The PAU Survey: Intrinsic alignments and clustering of narrow-band photometric galaxies

¹ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
e-mail: hj@star.ucl.ac.uk
² Institute for Theoretical Physics, Utrecht University, Princetonplein 5, 3584 CE Utrecht, The Netherlands
³ Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁴ Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁵ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁶ Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus Univ. A. de Barcelona, 08193 Bellaterra, Barcelona, Spain
⁷ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, 08193 Barcelona, Spain
⁸ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
⁹ National Centre for Nuclear Research, ul. Hoza 69, 00-681 Warsaw, Poland
¹⁰ Institute for Particle Physics and Astrophysics, ETH Zürich, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
¹¹ CIEMAT, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Avda. Complutenes 40, 28040 Madrid, Spain
¹² Instituto de Física Teórica IFT-UAM/CSIC, Universidad Autónoma de Madrid, 28049 Madrid, Spain
¹³ Ruhr-University Bochum, Astronomical Institute, German Centre for Cosmological Lensing, Universitätsstr. 150, 44801 Bochum, Germany
¹⁴ Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
¹⁵ Port d’Informació Científica (PIC), Campus UAB, C. Albareda s/n, 08193 Bellaterra, Barcelona, Spain

Received: 15 October 2020
Accepted: 30 December 2020

Abstract

We present the first measurements of the projected clustering and intrinsic alignments (IA) of galaxies observed by the Physics of the Accelerating Universe Survey (PAUS). With photometry in 40 narrow optical passbands (4500 Å–8500 Å), the quality of photometric redshift estimation is σ_z ∼ 0.01(1 + z) for galaxies in the 19 deg² Canada-France-Hawaii Telescope Legacy Survey W3 field, allowing us to measure the projected 3D clustering and IA for flux-limited, faint galaxies (i < 22.5) out to z ∼ 0.8. To measure two-point statistics, we developed, and tested with mock photometric redshift samples, ‘cloned’ random galaxy catalogues which can reproduce data selection functions in 3D and account for photometric redshift errors. In our fiducial colour-split analysis, we made robust null detections of IA for blue galaxies and tentative detections of radial alignments for red galaxies (∼1 − 3σ), over scales of 0.1 − 18 h⁻¹ Mpc. The galaxy clustering correlation functions in the PAUS samples are comparable to their counterparts in a spectroscopic population from the Galaxy and Mass Assembly survey, modulo the impact of photometric redshift uncertainty which tends to flatten the blue galaxy correlation function, whilst steepening that of red galaxies. We investigate the sensitivity of our correlation function measurements to choices in the random catalogue creation and the galaxy pair-binning along the line of sight, in preparation for an optimised analysis over the full PAUS area.