Far-Infrared Line Imaging of the Starburst Ring in NGC 1097 with the Herschel/PACS Spectrometer

TL;DR

This study uses Herschel/PACS far-infrared spectral maps to analyze the physical conditions and dynamics of the interstellar medium in the starburst ring of galaxy NGC 1097, revealing spatial variations in emission lines, gas density, and rotation.

Contribution

First spatially resolved far-infrared spectral mapping of NGC 1097's starburst ring, providing detailed insights into ISM properties and kinematics.

Findings

Enhanced emission in NE clumps along the ring.

Evidence of rapid rotation at ~220 km/s.

Variation in line ratios indicating changes in radiation field and gas density.

Abstract

NGC 1097 is a nearby SBb galaxy with a Seyfert nucleus and a bright starburst ring. We study the physical properties of the interstellar medium (ISM) in the ring using spatially resolved far-infrared spectral maps of the circumnuclear starburst ring of NGC 1097, obtained with the PACS spectrometer on board the Herschel Space Telescope. In particular, we map the important ISM cooling and diagnostic emission lines of [OI] 63 $\mu$m, [OIII] 88 $\mu$m, [NII] 122 $\mu$m, [CII] 158 $\mu$m and [NII] 205 $\mu$m. We observe that in the [OI] 63 $\mu$m, [OIII] 88 $\mu$m, and [NII] 122 $\mu$m line maps, the emission is enhanced in clumps along the NE part of the ring. We observe evidence of rapid rotation in the circumnuclear ring, with a rotation velocity of ~220$ km s$^{-1}$ (inclination uncorrected) measured in all lines. The [OI] 63 $\mu$m/[CII] 158 $\mu$m ratio varies smoothly throughout the central region, and is enhanced on the northeastern part of the ring, which may indicate a stronger radiation field. This enhancement coincides with peaks in the [OI] 63 $\mu$m and [OIII] 88 $\mu$m maps. Variations of the [NII] 122 $\mu$m/[NII] 205 $\mu$m ratio correspond to a range in the ionized gas density between 150 and 400 cm$^{-3}$.