FUSE Observations of Interstellar and Intergalactic Absorption Toward the X-ray Bright BL Lac Object Mrk 421

Abstract

High-quality Far-Ultraviolet Spectroscopic Explorer (FUSE) observations at 20 km /s resolution of interstellar and intergalactic absorption from 910 to 1187 A are presented for the X-ray bright BL Lac object Mrk 421. In this study we consider the O VI absorption between -140 to 165 km /s and its relationship to the lower ionization absorption and to the strong absorption produced by O VII and O VIII at X-ray wavelengths. The O VI absorption extending from -140 to 60 km /s is associated with strong low ionization gas absorption and originates in the Galactic thick disk / halo. This O VI appears to be produced by a combination of processes, including conductive interfaces between warm and hot gas and possibly cooling Galactic Fountain gas and hot halo gas bubbles. The O VI absorption extending from 60 to 165 km /s has unusual ionization properties in that there is very little associated low ionization absorption, with the exception of C III. This absorption is not observed toward two foreground halo stars, implying that it occurs in gas more distant than 3.5 kpc from the Galactic disk. Over the 60 to 165 km/s velocity range, O VI and C III absorption have the same kinematic behavior. N(O VI)/N(C III) = 10+/-3 over the 60 to 120 km/s velocity range. Given the association of O VI with C III, it is unlikely that the high velocity O VI co-exists with the hotter gas responsible for the O VII and O VIII absorption. The O VI positive velocity absorption wing might be tracing cooler gas entrained in a hot Galactic Fountain outflow. The O VII and O VIII absorption observed by Chandra and XMM-Newton may trace the hot gas in a highly extended (~100 kpc) Galactic corona or hot gas in the Local Group.

56 pages, 10 figures, to appear in ApJ Feb 2005

References in corpus (2)

• Physical Properties and Baryonic Content of Low-Redshift Intergalactic Ly-alpha and O VI Absorption Systems: The PG1116+215 Sight Line
• C II Radiative Cooling of the Diffuse Gas in the Milky Way

Cited by in corpus (26)

• The Search for the Missing Baryons at Low Redshift
• A huge reservoir of ionized gas around the Milky Way: Accounting for the Missing Mass?
• Multi-phase High-Velocity Clouds toward HE 0226-4110 and PG 0953+414
• X-Ray Absorption from the Milky Way Halo and the Local Group
• Chandra Detection of the First X-ray Forest along the Line of Sight To Mkn 421
• The Relationship Between Intergalactic HI/OVI and Nearby (z<0.017) Galaxies
• A Universal Density Structure for Circum-Galactic Gas
• Detection of Ne VIII in the Low-Redshift Warm-Hot IGM
• The O VII X-ray forest toward Markarian 421: Consistency between XMM-Newton and Chandra
• A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds
• High-Ion Absorption in Seven GRB Host Galaxies at z=2-4: Evidence for both Circumburst Plasma and Outflowing Interstellar Gas
• Warm-Hot Gas in and around the Milky Way: Detection and Implications of OVII Absorption toward LMC X-3
• Properties of O VI Absorption in the Local Interstellar Medium
• On the Putative Detection of z>0 X-ray Absorption Features in the Spectrum of Markarian 421
• Highly Ionized High-Velocity Clouds: Hot Intergalactic Medium or Galactic Halo?
• The COS Absorption Survey of Baryon Harbors (CASBaH): Warm-hot Circumgalactic Gas Reservoirs Traced by Ne VIII Absorption
• Characterizing Transition Temperature Gas in the Galactic Corona
• X-ray and UV spectroscopy of Galactic diffuse hot gas along the LMC X--3 sight line
• The low-redshift intergalactic medium as seen in archival legacy Hubble/STIS and FUSE data
• The High Velocity Gas toward Messier 5: Tracing Feedback Flows in the Inner Galaxy
• The Non-isothermality and Extent of Galactic Diffuse Hot Gas Toward Mrk~421
• Polarization of absorption lines as a diagnostics of circumstellar, interstellar and intergalactic magnetic fields: Fine structure atoms
• Simulating Anisotropic Thermal Conduction in Supernova Remnants, Implications for the Interstellar Medium
• The Surprisingly Constant Strength of O VI Absorbers over Cosmic Time
• Tracing Magnetic Fields with Ground State Alignment
• A High-Metallicity High Velocity Cloud along the MRK 421 Sight Line: A Tracer of Complex M?