Updated: 6 March 2011
Cooksey, Prochaska, Chen, Mulchaey, and Weiner 2007 (PDF; 2008, Astrophysical Journal, 676, 262)ABSTRACT:
We present a detailed analysis of the intergalactic metal-line absorption systems in the archival HST/STIS and FUSE ultraviolet spectra of the low-redshift quasar PKS1302−102 (zQSO = 0.2784). We supplement the archive data with CLOUDY ionization models and a survey of galaxies in the quasar field. There are 14 strong Lyα absorbers with column densities log NH I > 14. Of these, six are associated with at least C III λ977 absorption (log N(C++) > 13); this implies a redshift density dNC III/dz =38+14-10 (68% confidence limits) for the five detections with rest equivalent width Wr > 50 mÅ. Two systems show O VI λλ1031,1037 absorption in addition to C III (log N(O+5) > 14). One is a partial Lyman limit system (log NH I = 17) with associated C III, O VI, and Si III λ1206 absorption. There are two tentative O VI systems that do not have C III detected. For one O VI doublet with both lines detected at 3σ with Wr > 50 mÅ, dNO VI/dz = 7+9-4. We also search for O VI doublets without Lyα absorption but identify none. From CLOUDY modeling, these metal-line systems have metallicities spanning the range -3 ≤ [M/H] ≤-0.5. The two O VI systems with associated C III absorption cannot be single-phase, collisionally-ionized media based on the relative abundances of the metals and kinematic arguments. From the galaxy survey, we discover that the absorption systems are in a diverse set of galactic environments. Each metal-line system has at least one galaxy within 500 km s-1 and 600 h75-1 kpc with L > 0.1L∗.
Poster (PDF) presented at the 205th Meeting of the American Astronomical Society, San Diego, CA, 2005.ABSTRACT:
The baryonic content of the Universe is well known from Big Bang nucleosynthesis models, deuterium abundances, and the high-redshift Lyman-α forest. However, surveys of the nearby Universe reveal a dearth of baryons in stars, galaxies, and clusters. Recent cosmological simulations have placed the most likely reservoir of baryons at low redshift—upward of 40%—in moderately overdense (δ ~ 10−30), collisionally ionized gas, called the warm-hot intergalactic medium. With temperatures in the range 105−7 K, the WHIM proves tricky to observe. The most reasonable tracer is the O VI doublet λλ1031.93, 1037.62 Å, which dominates at ~3x105 K.
Presented here are preliminary results from analysis of far-ultraviolet FUSE and HST/STIS spectra of the quasar PKS1301−102 (zem = 0.286). Column densities and Doppler parameters are measured for metal-line systems, and the redshift density of O VI absorbers is determined. In addition, the FUV spectra are supported by a galaxy survey of the field surrounding PKS1302−102, made at Las Campanas Observatory. These observations will be used to determine whether the O VI absorbers are correlated with galaxies. This work was funded by FUSE grant NAG5-12496.