Central star formation in an early-type galaxy I~Zw~81 in the Bootes void

TL;DR

This study investigates the unusual star formation activity in the early-type galaxy I~Zw~81 within the Bootes void, revealing complex structural components, a star-forming disk, and the influence of a strong bar and minor mergers, despite hosting an AGN.

Contribution

First detailed multi-wavelength structural and spectral analysis of I~Zw~81, a massive barred lenticular galaxy in a void, highlighting its active star formation and structural complexity.

Findings

I~Zw~81 is a disk-dominated, star-forming galaxy with a bar and multiple structural components.

The galaxy's UV emission is concentrated in the central region, indicating active star formation.

A strong bar and minor mergers likely drive gas inflow and star formation, despite the presence of an AGN.

Abstract

The origin of star-formation in customarily passively evolving early-type massive galaxies is poorly understood. We present a case study of a massive galaxy, I~Zw~81, inside the Bootes void. The void galaxy is known to host an active galactic nuclei (AGN). Our detailed 2D decomposition of the surface brightness distribution in the $Canada$ $France$ $Hawaii$ $Telescope$ ($CFHT$) g- and r-bands revealed multiple structural components such as a nuclear point source, a bar, a ring, and an inner exponential disk followed by an outer low surface brightness (LSB) disk. I~Zw~81 turns out to be a disk-dominated galaxy with lenticular morphology. The modelling of the multi-wavelength spectral energy distribution (SED) shows that the galaxy is star-forming (SF), and belongs to the blue cloud. We find that the optical (g$-$r) color of the bar is bluer than the disks, and the far- and near-ultraviolet emission inside the galaxy observed with Ultraviolet Imaging Telescope (UVIT) onboard {\em AstroSat} is concentrated in the central few kpc region enclosing the bar. The strong bar might be playing a pivotal role in driving the gas inflow and causing SF activity in tandem with the minor merger-like interactions as evident from the deep $CFHT$ data. The low-luminosity AGN is insufficient to quench the central SF. The results are peculiar from the standpoint of a massive barred lenticular galaxy.