The final program was modified to accomodate last minute changes
including ones necessitated by late arrivals. Karen Masters,
Kristine Spekkens and Martha Haynes agreed to take minutes which
will be posted on the E-ALFA web page after editting. Where
possible, presentation materials will also be posted.
ALFA will be a 7 pixel multifeed array operating over the frequency
range (1.225 to 1.525 GHz).The central pixel will have a gain of 11
K/Jy while the others will achieve 8.5 K/Jy. The central pixel is
expected to have a system temperature of about 25K rising to close
to 35K at the lower frequency edge (28-31 K at 1375 MHz, 34-26 K at
1225 MHz). The Tsys may be reduced by the planned addition of a
spillover-reducing tertiary skirt. The outer pixels will have
slightly worse performance.
The E-ALFA workshop participants strongly encourage NAIC to reduce
Tsys as much as possible, particularly via the tertiary skirt.
A significant issue for E-ALFA is the coma lobe/sidelobe structure
associated with each of the offset feeds. The beams will vary from
3.5 to 4 arcmin, with the sky footprint showing a center-to-center
separation of ~2 beam widths. Contamination from these structures
will have to be taken into account in data analysis software.
More info on the ALFA hardware can be obtained at:
http://alfa.naic.edu/alfa_specs.html
The ALFA front end is being constructed by the CSIRO. The NAIC is
working on antenna controls, the IF/LO system, backend(s), data
acquisition and archiving. It is anticipated that the front end
will be delivered in April 2004, and that, following a period of
integration and commission, ALFA will be ready for astronomical
observations in early 2005.
NAIC indicated that a call for proposals was likely to take place
towards the end of this year (2003).
Where telescope motions might be similar for separate projects, the
possibility of piggybacking exists, if separate backend systems are
available. Current capability for spectral line observing relies
on the WAPPs and will offer 100 MHz with 4K channels and 3-level
sampling for each polarization and beam. A proposed enhancement
would add additional WAPPs to offer another separate 100 MHz, which
might be overlapped to give ~180 MHz required for searches to
higher redshift, or to provide the additional velocity resolution
that might benefit piggyback observations with G-ALFA in the
periphery and vicinity of the Milky Way.
The WAPPs may constitute an acceptable set of spectral
processors. The E-ALFA workshop strongly urges NAIC to provide the
enhanced WAPP capability delivering ~200 MHz spectral coverage and
higher than three-level sampling. It is important that each backend
spectrometer have its own LO capability, and that a full range of
bandwidth/channel number options be available for each.
RFI will pose a significant challenge to the E-ALFA
surveys. Methods both to mitigate and excise it need to be
vigorously pursued. Of particular note, the Galileo satellite
constellation will be fully operational in the 1260-1300 MHz range
by 2008. One approach to RFI identification might include
construction of extra WAPPs and employing additional feeds (say
horizon pointing) for cross-correlation purposes. Higher N-level
sampling is an effective means of combatting RFI and is thus also
desirable in the spectrometer.
The ALFA surveys discussed by the group are intended to address
science problems covering a wide range of topics, including those
which:
explore the HI mass function to the faintest levels
explore the dependence of the HIMF on environment and/or
redshift
map the distribution of luminous and dark matter
study the gas rich membership of nearby groups and clusters
study the population of gas rich systems in the Local Group and
the periphery of the Milky Way
study similar phenomena in other nearby systems
The workshop participants identified 5 broad survey catagories:
Galaxies in different environments, (e.g., Virgo, CVn)
Ultra deep survey (e.g., small area, several 100 ksec)
Deep strip survey (e.g., 1 deg X 300 deg Decl. strip)
Shallow all-sky survey (dubbed "ALFALFA")
ZOA survey
Considerable discussion focussed on outlining the science case for
the different surveys since the requirements should be driven by
the science.
The amount of telescope time required for any one of these surveys
is substantial, and it was thus recognized that this effort is
necessarily multi year/long term. At some time in the future, some
group will have to prioritize the projects, but it was agreed that
it is too early to tackle that now. NAIC requested input from the
E-ALFA participants on anticipated hardware & software needs,
survey strategies and other requirements as well as the development
of a clear assignment of tasks and responsibilities.
Since these surveys will be legacies of the Arecibo Observatory and
should be of broad use and interest, the final data products must
be of high quality and readibly accessibly by the entire
astronomical community for correlative and spin-off
studies. Furthermore, data analysis tools developed for the surveys
should be contributed back to NAIC for use by smaller ALFA
projects. This paradigm will require significant coordination
between the community and NAIC; NAIC will maintain an oversight
function. It is planned that NAIC will take responsibility for
initial stages of data processing (Phase I data products), such as
bandpass calibrated spectra. NAIC will archive all data at several
stages (raw, Phase I, Phase II). The survey teams themselves will
take responsibility for further processing and product production
(Phase II data products) such as cleaned maps, spectra at any
position, source catalogs, final archival products and access tools
(made available through NAIC). Since it is recognized that involved
teams have a distinct edge already, proprietary time will be
minimized and may be no longer than the time to validate data
quality. At the same time, provisions must be developed to protect
student thesis projects. It was recognized that there is a need to
specify uniform standards across the surveys to maximize their
combined scientific return.
It was agreed that the next step was the drafting of a white paper
which would lay out the basics of the surveys, their science
justification and strategies, and other details in order to provide
advice/input to NAIC on requirements from this group. A draft table
of contents for this white paper was developed along with a
preliminary list of volunteers who will take initial responsibility
both for drafting the sections and for eliciting input from
others. Specific sections were identified as follows: 1. Science
justification, survey Lister Staveley-Smith, Jessica Rosenberg,
strategies, and requirements Trish Henning, Steve Schneider and
Liese van Zee 2. Phase I data products Riccardo Giovanelli,
Christian Bruens 3. Detection algorithms, source Jon Davies, Erwin
de Blok, Martha Haynes, and Steve Schneider 4. Phase II data
products Martha Haynes and Lyle Hoffman 5. Archiving and Data
Access Martha Haynes 6. Follow-up Observations Noah Brosch and Wim
van Driel 7. Synergies with other surveys Riccardo Giovanelli,
Trish Henning, Karen (both ALFA and other) O'Neil and Mary Putman
8. Organization & Outreach Martha Haynes, Karen O'Neil and Alison
Peck 9. Funding support (NSF & Euro) Martha Haynes, Wim van Driel
and Liese van Zee
An interim steering committee consisting of Riccardo Giovanelli,
Steve Schneider, and Lister Staveley-Smith was elected and charged
with editting the individual sections to produce a draft white
paper to be presented to NAIC by 1 Jul 2003. The mechanisms for
establishing a longer term organizational structure will be
developed as part of this white paper, and a vote by the current
membership will be held on adoption of these mechanisms. The need
for openness in the writing of this document was emphasized. The
development of a final version of the white paper will be an
interative process between the E-ALFA committee and NAIC.
Chris Salter will serve as interim NAIC Point-of-Contact for
E-ALFA.
It was agreed that the next meeting of this group would be
targetted for fall 2003 at a location to be determined. The meeting
will be held over a weekend, somewhere where expenses can be
minimized. NAIC indicated the possibility of providing some travel
support to US participants for this next meeting.