286 research outputs found
The very first Pop III stars and their relation to bright z~6 quasars
We discuss the link between dark matter halos hosting the first PopIII stars
formed at redshift z > 40 and the rare, massive, halos that are generally
considered to host bright z~6 quasars. We show that within the typical volume
occupied by one bright high-z QSO the remnants of the first several thousands
PopIII stars formed do not end up in the most massive halos at z~6, but rather
live in a large variety of environments. The black hole seeds planted by these
very first PopIII stars can easily grow to M > 10^{9.5} Msun by z=6 assuming
Eddington accretion with radiative efficiency epsilon~0.1. Therefore quenching
of the accretion is crucial to avoid an overabundance of supermassive black
holes. We implement a simple feedback model for the growth of the seeds planted
by PopIII stars and obtain a z~6 BH mass function consistent with the observed
QSO luminosity function.Comment: 5 pages, to appear in the proceedings of "First Stars III", AIP
Conference Series, T. Abel, A. Heger and B. O'Shea ed
Distribution of the very first PopIII stars and their relation to bright z~6 quasars
We discuss the link between dark matter halos hosting the first PopIII stars
and the rare, massive, halos that are generally considered to host bright
quasars at high redshift z~6. The main question that we intend to answer is
whether the super-massive black holes powering these QSOs grew out from the
seeds planted by the first intermediate massive black holes created in the
universe. This question involves a dynamical range of 10^13 in mass and we
address it by combining N-body simulations of structure formation to identify
the most massive halos at z~6 with a Monte Carlo method based on linear theory
to obtain the location and formation times of the first light halos within the
whole simulation box. We show that the descendants of the first ~10^6 Msun
virialized halos do not, on average, end up in the most massive halos at z~6,
but rather live in a large variety of environments. The oldest PopIII
progenitors of the most massive halos at z~6, form instead from density peaks
that are on average one and a half standard deviations more common than the
first PopIII star formed in the volume occupied by one bright high-z QSO. The
intermediate mass black hole seeds planted by the very first PopIII stars at
z>40 can easily grow to masses m_BH>10^9.5 Msun by z=6 assuming Eddington
accretion with radiative efficiency \epsilon~0.1. Quenching of the black hole
accretion is therefore crucial to avoid an overabundance of supermassive black
holes at lower redshift. This can be obtained if the mass accretion is limited
to a fraction \eta~6*10^{-3} of the total baryon mass of the halo hosting the
black hole. The resulting high end slope of the black hole mass function at z=6
is \alpha ~ -3.7, a value within the 1\sigma error bar for the bright end slope
of the observed quasar luminosity function at z=6.Comment: 30 pages, 9 figures, ApJ accepte
Violent Relaxation Around a Massive Black Hole
I present galaxy models resulting from violent relaxation in the presence of
a pre-existing black hole. The models are computed by maximizing the entropy of
the stellar dynamical system. I show that their properties are very similar to
those of adiabatic growth models for a suitable choice of parameters. This
suggests that observations of nuclear light profiles and kinematics alone may
not be sufficient to discriminate between scenarios where a black hole grows
adiabatically in the core of a galaxy, and scenarios where the black hole
formation preceeds galaxy formation.Comment: 13 pages, 3 figures, uses aasms4.sty, to appear in ApJ
Measuring the mass of high-z galaxies with NGST
We discuss dynamical mass measurements of high-z galaxies with the Next
Generation Space Telescope (NGST). In particular, we review some of the
observational limits with the current instrument/telescope generation, we
discuss the redshift limits and caveats for absorption and emission lines
studies with NGST, and the existence of suitable targets at high redshift. We
also briefly summarize strengths and weaknesses of proposed NGST instruments
for dynamical studies.Comment: to appear in "The Mass of Galaxies at Low and High Redshift" R.
Bender and A. Renzini ed
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