A Multiwavelength Study of Tadpole Galaxies in the Hubble Ultra Deep Field

TL;DR

This study uses multiwavelength imaging to analyze the morphology, stellar mass, age, and metallicity of tadpole galaxies across redshifts 0.3 to 3.2, revealing their active assembly phase and morphological stability.

Contribution

It provides the first comprehensive multiwavelength morphological and physical property analysis of tadpole galaxies over a wide redshift range, highlighting their active assembly processes.

Findings

Most tadpole galaxies retain their asymmetric morphology in optical and near-infrared.

Tadpole galaxies have lower average stellar mass and metallicity than field galaxies.

They are in an active assembly phase, likely due to merging or gas accretion.

Abstract

Multiwavelength data are essential in order to provide a complete picture of galaxy evolution and to inform studies of galaxies' morphological properties across cosmic time. Here we present results of a multiwavelength investigation of the morphologies of "tadpole" galaxies at intermediate redshift (0.314<z<3.175) in the Hubble Ultra Deep Field. These galaxies were previously selected from deep Hubble Space Telescope (HST) F775W data based on their distinct asymmetric knot-plus-tail morphologies (Straughn et al. 2006). Here we use deep Wide Field Camera 3 near-infrared imaging in addition to the HST optical data in order to study the rest-frame UV/optical morphologies of these galaxies across the redshift range 0.3<z<3.2. This study reveals that the majority of these galaxies do retain their general asymmetric morphology in the rest-frame optical over this redshift range, if not the distinct "tadpole" shape. The average stellar mass of tadpole galaxies is lower than field galaxies, with the effect being slightly greater at higher redshift within the errors. Estimated from SED fits, the average age of tadpole galaxies is younger than field galaxies in the lower redshift bin, and the average metallicity is lower (whereas the specific star formation rate for tadpoles is roughly the same as field galaxies across the redshift range probed here). These average effects combined support the conclusion that this subset of galaxies is in an active phase of assembly, either late-stage merging or cold gas accretion causing localized clumpy star-formation.