We study the growth of black holes and stellar population in spheroids at
high redshift using several (sub)mm-loud QSO samples. Applying the same
criteria established in an earlier work, we find that, similar to IR QSOs at
low redshift, the far-infrared emission of these (sub)mm-loud QSOs mainly
originates from dust heated by starbursts. By combining low-z IR QSOs and
high-z (sub)mm-loud QSOs, we find a trend that the star formation rate
(\Mstardot) increases with the accretion rate (\Mdot). We compare the
values of \Mstardot/\Mdot for submm emitting galaxies (SMGs), far-infrared
ultraluminous/hyperluminous QSOs and typical QSOs, and construct a likely
evolution scenario for these objects. The (sub)mm-loud QSO transition phase has
both high \Mdot and \Mstardot and hence is important for establishing the
correlation between the masses of black holes and spheroids.Comment: 19 pages,3 figures,submitted to Chin. J. Astron. Astrophys. This
paper was first prepared for publication on August 10th, 200