Central regions of LIRGs: rings, hidden starbursts, Supernovae and star clusters

TL;DR

This paper investigates star formation processes in luminous IR galaxies using high-resolution spectroscopy, revealing structures like PAH rings, gas flows, and obscured supernovae, advancing understanding of starburst triggers and evolution in galaxy interactions.

Contribution

It presents new high-resolution integral field spectroscopy observations of LIRGs, identifying specific star-forming structures and phenomena, and analyzing their relation to galaxy interactions and starburst activity.

Findings

Detection of a nuclear PAH ring in NGC 1614.

Observation of gas inflows and outflows at galaxy nuclei.

Identification of highly obscured supernovae in LIRGs.

Abstract

We study star formation (SF) in very active environments, in luminous IR galaxies, which are often interacting. A variety of phenomena are detected, such as central starbursts, circumnuclear SF, obscured SNe tracing the history of recent SF, massive super star clusters, and sites of strong off-nuclear SF. All of these can be ultimately used to define the sequence of triggering and propagation of star-formation and interplay with nuclear activity in the lives of gas rich galaxy interactions and mergers. In this paper we present analysis of high-spatial resolution integral field spectroscopy of central regions of two interacting LIRGs. We detect a nuclear 3.3 um PAH ring around the core of NGC 1614 with thermal-IR IFU observations. The ring's characteristics and relation to the strong star-forming ring detected in recombination lines are presented, as well as a scenario of an outward expanding starburst likely initiated with a (minor) companion detected within a tidal feature. We then present NIR IFU observations of IRAS 19115-2124, aka the Bird, which is an intriguing triple encounter. The third component is a minor one, but, nevertheless, is the source of 3/4 of the SFR of the whole system. Gas inflows and outflows are detected at the locations of the nuclei. Finally, we briefly report on our on-going NIR adaptive optics imaging survey of several dozen LIRGs. We have detected highly obscured core-collapse SNe in the central kpc, and discuss the statistics of "missing SNe" due to dust extinction. We are also determining the characteristics of hundreds of super star clusters in and around the core regions of LIRGs, as a function of host-galaxy properties.