  Let $U$ be a silting object in a derived category over a dg-algebra $A$, and
let $B$ be the endomorphism dg-algebra of $U$. Under some appropriate
hypotheses, we show that if $U$ is good, then there exist a dg-algebra $C$, a
homological epimorphism $B\rightarrow C$ and a recollement among the
(unbounded) derived categories $\mathbf{D}(C,d)$ of $C$, $\mathbf{D}(B,d)$ of
$B$ and $\mathbf{D}(A,d)$ of $A$. In particular, the kernel of the left derived
functor $-\otimes^{\mathbb{L}}_{B}U$ is triangle equivalent to the derived
category $\mathbf{D}(C,d)$. Conversely, if $-\otimes^{\mathbb{L}}_{B}U$ admits
a fully faithful left adjoint functor, then $U$ is good. Moreover, we establish
a criterion for the existence of a recollement of the derived category of a
dg-algebra relative to two derived categories of weak non-positive dg-algebras.
Finally, some applications are given related to good cosilting objects, good
2-term silting complexes, good tilting complexes and modules, which recovers a
recent result by Chen and Xi.
