The PAU Survey: Measuring intrinsic galaxy alignments in deep wide fields as a function of colour, luminosity, stellar mass and redshift

Abstract

We present the measurements and constraints of intrinsic alignments (IA) in the Physics of the Accelerating Universe Survey (PAUS) deep wide fields, which include the W1 and W3 fields from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) and the G09 field from the Kilo-Degree Survey (KiDS). Our analyses cover 51deg$^{2}$, in the photometric redshift (photo-$z$) range $0.1 < z_{\mathrm{b}} < 1$ and a magnitude limit $i_{\mathrm{AB}}<22$. The precise photo-$z$s and the luminosity coverage of PAUS enable robust IA measurements, which are key for setting informative priors for upcoming stage-IV surveys. For red galaxies, we detect an increase in IA amplitude with both luminosity and stellar mass, extending previous results towards fainter and less massive regimes. As a function of redshift, we observe strong IA signals at intermediate ($z_{\mathrm{b}}\sim0.55$) and high ($z_{\mathrm{b}}\sim0.75$) redshift bins. However, we find no significant trend of IA evolution with redshift after accounting for the varying luminosities across redshift bins, consistent with the literature. For blue galaxies, no significant IA signal is detected, with $A_{1}=0.68_{-0.51}^{+0.53}$ when splitting only by galaxy colour, yielding some of the tightest constraints to date for the blue population and constraining a regime of very faint and low-mass galaxies.

Figures (24)

• Figure 1: $\sigma_{68}(\Delta_{z})$(left), outlier fraction (centre) and bias (right) as a function of $i_{\mathrm{AB}}$ (triangles down, bottom axis) and $z_{\mathrm{b}}$ (triangles up, top axis) for the used in this analysis.
• Figure 2: Division in active and passive galaxies following a NUV$rK$ diagram cut and a $T_{\mathrm{\texttt{BPZ}}}$ selection, coloured by the obtained with , as indicated by the colour bar to the right of each panel. The top regions delimited by the black lines correspond to passive galaxies, while the complementary regions correspond to active galaxies.
• Figure 3: $i_{\mathrm{AB}}$ distribution of the dense sample (left), the red galaxies with shapes (middle) and the blue galaxies with shapes (right) for each of the wide fields.
• Figure 4: Top: vs. of the galaxy mock catalogue from the MICE simulation (left) and of the objects from the W3 field that have (right), coloured by the number of objects in each pixel normalised by the median value. Bottom: $\sigma_{68}(\Delta_{z})$ vs. for the MICE simulation (left) and (right).
• Figure 5: Comparison of the distribution of $i_{\mathrm{AB}}$ (left) and $z_{\mathrm{b}}$ (right) for the wide fields and the MICE galaxy mock, indicating the similarity of the galaxy populations for both cases. This enables the use of MICE in order to perform some consistency tests, detailed in Appendix \ref{['sec:randoms']}, \ref{['sec:Comparison_zb_zs']} and \ref{['sec:error_estimation']}.