New Constraints on the Physical State of the IGM

Details New Constraints on the Physical State of the IGM New Constraints on the Physical State of the IGM

Dec 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aas...185.1303f&link_type=abstract

American Astronomical Society, 185th AAS Meeting, #13.03; Bulletin of the American Astronomical Society, Vol. 26, p.1330

Astronomy and Astrophysics

Astronomy

2

Scientific paper

The new determination of the physical size of the Lyalpha forest cloud from the double quasar Q1343+266AB (Bechtold et al 1994; Crotts et al. 1994) allows us to evaluate the Lyalpha cloud contribution to the cosmic baryon density Omega_ {b,Lyalpha }, which is estimated to be at least of a few times 10(-3) of Omega_o (critical closure density for the Universe), the same order as that of the damped Lyalpha or the Lyman limit systems at z~ 2.5. A firm lower bound of the Lyalpha cloud radius ~ 40 h(-1) kpc infers a lower limit of baryons mass included in the Lyalpha clouds. The dependence of Omega_ {b,Lyalpha } on the temperature of the IGM, together with the amount of baryon density allowed from the standard big bang nucleosynthesis, puts strong constraints on the temperature and density parameter space of the IGM at high redshift, in particular, the IGM temperature could not be higher than 10(6) K in order to keep the baryons from ending in the absorbers seen in QSO spectra (h=1, Omega_o =1.0). Gunn-Peterson effect also constrains the IGM physical conditions, but only excludes the lower temperature and higher density region presently. Further improvements of its upper limits will then push the constraint up to T_I ~ 10(4) K region, the probable temperature of a photoionized IGM. Majority of the IGM temperature and density parameter space will be covered by these constraints, which no longer depend on the pressure equilibrium between the cloud gas and the IGM as in the pressure confinement model of the Lyalpha cloud.

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