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Enhancing Multiplet Alignment Measurements with Imaging

Alexus Annika Kumwembe, Claire Lamman, Daniel Eisenstein, Jessica Nicole Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, Biprateep Dey, Peter Doel, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztanaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Mustapha Ishak, Jorge Jimenez, Dick Joyce, Robert Kehoe, Theodore Kisner, Ofer Lahav, Martin Landriau, Marc Manera, Ramon Miquel, Seshadri Nadathur, Nathalie Palanque-Delabrouille, Ignasi Perez-Rafols, Francisco Prada, Graziano Rossi, Eusebio Sanchez, David Schlegel, Hee-Jong Seo, Joseph Harry Silber, David Sprayberry, Gregory Tarle, Benjamin Alan Weaver

TL;DR

This paper addresses measuring galaxy intrinsic alignments driven by the large-scale tidal field by using imaging data to augment spectroscopic multiplet measurements. The authors construct six enhanced multiplet catalogs by pairing DESI Y1 LRG spectroscopic targets with nearby imaging LRG-like galaxies selected via color and magnitude cuts, and quantify alignment via $\cos(2\phi)$ as a function of projected separation $R$, with $\Pi_{\rm max}$ tied to $R$. The main finding is that imaging-based multiplets recover a signal with the same scale dependence and approximately equal SNR as the spectroscopic-only result, with stricter cuts giving the best agreement and looser cuts offering higher SNR at the cost of interloper dilution. This demonstrates that imaging can substantially improve the effective SNR of multiplet alignment measurements and enable application to larger surveys such as LSST. The work provides a proof-of-concept for combining imaging and spectroscopy to study IA and the tidal field.

Abstract

We demonstrate that measurements of the gravitational tidal field made with spectroscopic redshifts can be improved with information from imaging surveys. The average orientation of small groups of galaxies, or "multiplets" is correlated with large-scale structure and is used to measure the direction of tidal forces. Previously, multiplet intrinsic alignment has been measured in DESI using galaxies that have spectroscopic redshifts. The DESI Legacy Imaging catalog can be used to supplement multiplet catalogs. Our findings show that galaxy positions from the imaging catalog produce a measurement similar to the measurements made with only spectroscopic data. This demonstrates that imaging can improve our signal-to-noise ratio for multiplet alignment in DESI.

Enhancing Multiplet Alignment Measurements with Imaging

TL;DR

This paper addresses measuring galaxy intrinsic alignments driven by the large-scale tidal field by using imaging data to augment spectroscopic multiplet measurements. The authors construct six enhanced multiplet catalogs by pairing DESI Y1 LRG spectroscopic targets with nearby imaging LRG-like galaxies selected via color and magnitude cuts, and quantify alignment via as a function of projected separation , with tied to . The main finding is that imaging-based multiplets recover a signal with the same scale dependence and approximately equal SNR as the spectroscopic-only result, with stricter cuts giving the best agreement and looser cuts offering higher SNR at the cost of interloper dilution. This demonstrates that imaging can substantially improve the effective SNR of multiplet alignment measurements and enable application to larger surveys such as LSST. The work provides a proof-of-concept for combining imaging and spectroscopy to study IA and the tidal field.

Abstract

We demonstrate that measurements of the gravitational tidal field made with spectroscopic redshifts can be improved with information from imaging surveys. The average orientation of small groups of galaxies, or "multiplets" is correlated with large-scale structure and is used to measure the direction of tidal forces. Previously, multiplet intrinsic alignment has been measured in DESI using galaxies that have spectroscopic redshifts. The DESI Legacy Imaging catalog can be used to supplement multiplet catalogs. Our findings show that galaxy positions from the imaging catalog produce a measurement similar to the measurements made with only spectroscopic data. This demonstrates that imaging can improve our signal-to-noise ratio for multiplet alignment in DESI.

Paper Structure

This paper contains 5 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Data
  3. Methods
  4. Results
  5. Acknowledgments

Figures (1)

  • Figure 1: The tidal alignment of galaxy multiplets, each containing one spectroscopically-measured central galaxy. The gold line is the original measurement made with only spectroscopic data. Although amplitudes vary depending on multiplet definition, their scale-dependent response to large-scale shear is consistent.