Extended narrow-line emission in the bright Seyfert 1.5 galaxy HE 2211-3903

TL;DR

This study uses integral field spectroscopy to analyze the spatially resolved emission-line regions of the Seyfert 1.5 galaxy HE 2211-3903, revealing a large-scale ring, disk rotation, and evidence of AGN photoionization affecting the galaxy's interstellar medium.

Contribution

First detailed spatially resolved emission-line diagnostics of HE 2211-3903, revealing a large-scale ring and AGN influence on the galaxy's extended emission regions.

Findings

Discovery of a 6 kpc radius ring connected to the nucleus

Evidence of disk rotation pattern in gas kinematics

AGN photoionization influences extended emission-line regions

Abstract

Extended narrow-line regions (ENLRs) and extended emission-line regions (EELRs) have been the focus of integral field spectroscopy aiming at the inner kiloparsecs of nearby Seyfert galaxies as well as the larger environment of high redshift QSOs. Based on observations with the Wide Field Spectrograph WiFeS at the 2.3 m telescope of the Australian National University, we present spatially resolved emission-line diagnostics of the bright Seyfert 1.5 galaxy HE 2211-3903 which is drawn from a sample of the brightest Seyfert galaxies at z<0.06 with luminosities around the classical Seyfert/QSO demarcation. In addition to the previously known spiral arms of HE 2211-3903, the emission-line maps reveal a large scale ring with a radius of about 6 kpc which is connected to the active galactic nucleus (AGN) through a bar-like structure. The overall gas kinematics indicates a disk rotation pattern. The emission-line ratios show Seyfert-type, HII region-type, and composite classifications, while there is no strong evidence of LINER-type ratios. Shock ionization is likely to be negligible throughout the galaxy. The composite line ratios are explained via a mixing line between AGN and HII region photoionization. Composite line ratios are predominantly found in between the HII regions in the circum-nuclear region, the bar-like structure to the east of the nucleus, and the eastern half of the ring, suggesting AGN photoionization of the low-density interstellar medium in an ENLR on galaxy scales. The line ratios in the nucleus indicate N-enrichment, which is discussed in terms of chemical enrichment by Wolf-Rayet and Asymptotic Giant Branch stars during past and ongoing nuclear starburst activity.