Cold dust in giant barred galaxy NGC1365

TL;DR

This study maps the cold dust in galaxy NGC1365 using sub-millimeter observations, revealing dust properties, asymmetries, and gas dynamics that suggest rapid evolution driven by a strong bar.

Contribution

First detailed sub-millimeter mapping of NGC1365's dust properties and gas flow dynamics, highlighting asymmetries and rapid central mass evolution.

Findings

Most dust is at 20 K, with a warmer component at 40 K.

Eastern bar has over four times more dust than the western bar.

Gas inflow timescale to the center is approximately 300 million years.

Abstract

Observations of galaxies at sub-millimeter wavelengths, where the emission is mainly due to cold dust, are required to constrain the dust physical properties and provide important insight on the gas content of galaxies. We mapped NGC1365 at 870um with LABOCA, the Large APEX Bolometer Camera, allowing us to probe the central mass concentration as well as the rate at which the gas flows to the center. We obtained the dust physical properties both globally and locally for different locations in the galaxy. A 20 K modified black body represents about 98% of the total dust content of the galaxy, the rest can be represented by a warmer dust component of 40 K. The bar exhibits an east-west asymmetry in the dust distribution: The eastern bar is heavier than the western bar by more than a factor of 4. Integrating the dust SED, we derive a total infrared (IR) luminosity of 9.8 x 10^{10} L_{\odot} leading to a dust-enshrouded star formation rate of ~16.7 M_{\odot} per year in NGC1365. We derive the gas mass from the measurements of the dust emission resulting in a CO-to-H2 conversion factor of X_{CO}~1.2x10^{20} mol cm^{-2} (K km s^{-1})^{-1} in the central disk including the bar. Taking into account the metallicity variation, the central gas mass concentration is only ~20% at R<40" (3.6 kpc). On the other hand, the time-scale with which the gas flows into the center, ~300 Myr, is rather short. This indicates that the current central mass in NGC1365 is evolving fast due to the strong bar.