Multiphase gas in quasar absorption-line systems

Details Multiphase gas in quasar absorption-line systems Multiphase gas in quasar absorption-line systems

Nov 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...435l..97g&link_type=abstract

Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 435, no. 2, p. L97-L100

Astronomy and Astrophysics

Astrophysics

29

Absorption Spectra, Active Galaxies, Galactic Evolution, Galactic Radiation, Hydrogen, Intergalactic Media, Interstellar Gas, Line Spectra, Photoionization, Quasars, Galactic Halos, Helium, Hubble Space Telescope, Line Of Sight, Nitrogen Ions, Spectrum Analysis, Ultraviolet Absorption

Scientific paper

In the standard model for H I Lyman-limit (LL) quasar absorption-line systems, the absorbing matter is galactic disk and halo gas, heated and photoionized by the metagalactic radiation field produced by active galaxies. In recent Hubble Space Telescope (HST) observations (Reimers et al. 1992; Vogel & Reimers 1993; Reimers & Vogel 1993) of LL systems along the line of sight to the quasar HS 1700+6416, surprisingly high He I/H I ratios and a wide distribution of column densities of C, N, and O ions are deduced from extreme ultraviolet absorption lines. We show that these observations are incompatible with photoionization equilibrium by a single metagalactic ionizing background. We argue that these quasar absorption systems possess a multiphase interstellar medium similar to that of our Galaxy, in which extended hot, collisionally ionized gas is responsible for some or all of the high ionization stages of heavy elements. From the He/H ratios we obtain -4.0 less than or = log U less than or = -3.0, while the CNO ions are consistent with hot gas in collisional ionization equilibrium at log T = 5.3 and (O/H) = -1.6. The supernova rate necessary to produce these heavy elements and maintain the hot-gas energy budget of approximately 1041.5 ergs/s is approximately 10-2/yr, similar to that which maintains the 'three-phase' interstellar medium in our own Galaxy. As a consequence of the change in interpretation from photoionized gas to a multiphase medium, the derived heavy-element abundances (e.g., O/C) of these systems are open to question owing to substantial ionization corrections for unseen C V in the hot phase. The metal-line ratios may also lead to erroneous diagnostics of the shape of the metagalactic ionizaing spectrum and the ionizing parameter of the absorbers.

Affiliated with

Also associated with

No associations

Rating

Multiphase gas in quasar absorption-line systems does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Multiphase gas in quasar absorption-line systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiphase gas in quasar absorption-line systems will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1022376