Black vs. Dark: Rapid Growth of Supermassive Black Holes in Dark Matter Haloes at z ~ 6. (arXiv:1902.04165v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Shimasaku_K/0/1/0/all/0/1">Kazuhiro Shimasaku</a> (Univ. of Tokyo), <a href="http://arxiv.org/find/astro-ph/1/au:+Izumi_T/0/1/0/all/0/1">Takuma Izumi</a> (NAOJ)
We report on the relation between the mass of supermassive black holes
(SMBHs, M_BH) and that of hosting dark matter haloes (M_h) for 49 z ~ 6 QSOs
with [CII]158um velocity-width measurements. Here, we estimate M_h assuming
that the rotation velocity from FWHM_CII is equal to the circular velocity of
the halo; we have tested this procedure using z ~ 3 QSOs which also have
clustering-based M_h estimates. We find that a vast majority of the z ~ 6 SMBHs
are more massive than expected from the local M_BH – M_h relation, with one
third of the sample by factors >~ 10^2. The median mass ratio of the sample,
M_BH/M_h = 6 x 10^{-4}, means that 0.4% of the baryons in haloes are locked up
in SMBHs. The mass growth rates of our SMBHs amount to ~ 10% of the SFRs, or ~
1% of the mean baryon accretion rates, of the hosting galaxies. A large
fraction of the hosting galaxies are consistent with average galaxies in terms
of SFR and perhaps of stellar mass and size. Our study indicates that the
growth of SMBHs (M_BH ~ 10^{8-10} Msun) in luminous z ~ 6 QSOs greatly precedes
that of hosting haloes owing to efficient gas accretion even under normal star
formation activities, although we cannot rule out the possibility that
undetected SMBHs have local M_BH/M_h ratios. This preceding growth is in
contrast to much milder evolution of the stellar-to-halo mass ratio.
We report on the relation between the mass of supermassive black holes
(SMBHs, M_BH) and that of hosting dark matter haloes (M_h) for 49 z ~ 6 QSOs
with [CII]158um velocity-width measurements. Here, we estimate M_h assuming
that the rotation velocity from FWHM_CII is equal to the circular velocity of
the halo; we have tested this procedure using z ~ 3 QSOs which also have
clustering-based M_h estimates. We find that a vast majority of the z ~ 6 SMBHs
are more massive than expected from the local M_BH – M_h relation, with one
third of the sample by factors >~ 10^2. The median mass ratio of the sample,
M_BH/M_h = 6 x 10^{-4}, means that 0.4% of the baryons in haloes are locked up
in SMBHs. The mass growth rates of our SMBHs amount to ~ 10% of the SFRs, or ~
1% of the mean baryon accretion rates, of the hosting galaxies. A large
fraction of the hosting galaxies are consistent with average galaxies in terms
of SFR and perhaps of stellar mass and size. Our study indicates that the
growth of SMBHs (M_BH ~ 10^{8-10} Msun) in luminous z ~ 6 QSOs greatly precedes
that of hosting haloes owing to efficient gas accretion even under normal star
formation activities, although we cannot rule out the possibility that
undetected SMBHs have local M_BH/M_h ratios. This preceding growth is in
contrast to much milder evolution of the stellar-to-halo mass ratio.
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