NGC 4245: one or two bars, and where does the gas inflow stop?

TL;DR

This study investigates the stellar and gaseous dynamics and star formation history in the center of the barred galaxy NGC 4245, revealing a chemically distinct core and a star-forming ring linked to the galaxy's bar dynamics.

Contribution

It provides detailed kinematic and stellar population analysis of NGC 4245, identifying a compact star-forming ring and a chemically distinct core, supporting models of bar-driven secular evolution.

Findings

Presence of a chemically distinct, metal-rich core

Existence of a star-forming ring at 300 pc radius

Star formation linked to the inner Lindblad resonance

Abstract

We have studied stellar and gaseous kinematics as well as stellar population properties in the center of the early-type barred galaxy NGC 4245 by means of integral-field spectroscopy. We have found a chemically distinct compact core, more metal-rich by a factor of 2.5 than the bulge, and a ring of young stars with the radius of 300 pc. Current star formation proceeds in this ring; its location corresponds to the inner Lindblad resonance of the large-scale bar. The mean age of stars in the chemically distinct core is significantly younger than the estimate by Sarzi et al. (2005) for the very center, within R=0.25", made with the HST spectroscopy data. We conclude that the `chemically distinct core' is in fact an ancient ultra-compact star forming ring with radius less than 100 pc which marks perhaps the past position of the inner Lindblad resonance. In general, the pattern of star formation history in the center of this early-type gas-poor galaxy confirms the predictions of dynamical models for the secular evolution of a stellar-gaseous disk under the influence of a bar.