Hubble Space Telescope Morphologies of z ~ 2 Dust-obscured Galaxies. II. Bump Sources

May 2011 • 2011ApJ...733...21B

Authors • Bussmann, R. S. • Dey, Arjun • Lotz, J. • Armus, L. • Brown, M. J. I. • Desai, V. • Eisenhardt, P. • Higdon, J. • Higdon, S. • Jannuzi, B. T. • Le Floc'h, E. • Melbourne, J. • Soifer, B. T. • Weedman, D.

Abstract • We present Hubble Space Telescope imaging of 22 ultra-luminous infrared galaxies (ULIRGs) at z ≈ 2 with extremely red R - [24] colors (called dust-obscured galaxies, or DOGs) which have a local maximum in their spectral energy distribution (SED) at rest-frame 1.6 μm associated with stellar emission. These sources, which we call "bump DOGs," have star formation rates (SFRs) of 400-4000 M _sun yr^-1 and have redshifts derived from mid-IR spectra which show strong polycyclic aromatic hydrocarbon emission—a sign of vigorous ongoing star formation. Using a uniform morphological analysis, we look for quantifiable differences between bump DOGs, power-law DOGs (Spitzer-selected ULIRGs with mid-IR SEDs dominated by a power law and spectral features that are more typical of obscured active galactic nuclei than starbursts), submillimeter-selected galaxies, and other less-reddened ULIRGs from the Spitzer Extragalactic First Look Survey. Bump DOGs are larger than power-law DOGs (median Petrosian radius of 8.4 ± 2.7 kpc versus 5.5 ± 2.3 kpc) and exhibit more diffuse and irregular morphologies (median M ₂₀ of -1.08 ± 0.05 versus -1.48 ± 0.05). These trends are qualitatively consistent with expectations from simulations of major mergers in which merging systems during the peak SFR period evolve from M ₂₀ = -1.0 to M ₂₀ = -1.7. Less-obscured ULIRGs (i.e., non-DOGs) tend to have more regular, centrally peaked, single-object morphologies rather than diffuse and irregular morphologies. This distinction in morphologies may imply that less-obscured ULIRGs sample the merger near the end of the peak SFR period. Alternatively, it may indicate that the intense star formation in these less-obscured ULIRGs is not the result of a recent major merger.

Links

• PREPRINT http://arxiv.org/abs/1103.3527
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2011ApJ...733...21B
• ELECTR https://doi.org/10.1088%2F0004-637X%2F733%2F1%2F21
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2011ApJ...733...21B
• PDF https://stacks.iop.org/0004-637X/733/21/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2011ApJ...733...21B
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2011ApJ...733...21B