The SINS survey of z~2 galaxy kinematics: properties of the giant star forming clumps

TL;DR

This study investigates the properties of giant star-forming clumps in z~2 galaxies, revealing their gravitational instability origins, outflow activity, and potential for migration and disruption within galactic disks.

Contribution

It provides detailed observational insights into the kinematics, outflows, and chemical properties of star-forming clumps at high redshift, using deep SINFONI AO spectroscopy.

Findings

Clumps are gravitationally bound and formed from instability.

Outflows from clumps can exceed star formation rates.

Clumps may migrate inward or disrupt due to feedback.

Abstract

We have studied the properties of giant star forming clumps in five z~2 star-forming disks with deep SINFONI AO spectroscopy at the ESO VLT. The clumps reside in disk regions where the Toomre Q-parameter is below unity, consistent with their being bound and having formed from gravitational instability. Broad H{\alpha}/[NII] line wings demonstrate that the clumps are launching sites of powerful outflows. The inferred outflow rates are comparable to or exceed the star formation rates, in one case by a factor of eight. Typical clumps may lose a fraction of their original gas by feedback in a few hundred million years, allowing them to migrate into the center. The most active clumps may lose much of their mass and disrupt in the disk. The clumps leave a modest imprint on the gas kinematics. Velocity gradients across the clumps are 10-40 km/s/kpc, similar to the galactic rotation gradients. Given beam smearing and clump sizes, these gradients may be consistent with significant rotational support in typical clumps. Extreme clumps may not be rotationally supported; either they are not virialized, or they are predominantly pressure supported. The velocity dispersion is spatially rather constant and increases only weakly with star formation surface density. The large velocity dispersions may be driven by the release of gravitational energy, either at the outer disk/accreting streams interface, and/or by the clump migration within the disk. Spatial variations in the inferred gas phase oxygen abundance are broadly consistent with inside-out growing disks, and/or with inward migration of the clumps.