Anatomy of the Star-formation in a Tidally Disturbed Disk galaxy: NGC 3718

TL;DR

This study investigates star-forming complexes in the peculiar, tidally disturbed galaxy NGC 3718 across UV, optical, and near-IR wavelengths, revealing how minor mergers influence inside-out galaxy growth and star formation distribution.

Contribution

It provides a detailed analysis of star-forming complexes in a tidally disturbed galaxy, highlighting the impact of minor mergers on star formation patterns and galaxy evolution.

Findings

Higher star-formation density in the central disk.

Older star-forming complexes in the central region.

Younger complexes are located in outer tidal arms.

Abstract

We present a UV, optical and near-infrared (near-IR) study of the star-forming complexes in the nearby peculiar galaxy NGC 3718, using UVIT, GALEX, Spitzer and DECaLS imaging data. The galaxy has a disturbed optical morphology due to the multiple tidal arms, the warped disk and the prominent curved dust lanes, but in the near-IR, it appears to be a bulge-dominated galaxy. Its disturbed morphology makes it an excellent case to study star formation in a tidally disturbed galaxy that may have undergone a recent minor merger. To study the distribution and properties of the star-forming clumps (SFCs), we divided the galaxy within the R$_{25}$ (B band) radius into three parts --the upper, central and lower regions. Using the UV band images, we investigated the warped star-forming disk, the extended tidal arms, and the distribution and sizes of the 182 SFCs. Their distribution is 49, 60 and 73 in the galaxy's upper, central and lower regions, respectively. We determined the UV color, star-formation rates (SFRs), star-formation density ($\Sigma_{SFR}$) and ages of the SFCs.The central disk of the galaxy has a larger mean $\Sigma_{SFR}$ which is $\sim$3.3 and $\sim$1.6 times higher than the upper and lower regions, respectively. We also find that the SFCs in the central disk are older than those in the tidal arms. Our study thus shows that minor mergers can trigger the inside-out growth of galaxy disks, where the younger SFCs are in outer tidal arms and not in the inner disk.