Starburst galaxies in the COSMOS field: clumpy star-formation at redshift 0 < z < 0.5

TL;DR

This study systematically analyzes starburst galaxies at redshift 0 to 0.5 in the COSMOS field, focusing on their clumpy star formation, properties of star-forming regions, and potential evolutionary links to higher redshift systems.

Contribution

It provides detailed measurements of star-forming clumps in intermediate-redshift starburst galaxies and compares their properties across different galaxy types and redshifts.

Findings

Star-forming knots follow similar L(Hα) vs. size relations as local HII regions.

Clumps in central regions are more massive and have higher star formation rates.

Spatial resolution is crucial for understanding star-forming regions.

Abstract

At high redshift, starburst galaxies present irregular morphologies, with 10-20\%\ of their star formation occurring in giant clumps. These clumpy galaxies are considered to be the progenitors of local disk galaxies. To understand the properties of starbursts at intermediate and low redshift, it is fundamental to track their evolution and possible link with the systems at higher $z$. We present an extensive, systematic, and multi-band search and analysis of the starburst galaxies at redshift ($0 < z < 0.5$) in the COSMOS field, as well as detailed characteristics of their star-forming clumps by using Hubble Space Telescope/Advance Camera for Surveys (HST/ACS) images. Their principal properties, sizes, masses, and star formation rates are provided. The individual star-forming knots in our sample follow the same L(H$\alpha$) vs. size scaling relation than local giant HII regions (Fuentes-Masip et al. 2000). However, they slightly differ from the one provided using samples at high redshift. This result highlights the importance of spatially resolving the star-forming regions for this kind of study. Star-forming clumps in the central regions of Mknots galaxies are more massive, and present higher star formation rates, than those in the outskirts. This trend is smeared when we consider either the mass surface density or surface star formation rate. Sknot galaxies do show properties similar to both dwarf elliptical and irregulars in the surface brightness ($\mu$) versus M$_{host}$ diagram in the $B-$band (Amor\'in et al. 2012), and to spheroidals and ellipticals in the $\mu$ versus M$_{host}$ diagram in the $V-$band (Kormendy \&\ Bender 2012). Sknot galaxies might be transitional phases of the BCD class, with their properties consistent with spheroidal like, but blue structures.