Direct observation of the X-ray counterpart of the Hα filaments and of the sloshing spiral in the Perseus galaxy cluster

TL;DR

The study uses deep Chandra data and a Poisson General Morphological Component Analysis to disentangle ultra-faint X-ray components in the Perseus cluster, revealing direct X-ray counterparts to H-alpha filaments and a sloshing spiral. A 3D template-fitting approach, built on spatial maps from pGMCA and modeled with absorbed APEC components, yields thermodynamic properties across multiple annuli, finding filaments at $kT\approx 0.7$–$0.8$ keV and the sloshing spiral at $kT\approx 1.3$–$1.4$ keV with enhanced abundances. The results support a multiphase ICM with hot–cold gas condensation and merger-driven gas sloshing, demonstrating the power of blind-source separation for faint cluster structures. The work points to substantial gains with next-generation X-ray facilities like Athena, which will provide higher photon statistics and enable broader-scale studies with methods like pGMCA and 3D template fitting.

Abstract

Deep Chandra observations of the Perseus galaxy cluster have allowed for the discovery of X-ray counterparts to the Hα filamentary structures and of a sloshing spiral. However, both components are extremely faint, and their study is largely hindered by the volume-filling hot intracluster medium (ICM). Using the Poisson General Morphological Component Analysis (pGMCA) algorithm, a blind source separation method adapted for Poissonian statistics, we were able to extract detailed, clean morphological maps of these components. We then introduced a template fitting method to investigate their spectral characteristics. We report the first direct observation of about 1.35 keV low-energy emission from the sloshing spiral, and produce the most detailed and unpolluted map of the X-rays filaments thus far obtained.

Figures (5)

• Figure 1: Three components found by the pGMCA algorithm between $0.1$ and $1.8$ keV on the spectrally native, spatially rebinned data. On the left, spatial maps in square root and on the right, the associated integrated spectrum.
• Figure 2: Maps of the X-ray filaments and cold sloshing front. On the left, map of the X-ray filaments found by pGMCA between $0.5$ keV and $4.5$ keV on the spectrally rebinned, spatially native data, smoothed. On the right, map of the cold sloshing front retrieved by pGMCA between $0.5$ keV and $4.5$ keV on the spectrally rebinned, spatially native data, cleaned, smoothed For both images, the scale is in square root.
• Figure 3: On top, distribution of the X-ray and H$\alpha$ filaments. On the left, map of the X-ray filaments from Fig. \ref{['fig:both-images']}. On the right, H$\alpha$ filaments observed by the WIYN 3.5-m telescope, first presented in Conselice_2001. Superimposed, the green box regions we defined to extract the filaments profiles. The white annular regions are the ones used in our template fit (see results in Table \ref{['table:3d']}). For both images, the scale is in square root. On the bottom, normalized profiles extracted from the X-ray filamentary structures found in the the X-ray and H$\alpha$ filaments in red and black, respectively. The X-ray filaments are obtained with the pGMCA method, while the H$\alpha$ come from the WIYN 3.5-m telescope.
• Figure 4: Image of the sloshing spiral from Fig. \ref{['fig:both-images']} superimposed with spectral analysis regions. The white annular regions are the ones used in our template fit (see results in Table \ref{['table:3d']}), the green region is the one used in the traditional Xspec analysis (see Table \ref{['tab:xspec']}).
• Figure 5: Best fit for the template fitting method on all annular regions combined. The regions are shown in Fig. \ref{['fig:filaments-boxes-profiles']}, left, and Fig. \ref{['fig:cold-front']}.