Hi, I ran HaloProfiler on HaloAnalysis.out and here is the data for the first halo... # id center[0] center[1] center[2] RadiusMpc TotalMassMsun 0000 0.169329105 0.144388856 0.8246570556 3.1986507886 1.07530961369e+15 Then I ran sum_mass_in_sphere.py with the above center and radius ... from yt.mods import * fn = "RedshiftOutput0002" pf = load(fn) sp = pf.h.sphere([0.169329105,0.144388856,0.8246570556],3.1986507886/pf["mpc"]) baryon_mass, particle_mass = sp.quantities["TotalQuantity"]( ["CellMassMsun", "ParticleMassMsun"], lazy_reader=True) print "Total mass in sphere is %0.5e (gas = %0.5e / particles = %0.5e)" % \ (baryon_mass + particle_mass, baryon_mass, particle_mass) And got... Total mass in sphere is 1.27226e+15 (gas = 2.06890e+14 / particles = 1.06537e+15) Let me know if the TotalMassMsun should match. Because they don't. regards shankar KU Cosmology