A ug 2 01 1 The Arecibo Legacy Fast ALFA Survey : The α . 40 HI Source Catalog , its Characteristics and their Impact on the Derivation of the HI Mass Function

We present a current catalog of 21 cm HI line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ∼2800 deg of sky: the α.40 catalog. Covering 40% of the final survey area, the α.40 catalog contains 15855 sources in the regions 0730 < R.A. < 1630, +04 < Dec. < +16 and +24 < Dec. < +28 and 22 < Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853. e-mail: haynes@astro.cornell.edu, riccardo@astro.cornell.edu,amartin@astro.cornell.edu, betsey@astro.cornell.edu, ghallenbeck@astro.cornell.edu,shan@astro.cornell.edu, papastergis@astro.cornell.edu Department of Astronomy, U. Wisconsin, Madison, WI. e-mail: hess@astro.wisc.edu, wilcots@astro.wisc.edu Max Planck Institute for Extraterrestrial Physics and Max Planck Institute for Astrophysics, Garching bei Muenchen, Germany. e-mail: amelie@mpe.mpg.de Department of Physics, Lafayette College, Easton, PA 18042. e-mail: hoffmang@lafayette.edu National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903. e-mail: bkent@nrao.edu Department of Physics and Astronomy, Union College, Schenectady, NY. e-mail: koopmanr@union.edu Spitzer Science Center, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125.e-email: sabrina@ipac.caltech.edu Department of Physics and Astronomy, Colgate University, Hamilton, NY. e-mail: tbalonek@mail.colgate.edu Department of Math, Chemistry and Physics, West Texas A and M University, Box 60787, Canyon TX. e-mail: dcraig@wtamu.edu Department of Physics, P.O. Box 8031, Georgia Southern University, Statesboro, GA 30460. e-mail: shigdon@georgiasouthern.edu Department of Physics and Astronomy, Humboldt State University, Arcata, CA 95521. e-mail: David.Kornreich@humboldt.edu Physics Department, St. Lawrence University, 23 Romoda Drive, Canton, NY 13617. e-mail: jeff@stlawu.edu, aodonoghue@stlawu.edu Department of Physics and Astronomy, St. Mary’s College of California, 1928 St. Mary’s Road, Moraga, California 94575. e-mail: rpolowin@stmarys-ca.edu School of Physics, Astronomy and Computational Science, George Mason University, MS 3F3, Fairfax, VA 22030. e-mail: jrosenb4@gmu.edu Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, Ontario K7K 7B4, Canada. e-mail: Kristine.Spekkens@rmc.ca Department of Physics, Hartwick College, Johnstone Science Building, 1 Hartwick Drive, Oneonta, NY 13820. e-mail: TroischtP@hartwick.edu