vs. z (top) and vs. L_FIR (bottom) for QSO1 (blue symbols) and QSO2 (green symbols). Our four ULIRG QSO2 are the red open circles. References are as follows: green solid circles: QSO2 from VM13. Open green squares: QSO2 from KNC12. Green solid squares: QSO2 from C11 and C13. Green solid triangles: z ≥ 2 QSO2 from different works (DW) (Aravena et al. 2008; Martínez Sansigre et al. 2009; Yan et al. 2010; Polleta et al. 2011; Lacy et al. 2011) // Blue crosses: z ≥ 2 QSO1 from different works (DW) (Cox et al. 2002; Carilli et al. 2002; Walter et al. 2004; Krips et al. 2005; Riechers et al. 2006, 2009a,b; Gao et al. 2007; Maiolino et al. 2007; Coppin et al. 2008; Wang et al. 2010, 2011). Blue solid squares: QSO1 from C11 and C13. Open blue circles: z ≤ 0.2 QSO1 from different works (DW) (Evans et al. 2001, 2006; Scoville et al. 2003; Pott et al. 2006; Bertram et al. 2007). Filled blue circles: ULIRG QSO1 from Xia et al. 2012 (X12). Orange small diamonds: star forming ULIRGs at z ≤ 1 (C11, C13; Graciá Carpio et al. 2008 (GC08))