Extragalactic ALFA Survey Plans Arecibo Legacy Fast ALFA (ALFALFA) Team leader: Giovanelli (Cornell)...

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)

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

MHI vs. cz for 12s and 300s (AGES) integration, 1000 hrs each and HIPASS mass fcn, = -1.3

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)

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?

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)

AGES Observational Technique

• Drift scanning, versus “leapfrog”, individual step-and-stare pointings near meridian interleaved to cover sky (AGES precursor proposal)

Arecibo Ultra-Deep Survey (AUDS)

Strategy: Very long integration time on small patches of sky

STORRIE-LOMBARDI & WOLFE, 2000, ApJ 543, 552

PEI, FALL, & HAUSER 1999, ApJ, 522, 604

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Main Scientific Motivation: Evolution of gas from z < 0.15

More science goals

• The cosmic web

• Low column density gas in the local Universe

• Extragalactic OH megamaser emission

• Extragalactic HI absorption

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

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

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

Hydra wall andMonoceros extension

Puppis

Part of NormaSC

New

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PKS1343cluster

Puppisvoid

• ZOA in the AO sky cuts some important (known) LSS: Pisces-Perseus SC; Local, Orion, Taurus, edge of Monoceros voids

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.

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?

ZOA data processing

• If Drift, then based on AIPS++/HIPASS software

• If Leapfrog, then traditional ON/OFF, with rather complicated indexing