Formation Of Luminous Objects Research Articles

INFLUENCE OF PRIMORDIAL MAGNETIC FIELDS ON 21 CM EMISSION

Magnetic fields in the early universe can significantly alter the thermal evolution and the ionization history during the dark ages. This is reflected in the 21 cm line of atomic hydrogen, which is coupled to the gas temperature through collisions at high redshifts, and through the Wouthuysen-Field effect at low redshifts. We present a semi-analytic model for star formation and the build-up of a Lyman alpha background in the presence of magnetic fields, and calculate the evolution of the mean 21 cm brightness temperature and its frequency gradient as a function of redshift. We further discuss the evolution of linear fluctuations in temperature and ionization in the presence of magnetic fields and calculate the effect on the 21 cm power spectrum. At high redshifts, the signal is increased compared to the non-magnetic case due to the additional heat input into the IGM from ambipolar diffusion and the decay of MHD turbulence. At lower redshifts, the formation of luminous objects and the build-up of a Lyman alpha background can be delayed by a redshift interval of 10 due to the strong increase of the filtering mass scale in the presence of magnetic fields. This tends to decrease the 21 cm signal compared to the zero-field case. In summary, we find that 21 cm observations may become a promising tool to constrain primordial magnetic fields.

On the inhomogeneity of dark matter and luminous objects induced by infinitely long cosmic strings

view Abstract Citations (16) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Inhomogeneity of Dark Matter and Luminous Objects Induced by Infinitely Long Cosmic Strings Hara, Tetsuya ; Mahonen, Petri ; Miyoshi, Shigeru Abstract The inhomogeneity of cold dark matter due to the wake formed by an infinitely long straight cosmic string is investigated. The 1D motion of cold dark matter induced by infinitely long cosmic strings is solved analytically and numerically, and the homogeneous MW background radiation and the thickness of the wake are also estimated. The mass of the fragments within the wake is estimated from the thickness. The possibility of explaining the distribution and the change of number density of objects such as the Lyman-alpha clouds through such a dark matter fragmentation and clustering is discussed. The formation of luminous objects is also studied. The reionization of the universe and the formation of globular clusters, galaxies, and objects in the voids are addressed as well. Publication: The Astrophysical Journal Pub Date: July 1993 DOI: 10.1086/172897 Bibcode: 1993ApJ...412...22H Keywords: Computational Astrophysics; Dark Matter; Inhomogeneity; Luminosity; String Theory; Equations Of Motion; Lyman Alpha Radiation; Relic Radiation; Astrophysics; COSMOLOGY: THEORY; COSMOLOGY: DARK MATTER; COSMIC STRINGS; COSMOLOGY: LARGE-SCALE STRUCTURE OF UNIVERSE full text sources ADS |