SIMULATIONS OF EARLY BARYONIC STRUCTURE FORMATION WITH STREAM VELOCITY. I. HALO ABUNDANCE

Journal Article · Sat Mar 10 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/747/2/128· OSTI ID:22016239

Naoz, Smadar ^[1]; Yoshida, Naoki ^[2]

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1. CIERA, Northwestern University, Evanston, IL 60208 (United States)
2. IPMU, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan)

It has been recently shown that the relative velocity between the dark matter and the baryons (v{sub bc}) at the time of recombination can affect the structure formation in the early universe. We statistically quantify this effect using large cosmological simulations. We use three different high-resolution sets of simulations (with separate transfer functions for baryons and dark matter) that vary in box size, particle number, and the value of the relative velocity between dark matter and baryons. We show that the total number density of halos is suppressed by {approx}20% at z = 25 for v{sub bc} = 1{sigma}{sub vbc}, where {sigma}{sub vbc} is the variance of the relative velocity, while for v{sub bc} = 3.4{sigma}{sub vbc} the relative suppression at the same redshift reaches 50%, remaining at or above the 30% level all the way to z = 11. We also find a high abundance of 'empty halos', i.e., halos that have gas fraction below half of the cosmic mean baryonic fraction f-bar{sub b}. Specifically, we find that for v{sub bc} = 1{sigma}{sub vbc} all halos below 10{sup 5} M{sub Sun} are empty at z {>=} 19. The high abundance of empty halos results in significant delay in the formation of gas-rich minihalos and the first galaxies.

• OSTI ID: 22016239
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 747; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
BARYONS
COMPUTERIZED SIMULATION
COSMOLOGICAL MODELS
COSMOLOGY
DENSITY
GALACTIC EVOLUTION
GALAXIES
NONLUMINOUS MATTER
RECOMBINATION
RED SHIFT
STATISTICS
TRANSFER FUNCTIONS
UNIVERSE