Finite Resolution Deconvolution of Multi-Wavelength Imaging of 20,000 Galaxies in the COSMOS Field: The Evolution of Clumpy Galaxies Over Cosmic Time

TL;DR

This study employs a novel finite resolution deconvolution technique on ground-based images to analyze the evolution of clumpy star-forming galaxies over cosmic time, revealing trends in clumpiness and mass contribution from redshift 0.5 to 2.

Contribution

It introduces a new deconvolution method validated against HST data to resolve galaxy structures and study their clumpy fractions across a large galaxy sample.

Findings

Clumpy galaxy fraction decreases with stellar mass and redshift.

Clumps contribute more to galaxy mass at higher redshifts.

Most clumpy galaxies exhibit higher specific star formation rates.

Abstract

Compact star-forming clumps observed in distant galaxies are often suggested to play a crucial role in galaxy assembly. In this paper, we use a novel approach of applying finite resolution deconvolution on ground-based images of the COSMOS field to resolve 20,185 star-forming galaxies (SFG) at 0.5<z<2 to an angular resolution of 0.3", and study their clumpy fractions. A comparison between the deconvolved and HST images across four different filters shows good agreement and validates the deconvolution. We model spectral energy distributions using the deconvolved 14-band images to provide resolved surface brightness and stellar mass density maps for these galaxies. We find that the fraction of clumpy galaxies decreases with increasing stellar masses, and with increasing redshift: from ~30% at z ~ 0.7 to ~50% at z ~ 1.7. Using abundance matching, we also trace the progenitors for galaxies at z ~ 0.7 and measure the fractional mass contribution of clumps toward their total mass budget. Clumps are observed to have a higher fractional mass contribution toward galaxies at higher redshift: increasing from ~1% at z ~ 0.7 to ~5% at z ~ 1.7. Finally, the majority of clumpy SFGs have higher specific star formation rates (sSFR) compared to the average SFGs at fixed stellar mass. We discuss the implication of this result to in-situ clump formation due to disk instability.