Late time modification of structure growth and the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>S</mml:mi></mml:mrow><mml:mrow><mml:mn>8</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> tension
Mengxiang Lin, Bhuvnesh Jain, Marco Raveri, Eric J. Baxter, C. Chang, M. Gatti, S. Lee, J. Muir
Abstract
The ${S}_{8}$ tension between low-redshift galaxy surveys and the primary cosmic microwave background (CMB) signals a possible breakdown of the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. Recently differing results have been obtained using low-redshift galaxy surveys and the higher redshifts probed by CMB lensing, motivating a possible time-dependent modification to the growth of structure. We investigate a simple phenomenological model in which the growth of structure deviates from the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ prediction at late times, in particular as a simple function of the dark energy density. Fitting to galaxy lensing, CMB lensing, baryon acoustic oscillations, and supernovae datasets, we find significant evidence---$2.5--3\ensuremath{\sigma}$, depending on analysis choices---for a nonzero value of the parameter quantifying a deviation from $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$. The preferred model, which has a slower growth of structure below $z\ensuremath{\sim}1$, improves the joint fit to the data over $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$. While the overall fit is improved, there is weak evidence for galaxy and CMB lensing favoring different changes in the growth of structure.