Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-12-22
Mon.Not.Roy.Astron.Soc.403:1556,2010
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
15 pages, 6 figures, accepted by MNRAS
Scientific paper
10.1111/j.1365-2966.2009.16216.x
We consider the physical conditions and origin of the z = 0.0777 absorption system observed in C III, C II, Si III, C IV, O VI, and H I absorption along the line of sight towards the quasar PHL 1811. We analysed the HST/STIS and FUSE spectra of this quasar and compared the results to Cloudy photoionization and collisional ionization models in order to derive densities, temperatures, and metallicities of the absorbing gas. The absorption can be explained by two C III clouds, offset by 35 km/s in velocity, with metallicities of ~one-tenth the solar value. One cloud has a density of order n_H = 1.2 +0.9 -0.5 * 10^-3 cm^-3 (thickness 0.4 +0.3 -0.2 kpc) and produces the observed C II and Si III absorption, while the other has a density of order n_H = 1.2 +0.9 -0.5 * 10^-5 cm^-3 (thickness 80 +70 -40 kpc) and gives rise to the observed weak C IV absorption. Cloud temperatures are ~14,000 +3000 -2000 K and ~34,000 -4000 +2000 K for photoionized models. Although collisionally ionized clouds with T ~ 70,000 K are possible, they are less likely because of the short cooling time-scales involved. Previous studies revealed no luminous galaxy at the absorber's redshift, so it is probably related to tidal debris, ejected material, a dwarf galaxy, or other halo material in a galaxy group. Our models also indicate that one of the two clouds would produce detectable weak Mg II absorption if spectral coverage of that transition existed. We predict what the system would look like at z ~ 1 when the ionizing background radiation was more intense. We find that at z ~ 1 the denser component resembles a C IV absorber. The second C III cloud in this z = 0.0777 absorber may be analogous to a subset of the more diffuse O VI absorbers at higher redshift.
Charlton Jane C.
Lacki Brian C.
No associations
LandOfFree
The z = 0.0777 C III Absorber Towards PHL 1811 as a Case Study of a Low Redshift Weak Metal Line Absorber 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 The z = 0.0777 C III Absorber Towards PHL 1811 as a Case Study of a Low Redshift Weak Metal Line Absorber, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The z = 0.0777 C III Absorber Towards PHL 1811 as a Case Study of a Low Redshift Weak Metal Line Absorber will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-306503