The H alpha Galaxy Survey. IV. Star formation in the local Universe - AstrophysicsReport as inadecuate

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Abstract: We present an analysis of the star formation properties of field galaxieswithin the local volume out to a recession velocity limit of 3000 km-s. Aparent sample of 863 star-forming galaxies is used to calculate a B-bandluminosity function. This is then populated with star formation informationfrom a subsample of 327 galaxies, for which we have H alpha imaging, firstly bycalibrating a relationship between galaxy B-band luminosity and star formationrate, and secondly by a Monte Carlo simulation of a representative sample ofgalaxies, in which star formation information is randomly sampled from theobserved subset. The total star formation rate density of the local Universe isfound to be between 0.016 and 0.023 MSun-yr-cubic Mpc, with the uncertaintiesbeing dominated by the internal extinction correction used in convertingmeasured H alpha fluxes to star formation rates. If our internally derivedB-band luminosity function is replaced by one from the Sloan Digital Sky Surveyblue sequence, the star formation rate densities are approx. 60% of the abovevalues. We also calculate the contribution to the total star formation ratedensity from galaxies of different luminosities and Hubble T-types. The largestcontribution comes from bright galaxies with B absolute mag of approx. -20 mag,and the total contribution from galaxies fainter than -15.5 mag is less than10%. Almost 60% of the star formation rate density comes from galaxies of typesSb, Sbc or Sc; 9% from galaxies earlier than Sb and 33% from galaxies laterthan Sc. Finally, 75 - 80% of the total star formation in the local Universe isshown to be occurring in disk regions, defined as being >1 kpc from the centresof galaxies.

Author: P. A. James 1, J. H. Knapen 2, N. S. Shane 1 and 3, I. K. Baldry 1, R. S. de Jong 4 1 Liverpool John Moores University, 2 Institu


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