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Unveiling Chemical Enrichment in the Abell 2029 Core with XRISM, XMM-Newton, and Chandra

Arnab Sarkar, Eric D. Miller, Brian McNamara, Ming Sun, Richard Mushotzky, Stefano Ettori, Lorenzo Lovisari, Irina Zhuravleva, Naomi Ota

TL;DR

The paper presents a multi-instrument X-ray study of the Abell 2029 core, combining XRISM Resolve/Xtend data with XMM-Newton and Chandra to measure nine elemental abundances. It employs a two-temperature collisional ionization equilibrium model across instruments to derive robust X/Fe patterns, noting Resolve’s strength in resolving S/Fe, Ar/Fe, Ca/Fe and Ni/Fe. By comparing observed X/Fe ratios to SNcc and SNIa yields, the study finds that a SNcc model with low initial metallicity ($Z_{init}=0.001$) plus a sub-Chandrasekhar-mass, double-degenerate SNIa scenario best reproduces the central enrichment, with a SNIa/SNe fraction of ~0.30; a Ca-rich gap transient component further improves the Ca/Fe match. The results reveal a complex enrichment history in A2029’s core and demonstrate the crucial role of high-resolution X-ray spectroscopy in constraining SN progenitor channels in the ICM.

Abstract

We present new measurements of the chemical abundance pattern in the core of the nearby galaxy cluster Abell~2029, based on XRISM observations with Resolve (37 ks) and Xtend (500 ks), combined with archival data from XMM-Newton (EPIC, RGS) and Chandra. Fe abundances derived from Resolve, Xtend, and EPIC are broadly consistent, while RGS gives systematically lower values. Because the XRISM gate valve remained closed during these observations, Resolve spectral fitting is restricted to the 2--10 keV band, providing reliable constraints only for elements with strong lines in this band (S, Ar, Ca, Fe, Ni). Abundances of the $α$-elements are therefore derived using complementary observations from Xtend, EPIC, RGS, and Chandra. We construct an average X/Fe pattern in the cluster core by using Resolve exclusively for S/Fe, Ar/Fe, Ca/Fe, and Ni/Fe, and RGS + Xtend for O/Fe. The Ne/Fe ratio is averaged from Xtend, EPIC, RGS, and Chandra measurements; Mg/Fe from EPIC and Chandra measurements; and Si/Fe from Xtend, EPIC, and Chandra. Comparison with the supernovae yield models indicates that the observed abundance pattern in A2029 core is best reproduced by a combination of core-collapsed yields from low-metallicity progenitors ($Z_{\rm init}=0.001$) and a sub-Chandrasekhar-mass, double-degenerate Type Ia model. Additionally, we find an excess in Ca abundance in the core of A2029 that cannot be reproduced by the standard supernovae yield models.

Unveiling Chemical Enrichment in the Abell 2029 Core with XRISM, XMM-Newton, and Chandra

TL;DR

The paper presents a multi-instrument X-ray study of the Abell 2029 core, combining XRISM Resolve/Xtend data with XMM-Newton and Chandra to measure nine elemental abundances. It employs a two-temperature collisional ionization equilibrium model across instruments to derive robust X/Fe patterns, noting Resolve’s strength in resolving S/Fe, Ar/Fe, Ca/Fe and Ni/Fe. By comparing observed X/Fe ratios to SNcc and SNIa yields, the study finds that a SNcc model with low initial metallicity () plus a sub-Chandrasekhar-mass, double-degenerate SNIa scenario best reproduces the central enrichment, with a SNIa/SNe fraction of ~0.30; a Ca-rich gap transient component further improves the Ca/Fe match. The results reveal a complex enrichment history in A2029’s core and demonstrate the crucial role of high-resolution X-ray spectroscopy in constraining SN progenitor channels in the ICM.

Abstract

We present new measurements of the chemical abundance pattern in the core of the nearby galaxy cluster Abell~2029, based on XRISM observations with Resolve (37 ks) and Xtend (500 ks), combined with archival data from XMM-Newton (EPIC, RGS) and Chandra. Fe abundances derived from Resolve, Xtend, and EPIC are broadly consistent, while RGS gives systematically lower values. Because the XRISM gate valve remained closed during these observations, Resolve spectral fitting is restricted to the 2--10 keV band, providing reliable constraints only for elements with strong lines in this band (S, Ar, Ca, Fe, Ni). Abundances of the -elements are therefore derived using complementary observations from Xtend, EPIC, RGS, and Chandra. We construct an average X/Fe pattern in the cluster core by using Resolve exclusively for S/Fe, Ar/Fe, Ca/Fe, and Ni/Fe, and RGS + Xtend for O/Fe. The Ne/Fe ratio is averaged from Xtend, EPIC, RGS, and Chandra measurements; Mg/Fe from EPIC and Chandra measurements; and Si/Fe from Xtend, EPIC, and Chandra. Comparison with the supernovae yield models indicates that the observed abundance pattern in A2029 core is best reproduced by a combination of core-collapsed yields from low-metallicity progenitors () and a sub-Chandrasekhar-mass, double-degenerate Type Ia model. Additionally, we find an excess in Ca abundance in the core of A2029 that cannot be reproduced by the standard supernovae yield models.

Paper Structure

This paper contains 17 sections, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Data reduction
  3. XRISM/Resolve
  4. XRISM/Xtend
  5. XMM-Newton/EPIC
  6. XMM-Newton/RGS
  7. Chandra
  8. Spectral fitting
  9. Results
  10. Temperature measurement
  11. Elemental abundances
  12. Systematic uncertainty
  13. Discussion
  14. Cluster core enrichment
  15. SNIa and SNcc contributions in metal enrichment
  16. ...and 2 more sections

Figures (5)

  • Figure 1: Top-Left: XRISM/Xtend count image of A2029 in the 0.6--10 keV energy band. Top-Right: Exposure-corrected, background-subtracted Chandra ACIS-I image of A2029 in the 0.5--7 keV energy band. Black surface brightness contours highlight the cold-gas sloshing spiral in the cluster center. Bottom: Exposure corrected, QPB-subtracted, merged XMM-Newton EPIC image of A2029. White boxes in all three panels represent the XRISM/Resolve field of view (FOVs) used to extract spectra from all three instruments.
  • Figure 2: Top-Left: XRISM/Resolve full-array spectrum of A2029 (except pixels 12 and 27) from the central region, shown along with the best-fit model (red:total, blue:NXB). Top-Right: XRISM/Xtend spectrum from the central $3'\times3'$ region (matching Resolve FoV) of A2029 with best-fit model (red). Middle-Left: EPIC/MOS1 (black), EPIC/MOS2 (red), and EPIC/pn (blue) spectra from the similar region used for Xtend, with best-fit models. Middle-Right: RGS1 (black) and RGS2 (red) first-order spectra extracted from a cross-dispersion region of $0.8'$, with best-fit models. Bottom: Chandra/ACIS spectrum of A2029 from the central $3'\times3'$ region, with the best-fit model. For each instrument, the spectra from multiple observations have been combined to plot a single spectrum. In all panels, the lower sub-panels show the ratio between the observed data and the best-fit total models.
  • Figure 3: Top: Absolute elemental abundance of different light and heavy elements in the central region of A2029 measured using XRISM (Resolve+Xtend), XMM-Newton (MOS+pn, RGS), and Chandra (ACIS). Bottom: Abundance ratios of different elements with respective to Fe (X/Fe). Grey boxes and tiehorizontals represents the X/Fe for CHEERS samples of clusters/groups 2018MNRAS.478L.116M and Perseus cluster 2019MNRAS.483.1701S.
  • Figure 4: Average elemental abundance ratios of different elements at A2029 center (black data) fitted with SNcc 2013ARAA..51..457N and SNIa (blue) yield models. Top-Left: SNIa yield assuming a pure deflagration explosion mechanism 2014MNRAS.438.1762F, top-right: SNIa yield assuming a delayed-detonation explosion mechanism 2013MNRAS.429.1156S, bottom-left: SNIa yield assuming a single-degenerate explosion mechanism 2010ApJ...714L..52S, and bottom-right: SNIa yield assuming a double-degenerate explosion mechanism 2012ApJ...747L..10P.
  • Figure 5: Average elemental abundance ratios of different elements at A2029 center (black data) fitted with SNcc 2013ARAA..51..457N and SNIa yield assuming a double-degenerate explosion mechanism 2012ApJ...747L..10P and Ca-gap transients 2011ApJ...738...21W.