A new observable of the large-scale structure: the position-dependent two-point correlation function

June 01, 2015

Observations of the large-scale structure, such as galaxy surveys, are one of the most important tools to study our universe. In particular, how the growth of structure is affected by the large-scale environment can be used to test our understanding of gravity, as well as the physics of inflation. A research group at MPA has recently developed a new technique to extract this signal more efficiently from real observations. Specifically, we divide a galaxy survey into sub-volumes, quantify the structure and the environment in each sub-volume, and measure the correlation between these two quantities. This technique thus opens a new avenue to critically test fundamental physics from real observations.

Fig. 1: Projected slice of the galaxies observed in the SDSS with distances (redshifts). (The position on the sky is measured in observation coordinates: RA labelled in hours, with DEC being projected onto the plane.) The yellow, red, and white points are the main galaxy sample, the red luminous galaxies, and the BOSS CMASS sample, respectively.

Fig. 2: The two-point correlation function of the BOSS DR10 CMASS sample. The orange data points are the measurements for the observed galaxies, the dashed line denotes the expectation from the currently accepted cosmological model. 

Fig. 3: The division of the BOSS DR10 CMASS sample into sub-volumes on the sky. Each coloured block extends over the whole redshift range.
Fig. 4: First measurement of the integrated three-point function from the BOSS DR10 CMASS sample. The thick black solid line shows the measurement for real data, the thin green lines show the results for each of the 600 mock realisations, while the thick red dashed line shows the mean of the mock realisations.

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