The Low-redshift IGM: HI And Metal Absorbers At z < 0.4

Details The Low-redshift IGM: HI And Metal Absorbers At z < 0.4 The Low-redshift IGM: HI And Metal Absorbers At z < 0.4

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.5406s&link_type=abstract

American Astronomical Society, AAS Meeting #211, #54.06; Bulletin of the American Astronomical Society, Vol. 39, p.824

Statistics

Scientific paper

We present new results from a major ultraviolet spectroscopic survey of the low-redshift intergalactic medium (IGM) using HST/STIS and FUSE observations toward 28 AGN. Our survey analyzes HI absorption systems (Lya,Lyb) at redshifts below 0.4 and corresponding absorbers in 7 metal ions (OVI, CIII, CIV, SiIII, SiIV, NV, FeIII). Of the low-z baryons, we estimate that 30% reside in the photoionized Lya forest and 10% in warm/hot IGM traced by OVI. We find 650 HI absorbers over redshift pathlength (Delta-z=5.27) with numerous metal absorbers (83 OVI systems, 53 SiIII, 39 CIII, 24 CIV, 24 NV, 20 SiIV, 14 FeIII), a substantial improvement over previous low-z studies. With correction for incompleteness, our survey yields line frequencies and column-density distributions: f(N_HI)=N^-1.7 and dN/dz = 129(+/-6) to 30mA equivalent width in Lya, and f(N_OVI)=N^-2.0 and dN/dz=40(+14,-8) to 10mA in OVI 1032A. Improved statistics for weak OVI absorbers yields a ratio [Omega_WHIM/Omega_b]=8.6+/-0.8% (for log N_OVI>13.0). NV follows a similar pattern; both ions provide reliable tracers of WHIM at 10^5-10^6 K. CIV is probably not a WHIM tracer; many absorbers contain multiphase gas, with both collisional ionization and photoionization. CIII, SiIII, and SiIV are well correlated with HI and show patterns typical of photoionization. Adjacent ion stages (CIII/IV, SiIII/IV) constrain the mean photoionization parameter to be log U = -1.5(+/-0.2). Comparison of SiIV and CIV with high-z surveys suggests an increase in line density, consistent with a rise in IGM metallicity at low z. From z=2-6, the CIV abundance is nearly constant at Omega(CIV)=(2-3)x10^-8. At z less than 0.1, we measure Omega(CIV)=(7.7+/-1.5)x10^-8, consistent with star formation over the past 10 Gyr. We search for evolution in IGM absorbers and baryon content (HI, OVI) at z<0.4 and compare to predictions from numerical simulations.

Affiliated with

Also associated with

No associations

Rating

The Low-redshift IGM: HI And Metal Absorbers At z < 0.4 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 Low-redshift IGM: HI And Metal Absorbers At z < 0.4, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Low-redshift IGM: HI And Metal Absorbers At z < 0.4 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1477773