Extreme gas fractions in clumpy, turbulent disk galaxies at z~0.1

Abstract

In this letter we report the discovery of CO fluxes, suggesting very high gas fractions in three disk galaxies seen in the nearby Universe (z ~ 0.1). These galaxies were investigated as part of the DYnamics of Newly Assembled Massive Objects (DYNAMO) survey. High-resolution Hubble Space Telescope imaging of these objects reveals the presence of large star forming clumps in the bodies of the galaxies, while spatially resolved spectroscopy of redshifted Halpha reveals the presence of high dispersion rotating disks. The internal dynamical state of these galaxies resembles that of disk systems seen at much higher redshifts (1 < z < 3). Using CO(1-0) observations made with the Plateau de Bure Interferometer, we find gas fractions of 20-30% and depletion times of tdep ~ 0.5 Gyr (assuming a Milky Way-like CO conversion factor). These properties are unlike those expected for low- redshift galaxies of comparable specific star formation rate, but they are normal for their high-z counterparts. DYNAMO galaxies break the degeneracy between gas fraction and redshift, and we show that the depletion time per specific star formation rate for galaxies is closely tied to gas fraction, independent of redshift. We also show that the gas dynamics of two of our local targets corresponds to those expected from unstable disks, again resembling the dynamics of high-z disks. These results provide evidence that DYNAMO galaxies are local analogues to the clumpy, turbulent disks, which are often found at high redshift.

Accepted to ApJ Letters

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• The SAMI Galaxy Survey: Gas velocity dispersions in low-$z$ star-forming galaxies and the drivers of turbulence
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• The connection between the peaks in velocity dispersion and star-forming clumps of turbulent galaxies
• Gas Content and Kinematics in Clumpy, Turbulent Star-forming Disks
• Angular momentum of $z\sim 1.5$ galaxies and their local analogues with adaptive optics
• Giant Star Forming Complexes in High-z Main Sequence Galaxy Analogues: The Internal Structure of Clumps in DYNAMO Galaxies
• GASP VIII: Capturing the birth of a Tidal Dwarf Galaxy in a merging system at z~0.05
• Stellar Masses of Clumps in Gas-rich, Turbulent Disk Galaxies
• Stellar angular momentum distribution linked to galaxy morphology
• Photoelectric heating effects on the evolution of luminous disk galaxies
• CO Excitation in High-z Main Sequence Analogues: Resolved CO(4-3)/CO(3-2) Line Ratios in DYNAMO Galaxies
• Deep Large Binocular Camera r-band Observations of the GOODS-N Field
• Unveiling the gravitationally unstable disc of a massive star-forming galaxy using NOEMA and MUSE
• K-Band Imaging of the Nearby, Clumpy Turbulent Disk Galaxy DYNAMO G04-1
• Galaxy Zoo: Clump Scout: Surveying the Local Universe for Giant Star-forming Clumps
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