A metal-rich elongated structure in the core of the group NGC4325

TL;DR

This study investigates the metal distribution in the core of galaxy group NGC4325, revealing a filamentary iron structure likely influenced by past AGN activity, with supernova winds contributing minimally to overall metal enrichment.

Contribution

The paper combines X-ray spectral mapping and optical spectral analysis to link iron filamentary structures with past AGN activity and models supernova contributions to IGM enrichment.

Findings

Iron filament correlates with the central galaxy and suggests past AGN activity.

Supernova winds contribute less than 3% to the IGM metal enrichment.

Oxygen is well mixed, indicating early production during group formation.

Abstract

We used X-ray 2D spectrally resolved maps to resolve structure in temperature and metal abundance. To perform stellar population analysis we applied the spectral fitting technique with STARLIGHT to the optical spectrum of the central galaxy. We simulated the chemical evolution of the central galaxy. While the temperature, pseudo-pressure, and pseudo-entropy maps showed no inhomogeneities, the iron spatial distribution shows a filamentary structure in the core of this group, which is spatially correlated with the central galaxy, suggesting a connection between the two. The analysis of the optical spectrum of the central galaxy showed no contribution by any recent AGN activity. Using the star formation history as input to chemical evolution models, we predicted the iron and oxygen mass released by supernovae (SNe) winds in the central galaxy up to the present time. Comparing the predicted amount of mass released by the NGC4325 galaxy to the ones derived through X-ray analysis we conclude that the winds from the central galaxy alone play a minor role in the IGM metal enrichment of this group inside r2500. The SNe winds are responsible for no more than 3% of it and of the iron mass and 21% of the oxygen mass enclosed within r2500. Our results suggest that oxygen has been produced in the early stages of the group formation, becoming well mixed and leading to an almost flat profile. Instead, the iron distribution is centrally peaked, indicating that this element is still being added to the IGM specifically in the core by the SNIa. A possible scenario to explain the elongated iron-rich structure in the core of the NGC4325 is a past AGN activity, in which our results suggest an episode older than ~10^7-10^8 yrs and younger than 5x10^8.