extragalactic alfa survey plans arecibo legacy fast alfa (alfalfa) team leader: giovanelli (cornell)...
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Extragalactic ALFA Survey Plans
• Arecibo Legacy Fast ALFA (ALFALFA) Team leader: Giovanelli (Cornell)
• Arecibo Galaxy Environments Survey (AGES) Team leader: Davies (Cardiff)
• ALFA Ultra-Deep Survey (AUDS). Team leader: Freudling (ESO)
• Zone of Avoidance Survey (ZOA). Team leader: Henning (New Mexico)
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Arecibo Galaxy Environments Survey
• HI mass function in various environments
• Spatial distribution of HI-selected galaxies
• Identify individual low MHI and low NHI objects, cp. to QSO absorption line studies and simulations
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MHI vs. cz for 12s and 300s (AGES) integration, 1000 hrs each and HIPASS mass fcn, = -1.3
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AGES
• Exact survey regions tbd, but include:
• Virgo, to MHI 6 x 106 M to compare HI of cluster galaxies with “field”, effects of cluster environment on galaxy evolution, search for low MHI galaxy companions, HI clouds. 300sec integration 6 x 106 M (5 sigma and 30 km/s width)
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AGES
• A Local Void: search for HI associated with very LSB galaxies, or clouds
• Virgo Southern extension: if galaxies fall into clusters along filaments, these should be in intermediate state between galaxies in field and cluster, eg. more dwarfs per giant in cluster, cluster dwarfs gas poor – opposite of field. When does transformation begin?
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AGES
• Groups and individual galaxies: observe number of isolated galaxies, groups, investigate link between dwarf companions and HVCs, and HI at large distances from center of galaxies. First target is NGC2903, precursor study (Irwin, Queen’s)
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AGES Observational Technique
• Drift scanning, versus “leapfrog”, individual step-and-stare pointings near meridian interleaved to cover sky (AGES precursor proposal)
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Arecibo Ultra-Deep Survey (AUDS)
Strategy: Very long integration time on small patches of sky
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STORRIE-LOMBARDI & WOLFE, 2000, ApJ 543, 552
PEI, FALL, & HAUSER 1999, ApJ, 522, 604
Extrapola
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Main Scientific Motivation: Evolution of gas from z < 0.15
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More science goals
• The cosmic web
• Low column density gas in the local Universe
• Extragalactic OH megamaser emission
• Extragalactic HI absorption
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Possible survey parameters
• Need to be sensitive to MHI~109-10 M
• 200 km/sec linewidth 0.2mJy at z~0.16• rms~0.05 mJy/beam (260x deeper than HIPASS)• 0.36 deg2 in 1000 hrs, or 70 hrs/beam• Volume = 8000 Mpc3
• 160 galaxies in range 109-10 M
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Precursor Proposal to test sensitivity limitations on small region: __
• σTint for long integrations?• RFI• Baselines, standing waves• Efficiency (time on “source”)
proposal: 70 hours of repeated drift scans over an area with known gas rich galaxies within 200MHz bandpass
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Zone of Avoidance (ZOA)
• 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
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Hydra wall andMonoceros extension
Puppis
Part of NormaSC
New
NewNew
PKS1343cluster
Puppisvoid
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• ZOA in the AO sky cuts some important (known) LSS: Pisces-Perseus SC; Local, Orion, Taurus, edge of Monoceros voids
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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
• Would look much like an E-ALFA survey, trace large-scale structure further north than Parkes with better positions.
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ZOA with ALFA, cont.• Option 2: PALFA
Galactic plane survey, |b| < 5°, all AO longitudes300 s beam-1 oodles of time Step and stare mode, tiling to cover sky at ½
power point
• Enormously deep, but observing mode introduces complications from varying feed-sky geometry
• A concern: Need 2 spectrometers for any commensal observing. Timing?
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ZOA data processing
• If Drift, then based on AIPS++/HIPASS software
• If Leapfrog, then traditional ON/OFF, with rather complicated indexing