NGC6240: Merger-Induced Star Formation & Gas Dynamics

TL;DR

This study uses high-resolution spectroscopic and interferometric data to analyze the gas dynamics, star formation, and stellar populations in the merging galaxy system NGC6240, revealing the complex interplay of merger processes.

Contribution

It provides detailed spatially resolved kinematic and stellar population analysis of NGC6240, highlighting the impact of merger-induced star formation and the remnants of progenitor bulges.

Findings

Only 1/3 of K-band continuum is from recent star formation.

Less than 30% of bolometric luminosity is due to starburst.

Nuclei are remnants of progenitor bulges.

Abstract

We present spatially resolved integral field spectroscopic K-band data at a resolution of 0.13" (60pc) and interferometric CO(2-1) line observations of the prototypical merging system NGC6240. Despite the clear rotational signature, the stellar kinematics in the two nuclei are dominated by dispersion. We use Jeans modelling to derive the masses and the mass-to-light ratios of the nuclei. Combining the luminosities with the spatially resolved Br-gamma equivalent width shows that only 1/3 of the K-band continuum from the nuclei is associated with the most recent star forming episode; and that less than 30% of the system's bolometric luminosity and only 9% of its stellar mass is due to this starburst. The star formation properties, calculated from typical merger star formation histories, demonstrate the impact of different assumptions about the star formation history. The properties of the nuclei, and the existence of a prominent old stellar population, indicate that the nuclei are remnants of the progenitor galaxies' bulges.