The Survey for Ionized Gas in the Galaxy, Made with Arecibo

SIGGMA – the ALFA RRL Survey

Robert Minchin

What?

• ALFA survey for Hydrogen, Helium and Carbon Radio Recombination Lines:– H163α – H174α– He163α – He174α– C163α – C174α

• Commensal with P-ALFA in the inner Galaxy• Lead project (supporting P-ALFA and ALFA

ZOA) in the outer Galaxy

Where?

Milky Way image: NASA/JPL-Caltech/R. Hurt

Inner Galaxy30° < l < 75°

Outer Galaxy175° < l 207°

Why?

• Identification of HII regions• Measure electron temperatures (via line to

continuum ratio)• Probe properties of nebular Photo-

Dissociation Regions (withcarbon RRLs)• Look for extended emission from the Warm

Interstellar Medium

When?

• Observations started in 2010• Currently on-going

How?• ‘Leapfrog’ mapping based on the P-ALFA tiling

pattern• Co-addition of the H, He and C lines within the

300 MHz ALFA bandpass

Who?

• Loren Anderson (WVU) – PI• Robert Minchin (Arecibo)• Yervant Terzian (Cornell)• Ed Churchwell (UWM)• Bin Liu (NAO/CAS)• Anish Roshi (NRAO)• Logan Hough (WVU)

Results?