Observations of AGN-driven feedback: dynamics and ionization of the filaments in M87

TL;DR

This study provides a detailed kinematic and ionization analysis of the warm ionized filaments in M87, revealing complex motions, AGN-related ionization processes, and multi-phase gas dynamics using new integral field spectroscopy combined with archival data.

Contribution

It offers the first comprehensive multi-phase view of M87's filaments, combining new integral field spectroscopy with archival data to analyze their kinematics and ionization in detail.

Findings

Filaments exhibit complex, non-rotational motions.

Ionization is dominated by AGN-related processes, including shocks.

Filaments follow a strong Hα-X-ray brightness correlation, with deviations indicating uplift or analysis limitations.

Abstract

We present a comprehensive kinematic and ionization analysis of the warm ionized filaments ($10^4$ K) in M87, the central galaxy of the Virgo cluster, using new integral field spectroscopy from MEGARA (GTC) and SITELLE (CFHT). MEGARA targets the southeastern (SE) filaments (3 kpc from the nucleus), coincident with the only known molecular gas clump, and the far eastern (FE) filament (15 kpc), spatially isolated within an old radio lobe. SITELLE fully maps the filaments, offering the first complete views of their kinematics and excitation. Combined with archival ALMA, MUSE and Chandra data, these observations offer a multi-phase view of gas dynamics. The filaments display complex motions inconsistent with simple rotation. Velocity structure functions (VSFs) of the warm and cold gas in the central and SE filaments show consistent steep slopes (2/3) and flattening on small scales of a few hundred parsecs, possibly suggesting energy injection from Type Ia supernovae, though interpretation is method-limited. The FE filament shows a lower VSF amplitude, suggesting less active driving. ALMA CO emission is co-spatial and kinematically aligned with the ionized gas, the latter showing broader velocity dispersions. Ionization diagnostics indicate AGN-related processes (e.g., shocks) dominate, with higher-energy excitation near the radio lobes and lower-energy fossil feedback signatures in the FE filament. Finally, the filaments follow the same strong H$\alpha$-X-ray surface brightness correlation seen in other clusters, supporting local thermal coupling between phases. However, the FE filament deviates from this trend, possibly due to uplift from past AGN outbursts or limitations in the analysis method.