Galaxy Size Problem at z=3 Simulated Galaxies Are Too Small(8)

Using state-of-the-art adaptive mesh refinement cosmological hydrodynamic simulations with a spatial resolution of 0.15 h-1kpc on a cosmological volume (20 h-1Mpc), we investigate the sizes of galaxies at z=3 in the standard cold dark matter model where re

Fig.2.—Histogramsofhalf-lightradii(rhl)ofsimulatedgalaxiesatz=3intheobservedg′-band.Ineachpanel,redsolidhistogramrepresentsgalaxieswithhighSFR(>10M⊙yr 1)thatweidentifyasLBGs,whilegreendottedhistogramrepresentsthosewithlowSFR(<10M⊙yr 1),insixorthogonalprojectiondirections.Panels(a),(b),and(c)showhistogramsofhalf-lightradii,respectively,beforedustattenuation,afterdustattenuation,andafterdustattenuationandPSF ltering.(SeetextfordetailsonhowdustattenuationandPSF lteringwereapplied.)In(a),ahistogramofhalf-stellar-massradiiisshowninblackdashedlineforcomparison.Theintrinsicrhlin(a)rangebetween0.2and0.6kpc(proper)butpeakat～1kpcforLBGsafterdustattenuationisapplied.Thethickbluesolidhistogramin(c)istheobservedsizedistributionforthe140galaxiesinthez=3redshiftbinofFergusonetal.(2004),normalizedtothenumberofLBGsinoursimulation.