Star Formation History in the Central Region of the Barred Galaxy NGC 7177

TL;DR

This study uses integral-field spectroscopy to analyze the gas and stellar kinematics, age distribution, and secular evolution of the barred galaxy NGC 7177, revealing gas inflow, a nuclear star formation ring, and the transformation of the bar into a pseudo-bulge.

Contribution

It provides new insights into the secular evolution of NGC 7177, showing the transformation of its bar into a pseudo-bulge and the inward migration of its star formation ring.

Findings

Gas inflow along the bar's dust lanes to the nuclear ring.

The bar is thick and has evolved into a pseudo-bulge.

The star formation ring has migrated inward over 1-2 Gyr.

Abstract

Using the method of integral-field (3D) spectroscopy, we have investigated the kinematics and distribution of the gas and stars at the center of the early-type spiral galaxy with a medium scale bar NGC 7177 as well as the change in the mean age of the stellar population along the radius. A classical picture of radial gas inflow to the galactic center along the shock fronts delineated by dust concentration at the leading edges of the bar has been revealed. The gas inflow is observed down to a radius R = 1".5 -- 2", where the gas flows at the inner Lindblad resonance concentrate in an azimuthally highly inhomogeneous nuclear star formation ring. The bar in NGC 7177 is shown to be thick in z coordinate; basically, it has already turned into a pseudo-bulge as a result of secular dynamical evolution. The mean stellar age inside the star formation ring, in the galactic nucleus, is old, ~10 Gyr. Outside, at a distance R = 6" - 8" from the nucleus, the mean age of the stellar population is ~2 Gyr. If we agree that the bar in NGC 7177 is old, then, obviously, the star formation ring has migrated radially inward in the last 1-2 Gyr, in accordance with the predictions of some dynamical models.