Hα3: an Hα imaging survey of HI selected galaxies from ALFALFA ^⋆

V. The Coma supercluster survey completion

¹ Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
e-mail: giuseppe.gavazzi@mib.infn.it; guido.consolandi@mib.infn.it, e.viscardi4@campus.unimib.it
² Universitäts-Sternwarte München, Schenierstrasse 1, 81679 München, Germany
³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
⁴ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, 3122 Victoria, Australia
⁵ Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
⁶ Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101, USA
⁷ Instituto de Astronomía, Universidad Nacional Autónoma de México, Carretera Tijuana-Ensenada, km 103, 22860 Ensenada, B.C., Mexico
⁸ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁹ Center for Radiophysics and Space Research, Space Science Building, Ithaca, NY 14853, USA

Received: 17 November 2014
Accepted: 19 December 2014

Abstract

Neutral hydrogen represents the major observable baryonic constituent of galaxies that fuels the formation of stars through transformation of molecular hydrogen. The emission of the hydrogen recombination line Hα is the most direct tracer of the process that transforms gas (fuel) into stars. We continue to present Hα3 (acronym for Hα − αα), an extensive Hα+[NII] narrow-band imaging campaign of galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA), using the instrumentation available at the San Pedro Martir (SPM) observatory (Mexico). In 48 nights since 2011 we were able to carry out the Hα imaging observations of 724 galaxies in the region of the Coma supercluster 10^h < RA < 16^h ; 24° < Dec < 28° and 3900 <cz< 9000 km s^-1. Of these, 603 are selected from the ALFALFA and constitute a 97% complete sample. They provide for the first time a complete census of the massive star formation properties of local gas-rich galaxies belonging to different environments (cluster vs. filaments), morphological types (spirals vs. dwarf Irr), over a wide range of stellar mass (~ 10⁸ − 10^11.5M_⊙) in the Coma supercluster. The present Paper V provides Hα data and derived star formation rates for the observed galaxies.