The clustering of galaxies in the DESI imaging legacy surveys DR8: I. The luminosity and color dependent intrinsic clustering

In a recent study, we developed a method that models the impact of photometric redshift uncertainty on the two-point correlation function (2PCF). Using this method, we simultaneously obtained both the intrinsic clustering strength and the photometric redshift errors by fitting the projected 2PCF with two integration depths along the line-of-sight. Herein, we apply this method to the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 8 (LS DR8), which is the largest galaxy sample currently available. We separate the galaxies into 20 samples in eight redshift bins, from z = 0.1 to z = 1.0, and several z-band absolute magnitude bins, with Mz ≤ −20. These galaxies are further divided into red and blue subsamples according to their M r 0.5 - M z 0.5 colors. We measure the projected 2PCFs for all these galaxy subsamples and fit them using our photometric redshift 2PCF model. We find that the photometric redshift errors are smaller in the red subsamples than in the overall population. In contrast, some systematic photometric redshift errors exist in the blue subsamples, such that some of the subsamples show a significantly enhanced 2PCF on large scales. Therefore, separately focusing only on the red subsamples and on all the subsamples, we find that the biases of the galaxies in these subsamples exhibit clear color, redshift, and luminosity dependencies; the brighter red galaxies at higher redshift are more biased than their bluer and low-redshift counterparts. Apart from the best-fit set of parameters, σz and b, from this state-of-the-art photometric redshift survey, we obtain high-precision intrinsic clustering measurements for these 40 red- and all-galaxy subsamples. These measurements, on large and small scales, hold important information regarding cosmology and galaxy formation that will be used in our subsequent probes in this series.