Tracing cool molecular gas and star formation on similar to 100 pc scales within a z similar to 2.3 galaxy

A. P. Thomson*, R. J. Ivison, Frazer N. Owen, A. L. R. Danielson, A. M. Swinbank, Ian Smail

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We present new, high-angular resolution interferometric observations with the Karl G. Jansky Very Large Array of (CO)-C-12 J = 1-0 line emission and 4-8 GHz continuum emission in the strongly lensed, z = 2.3 submillimetre galaxy, SMM J21352-0102. Using these data, we identify and probe the conditions in similar to 100 pc clumps within this galaxy, which we consider to be potential giant molecular cloud complexes, containing up to half of the total molecular gas in this system. In combination with far-infrared and submillimetre data, we investigate the far-infrared/radio correlation, measuring q(IR) = 2.39 +/- 0.17 across SMM J21352. We search for variations in the properties of the interstellar medium (ISM) throughout the galaxy by measuring the spatially resolved q(IR) and radio spectral index, alpha(radio), finding ranges q(IR) = [2.1, 2.6] and alpha(radio) = [-1.5, -0.7]. We argue that these ranges in alpha(radio) and q(IR) may reflect variations in the age of the ISM material. Using multi-J (CO)-C-12 data, we quantitatively test a recent theoretical model relating the star formation rate surface density to the excitation of (CO)-C-12, finding good agreement between the model and the data. Lastly, we study the Schmidt-Kennicutt relation, both integrated across the system and within the individual clumps. We find small offsets between SMM J21352 and its clumps relative to other star-forming galaxy populations on the Schmidt-Kennicutt plot - such offsets have previously been interpreted as evidence for a bi-modal star formation law, but we argue that they can be equally well explained as arising due to a combination of observational uncertainties and systematic biases in the choice of model used to interpret the data.

Original languageEnglish
Pages (from-to)1874-1886
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume448
Issue number2
DOIs
Publication statusPublished - 1 Apr 2015

Keywords

  • ISM: molecules
  • galaxies: active
  • galaxies: high-redshift
  • galaxies: ISM
  • galaxies: starburst
  • DEEP FIELD-SOUTH
  • HIGH-REDSHIFT GALAXIES
  • FAR-INFRARED/RADIO CORRELATION
  • MASSIVE DISK GALAXIES
  • SUBMILLIMETER GALAXIES
  • ALMA SURVEY
  • FORMING GALAXIES
  • INTERSTELLAR-MEDIUM
  • STARBURST GALAXIES
  • SPIRAL GALAXIES

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