XRISM-Subaru views of Abell 754: Energetic ICM Motions Revealed by XRISM/Resolve
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| Formato: | Preprint |
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2025
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| author | Omiya, Yuki Okabe, Nobuhiro Nakazawa, Kazuhiro Ota, Naomi Ichinohe, Yuto Ueda, Shutaro Nguyen-dang, Nhan T. |
| author_facet | Omiya, Yuki Okabe, Nobuhiro Nakazawa, Kazuhiro Ota, Naomi Ichinohe, Yuto Ueda, Shutaro Nguyen-dang, Nhan T. |
| contents | We present high-resolution X-ray spectroscopy of the merging cluster Abell~754 using \textit{XRISM}/Resolve. In GO1 phase, \textit{XRISM}/Resolve observed Abell 754 in two deep pointings, targeting the eastern primary core (114~ks) and the middle of the X-ray filamentary structure (190~ks). Spectral fits to full field-of-view data reveal a line-of-sight velocity difference of $656 \pm 35$~km~s$^{-1}$ between the two pointing, corresponding to a bulk Mach number of 0.45$\pm$0.03. Velocity dispersions are measured to be $220^{+26}_{-29}$~km~s$^{-1}$ and $279^{+24}_{-23}$~km~s$^{-1}$ in the eastern and middle pointing, respectively. Within the eastern core, the velocity dispersion shows spatial variation, reaching $497^{+144}_{-117}$~km~s$^{-1}$ in the southern core with high temperature -- among the largest values yet reported in galaxy clusters to date. Narrow-band analysis of the Fe-K complex in this region reveals systematically higher temperatures derived from He-like and H-like Fe line ratio compared to those obtained via broadband fits, indicating multi-phase structures. Two-temperature modeling further separates a cooler core phase from a hotter, shock or turbulence-heated phase whose velocity is blueshifted, similar to that of the middle pointing. These results point to a mixing interface where post-shock gas from the south overlaps, in projection, with cooler core gas, inflating the observed line widths in this region. Weak-lensing analysis with Subaru/HSC and Suprime-cam confirms that the eastern component is about twice as massive as the western one, consistent with disruption and gas stripping of the latter. The curved morphology of the eastern X-ray core, together with the measured kinematics, is naturally explained by an off-axis, post--core-passage merger that imparts angular momentum and drives large-scale rotational and fallback flows. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_16553 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | XRISM-Subaru views of Abell 754: Energetic ICM Motions Revealed by XRISM/Resolve Omiya, Yuki Okabe, Nobuhiro Nakazawa, Kazuhiro Ota, Naomi Ichinohe, Yuto Ueda, Shutaro Nguyen-dang, Nhan T. Astrophysics of Galaxies High Energy Astrophysical Phenomena We present high-resolution X-ray spectroscopy of the merging cluster Abell~754 using \textit{XRISM}/Resolve. In GO1 phase, \textit{XRISM}/Resolve observed Abell 754 in two deep pointings, targeting the eastern primary core (114~ks) and the middle of the X-ray filamentary structure (190~ks). Spectral fits to full field-of-view data reveal a line-of-sight velocity difference of $656 \pm 35$~km~s$^{-1}$ between the two pointing, corresponding to a bulk Mach number of 0.45$\pm$0.03. Velocity dispersions are measured to be $220^{+26}_{-29}$~km~s$^{-1}$ and $279^{+24}_{-23}$~km~s$^{-1}$ in the eastern and middle pointing, respectively. Within the eastern core, the velocity dispersion shows spatial variation, reaching $497^{+144}_{-117}$~km~s$^{-1}$ in the southern core with high temperature -- among the largest values yet reported in galaxy clusters to date. Narrow-band analysis of the Fe-K complex in this region reveals systematically higher temperatures derived from He-like and H-like Fe line ratio compared to those obtained via broadband fits, indicating multi-phase structures. Two-temperature modeling further separates a cooler core phase from a hotter, shock or turbulence-heated phase whose velocity is blueshifted, similar to that of the middle pointing. These results point to a mixing interface where post-shock gas from the south overlaps, in projection, with cooler core gas, inflating the observed line widths in this region. Weak-lensing analysis with Subaru/HSC and Suprime-cam confirms that the eastern component is about twice as massive as the western one, consistent with disruption and gas stripping of the latter. The curved morphology of the eastern X-ray core, together with the measured kinematics, is naturally explained by an off-axis, post--core-passage merger that imparts angular momentum and drives large-scale rotational and fallback flows. |
| title | XRISM-Subaru views of Abell 754: Energetic ICM Motions Revealed by XRISM/Resolve |
| topic | Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2510.16553 |