Arecibo Observatory, a facility of the National Astronomy and
 Ionosphere Center.  Operated by Cornell University under a
 cooperative agreement with the National Science Foundation
Arecibo L-band Feed Array
Arecibo L-Band Feed Array
The National Science Foundation of the United States of America Cornell University

AGES- Arecibo Galaxy Environment Study

In Brief:

AGES is a sub-group of the Extragalactic ALFA (EALFA) consortium. The group aim to make use of the newly installed ALFA on the Arecibo Telescope to conduct medium-senstivity observations of specific regions of interest on the sky, focussing on galaxy groups and individual galaxies.

AGES is a compromise between the larger-scale, but much less sensitive ALFALFA (drift mapping) and the deeper AUDS (drift-and-chase) surveys. In this way, AGES will piggyback onto these surveys: expanding the survey area and target list of AUDS substantially and increasing integration times of ALFALFA to yeild an effective 300s per point. The overall improvement of the sensitivity of ALFALFA will be a factor of ~5.

Proposed regions of interest are detailed in the percursor proposal. They are summarised here:
  • The Virgo Cluster - Collaboration with ALFALFA
  • A Local Void - Collaboration with ALFALFA
  • The Virgo Southern Extension- Collaboration with ALFALFA
  • Galaxy groups and individual Galaxies.- Collaboration with ALFALFA, AUD
  • Deep observations of NGC2903 (Judith Irwin)
  • Zone of Avoidance (ZOA), northern extension (Trish Henning) - Collaboration with ALFALFA,PALFA and GALFA

Current Matters of consideration for AGES:
  • Observing modes and techniques:
  • The observing modes must be developed around the need to make a large number of long-ish integrations. Two modes are discussed in the precursor proposal:
    • Drift scanning - this mode will be used by ALFALFA and there is substantial potential for collaboration with this group for development, particularly in regards to data processing piplines.
    • Modified 'Leapfrog' - Again, a variant of this mode will be used by the PALFA consortia (see a discussion of tiling modes here). Recent measurements suggest that this mode can yeild 80-90% efficiency of telescope time (see a preliminary report on a test of the leapfrog mode here).
    Is a long strip, or shorter but wider patch, the most appropriate technique?
  • Data processing and reduction:
  • What is the best way to process the large volumes of data which will accumulate? No doubt, some cooperation with other EALFA groups and other ALFA consortia are necessary. Discussions on this matter are underway at Cardiff.
    An analysis of signal identification and extraction techniques have been developed for locating HI signal within large datacubes. See 2001MNRAS.328.1151D. This aspect also has substantial potential for collaboration with other EALFA and ALFA groups.
  • Calibration Strategy:
  • Using existing standard gain correction curves, checked for stability with cross scans at the start and end of each observation run.
  • Beam Maps:
  • Beam maps to be collected into a library which will ultimately hold contributions from all projects within the EALFA consortium.
  • Baselines:
  • Baseline corrections to be made using template bandpasses collected from the periphery of the strips (see also 2001AAS...198.8905R).
  • RFI:
  • Interference from the Puntas Salinas and Pico de Este radars can be managed under an existing coordination agreement with the FAA. The operating radar blanker at AO will be used to 'turn off' the receiver to prevent problems caused by the San Juan radar. GPS3 interference is minimal, and can be removed during processing.

Current status of AGES:
  • 29th Jul 2004: Jon Davies accepts position on ALFA coordinating committee as AGES representive.
  • 9th Sept. 2004: Referees award a grade 'A' for the precursor proposals for AGES. Click here for the referee report.
  • 20th Sept. 2004 ~60 hours awarded for AGES pre-cursor experiments. Here is the schedule.
  • 16th Nov. Begin observing to test leapfrog mode. Here is an observations log
  • 19th Nov. Begin observing to test drift mapping of M74. Here is an observations log
  • 6th Dec. Test Observations for Leapfrog mode complete
  • 19th Dec. Test Observations for Drift mode complete
  • All data is currently being reduced and tested to assist in the development of future observing strategies.
  • 15th Feb 2005: Application for VST time. You can see the postscript version of the proposal here
    Contact John Davies, Bobbie Minchin or Robbie Auld for information on the Drift.
    Contact Steve Schneider or Erik Muller for information on the Leapfrog.

AGES Documentation:
The Precursor Proposal - including science justification for precursor project, discussion of observing modes
Study by Spitzak & Schneider (1998) using 'leapfrog' mode with Arecibo L-Band Wide receiver.

Davies, J.Cardiff Hoffman, L.Lafaette Spekkens, K.Cornell
Auld, R.Cardiff Irwin, J.Queens
Boselli, A.Marseille Karachentsev, I.Moscow
Bothun, G.Oregon Kilborn, V.Swinbourne
de Blok, E.Cardiff Koribalski, B.ATNF
Briggs, F.ANU Linder, S.STSci
Brosch N.Wise Observatory Maarten BaesESO
Brinks, E.Mexico Minchin, R.Cardiff
Catinella, B.Arecibo Muller, E.Arecibo
van Driel, W.Meudon Momjain, E.Arecibo
Disney, M.Cardiff Putman, M.Michigan
Gavazzi, G.Milan O'Neil, K.NRAO
Giovanelli, R.Cornell Rosenberg, J.Colorado
Haynes, M.Cornell Sabatini, S.Rome
Henning, T.UNM Schneider, S.Massachusetts

last update Tue Dec 20 14:21:16 AST 2005
Erik Muller