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Description
Using the SDSS spectra of quasars included in the DR7Q or DR12Q catalogs, we search for MgII{lambda}{lambda}2796,2803 narrow absorption doublets in the spectra data around MgII{lambda}2798 emission lines. We obtain 17316 MgII doublets, within the redshift range of 0.3299<=z_abs_<=2.5663. We find that a velocity offset of {upsilon}_r_<6000km/s is a safe boundary to constrain the vast majority of associated Mg ii systems, although we find some doublets at {upsilon}_r_>6000km/s. If associated Mg ii absorbers are defined by {upsilon}_r_<6000km/s, ~33.3% of the absorbers are supposed to be contaminants of intervening systems. Removing the 33.3% contaminants, ~4.5% of the quasars present at least one associated MgII system with W_r_^{lambda}2796^>=0.2{AA}. The fraction of associated MgII systems with high-velocity outflows correlates with the average luminosities of their central quasars, indicating a relationship between outflows and the quasar feedback power. The {upsilon}_r_ distribution of the outflow MgII absorbers is peaked at 1023km/s, which is smaller than the corresponding value of the outflow CIV absorbers. The redshift number density evolution of absorbers (dn/dz) limited by {upsilon}_r_{>}-3000km/s differs from that of absorbers constrained by {upsilon}_r_>2000km/s. Absorbers limited by {upsilon}_r_>2000km/s and higher values exhibit profiles similar to dn/dz. In addition, the dn/dz is smaller when absorbers are constrained with larger {upsilon}_r_. The distributions of equivalent widths, and the ratio of W_r_^{lambda}2796^/W_r_^{lambda}2803^, are the same for associated and intervening systems, and independent of quasar luminosity.
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