A near-infrared morphological comparison of high-redshift submm and radio galaxies: massive star-forming discs vs relaxed spheroids - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




A near-infrared morphological comparison of high-redshift submm and radio galaxies: massive star-forming discs vs relaxed spheroids - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We present deep, high-quality K-band images of complete subsamples ofpowerful radio and sub-mm galaxies at z=2. The data were obtained in the bestavailable seeing at UKIRT and Gemini North, with integration times scaled toensure that comparable rest-frame surface brightness levels are reached for allgalaxies. We fit two-dimensional axi-symmetric galaxy models to determinegalaxy morphologies at rest-frame optical wavelengths > 4000A, varyingluminosity, axial ratio, half-light radius, and Sersic index. We find that,while some images show evidence of galaxy interactions, >95% of the rest-frameoptical light in all galaxies is well-described by these simple models. We alsofind a clear difference in morphology between these two classes of galaxy; fitsto the individual images and image stacks reveal that the radio galaxies aremoderately large =8.4+-1.1kpc; median r{1-2}=7.8, de Vaucouleursspheroids = 4.07+-0.27; median n=3.87, while the sub-mm galaxies appearto be moderately compact =3.4+-0.3kpc; median r{1-2}=3.1kpcexponential discs =1.44+-0.16; median n=1.08. We show that the z=2 radiogalaxies display a well-defined Kormendy relation but that, while larger thanother recently-studied high-z massive galaxy populations, they are still ~1.5times smaller than their local counterparts. The scalelengths of the starlightin the sub-mm galaxies are comparable to those reported for the molecular gas.Their sizes are also similar to those of comparably massive quiescent galaxiesat z>1.5. In terms of stellar mass surface density, the majority of the radiogalaxies lie within the locus defined by local ellipticals. In contrast, whilebest modelled as discs, most of the sub-mm galaxies have higher stellar massdensities than local galaxies, and appear destined to evolve into present-daymassive ellipticals.



Author: T. A. Targett 1, J. S. Dunlop 1, R. J. McLure 1, P. N. Best 1, M. Cirasuolo 1, O. Almaini 2 1 University of Edinburgh, UK, 2 Univ

Source: https://arxiv.org/



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