PHYSICAL PROPERTIES of A PILOT SAMPLE of SPECTROSCOPIC CLOSE PAIR GALAXIES at z ∼ 2

Abstract

We use Hubble Space Telescope Wide-field Camera 3 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 long-slit spectroscopy obtained in excellent seeing conditions (FWHM ∼0.5 arcsec) to obtain Hα-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 the six candidate pairs observed, companions (estimated mass ratios 5:1 and 7:1) are detected for two galaxies down to a limiting emission-line flux of erg s-1 cm-2. 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 a total SFR, SFR surface densities, and stellar masses consistent on average with the overall star-forming galaxy population.