TY - JOUR
T1 - Coupled spheroid and black hole formation, and the multifrequency detectability of active galactic nuclei and submillimetre sources
AU - Archibald, E. N.
AU - Dunlop, James
AU - Jimenez, R.
AU - Friaça, A. C. S.
AU - McLure, R. J.
AU - Hughes, D. H.
PY - 2002/10/1
Y1 - 2002/10/1
N2 - We use a simple model of spheroid formation to explore the relationship
between the creation of stars and dust in a massive protogalaxy and the
growth of its central black hole. This model predicts that submillimetre
luminosity peaks after only ~=0.2 Gyr. However, without a very massive
seed black hole, Eddington-limited growth means that a black hole mass
of 109 Msolar, and hence very luminous active
galactic nuclei (AGN) activity, cannot be produced until >0.5 Gyr
after the formation of the first massive stars in the halo. The model
thus predicts a time-lag between the peak of submillimetre luminosity
and AGN luminosity in a massive protoelliptical of a few times
108 yr. For a formation redshift z~= 5, this means that
powerful AGN activity is delayed until z~= 3.5, by which time star
formation in the host is ~=90 per cent complete, and submillimetre
luminosity has declined to ~=25 per cent of its peak value. This
provides a natural explanation for why successful submillimetre
detections of luminous radio galaxies are largely confined to z >
2.5. Conversely the model also predicts that while all high-redshift
luminous submillimetre-selected sources should contain an active (and
growing) black hole, the typical luminosity of the AGN in such objects
is ~=1000 times smaller than that of the most powerful AGN. This is
consistent with the almost complete failure to detect submillimetre
selected galaxies with existing X-ray surveys. Finally, the model yields
a black hole-spheroid mass ratio, which evolves rapidly in the first
Gyr, but asymptotes to ~=0.001-0.003 in agreement with results at low
redshift. This ratio arises not because the AGN terminates star
formation, but because fuelling of the massive black hole is linked to
the total mass of gas available for star formation in the host.
AB - We use a simple model of spheroid formation to explore the relationship
between the creation of stars and dust in a massive protogalaxy and the
growth of its central black hole. This model predicts that submillimetre
luminosity peaks after only ~=0.2 Gyr. However, without a very massive
seed black hole, Eddington-limited growth means that a black hole mass
of 109 Msolar, and hence very luminous active
galactic nuclei (AGN) activity, cannot be produced until >0.5 Gyr
after the formation of the first massive stars in the halo. The model
thus predicts a time-lag between the peak of submillimetre luminosity
and AGN luminosity in a massive protoelliptical of a few times
108 yr. For a formation redshift z~= 5, this means that
powerful AGN activity is delayed until z~= 3.5, by which time star
formation in the host is ~=90 per cent complete, and submillimetre
luminosity has declined to ~=25 per cent of its peak value. This
provides a natural explanation for why successful submillimetre
detections of luminous radio galaxies are largely confined to z >
2.5. Conversely the model also predicts that while all high-redshift
luminous submillimetre-selected sources should contain an active (and
growing) black hole, the typical luminosity of the AGN in such objects
is ~=1000 times smaller than that of the most powerful AGN. This is
consistent with the almost complete failure to detect submillimetre
selected galaxies with existing X-ray surveys. Finally, the model yields
a black hole-spheroid mass ratio, which evolves rapidly in the first
Gyr, but asymptotes to ~=0.001-0.003 in agreement with results at low
redshift. This ratio arises not because the AGN terminates star
formation, but because fuelling of the massive black hole is linked to
the total mass of gas available for star formation in the host.
U2 - 10.1046/j.1365-8711.2002.05725.x
DO - 10.1046/j.1365-8711.2002.05725.x
M3 - Article
VL - 336
SP - 353
EP - 362
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
ER -