Journal Article

Suppression of small baryonic structures due to a primordial magnetic field

Luiz Felippe S. Rodrigues, Rafael S. de Souza and Reuven Opher

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 1, pages 482-485
Published in print July 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI:
Suppression of small baryonic structures due to a primordial magnetic field

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We investigate the impact of the existence of a primordial magnetic field on the filter mass, characterizing the minimum baryonic mass that can form in dark matter (DM) haloes. For masses below the filter mass, the baryon content of DM haloes are severely depressed. The filter mass is the mass when the baryon to DM mass ratio in a halo is equal to half the baryon to DM ratio of the Universe. The filter mass has previously been used in semi-analytic calculations of galaxy formation, without taking into account the possible existence of a primordial magnetic field. We examine here its effect on the filter mass. For homogeneous comoving primordial magnetic fields of B0∼ 1 or 2 nG and a re-ionization epoch that starts at a redshift zs= 11 and is completed at zr= 8, the filter mass is increased at redshift 8, for example, by factors of 4.1 and 19.8, respectively. The dependence of the filter mass on the parameters describing the re-ionization epoch is investigated. Our results are particularly important for the formation of low-mass galaxies in the presence of a homogeneous primordial magnetic field. For example, for B0∼ 1 nG and a re-ionization epoch of zs∼ 11 and zr∼ 7, our results indicate that galaxies of total mass M∼ 5 × 108 M need to form at redshifts zF≳ 2.0, and galaxies of total mass M∼ 108 M at redshifts zF≳ 7.7.

Keywords: galaxies: formation; galaxies: haloes; magnetic fields; large-scale structure of Universe

Journal Article.  2478 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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