Euclid preparation. XX. The Complete Calibration of the Color-Redshift Relation survey: LBT observations and data release

Saglia, R.; De Nicola, S.; Fabricius, M.; Guglielmo, V.; Snigula, J.; Z??ller, R.; Bender, R.; Heidt, J.; Masters, D.; Stern, D.; Paltani, S.; Amara, A.; Auricchio, N.; Baldi, M.; Bodendorf, C.; Bonino, D.; Branchini, E.; Brescia, M.; Brinchmann, J.; Camera, S.; Capobianco, V.; Carbone, C.; Carretero, J.; Castellano, M.; Cavuoti, S.; Cledassou, R.; Congedo, G.; Conselice, C. J.; Conversi, L.; Copin, Y.; Corcione, L.; Courbin, F.; Cropper, M.; Da Silva, A.; Degaudenzi, H.; Douspis, M.; Dubath, F.; Duncan, C. A. J.; Dupac, X.; Dusini, S.; Farrens, S.; Frailis, M.; Franceschi, E.; Galeotta, S.; Garilli, B.; Gillard, W.; Gillis, B.; Giocoli, C.; Grazian, A.; Grupp, F.; Haugan, S. V. H.; Hoekstra, H.; Holmes, W.; Hormuth, F.; Hornstrup, A.; Jahnke, K.; K??mmel, M.; Kermiche, S.; Kiessling, A.; Kunz, M.; Kurki-Suonio, H.; Laureijs, R.; Ligori, S.; Lilje, P. B.; Lloro, I.; Maiorano, E.; Marggraf, O.; Markovic, K.; Marulli, F.; Massey, R.; Mccracken, H. J.; Melchior, M.; Meylan, G.; Moresco, M.; Moscardini, L.; Munari, E.; Niemi, S. M.; Padilla, C.; Pasian, F.; Pedersen, K.; Percival, W. J.; Pettorino, V.; Pires, S.; Poncet, M.; Popa, L.; Pozzetti, L.; Raison, F.; Renzi, A.; Rhodes, J.; Riccio, G.; Romelli, E.; Rossetti, E.; Sapone, D.; Sartoris, B.; Schneider, P.; Secroun, A.; Seidel, G.; Sirignano, C.; Sirri, G.; Stanco, L.; Tallada-Cresp??, P.; Tavagnacco, D.; Taylor, A. N.; Tereno, I.; Toledo-Moreo, R.; Torradeflot, F.; Tutusaus, I.; Valentijn, E. A.; Valenziano, L.; Vassallo, T.; Wang, Y.; Zacchei, A.; Zamorani, G.; Zoubian, J.; Andreon, S.; Bardelli, S.; Graci??-Carpio, J.; Maino, D.; Mauri, N.; Tramacere, A.; Zucca, E.; Alvarez Ayllon, A.; Aussel, H.; Baccigalupi, C.; Balaguera-Antol??nez, A.; Ballardini, M.; Biviano, A.; Bolzonella, M.; Bozzo, E.; Burigana, C.; Cabanac, R.; Cappi, A.; Carvalho, C. S.; Casas, S.; Castignani, G.; Cooray, A.; Coupon, J.; Courtois, H. M.; Davini, S.; Desprez, G.; Dole, H.; Escartin, J. A.; Escoffier, S.; Farina, M.; Fotopoulou, S.; Ganga, K.; Garcia-Bellido, J.; George, K.; Giacomini, F.; Gozaliasl, G.; Hildebrandt, H.; Hook, I.; Ilbert, O.; Kansal, V.; Kashlinsky, A.; Keihanen, E.; Kirkpatrick, C. C.; Loureiro, A.; Mac??as-P??rez, J.; Magliocchetti, M.; Mainetti, G.; Maoli, R.; Martinelli, M.; Martinet, N.; Metcalf, R. B.; Morgante, G.; Nadathur, S.; Nucita, A. A.; Patrizii, L.; Popa, V.; Porciani, C.; Potter, D.; Pourtsidou, A.; Reimberg, P.; S??nchez, A. G.; Sakr, Z.; Schirmer, M.; Sefusatti, E.; Sereno, M.; Stadel, J.; Teyssier, R.; Valieri, C.; Valiviita, J.; Veropalumbo, A.; Viel, M.

doi:10.1051/0004-6361/202243604

The Complete Calibration of the Color-Redshift Relation survey (C3R2) is a spectroscopic program designed to empirically calibrate the galaxy color-redshift relation to the Euclid depth (I-E = 24.5), a key ingredient for the success of Stage IV dark energy projects based on weak lensing cosmology. A spectroscopic calibration sample that is as representative as possible of the galaxies in the Euclid weak lensing sample is being collected, selecting galaxies from a self-organizing map (SOM) representation of the galaxy color space. Here, we present the results of a near-infrared H- and K-band spectroscopic campaign carried out using the LUCI instruments at the LBT. For a total of 251 galaxies, we present new highly reliable redshifts in the 1.3 <= z <= 1.7 and 2 <= z <= 2.7 ranges. The newly-determined redshifts populate 49 SOM cells that previously contained no spectroscopic measurements and almost twice the occupation numbers of an additional 153 SOM cells. A final optical ground-based observational effort is needed to calibrate the missing cells, in particular in the redshift range 1.7 <= z <= 2.7, which lack spectroscopic calibration. In the end, Euclid itself will deliver telluric-free near-IR spectra that can complete the calibration.