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تسجيل مستخدم جديدALMA reveals potential evidence for spiral arms, bars, and rings in high-redshift submillimeter galaxies
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We present sub-kpc-scale mapping of the 870 $mu$m ALMA continuum emission in six luminous ($L_{rm IR}~sim~5~times10^{12}$ L$_{odot}$) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. Our high-fidelity 0.07$$-resolution imaging ($sim$500 pc) reveals robust evidence for structures with deconvolved sizes of $lesssim$0.5-1 kpc embedded within (dominant) exponential dust disks. The large-scale morphologies of the structures within some of the galaxies show clear curvature and/or clump-like structures bracketing elongated nuclear emission, suggestive of bars, star-forming rings, and spiral arms. In this interpretation, the ratio of the `ring and `bar radii (1.9$pm$0.3) agrees with that measured for such features in local galaxies. These potential spiral/ring/bar structures would be consistent with the idea of tidal disturbances, with their detailed properties implying flat inner rotation curves and Toomre-unstable disks (Q<1). The inferred one-dimensional velocity dispersions ($sigma_{rm r}lesssim$ 70-160 km s$^{-1}$) are marginally consistent with the limits implied if the sizes of the largest structures are comparable to the Jeans length. We create maps of the star formation rate density ($Sigma_{rm SFR}$) on $sim$500 pc scales and show that the SMGs are able to sustain a given (galaxy-averaged) $Sigma_{rm SFR}$ over much larger physical scales than local (ultra-)luminous infrared galaxies. However, on 500 pc scales, they do not exceed the Eddington limit set by radiation pressure on dust. If confirmed by kinematics, the potential presence of non-axisymmetric structures would provide a means for net angular momentum loss and efficient star formation, helping to explain the very high star formation rates measured in SMGs.
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We study the physical properties of giant molecular cloud associations (GMAs) in M100 (NGC 4321) using the ALMA Science Verification feathered (12-m+ACA) data in 12CO (1-0). To examine the environmental dependence of GMA properties, GMAs are classifi
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We propose a new theory to explain the formation of spiral arms and of all types of outer rings in barred galaxies. We have extended and applied the technique used in celestial mechanics to compute transfer orbits. Thus, our theory is based on the ch
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