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Abstract: We study the growth of massive galaxies from z=2 to the present using datafrom the NEWFIRM Medium Band Survey. The sample is selected at a constantnumber density of n=2x10^-4 Mpc^-3, so that galaxies at different epochs can becompared in a meaningful way. We show that the stellar mass of galaxies at thisnumber density has increased by a factor of ~2 since z=2, following therelation logM=11.45-0.15z. In order to determine at what physical radii thismass growth occurred we construct very deep stacked rest-frame R-band images atredshifts z=0.6, 1.1, 1.6, and 2.0. These image stacks of typically 70-80galaxies enable us to characterize the stellar distribution to surfacebrightness limits of ~28.5 mag-arcsec^2. We find that massive galaxiesgradually built up their outer regions over the past 10 Gyr. The mass within aradius of r=5 kpc is nearly constant with redshift whereas the mass at 5-75 kpchas increased by a factor of ~4 since z=2. Parameterizing the surfacebrightness profiles we find that the effective radius and Sersic n parameterevolve as r e~1+z^-1.3 and n~1+z^-1.0 respectively. The data demonstratethat massive galaxies have grown mostly inside-out, assembling their extendedstellar halos around compact, dense cores with possibly exponential radialdensity distributions. Comparing the observed mass evolution to the averagestar formation rates of the galaxies we find that the growth is likelydominated by mergers, as in-situ star formation can only account for ~20% ofthe mass build-up from z=2 to z=0. The main uncertainties in this study arepossible redshift-dependent systematic errors in the total stellar masses andthe conversion from light-weighted to mass-weighted radial profiles.



Autor: Pieter G. van Dokkum, Katherine E. Whitaker, Gabriel Brammer, Marijn Franx, Mariska Kriek, Ivo Labbe, Danilo Marchesini, Ryan Qua

Fuente: https://arxiv.org/







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