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Euclid: Constraining ensemble photometric redshift distributions with stacked spectroscopy

Cagliari, M. S. and Granett, B. R. and Guzzo, L. and Bolzonella, M. and Pozzetti, L. and Tutusaus, I. and Camera, S. and Amara, A. and Auricchio, N. and Bender, R. and Bodendorf, C. and Bonino, D. and Branchini, E. and Brescia, M. and Capobianco, V. and Carbone, C. and Carretero, J. and Castander, F. J. and Castellano, M. and Cavuoti, S. and Cimatti, A. and Cledassou, R. and Congedo, G. and Conselice, C. J. and Conversi, L. and Copin, Y. and Corcione, L. and Cropper, M. and Degaudenzi, H. and Douspis, M. and Dubath, F. and Dusini, S. and Ealet, A. and Ferriol, S. and Fourmanoit, N. and Frailis, M. and Franceschi, E. and Franzetti, P. and Garilli, B. and Giocoli, C. and Grazian, A. and Grupp, F. and Haugan, S. V. H. and Hoekstra, H. and Holmes, W. and Hormuth, F. and Hudelot, P. and Jahnke, K. and Kermiche, S. and Kiessling, A. and Kilbinger, M. and Kitching, T. and Kümmel, M. and Kunz, M. and Kurki-Suonio, H. and Ligori, S. and Lilje, P. B. and Lloro, I. and Maiorano, E. and Mansutti, O. and Marggraf, O. and Markovic, K. and Massey, R. and Meneghetti, M. and Merlin, E. and Meylan, G. and Moresco, M. and Moscardini, L. and Niemi, S. M. and Padilla, C. and Paltani, S. and Pasian, F. and Pedersen, K. and Percival, W. J. and Pettorino, V. and Pires, S. and Poncet, M. and Popa, L. and Raison, F. and Rebolo, R. and Rhodes, J. and Rix, H.-W. and Roncarelli, M. and Rossetti, E. and Saglia, R. and Scaramella, R. and Schneider, P. and Scodeggio, M. and Secroun, A. and Seidel, G. and Serrano, S. and Sirignano, C. and Sirri, G. and Tavagnacco, D. and Taylor, A. N. and Tereno, I. and Toledo-Moreo, R. and Valentijn, E. A. and Valenziano, L. and Wang, Y. and Welikala, N. and Weller, J. and Zamorani, G. and Zoubian, J. and Baldi, M. and Farinelli, R. and Medinaceli, E. and Mei, S. and Polenta, G. and Romelli, E. and Vassallo, T. and Humphrey, A. (2022) Euclid: Constraining ensemble photometric redshift distributions with stacked spectroscopy. Astronomy and Astrophysics, 660 . Art. No. A9. ISSN 0004-6361. doi:10.1051/0004-6361/202142224.

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Context. The ESA Euclid mission will produce photometric galaxy samples over 15 000 square degrees of the sky that will be rich for clustering and weak lensing statistics. The accuracy of the cosmological constraints derived from these measurements will depend on the knowledge of the underlying redshift distributions based on photometric redshift calibrations. Aims. A new approach is proposed to use the stacked spectra from Euclid slitless spectroscopy to augment broad-band photometric information to constrain the redshift distribution with spectral energy distribution fitting. The high spectral resolution available in the stacked spectra complements the photometry and helps to break the colour-redshift degeneracy and constrain the redshift distribution of galaxy samples. Methods. We modelled the stacked spectra as a linear mixture of spectral templates. The mixture may be inverted to infer the underlying redshift distribution using constrained regression algorithms. We demonstrate the method on simulated Vera C. Rubin Observatory and Euclid mock survey data sets based on the Euclid Flagship mock galaxy catalogue. We assess the accuracy of the reconstruction by considering the inference of the baryon acoustic scale from angular two-point correlation function measurements. Results. We selected mock photometric galaxy samples at redshift z > 1 using the self-organising map algorithm. Considering the idealised case without dust attenuation, we find that the redshift distributions of these samples can be recovered with 0.5% accuracy on the baryon acoustic scale. The estimates are not significantly degraded by the spectroscopic measurement noise due to the large sample size. However, the error degrades to 2% when the dust attenuation model is left free. We find that the colour degeneracies introduced by attenuation limit the accuracy considering the wavelength coverage of Euclid near-infrared spectroscopy.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Cagliari, M. S.0000-0002-2912-9233
Granett, B. R.0000-0003-2694-9284
Meneghetti, M.0000-0003-1225-7084
Rhodes, J.0000-0002-4485-8549
Wang, Y.0000-0002-4749-2984
Additional Information:© ESO 2022. Received 15 September 2021; Accepted 18 January 2022; Published online 30 March 2022. This paper is published on behalf of the Euclid Consortium. The Euclid Consortium acknowledges the European Space Agency and a number of agencies and institutes that have supported the development of Euclid, in particular the Academy of Finland, the Agenzia Spaziale Italiana, the Belgian Science Policy, the Canadian Euclid Consortium, the Centre National d’Etudes Spatiales, the Deutsches Zentrum für Luft-und Raumfahrt, the Danish Space Research Institute, the Fundação para a Ciência e a Tecnologia, the Ministerio de Economia y Competitividad, the National Aeronautics and Space Administration, the National Astronomical Observatory of Japan, the Netherlandse Onderzoekschool Voor Astronomie, the Norwegian Space Agency, the Romanian Space Agency, the State Secretariat for Education, Research and Innovation (SERI) at the Swiss Space Office (SSO), and the United Kingdom Space Agency. A complete and detailed list is available on the Euclid web site ( This work has made use of CosmoHub. CosmoHub has been developed by the Port d’Informació Científica (PIC), maintained through a collaboration of the Institut de Física d’Altes Energies (IFAE) and the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) and the Institute of Space Sciences (CSIC & IEEC), and was partially funded by the “Plan Estatal de Investigación Científica y Técnica y de Innovación” programme of the Spanish government.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
European Space Agency (ESA)UNSPECIFIED
Academy of FinlandUNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Belgian Federal Science Policy Office (BELSPO)UNSPECIFIED
Canadian Euclid ConsortiumUNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Danish Space Research InstituteUNSPECIFIED
Fundação para a Ciência e a Tecnologia (FCT)UNSPECIFIED
Ministerio de Economía y Competitividad (MINECO)UNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Norwegian Space AgencyUNSPECIFIED
Romanian Space AgencyUNSPECIFIED
State Secretariat for Education, Research and Innovation (SERI)UNSPECIFIED
Swiss Space Office (SSO)UNSPECIFIED
United Kingdom Space Agency (UKSA)UNSPECIFIED
Plan Estatal de Investigación Científica y Técnica y de InnovaciónUNSPECIFIED
Subject Keywords:methods: data analysis – methods: statistical – galaxies: distances and redshifts – large-scale structure of Universe
Record Number:CaltechAUTHORS:20220427-735231000
Persistent URL:
Official Citation:Euclid: Constraining ensemble photometric redshift distributions with stacked spectroscopy. M. S. Cagliari, B. R. Granett, L. Guzzo, M. Bolzonella, L. Pozzetti, I. Tutusaus, S. Camera, A. Amara, N. Auricchio, R. Bender, C. Bodendorf, D. Bonino, E. Branchini, M. Brescia, V. Capobianco, C. Carbone, J. Carretero, F. J. Castander, M. Castellano, S. Cavuoti, A. Cimatti, R. Cledassou, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, L. Corcione, M. Cropper, H. Degaudenzi, M. Douspis, F. Dubath, S. Dusini, A. Ealet, S. Ferriol, N. Fourmanoit, M. Frailis, E. Franceschi, P. Franzetti, B. Garilli, C. Giocoli, A. Grazian, F. Grupp, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, P. Hudelot, K. Jahnke, S. Kermiche, A. Kiessling, M. Kilbinger, T. Kitching, M. Kümmel, M. Kunz, H. Kurki-Suonio, S. Ligori, P. B. Lilje, I. Lloro, E. Maiorano, O. Mansutti, O. Marggraf, K. Markovic, R. Massey, M. Meneghetti, E. Merlin, G. Meylan, M. Moresco, L. Moscardini, S. M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, M. Poncet, L. Popa, F. Raison, R. Rebolo, J. Rhodes, H.-W. Rix, M. Roncarelli, E. Rossetti, R. Saglia, R. Scaramella, P. Schneider, M. Scodeggio, A. Secroun, G. Seidel, S. Serrano, C. Sirignano, G. Sirri, D. Tavagnacco, A. N. Taylor, I. Tereno, R. Toledo-Moreo, E. A. Valentijn, L. Valenziano, Y. Wang, N. Welikala, J. Weller, G. Zamorani, J. Zoubian, M. Baldi, R. Farinelli, E. Medinaceli, S. Mei, G. Polenta, E. Romelli, T. Vassallo and A. Humphrey. A&A, 660 (2022) A9; DOI:
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ID Code:114503
Deposited By: Tony Diaz
Deposited On:27 Apr 2022 23:26
Last Modified:27 Apr 2022 23:26

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