Abstract
We present H\alpha fluxes, star formation rates (SFRs) and equivalent
widths (EWs) for a sample of 156 nearby galaxies observed in the 12CO J=3-2
line as part of the James Clerk Maxwell Telescope Nearby Galaxies Legacy
Survey. These are derived from images and values in the literature and from new
H\alpha images for 72 galaxies which we publish here. We describe the sample,
observations and procedures to extract the H\alpha fluxes and related
quantities. We discuss the SFR properties of our sample and confirm the
well-known correlation with galaxy luminosity, albeit with high dispersion. Our
SFRs range from 0.1 to 11 Msun yr-1 with a median SFR value for the complete
sample of 0.2 Msun yr-1. This median values is somewhat lower than similar
published measurements, which we attribute, in part, to our sample being
HI-selected and, thus, not biased towards high SFRs as has frequently been the
case in previous studies. Additionally, we calculate internal absorptions for
the H\alpha line, A(H\alpha), which are lower than many of those used in
previous studies. Our derived EWs, which range from 1 to 880\AA with a median
value of 27\AA, show little dependence with luminosity but rise by a factor
of five from early- to late-type galaxies. This paper is the first in a series
aimed at comparing SFRs obtained from H\alpha imaging of galaxies with
information derived from other tracers of star formation and atomic and
molecular gas.
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