High Resolution X-ray Spectroscopy of the Local Hot Gas along the 3C 273 Sightline

Abstract

X-ray observations of highly ionized metal absorption lines at z=0 provide critical information of the hot gas distribution in and around the Milky Way. We present a study of more than ten-year Chandra and XMM-Newton observations of 3C 273, one of the brightest extragalactic X-ray sources. Compared with previous work, We obtain much tighter constraints of the physical properties of the X-ray absorber. We also find a large, non-thermal velocity at ~ 100 - 150 km/s is the main reason for the higher line equivalent width when compared with other sightlines. Using joint analysis with X-ray emission and ultraviolet observations, we derive a size of 5 - 15 kpc and a temperature of (1.5-1.8) 10^6 K for the X-ray absorber. The 3C 273 sightline passes through a number of Galactic structures, including the radio Loop I, IV, the North Polar Spur, and the neighborhood of the newly discovered "Fermi bubbles". We argue that the X-ray absorber is unlikely associated with the nearby radio Loop I and IV; however, the non-thermal velocity can be naturally explained as the result of the expansion of the "Fermi bubbles". Our data implies an shock-expansion velocity of 200 - 300 km/s. Our study indicates a likely complex environment for the production of the Galactic X-ray absorbers along different sightlines, and highlights the significance of probing galactic feedback with high resolution X-ray spectroscopy.

5 pages, 3 figures, accepted for publication in ApJL

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• Fermi and eRosita bubbles as relics of the past activity of the Galactic black hole
• The Properties of the Galactic Hot Gaseous Halo from X-ray Emission
• Clues to the origin of Fermi Bubbles from OVIII/OVII line ratio
• Suzaku X-ray Observations of the Fermi Bubbles: Northernmost Cap and Southeast Claw Discovered with MAXI-SSC
• Cosmic Rays in a Galactic Breeze
• Metal Enrichment in the Fermi Bubbles as a Probe of Their Origin
• The ionic composition of the local absorber towards 3C 273