2025/09/02 by Mukesh Singh Bisht, Bisht, Mukesh Singh, Sanskriti Das +9
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Cosmic Phenomena #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · pdf · doi:10.48550/arxiv.2509.02019
openalex publication_date 2025/09/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present the first simultaneous detection of four distinct highly ionized z=0 absorbing phases using Chandra and XMM-Newton grating spectra toward the blazar PKS 2155\hbox-304. We detect the MgXII Kα absorption line for the first time in the circumgalactic medium (CGM) of the Milky Way. Along with MgXII Kα, we detect SiXIV Kα absorption, which are the tell-tale signatures of the hot 'super-virial' gas in the CGM. Both from the model-independent calculations and hybrid-ionization modeling, we infer four phases at distinct temperatures, hot 'super-virial' (5.4+1.9-0.8 × 107 K), warm-hot 'virial' (1.8+0.3-0.2 × 106 K), warm 'sub-virial' (2.2± 0.5 × 105 K), and cool phase (<1.7 × 105 K). The warm-hot and hot phases are α-enhanced, and [C/O] and [Ne/O] are super-solar in the warm-hot phase, while [Mg/O] and [Si/O] are super-solar in the hot phase. The low-ionization lines are blue-shifted (v\rm los ≈ -100 km s-1), whereas the high-ionization lines are red-shifted. It suggests a scenario of infalling sub-virial, quasi-static virial, and outflowing super-virial phases along this sightline. Earlier studies on individual sightlines were confined to the Northern Hemisphere. Our sightline is located in the Southern hemisphere, demonstrating that hot super-virial gas is also present at Southern Galactic latitudes as well. This confirms a more widespread distribution of the super-virial gas across both hemispheres.