The Hα and Infrared Star Formation Rates for the Nearby Field Galaxy Survey

We investigate the H-alpha and infrared star formation rate (SFR) diagnosticsfor galaxies in the Nearby Field Galaxy Survey (NFGS). For the 81 galaxies inour sample, we derive H-alpha fluxes (included here) from integrated spectra.There is a strong correlation between the ratio of far-infrared to opticalluminosities L(FIR)/L(H-alpha) and the extinction E(B-V) measured with theBalmer decrement. Before reddening correction, the SFR(IR) and SFR(H-alpha) arerelated to each other by a power-law. Correction of the SFR(H-alpha) forextinction using the Balmer decrement and a classical reddening curve bothreduces the scatter in the SFR(IR)-SFR(H-alpha) correlation and results in amuch closer agreement (within ~10%) between the two SFR indicators. This SFRrelationship spans 4 orders of magnitude and holds for all Hubble types withIRAS detections in the NFGS. A constant ratio between the SFR(IR) andSFR(H-alpha) for all Hubble types, including early types (S0-Sab), suggeststhat the IR emission in all of these objects results from a young stellarpopulation.Comment: 23 pages, 5 figures, 1 table. Accepted for publication in the Astronomical Journal. V2: Important changes: IRAS fluxes updated. Only moderate and good quality IRAS FIR fluxes are now used, resulting in slight changes to the equations and figures. The IR and H-alpha SFRs now agree to within ~10%, rather than ~30% as quoted previousl