Stellar Population Properties and Evolution Analysis of NGC 628 with the Panchromatic Photometry

TL;DR

This study uses multi-wavelength photometry and stellar population synthesis to map the age, metallicity, and reddening of NGC 628, revealing a pseudobulge, distinct disk regions, and insights into galaxy evolution processes.

Contribution

It provides spatially resolved stellar population maps of NGC 628 and interprets their implications for galaxy formation and secular evolution.

Findings

The bulge is a disk-like pseudobulge with a S{\'e}rsic index near exponential.

The disk has two regions with different age and metallicity gradients.

The galaxy's evolution is driven by secular processes and possible gas accretion events.

Abstract

Panchromatic spectral energy distribution (SED) from the ultraviolet (UV), optical to infrared (IR) photometry of NGC 628, combined with the evolutionary stellar population synthesis, is used to derive the spatially resolved age, metallicity and reddening maps. These parameter distributions show that the bulge of this galaxy is a disk-like pseudobulge, which has the S{\'e}rsic index close to the exponential law, rich gas, and a young circumnuclear ring structure. We also discover the disk has two distinct regions with different radial age and metallicity gradients. The inner region is older and has a much steeper age gradient than the outer region of the disk. Both these two regions and the central young structure can be seen in the radial profile of the optical color. Based on the age and reddening distributions, we consider that the pseudobulge and disk are likely to have grown via the secular evolution, which is the redistribution of mass and energy through the angular momentum transport caused by the non-axisymmetric potential of the spirals. However, possible gas accretion events could affect the outer region of the disk, due to abundant H{\sc i} gas accumulating in the outer disk.