Chemical Enrichment of Isolated Relic Galaxy Mrk1216

TL;DR

This study leverages XMM-Newton EPIC and RGS data to examine the hot ISM of the isolated relic galaxy Mrk1216, deriving radial temperature and multi-element abundance profiles out to about $R_{500}$. By applying a VGADEM multi-temperature model and the SNeRatio yields framework, the authors find a centrally enhanced $[Mg/Fe]$ and a nearly flat relative SNIa contribution with $R_{Ia}\approx0.17$ up to $\sim0.42\,R_{500}$, consistent with an early-enrichment scenario in a relic, minimally interacted system. The results support the picture that relic galaxies preserve rapid early star formation signatures and exhibit limited later enrichment, highlighting the value of isolated relics as benchmarks for early galaxy evolution while noting IMF-related modelling uncertainties. Future high-resolution X-ray spectroscopy and refined chemical-evolution models (e.g., with IGIMF) are needed to fully interpret SN yields and enrichment histories in such systems.

Abstract

In this study, we investigate the chemical enrichment and structural evolution of the isolated elliptical relic galaxy Mrk1216 through X-ray observations. As a red-nugget relic, Mrk1216 provides a rare window into the early Universe, owing to its minimal interaction with the surrounding environment. Using data from the XMM-Newton telescope, we model the X-ray emission of its interstellar medium to derive radial temperature and abundance profiles. We find that the central region exhibits an elevated [Mg/Fe] ratio compared to typical early-type galaxies, consistent with a brief but intense star formation episode during its early assembly-a hallmark of relic systems. The nearly flat SNIa ratio profile ($R_{Ia} \sim 0.17$) extending to $\sim0.42R_{500}$ supports an early-enrichment scenario. These results highlight the importance of relic galaxies as benchmarks for studying early galaxy evolution and chemical enrichment. Future high-resolution missions and more advanced theoretical models incorporating more realistic initial mass functions are needed to fully assess their implications.

Figures (8)

• Figure 1: Adaptively smoothed and combined image of Mrk1216. The solid white annuli mark the regions selected for analysis, extending out to $R_{500}$. The central region is coloured black for visual clarity. The green dashed annulus indicates the background region.
• Figure 2: Left: Adaptively smoothed and combined image of Mrk1216. White lines show the RGS spectral region. Right: Spectral fit of the RGS region.
• Figure 3: Black data points show the surface brightness profile of Mrk1216. The red line shows the best-fit model, consisting of $\beta_1$, $\beta_2$, and constant background terms. The constant background is plotted as a green line with light-green $3\sigma$ uncertainty. Six annuli were selected for spectra, with the sixth for background. Alternating grey areas mark annuli, the pink region marks the background annulus. Black lines at bottom right mark $R_{2500}$, $R_{500}$, and $R_{200}$ from left to right.
• Figure 4: Radial temperature profile of Mrk1216. The derived multi-temperature plasma emission model (VGADEM) calculates the mean ($\mu_{kT}$) and standard ($\sigma_{kT}$) deviation of temperature values for a specific region. Temperature values from buote2019extremely are shown in magenta for comparison.
• Figure 5: Radial abundance profiles (Mg, Si, S and Fe) of Mrk1216 and groups average from mernier2017radial.