DYNAMO - I. A sample of Hα-luminous galaxies with resolved kinematics

DYNAMO is a multiwavelength, spatially resolved survey of local (z similar to 0.1) star-forming galaxies designed to study evolution through comparison with samples at z similar or equal to 2. Half of the sample has integrated H alpha luminosities of >10(42) erg s(-1), the typical lower limit for resolved spectroscopy at z similar or equal to 2. The sample covers a range in stellar mass (10(9)-10(11) M-circle dot) and star formation rate (0.2-100 M-circle dot yr(-1)). In this first paper of a series, we present integral-field spectroscopy of H alpha emission for the sample of 67 galaxies. We infer gas fractions in our sample as high as similar or equal to 0.8, higher than typical for local galaxies. Gas fraction correlates with stellar mass in galaxies with star formation rates below 10 M-circle dot yr(-1), as found by COLDGASS, but galaxies with higher star formation rates have higher than expected gas fractions. There is only a weak correlation, if any, between gas fraction and gas velocity dispersion. Galaxies in the sample visually classified as disc-like are offset from the local stellar mass Tully-Fisher relation to higher circular velocities, but this offset vanishes when both gas and stars are included in the baryonic Tully-Fisher relation. The mean gas velocity dispersion of the sample is similar or equal to 50 km s(-1), and V/sigma ranges from 2 to 10 for most of the discs, similar to 'turbulent' galaxies at high redshift. Half of our sample show disc-like rotation, while similar to 20 per cent show no signs of rotation. The division between rotating and non-rotating is approximately equal for the sub-samples with either star formation rates >10 M-circle dot yr(-1), or specific star formation rates typical of the star formation 'main sequence' at z similar or equal to 2. Across our whole sample, we find good correlation between the dominance of 'turbulence' in galaxy discs (as expressed by V/sigma) and gas fraction as has been predicted for marginally stable Toomre discs. Comparing our sample with many others at low-and high-redshift reveals a correlation between gas velocity dispersion and star formation rate. These findings suggest the DYNAMO discs are excellent candidates for local galaxies similar to turbulent z similar or equal to 2 disc galaxies.