Amount of intergalactic dust: constraints from distant supernovae and thermal history of intergalactic medium

This paper examines the allowed amount of IG (intergalactic) dust, which is constrained by extinction and reddening of distant SNe and thermal history of IGM (intergalactic medium) affected by dust photoelectric heating. Based on the observational cosmic star formation history, we find an upper bound of χ, the mass ratio of the IG dust to the total metal in the Universe, as χ . 0.1 for 10Å . a . 0.1μm and χ . 0.1(a/0.1μm) for 0.1μm . a . 1μm, where a is a characteristic grain size of the IG dust. This upper bound of χ ∼ 0.1 suggests that the dust-to-metal ratio in the IGM is smaller than the current Galactic value. The corresponding allowed density of the IG dust increases from ∼ 10 g cm at z = 0 to ∼ 10 g cm at z ∼ 1, and keeps almost the value toward higher redshift. This causes IG extinction of . 0.2 mag at the observer’s B-band for z ∼ 1 sources and that of . 1 mag for higher redshift sources. Furthermore, if E(B − V ) ∼ 0.1 mag at the observer’s frame against z & 1 sources is detected, we can conclude that a typical size of the IG dust is . 100 Å. The 2175 Å absorption feature of small graphite may be found as a local minimum at z ∼ 2.5 in a plot of the observed E(B − V ) as a function of the source redshift. Finally, the IGM mean temperature at z . 1 can be still higher than 10 K, provided the size of the IG dust is . 100 Å.