map galaxies, large-scale structure in regions of bad obscuration and stellar confusion

Hydra wall andMonoceros extension

Puppis

Part of NormaSC

New

NewNew

PKS1343cluster

Puppisvoid

• ZOA in the AO sky cuts some important (known) LSS: Pisces-Perseus SC; Local, Orion, Taurus, edge of Monoceros voids

ZOA with ALFA• Due to likely pressure on popular, low-b portions

of AO sky, best bet is commensal observing

• Option 1: GALFASingle, or double-drift mapping of |b| < 5°Uniform sky sensitivityNyquist sampling with double drift. Time needed is

~460 hours

• Would look much like an E-ALFA survey, but would add much to Parkes info? Better positions, further north, but not much deeper

ZOA with ALFA, cont.• Option 2: PALFA

Galactic plane survey, |b| < 5°, 32° < l < 80°, “possibly also anticenter”

Intermediate latitude survey, to 10° or beyond (tbd)300 sec beam-1 oodles of time, but point and stare

mode. Total time 2000 – 3000 hours

• Enormously deep, but observing mode introduces complications from varying feed-sky geometry

• Really want 200 MHz backend