Year: 2012
Type: article
Abstract: We present Karl G. Jansky Very Large Array observations of the CO(2–1) emission in the z = 4.05 submillimeter galaxy (SMG) GN20. These high-resolution data allow us to image the molecular gas at 1.3 kpc resolution just 1.6 Gyr after the big bang. The data reveal a clumpy, extended gas reservoir, 14 ± 4 kpc in diameter, in unprecedented detail. A dynamical analysis shows that the data are consistent with a rotating disk of total dynamical mass 5.4 ± 2.4 × 10 11 M ☉ . We use this dynamical mass estimate to constrain the CO-to-H 2 mass conversion factor (α CO ), finding α CO = 1.1 ± 0.6 M ☉ (K km s −1 pc 2 ) −1 . We identify five distinct molecular gas clumps in the disk of GN20 with masses a few percent of the total gas mass, brightness temperatures of 16–31K, and surface densities of >3200–4500 × (α CO /0.8) M ☉ pc −2 . Virial mass estimates indicate they could be self-gravitating, and we constrain their CO-to-H 2 mass conversion factor to be <0.2–0.7 M ☉ (K km s −1 pc 2 ) −1 . A multiwavelength comparison demonstrates that the molecular gas is concentrated in a region of the galaxy that is heavily obscured in the rest-frame UV/optical. We investigate the spatially resolved gas excitation and find that the CO(6–5)/CO(2–1) ratio is constant with radius, consistent with star formation occurring over a large portion of the disk. We discuss the implications of our results in the context of different fueling scenarios for SMGs.
Source: The Astrophysical Journal
Authors: J. A. Hodge, C. L. Carilli, F. Walter, W. J. G. de Blok, D. Riechers, E. Daddi, L. Lentati
Institutions: Max Planck Institute for Astronomy, University of Cambridge, National Radio Astronomy Observatory, University of Cape Town, Netherlands Institute for Radio Astronomy, California Institute of Technology, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Astrophysique, Instrumentation et Modélisation, Université Paris Diderot
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1974350456