Steinhardt, Charles. L. and Capak, Peter and Masters, Dan and Speagle, Josh S. (2016) The Impossibly Early Galaxy Problem. Astrophysical Journal, 824 (1). Art. No. 21. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20160707-104137561
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The current hierarchical merging paradigm and ΛCDM predict that the z ~ 4 – 8 universe should be a time in which the most massive galaxies are transitioning from their initial halo assembly to the later baryonic evolution seen in star-forming galaxies and quasars. However, no evidence of this transition has been found in many high-redshift galaxy surveys including CFHTLS, Cosmic Assembly Near-infrared Deep Extragalactic Survey (CANDELS), and Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH), which were the first studies to probe the high-mass end at these redshifts. Indeed, if halo mass to stellar mass ratios estimated at lower-redshift continue to z ~ 6 - 8, CANDELS and SPLASH report several orders of magnitude more M ~ 10^(12-13)M⊙ halos than is possible to have been formed by those redshifts, implying that these massive galaxies formed impossibly early. We consider various systematics in the stellar synthesis models used to estimate physical parameters and possible galaxy formation scenarios in an effort to reconcile observation with theory. Although known uncertainties can greatly reduce the disparity between recent observations and cold dark matter merger simulations, there remains considerable tension with current theory even if taking the most conservative view of the observations.
|Additional Information:||© 2016 The American Astronomical Society. Received 2015 June 3; accepted 2016 April 8; published 2016 June 6. The authors would like to thank Michaela Bagley, Peter Behroozi, Rychard Bouwens, Andreas Faisst, Steven Finkelstein, Hendrik Hildebrandt, Alexander Karim, Olivier Le Fevre, Nick Lee, Surhud More, Dave Sanders, Johannes Staguhn, and Dominic Yurk for helpful comments.|
|Group:||COSMOS, Infrared Processing and Analysis Center (IPAC)|
|Subject Keywords:||dark matter – galaxies: evolution – galaxies: formation|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||07 Jul 2016 19:28|
|Last Modified:||07 Jul 2016 19:28|
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