TY - JOUR
T1 - Understanding the strong intervening OVI absorber at zabs ~ 0.93 towards PG1206+459
AU - Rosenwasser, B.
AU - Muzahid, S.
AU - Charlton, J. C.
AU - Kacprzak, G. G.
AU - Wakker, B. P.
AU - Churchill, C. W.
N1 - Funding Information:
This study is based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. We thank the referee for a helpful and detailed report that improved this work. Support for this research was provided by NASA through grant HST GO-12466 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. G.G.K acknowledges the support of the Australian Research Council through the award of a Future Fellowship (FT140100933). Some of the data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership amongst the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Observations were supported by Swinburne Keck program 2014A_W178E.
Publisher Copyright:
© 2018 The Author(s).
PY - 2018/5/11
Y1 - 2018/5/11
N2 - We have obtained new observations of the partial Lyman limit absorber at zabs=0.93 towards quasar PG 1206+459, and revisit its chemical and physical conditions. The absorber, with N(H I) ~ 1017.0 cm-2 and absorption lines spread over ≳1000 km s-1 in velocity, is one of the strongest known OVI absorbers at logN(O VI) = 15.54±0.17. Our analysis makes use of the previously known low- (e.g. MgII), intermediate- (e.g. Si IV), and high-ionization (e.g. CIV, NV, Ne VIII) metal lines along with new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS) observations that cover OVI and an HST/ACS image of the quasar field. Consistent with previous studies, we find that the absorber has a multiphase structure. The low-ionization phase arises from gas with a density of log(nH/cm-3) ~ -2.5 and a solar to supersolar metallicity. The high-ionization phase stems from gas with a significantly lower density, i.e. log(nH/cm-3) ~ -3.8, and a near-solar to solar metallicity. The high-ionization phase accounts for all of the absorption seen in CIV, NV, and OVI. We find the the detected Ne VIII, reported by Tripp et al. (2011), is best explained as originating in a stand-alone collisionally ionized phase at T ~ 105.85 K, except in one component in which both OVI and Ne VIII can be produced via photoionization. We demonstrate that such strong OVI absorption can easily arise from photoionization at z ≳ 1, but that, due to the decreasing extragalactic UV background radiation, only collisional ionization can produce large OVI features at z ~ 0. The azimuthal angle of ~88° of the disc of the nearest (68 kpc) luminous (1.3L*) galaxy at zgal =0.9289, which shows signatures of recent merger, suggests that the bulk of the absorption arises from metal enriched outflows.
AB - We have obtained new observations of the partial Lyman limit absorber at zabs=0.93 towards quasar PG 1206+459, and revisit its chemical and physical conditions. The absorber, with N(H I) ~ 1017.0 cm-2 and absorption lines spread over ≳1000 km s-1 in velocity, is one of the strongest known OVI absorbers at logN(O VI) = 15.54±0.17. Our analysis makes use of the previously known low- (e.g. MgII), intermediate- (e.g. Si IV), and high-ionization (e.g. CIV, NV, Ne VIII) metal lines along with new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS) observations that cover OVI and an HST/ACS image of the quasar field. Consistent with previous studies, we find that the absorber has a multiphase structure. The low-ionization phase arises from gas with a density of log(nH/cm-3) ~ -2.5 and a solar to supersolar metallicity. The high-ionization phase stems from gas with a significantly lower density, i.e. log(nH/cm-3) ~ -3.8, and a near-solar to solar metallicity. The high-ionization phase accounts for all of the absorption seen in CIV, NV, and OVI. We find the the detected Ne VIII, reported by Tripp et al. (2011), is best explained as originating in a stand-alone collisionally ionized phase at T ~ 105.85 K, except in one component in which both OVI and Ne VIII can be produced via photoionization. We demonstrate that such strong OVI absorption can easily arise from photoionization at z ≳ 1, but that, due to the decreasing extragalactic UV background radiation, only collisional ionization can produce large OVI features at z ~ 0. The azimuthal angle of ~88° of the disc of the nearest (68 kpc) luminous (1.3L*) galaxy at zgal =0.9289, which shows signatures of recent merger, suggests that the bulk of the absorption arises from metal enriched outflows.
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U2 - 10.1093/MNRAS/STY211
DO - 10.1093/MNRAS/STY211
M3 - Article
AN - SCOPUS:85045450250
VL - 476
SP - 2258
EP - 2277
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -