Disclosing Submillimeter Galaxy Formation: Mergers or Secular Evolution?
Siu-Wang 瀟弘 Chan 陳, Yiping Ao, Qing-hua Tan
The Astrophysical Journal·2025
We analyze the morphology of 125 submillimeter galaxies (SMGs) in the PRIMER-COSMOS field using double Sérsic modeling on JWST NIRCam images across six bands (F150W, F200W, F277W, F356W, F410M, and F444W), with SMGs being classified by the bulge Sérsic index (n_bulge) and bulge-to-total luminosity ratio (B/T). The Kolmogorov–Smirnov test between the bright (SFR > 175M⊙ yr−1) and the faint groups (SFR 0.5, n > 4) versus pseudo-bulges (B/T < 0.35, n < 2). In the F277W, nonparametric morphological measurements indicate predominantly disk-dominated patterns, with only 24% of SMGs demonstrating merger signatures. After the removal of SMGs with disturbed morphology, the bulge classification scheme in F277W shows pseudo-bulges (21%) and clump migration bulges (16%) from secular evolution, compared to 4% merger-built bulges. Surprisingly, 48% of SMGs defy the classification scheme, showing high B/T (∼0.7) but low Sérsic index (n_bulge ≤ 1). Bars are confirmed in 7% of SMGs. This work suggests that secular evolution takes precedence over major mergers, supporting the idea that isolated evolution fueled by filamentary gas inflow plays a nonnegligible role in the formation of SMGs.