Radio observations of the Milky Way are of vital importance for understanding what really occurs within galaxies. The unique sensitivity of Arecibo's 305m dish is now enhanced 7-fold with ALFA to provide an unprecedented new tool for the investigation of star formation and evolution, the recycling of material between stars and the interstellar medium (ISM), the large-scale transfer of energy among the different components of the ISM, and the evolution of elemental abundances over cosmic timescales. These phenomena can be observed with ALFA over the portion of the Galactic sky between declinations of -1.33 and +38.03 degrees, marked below in red.
The background image is 21cm line emission from neutral atomic hydrogen (H I). The line peak brightness is shown to emphasize high-latitude features. This all-sky map is from Kalberla et al. (2005), who combined 25m and 30m telescope observations from Dwingeloo and Argentina. Arecibo can observe about 32% of this area, but with 10 times the angular resolution and 5 times the velocity resolution in the H I line!
The ALFA sky coverage nicely complements the CGPS, VGPS, and SGPS components of the International Galactic Plane Survey shown in the map. ALFA can observe the Galactic disk in both the inner and outer Galaxy in the first and third quadrants, supplementing the superior IGPS angular resolution in the plane with better sensitivity and spectral resolution. And unlike the IGPS, Galactic ALFA surveys will also cover a large, continuous area off the plane, where isolated clouds and disk-halo energy exchanges can be studied.
ALFA is open to all telescope users through the normal proposal process. A consortium was formed in 2003 to conduct large surveys of the Galactic ISM with ALFA. The consortium is open to new members, but membership is not required to use ALFA. However, telescope users are encouraged to consult the documentation assembled by the consortium for general use.
One particular strength of ALFA is commensal observing, in which multiple backends can be used in parallel, enabling different science projects to use the same telescope pointing simultaneously. Commensal observing is especially powerful for sky surveys. A number of ALFA surveys are being observed commensally with each other to maximize the scientific return per hour of telescope time. The same option exists for smaller proposals.
|GALFA-1: 2003 March 21-23, Arecibo Observatory|
|GALFA-2: 2003 June 18, Boston University|
|GALFA-3: 2004 August 29, Arecibo Observatory|
In addition to these general consortium meetings, the various GALFA sub-consortia concerned with specific surveys have regular teleconferences and occasional face-to-face meetings to discuss survey technical details, logistics, and science. For further information about these sub-consortia, please see the following section on survey groups.
Many GALFA - H I projects have been pursued since 2004. The largest of these currently underway is the Turn On GALFA Survey (TOGS), which runs commensally during E-ALFA observations for the ALFALFA and AGES projects. Another project with multiple commensal partners is the I-GALFA survey of the inner parts of the Galactic disk. All GALFA - H I observations use the specially-designed GALSPECT backend, covering a 1413 km/s range with 7679 channels, each 0.184 km/s wide. A considerable body of information on GALFA-H I observing, data processing software, and science is available on the GALFA documentation page. Specific information on the current H I reduction software and how to use it can be found on the GSR version page. The GALFA - H I project coordinator is Snezana Stanimirovic.
GALFACTS pilot observations were carried out in project a1947 to test observing and data processing techniques. The full GALFACTS survey (project a2130) awaits a new backend, currently being commissioned, that will cover 300 MHz in over 1000 channels to eliminate contamination by RFI and ``unwrap'' frequency-dependent Faraday rotation effects. Further information can be found at the University of Calgary GALFACTS website and in several GALFA science documents. The GALFACTS Principle Investigator is Russ Taylor.
Precursor observations were made as part of project a1943. A 2000-hour RRL survey of the inner Galaxy for |b| < 5 deg is planned (project a2064), and may be observed commensally with P-ALFA. A new, specialized backend spectrometer is being designed for this undertaking. For further details on the survey and RRL science, please see the 2005 RRL White Paper and 2003 GALFA White Paper. The GALFA-RRL Principle Investigator is Yervant Terzian.
For specific details on data availability, potential users are encouraged to contact one of the following individuals:
|Galactic H I Line Data : Steven Gibson|
|Full-Stokes Continuum Data : Russ Taylor|
|Recombination-Line Data : Yervant Terzian|
Although GALFA surveys are only just beginning, a number of exciting results have already emerged. The image above shows the first GALFA H I map. The links below give more details on this and several other results.
|GALFACTS Team Ready to Go (Nov 15, 2007)|
|The Many Streams of the Magellanic Stream (Nov 12, 2007)|
|The Multi-Phase ISM in Perseus (Apr 19, 2007)|
|GALFA Eye on Taurus (Dec 20, 2005)|
|GALFA Studies Forbidden Velocity Line Wings (PDF) (Dec 19, 2005)|
|GALFACTS Precursor Observations See Galactic Magnetic Field (Dec 18, 2005)|
|First GALFA H I Map (Nov 29, 2004)|
|First ``Wave'' for GALFA Observations (Sep 3, 2004)|
|``Velocity Spectrum for H I at High Latitudes'', Chepurnov, A., Lazarian, A., Stanimirovic, S., Peek, J. E. G., & Heiles, C., submitted [astro-ph/0611462]|
|``The Many Streams of the Magellanic Stream'', Stanimirovic, S., Hoffman, S., Heiles, C., Douglas, K. A., Putman, M., & Peek, J. E. G., 2008, ApJ, 680, 276 [arXiv:0802.1349]|
|``A New Technique for Heterodyne Spectroscopy: Least-Squares Frequency Switching (LSFS)'', Heiles, C. 2007, PASP, 119, 643 [arXiv:0707.2399]|
|``Reconstructing Deconstruction: High-Velocity Cloud Distance through Disruption Morphology'', Peek, J. E. G., Putman, M. E., McKee, C. F., Heiles, C., & Stanimirovic, S. 2006, ApJ, 656, 907 [astro-ph/0610429]|
|``First Results from the Arecibo Galactic H I Survey: The Disk/Halo Interface Region in the Outer Galaxy'', Stanimirovic, S., Putman, M., Heiles, C., Peek, J. E. G., Goldsmith, P. F., Koo, B.-C., Krco, M. Lee, J.-J., Mock, J., Muller, E., Pandian, J. D., Parsons, A., Tang, Y., Werthimer, D. 2006, ApJ, 653, 1210 [astro-ph/0609137]|
|``Mapping Hydrogen in the Galaxy, Galactic Halo, and Local Group with ALFA: The GALFA-H I Survey Starting with TOGS'', Gibson, S. J., Douglas, K. A., Heiles, C., Korpela, E. J., Peek, J. E. G., Putman, M., & Stanimirovic, S. 2008, in The Evolution of Galaxies through the Neutral Hydrogen Window, at Arecibo Observatory, Puerto Rico, February 1-3; to be published in AIP conference proceedings, edited by R. Minchin & E. Momjian [arXiv:0805.0017v1]|
|``A Sharper View of MBM 53-55 in GALFA H I Emission'', Gibson, S. J., Korpela, E. J., Stanimirovic, S., Heiles, C., Douglas, K. A., Peek, J. E. G., & Putman, M. 2007, Bull. A.A.S., 39, 988 [#211, #139.18] [Electronic Poster]|
|``How Far Is the Tip of the Magellanic Stream?'', Stanimirovic, S., Hoffman, S., Heiles, C., Douglas, K., Putman, M., & Peek, J. 2007, Bull. A.A.S., 39, 988 [#211, #139.17]|
|``The Many Streams of the Magellanic Stream'', Hoffman, S. M., Stanimirovic, S., Heiles, C., Douglas, K. A., Putman, M., & Peek, J. E. G. 2007, Bull. A.A.S., 39, 985 [#211, #139.04]|
|``Halo Gas of M33'', Putman, M. E., Peek, J. E. G., Douglas, K. A., Heiles, C., Gibson, S. J., Korpela, E. J., & Stanimirovic, S., 2007, Bull. A.A.S., 40, ?? [#211, #095.34]|
|``H I in Local Group Dwarf Galaxies'', Grcevich, J., Putman, M., & Peek, J. E. G. 2007, Bull. A.A.S., 39, 895 [#211, #095.07]|
|``The Atomic Component of the Taurus Molecular Cloud Complex: Measurements and Implications'', Krco, M., Goldsmith, P. F., & Brown, R. L. 2007, Bull. A.A.S., 39, 780 [#211, #029.02]|
|``Hidden Galactic Accretion: The Discovery of Low-Velocity Halo Clouds'', Peek, J. E. G., Putman, M. Sommer-Larsen, J., Heiles, C., Stanimirovic, S., Douglas, K., Gibson, S., & Korpela, E. J., 2007, Bull. A.A.S., 39, 760 [#211, #014.08]|
|``Mapping the Galaxy in H I with GALFA'', Peek, J. E. G., Stanimirovic, S., Putman, M. E., Heiles, C., Douglas, K., Korpela, E., & Gibson, S. J., Mapping the Galaxy and Nearby Galaxies, Ishigaki Island, Okinawa, Japan, 2006 June 26-30|
|``Recent Results from GALFA: `GoldenEye' on Disk/Halo Interfaces'', Stanimirovic, S. 2006, Bull. A.A.S., 38, 110 [#208, #34.02]|
|``ALFA Surveys as Complements to Other Major Surveys'', Haynes, M. P. 2005, Bull. A.A.S., 37, 1489 [#207, #192.08], part of Special Session 192|
|``GALFACTS: A Full-Stokes Continuum Survey of the Arecibo Sky'', Gibson, S. J. 2005, Bull. A.A.S., 37, 1489 [#207, #192.07], part of Special Session 192|
|``GALFA-H I : The First 1000 Square Degrees'', Goldston, J. E., & GALFA-H I Consortium 2005, Bull. A.A.S., 37, 1489 [#207, #192.06], part of Special Session 192|
|``Optimized Mapping Modes and Algorithms for ALFA'', Goldston, J. 2004, Bull. A.A.S., 36, 1476 [#205, #78.08], part of Special Session 205|
|``GALFA Hardware and Calibration Techniques'', Heiles, C., Goldston, J., Mock, J., Parsons, A., Stanimirovic, S., & Werthimer, D. 2004, Bull. A.A.S., 36, 1476 [#205, #78.07], part of Special Session 205|
|``Arecibo Survey of Radio Recombination Lines'', Terzian, Y. 2004, Bull. A.A.S., 36, 1476 [#205, #78.06], part of Special Session 205|
|``A Full-Stokes ALFA Continuum Survey'', Taylor, A. R. 2004, Bull. A.A.S., 36, 1475 [#205, #78.05], part of Special Session 205|
|``ALFA and HVCs: If Jodie Foster Knew What She Could Discover Now . . .'', Putman, M. E. 2004, Bull. A.A.S., 36, 1475 [#205, #78.04], part of Special Session 205|
|``Using ALFA to Study H I and Molecular Clouds'', Arce, H. G., & GALFA-H I Consortium 2004, Bull. A.A.S., 36, 1475 [#205, #78.03], part of Special Session 205|
|``A New Era of Galactic H I Science with ALFA'', Stanimirovic, S., & GALFA-H I Collaboration 2004, Bull. A.A.S., 36, 1475 [#205, #78.02], part of Special Session 205|
|``Introduction to ALFA and the GALFA Consortium'', Goldsmith, P. F. 2004, Bull. A.A.S., 36, 1475 [#205, #78.01], part of Special Session 205|
|Science Documents, Observing Proposals, and Consortium Policy|
|Observing Procedures and Data Processing Software|
|Hardware Details (Spectrometer Backends, etc.)|
|General ALFA Technical Memos|
|E-ALFA Memos and Documents|
|P-ALFA Memos and Documents|
|Arecibo Technical Memos|
|Arecibo Observatory Astronomy Reference Pages|
|Phil Perillat's Arecibo Resources|
|Arecibo Observatory 305m Telescope Schedule|
|Control Interface Module for Arecibo (CIMA; telescope control software)|
|U. Michigan - Turn On GALFA Survey (TOGS) website|
|U. Calgary - Galactic ALFA Continuum Transit Survey (GALFACTS) website|
|Arecibo Obs. - Inner Galaxy ALFA (I-GALFA) survey website|
|GALFA - H I : see the GALFA - H I projects table|
|GALFA - CON : Russ Taylor|
|GALFA - RRL : Yervant Terzian|