We present direct constraints on galaxy intrinsic alignments (IAs) using the Dark Energy Survey Year 3 (DES Y3), the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and its precursor, the Baryon Oscillation Spectroscopic Survey (BOSS). Our measurements incorporate photometric red sequence (redMaGiC) galaxies from DES with median redshift z ∼ 0.2–1.0, luminous red galaxies from eBOSS at z ∼ 0.8, and also an SDSSIII BOSS CMASS sample at z ∼ 0.5. We measure twopoint IA correlations, which we fit using a model that includes lensing, magnification, and photometric redshift error. Fitting on scales 6 Mpc h−1 < rp < 70 Mpc h−1, we make a detection of IAs in each sample, at 5σ–22σ (assuming a simple oneparameter model for IAs). Using these red samples, we measure the IA–luminosity relation. Our results are statistically consistent with previous results, but offer a significant improvement in constraining power, particularly at low luminosity. With this improved precision, we see detectable dependence on colour between broadly defined red samples. It is likely that a more sophisticated approach than a binary red/blue split, which jointly considers colour and luminosity dependence in the IA signal, will be needed in future. We also compare the various signal components at the bestfitting point in parameter space for each sample, and find that magnification and lensing contribute $\sim 2\!\!18~{{\ \rm per\ cent}}$ of the total signal. As precision continues to improve, it will certainly be necessary to account for these effects in future direct IA measurements. Finally, we make equivalent measurements on a sample of emissionline galaxies from eBOSS at z ∼ 0.8. We constrain the nonlinear alignment amplitude to be $A_1=0.07^{+0.32}_{0.42}$ (A1 < 0.78 at 95 per cent CL).
 Award ID(s):
 1716131
 NSFPAR ID:
 10286738
 Date Published:
 Journal Name:
 Monthly Notices of the Royal Astronomical Society
 Volume:
 491
 Issue:
 4
 ISSN:
 00358711
 Page Range / eLocation ID:
 5330 to 5350
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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