Physical Properties of a Pilot Sample of Spectroscopic Close Pair Galaxies at z ~ 2

Creators: Law, David R.; Shapley, Alice E.; Checlair, Jade; Steidel, Charles C.

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 3σ limiting emission-line flux of ~ 10^(-17) 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 z ~ 2 star-forming galaxy population.

Additional Information

© 2015 American Astronomical Society. Received 2015 January 30; accepted 2015 June 25; published 2015 July 30. These results are based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. D.R.L. and C.C.S. have been supported by grant GO-11694 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. C.C.S. has been supported by the U.S. National Science Foundation through grants AST-0606912 and AST-0908805. A.E.S. acknowledges support from the David and Lucile Packard Foundation. D.R.L. thanks Kristen Kulas for assistance obtaining the Keck/NIRSPEC spectroscopy, Dawn Erb for making available previous NIRSPEC observations of Q2343-BX429, and George Becker for sharing a copy of his IDL-based NIRSPEC data reduction code. Finally, we extend thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests.

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Published - Law_2016p160.pdf

Submitted - 1507.00721v1.pdf

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