Stellar and Molecular Gas Kinematics of NGC1097: Inflow Driven by a Nuclear Spiral

TL;DR

This study investigates the gas and stellar dynamics in NGC1097's nucleus, revealing inflow mechanisms driven by nuclear spirals that influence starburst activity and central gas accretion.

Contribution

It provides detailed kinematic analysis and hydrodynamical modeling of nuclear spirals, quantifying inflow rates and their role in feeding the galaxy's core.

Findings

Inflow rate along arms is approximately 1.2 solar masses per year.

Net accretion rate to the central region is much smaller, around 0.06 solar masses per year.

Nuclear spirals can sustain gas inflow for up to a gigayear.

Abstract

We present spatially resolved distributions and kinematics of the stars and molecular gas in the central 320pc of NGC1097. The stellar continuum confirms the previously reported 3-arm spiral pattern extending into the central 100pc. The stellar kinematics and the gas distribution imply this is a shadowing effect due to extinction by gas and dust in the molecular spiral arms. The molecular gas kinematics show a strong residual (i.e. non-circular) velocity, which is manifested as a 2-arm kinematic spiral. Linear models indicate that this is the line-of-sight velocity pattern expected for a density wave in gas that generates a 3-arm spiral morphology. We estimate the inflow rate along the arms. Using hydrodynamical models of nuclear spirals, we show that when deriving the accretion rate into the central region, outflow in the disk plane between the arms has to be taken into account. For NGC1097, despite the inflow rate along the arms being ~1.2Msun/yr, the net gas accretion rate to the central few tens of parsecs is much smaller. The numerical models indicate that the inflow rate could be as little as ~0.06Msun/yr. This is sufficient to generate recurring starbursts, similar in scale to that observed, every 20-150Myr. The nuclear spiral represents a mechanism that can feed gas into the central parsecs of the galaxy, with the gas flow sustainable for timescales of a Gigayear.