Metal-rich absorbers at high redshifts: abundance patterns
  (Abbreviated) From six spectra of high-z QSOs, we select eleven metal-rich,
Z>=Z_solar, and optically-thin to the ionizing radiation, N(HI)<10^17 cm^-2,
absorption systems ranging between z=1.5 and z=2.9 and revealing lines of
different ions in subsequent ionization stages. The majority of the systems (10
from 11) show abundance patterns which relate them to outflows from low and
intermediate mass stars. All systems have sub-kpc linear sizes along the
line-of-sight with many less than 20 pc. In several systems, silicon is
deficient, presumably due to the depletion onto dust grains in the envelopes of
dust-forming stars and the subsequent gas-dust separation. At any value of
[C/H], nitrogen can be either deficient, [N/C]<0, or enhanced, [N/C]>0, which
supposes that the nitrogen enrichment occurs irregularly. In some cases, the
lines of MgII 2796, 2803 appear to be shifted, probably as a result of an
enhanced content of heavy isotopes 25Mg and 26Mg in the absorbing gas relative
to the solar isotopic composition. Seven absorbers are characterized by low
mean ionization parameter U, log U<-2.3, among them only one system has a
redshift z>2 whereas all others are found at z ~= 1.8. Comparing the space
number density of metal-rich absorbers with the comoving density of
star-forming galaxies at z ~= 2, we estimate that the circumgalactic volume of
each galaxy is populated by 10^7 - 10^8 such absorbers with total mass
<=1/100th of the stellar galactic mass. Possible effects of high metal content
on the peak values of star-forming and AGN activities at z~2 are discussed.
