The Arecibo Legacy Fast ALFA Survey

ALFALFA Sky Coverage

ALFALFA was originially intended to cover 7074 square degrees of the high galactic latitude sky accessible to the Arecibo telescope, i.e. the regions between 0° and +36° in Declination (subdivided into 9 bands of tiles, each 4° wide), 07h30m to 16h30m and 22h to 03h in Right Ascension. In the end, some parts of the spring sky were observed only from 08h30m to 15h30m so that the final coverage is only of about 6300 square degrees.

The survey was conducted in drift mode, following a 2--pass strategy (i.e. each Declination band was scanned at two different epochs, separated by a few months) with the ALFA system. The total allocation, including overhead was 4,741.5 hours allocated in 808 separate observing periods between 5 Feb 2005 and 26 Oct 2013.

Final sky coverage of the ALFALFA survey, in the Virgo (upper) and anti-Virgo (lower) directions. In each panel, the solid red lines outline the proposed survey area. The Arecibo telescope is located at a latitude of 18°21' N and can survey zenith angles less than 20°, but the sensitivity drops sharply at Z.A. > 18°. The dotted red lines make the designated ALFALFA "tile" boundaries while the blue hatched areas reflect the actual final sky coverage. The cyan lines mark the lines of b = +20° (upper) and -20° (lower) while the green lines trace SGL = -10°, 0° and +10°. Blue filled circles mark galaxies with observed heliocentric recessional velocities cz < 700 km/s while open magenta circles denote objects believed to lie with 10 Mpc (Karachentsev et al. 2004), based largely on primary distances.
Figure by mph (01/05).

Last modified: Sun Feb 17 13:53:54 EST 2013 by martha