Abstract
We use Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3) rest-frame
optical imaging to select a pilot sample of star-forming galaxies in the
redshift range z = 2.00-2.65 whose multi-component morphologies are consistent
with expectations for major mergers. We follow up this sample of major merger
candidates with Keck/NIRSPEC longslit spectroscopy obtained in excellent seeing
conditions (FWHM ~ 0.5 arcsec) to obtain Halpha-based redshifts of each of the
morphological components in order to distinguish spectroscopic pairs from false
pairs created by projection along the line of sight. Of six pair candidates
observed, companions (estimated mass ratios 5:1 and 7:1) are detected for two
galaxies down to a 3sigma limiting emission-line flux of ~ 10^-17 erg/s/cm2.
This detection rate is consistent with a ~ 50% false pair fraction at such
angular separations (1-2 arcsec), and with recent claims that the
star-formation rate (SFR) can differ by an order of magnitude between the
components in such mergers. The two spectroscopic pairs identified have total
SFR, SFR surface densities, and stellar masses consistent on average with the
overall z ~ 2 star forming galaxy population.
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