The hierarchical model of galaxy evolution suggests that mergers have a substantial impact on the intricate processes that drive stellar assembly within a galaxy. However, accurately measuring the contribution of accretion to a galaxy’s total stellar mass and its balance with in situ star formation poses a persistent challenge, as it is neither directly observable nor easily inferred from observational properties. Using data from MaNGA, we present theory-motivated predictions for the fraction of stellar mass originating from mergers in a statistically significant sample of nearby galaxies. Employing a robust machine learning model trained on mock MaNGA analogues (MaNGIA) obtained from a cosmological simulation (TNG50), we unveil that in situ stellar mass dominates almost across the entire stellar mass spectrum (10⁹ M_⊙ < M_⋆ < 10¹² M_⊙). Only in more massive galaxies (M_⋆ > 10¹¹ M_⊙) does accreted mass become a substantial contributor, reaching up to 35–40% of the total stellar mass. Notably, the ex situ stellar mass in the nearby Universe exhibits notable dependence on galaxy characteristics, with higher accreted fractions favoured being by elliptical, quenched galaxies and slow rotators, as well as galaxies at the centre of more massive dark matter haloes.

星系演化的分层模型表明，合并对驱动星系内恒星聚集的复杂过程具有重大影响。然而，准确测量吸积对星系总恒星质量的贡献及其与原位恒星形成的平衡提出了持续的挑战，因为它既不能直接观测到，也不能轻易地从观测特性中推断出来。利用来自 MaNGA 的数据，我们对源自统计上显着的附近星系样本中的合并的恒星质量分数提出了基于理论的预测。采用在宇宙学模拟 (TNG50) 中获得的模拟 MaNGA 类似物 (MaNGIA) 上训练的稳健机器学习模型，我们发现原位恒星质量几乎在整个恒星质谱中占据主导地位 (10 ⁹ M _⊙ < M _⋆ < 10 ¹² M _⊙ ）。只有在质量更大的星系 (M _⋆ > 10 ¹¹ M _⊙ ) 中，吸积质量才成为重要贡献者，达到总量的 35-40%恒星质量。值得注意的是，附近宇宙中的异位恒星质量表现出对星系特征的显着依赖性，椭圆形、猝灭星系和慢速旋转体以及位于更大质量暗物质晕中心的星系有利于更高的吸积分数。