The VIMOS Ultra-Deep Survey: A major merger origin for the high fraction of galaxies at $2<z<6$ with two bright clump

Understand

(Abridged) The properties of stellar clumps in star forming galaxies and their evolution over the redshift range $2\lesssim z \lesssim 6$ are presented and discussed in the context of the build-up of massive galaxies at early cosmic times.

• We use HST/ACS images of galaxies with spectroscopic redshifts from the VIMOS Ultra Deep Survey (VUDS) to identify clumps within a 20 kpc radius.
• We find that the population of galaxies with more than one clump is dominated by galaxies with two clumps, representing $\sim21-25$\% of the population, while the fraction of galaxies with 3, or 4 and more, clumps is 8-11 and 7-9\%, respectively.
• The fraction of clumpy galaxies is in the range $\sim35-55\%$ over $2<z<6$, increasing at higher redshifts, indicating that the fraction of irregular galaxies remains high up to the highest redshifts.