AKARI infrared observations of edge-on spiral galaxy NGC 3079

TL;DR

This study uses AKARI infrared imaging to analyze the dust and PAH properties of NGC 3079, revealing spatial variations, high gas-to-dust ratios, and signs of an early starburst phase.

Contribution

First detailed infrared imaging analysis of NGC 3079 revealing dust, PAH properties, and star formation activity with spatial variation.

Findings

Dust temperature of 28-33 K in the galaxy.

High gas-to-dust mass ratios (~860 to 1100).

Evidence of early-phase starburst activity.

Abstract

We present AKARI near- to far-infrared images of the nearby edge-on spiral galaxy NGC 3079 in 10 photometric bands. The spectral energy distribution consists of continuum emission from dust with a single temperature of 28-33 K together with strong mid-infrared emission features from polycyclic aromatic hydrocarbons (PAHs). We derive the dust masses of 5.6x10^6 M_sun and 1.4x10^7 M_sun for the central 4 kpc region and the whole galaxy, respectively, and find that a gas-to-dust mass ratio is unusually high in the central region (\sim 1100) and even for the whole galaxy (\sim 860). The ratio of the surface brightness distribution at the wavelength of 7 um to that at 11 um suggests that the properties of PAHs have spatial variations. Emission from ionized and neutral PAHs is relatively strong in the center and the disk regions, respectively, suggesting stronger radiation field and thus relatively active star formation in the center. Yet the total infrared luminosities of the galaxy indicate rather low star formation rates. These results suggest that NGC 3079 is in an early-phase starburst stage.