1206.2395 (Tassos Fragos et al.)

X-ray Binary Evolution Across Cosmic Time    [PDF]

Tassos Fragos, Bret Lehmer, Michael Tremmel, Panayiotis Tzanavaris, Antara Basu-Zych, Krzysztof Belczynski, Ann Hornschemeier, Leigh Jenkins, Vassiliki Kalogera, Andrew Ptak, Andreas Zezas

High redshift galaxies permit the study of the formation and evolution of X-ray binary populations on cosmological timescales, probing a wide range of metallicities and star-formation rates. In this paper, we present results from a large scale population synthesis study that models the X-ray binary populations from the first galaxies of the universe until today. We use as input to our modeling the Millennium II Cosmological Simulation and the updated semi-analytic galaxy catalog by Guo et al. (2011) to self-consistently account for the star formation history and metallicity evolution of the universe. Our modeling, which is constrained by the observed X-ray properties of local galaxies, gives predictions about the global scaling of emission from X-ray binary populations with properties such as star-formation rate and stellar mass, and the evolution of these relations with redshift. Our simulations show that the X-ray luminosity density (X-ray luminosity per unit volume) from X-ray binaries in our Universe today is dominated by low-mass X-ray binaries, and it is only at z>2.5 that high-mass X-ray binaries become dominant. We also find that there is a delay of ~1.1 Gyr between the peak of X-ray emissivity from low-mass Xray binaries (at z~2.1) and the peak of star-formation rate density (at z~3.1). The peak of the X-ray luminosity from high-mass X-ray binaries (at z~3.9), happens ~0.8 Gyr before the peak of the star-formation rate density, which is due to the metallicity evolution of the Universe. Finally, we found that at z<2.5 the evolution of the X-ray luminosity per unit stellar mass is related to the average age of the low-mass X-ray binary population, while at z>2.5, it becomes approximately proportional to the specific star-formation rate (star-formation rate per unit stellar mass).

View original: http://arxiv.org/abs/1206.2395