THE INTERSTELLAR MEDIUM IN DISTANT STAR-FORMING GALAXIES: TURBULENT PRESSURE, FRAGMENTATION, AND CLOUD SCALING RELATIONS IN A DENSE GAS DISK AT z = 2.3
- Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)
- Max Planck Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)
- Institut de Radioastronomie Millimetrique, 300 rue de la Piscine, Domaine Universitaire, F-38406 Saint Martin d'Heres (France)
- Institute for Astronomy, University of Edinburgh, Edinburgh EH9 3HJ (United Kingdom)
- CRAL, Observatoire de Lyon, Universite de Lyon 1, 9 avenue Ch. Andre, F-69561 Saint-Genis Laval (France)
- Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
We have used the Institut de Radioastronomie Millimetrique (IRAM) Plateau de Bure Interferometer and the Expanded Very Large Array to obtain a high-resolution map of the CO(6-5) and CO(1-0) emission in the lensed, star-forming galaxy SMM J2135-0102 at z = 2.32. The kinematics of the gas are well described by a model of a rotationally supported disk with an inclination-corrected rotation speed, v{sub rot} = 320 {+-} 25 km s{sup -1}, a ratio of rotational-to-dispersion support of v/{sigma} = 3.5 {+-} 0.2, and a dynamical mass of (6.0 {+-} 0.5) Multiplication-Sign 10{sup 10} M{sub Sun} within a radius of 2.5 kpc. The disk has a Toomre parameter, Q = 0.50 {+-} 0.15, suggesting that the gas will rapidly fragment into massive clumps on scales of L{sub J} {approx} 400 pc. We identify star-forming regions on these scales and show that they are {approx}10 Multiplication-Sign denser than those in quiescent environments in local galaxies, and significantly offset from the local molecular cloud scaling relations (Larson's relations). The large offset compared to local molecular cloud line-width-size scaling relations implies that supersonic turbulence should remain dominant on scales {approx}100 Multiplication-Sign smaller than in the kinematically quiescent interstellar medium (ISM) of the Milky Way, while the molecular gas in SMM J2135 is expected to be {approx}50 Multiplication-Sign denser than that in the Milky Way on all scales. This is most likely due to the high external hydrostatic pressure we measure for the ISM, P{sub tot}/k{sub B} {approx} (2 {+-} 1) Multiplication-Sign 10{sup 7} K cm{sup -3}. In such highly turbulent ISM, the subsonic regions of gravitational collapse (and star formation) will be characterized by much higher critical densities, n{sub crit} > = 10{sup 8} cm{sup -3}, a factor {approx}>1000 Multiplication-Sign more than the quiescent ISM of the Milky Way.
- OSTI ID:
- 21612654
- Journal Information:
- Astrophysical Journal, Vol. 742, Issue 1; Other Information: DOI: 10.1088/0004-637X/742/1/11; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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