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Euclid preparation. Impact of galaxy intrinsic alignment modelling choices on Euclid 3x2pt cosmology

Euclid Collaboration, D. Navarro-Gironés, I. Tutusaus, M. Crocce, S. Gouyou Beauchamps, R. Paviot, B. Joachimi, J. Ruiz-Zapatero, D. Sciotti, N. Tessore, G. Cañas-Herrera, P. Carrilho, J. M. Coloma-Nadal, H. Hoekstra, A. Porredon, B. Altieri, S. Andreon, C. Baccigalupi, M. Baldi, S. Bardelli, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, V. F. Cardone, J. Carretero, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Escoffier, M. Farina, R. Farinelli, S. Farrens, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, S. Kermiche, A. Kiessling, M. Kilbinger, B. Kubik, K. Kuijken, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, E. Medinaceli, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, S. -M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, C. Rosset, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, P. Tallada-Crespí, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, Y. Wang, J. Weller, F. M. Zerbi, E. Zucca, M. Ballardini, M. Bolzonella, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, T. Castro, J. A. Escartin Vigo, L. Gabarra, J. García-Bellido, J. Macias-Perez, R. Maoli, J. Martín-Fleitas, N. Mauri, R. B. Metcalf, P. Monaco, A. Pezzotta, M. Pöntinen, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, L. Bazzanini, J. Bel, D. Bertacca, M. Bethermin, F. Beutler, A. Blanchard, L. Blot, M. Bonici, M. L. Brown, S. Bruton, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, P. Dimauro, V. Duret, M. Y. Elkhashab, Y. Fang, P. G. Ferreira, A. Finoguenov, A. Franco, K. Ganga, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, E. J. Gonzalez, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, M. Magliocchetti, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, A. Montoro, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, L. Pagano, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, C. Pattison, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, K. Rojas, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, E. Sellentin, L. C. Smith, K. Tanidis, F. Tarsitano, R. Teyssier, A. Troja, D. Vergani, F. Vernizzi, G. Verza, P. Vielzeuf, S. Vinciguerra, N. A. Walton, A. H. Wright, S. -S. Li

Abstract

The Euclid galaxy survey will provide unprecedented constraints on cosmology, but achieving unbiased results will require an optimal characterisation and mitigation of systematic effects. Among these, the intrinsic alignments (IA) of galaxies are one of the dominant contaminants of the weak lensing (WL) and galaxy-galaxy lensing (GGL) probes. In this work, we assess IA modelling choices for Euclid DR1 3x2pt analyses by comparing the performance of the two most commonly used IA models, nonlinear alignment (NLA) and tidal alignment tidal torquing (TATT), along with several variations. Our analyses combine three perspectives: i) the constraining power on the IA and cosmological parameters for each IA model, ii) the bias that results when the IA analysis model differs from the model used to generate the synthetic data vector, and iii) the degeneracies between IA and photometric redshift (photo-z) nuisance parameters. Among the IA models analysed, the redshift-dependent TATT model (zTATT) provides the most flexible description of IA, with a similar constraining power compared to simpler IA models, making it a well-motivated choice for Euclid DR1 3x2pt analyses.

Euclid preparation. Impact of galaxy intrinsic alignment modelling choices on Euclid 3x2pt cosmology

Abstract

The Euclid galaxy survey will provide unprecedented constraints on cosmology, but achieving unbiased results will require an optimal characterisation and mitigation of systematic effects. Among these, the intrinsic alignments (IA) of galaxies are one of the dominant contaminants of the weak lensing (WL) and galaxy-galaxy lensing (GGL) probes. In this work, we assess IA modelling choices for Euclid DR1 3x2pt analyses by comparing the performance of the two most commonly used IA models, nonlinear alignment (NLA) and tidal alignment tidal torquing (TATT), along with several variations. Our analyses combine three perspectives: i) the constraining power on the IA and cosmological parameters for each IA model, ii) the bias that results when the IA analysis model differs from the model used to generate the synthetic data vector, and iii) the degeneracies between IA and photometric redshift (photo-z) nuisance parameters. Among the IA models analysed, the redshift-dependent TATT model (zTATT) provides the most flexible description of IA, with a similar constraining power compared to simpler IA models, making it a well-motivated choice for Euclid DR1 3x2pt analyses.
Paper Structure (28 sections, 25 equations, 16 figures, 4 tables)

This paper contains 28 sections, 25 equations, 16 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Modelling
  3. Angular power spectra
  4. Models for intrinsic alignment of galaxies
  5. NLA
  6. TATT
  7. Forecast pipeline
  8. Likelihood
  9. Parameters and priors
  10. Covariance matrix
  11. Scale cuts
  12. Synthetic data vectors
  13. Flagship simulation
  14. Sample definition
  15. Measurement of IA values in Flagship
  16. ...and 13 more sections

Figures (16)

  • Figure 1: Scale cuts for , , and as a function of redshift for different $k_{\mathrm{max}}$. The assumed model is and magnification contributions are included.
  • Figure 2: Normalised true redshift distribution, $z_{\mathrm{s}}$, of sources and lenses for the galaxy samples defined in Sect. \ref{['sec:Sample_definition']}.
  • Figure 3: constraints for the measured Flagship $C_{\ell}$ described in Sect. \ref{['sec:IA_values_FS']} when using the (tan) and the (blue) models. The dashed lines correspond to the maximum of the posterior distributions of the parameters, which are used to generate the synthetic in Sect. \ref{['sec:generation_synt_DVs']}.
  • Figure 4: (left) and cosmological parameters (right) constraints for (blue) and (tan) at different scale cuts in the $C_{\ell}$, $k_{\rm{max}}=1\,h\rm{Mpc}^{-1}$ (unfilled) and $k_{\rm{max}}=3\,h\rm{Mpc}^{-1}$ (filled). The dashed lines indicate the fiducial values of the parameters. The tan contours on the right plot are not well distinguished because they overlap with the blue ones.
  • Figure 5: Comparison of the (blue) and (tan) $C_{\ell}$ for the cross-correlation of the source redshift bin 1 with the other bins. Vertical lines show the scale cuts applied to the analysis for $k_{\rm{max}}=1\,h\rm{Mpc}^{-1}$ (dashed line) and $k_{\rm{max}}=3\,h\rm{Mpc}^{-1}$ (solid line) in the $C(\ell)$s.
  • ...and 11 more figures