Massive Clumps in Local Galaxies: Comparisons with High-Redshift Clumps

TL;DR

This study compares local UV-bright, clumpy galaxies with high-redshift clumpy galaxies and normal spirals, revealing similarities in star formation and clump properties, and suggesting a link via turbulence and surface density trends.

Contribution

It provides a comparative analysis of clump properties across local, high-redshift, and normal spiral galaxies, highlighting their similarities and differences in star formation and turbulence.

Findings

Large Kiso galaxies resemble UDF clumpies in star formation and clump properties.

Clump masses and surface densities are smaller in normal spirals.

Turbulent speeds and surface densities increase from normal to Kiso to UDF galaxies.

Abstract

Local UV-bright galaxies in the Kiso survey include clumpy systems with kpc-size star complexes that resemble clumpy young galaxies in surveys at high redshift. We compare clump masses and underlying disks in several dozen galaxies from each of these surveys to the star complexes and disks of normal spirals. Photometry and spectroscopy for the Kiso and spiral sample come from the Sloan Digital Sky Survey. We find that the largest Kiso clumpy galaxies resemble UDF clumpies in terms of the star formation rates, clump masses, and clump surface densities. Clump masses and surface densities in normal spirals are smaller. If the clump masses are proportional to the turbulent Jeans mass in the interstellar medium, then for the most luminous galaxies in the sequence of normal:Kiso:UDF, the turbulent speeds and surface densities increase in the proportions 1.0:4.7:5.0 and 1.0:4.0:5.1, respectively, for fixed restframe B-band absolute magnitude. For the least luminous galaxies in the overlapping magnitude range, the turbulent speed and surface density trends are 1.0:2.7:7.4 and 1.0:1.4:3.0, respectively. We also find that while all three types have radially decreasing disk intensities when measured with ellipse-fit azimuthal averages, the average profiles are more irregular for UDF clumpies (which are viewed in their restframe UV) than for Kiso galaxies (viewed at g-band), and major axis intensity scans are even more irregular for the UDF than Kiso galaxies. Local clumpy galaxies in the Kiso survey appear to be intermediate between UDF clumpies and normal spirals.