Central Spiral Structure of Molecular Gas in Maffei 2

TL;DR

This study investigates the distribution and motion of molecular gas in Maffei 2's central region, revealing a nuclear spiral structure linked to bar dynamics, with implications for star formation and mass concentration.

Contribution

It provides detailed observations of the molecular gas structures and kinematics in Maffei 2's nucleus, highlighting the connection between bar orbits and spiral formation, and estimating the central mass concentration.

Findings

The molecular gas forms a nuclear spiral connected to bar structures.

Mass concentration within 35 pc is approximately 2 x 10^8 solar masses.

Dense gas formation occurs at orbit crossing points, leading to star formation after ~2 x 10^5 years.

Abstract

Distribution and kinematics of molecular gas in the central region of the barred spiral galaxy Maffei 2 were investigated using a data set of 12CO(1-0), 12CO(2-1), CS(2-1) lines and 103 GHz continuum. We found that the offset ridges along the kpc-scale bar continue to the central spiral structure embedded in the weak oval structure which is regarded as x2 orbit in the bar potential. The spiral structure continues toward the center diverging from the oval structure. The size of these structures is less than R ~ 100 pc. The mass concentration within R = 35 pc is estimated to be 2 X 10^8 Mo. The high mass concentration is consistent with theoretical predictions concerning the creation of such a nuclear spiral structure. A comparison with the tracers of dense gas and star-forming region suggests that the dense molecular gas traced by CS(2-1) line is formed at the crossing points of x1 and x2 orbits and the star-forming region appears after 2 X 10^5 yr which is comparable with the free-fall time of the dense gas traced by the CS line (~ 10^5 cm^-3).