Euclid: the potential of slitless infrared spectroscopy: a z = 5.4 quasar and new ultracool dwarfs

Bañados, E.; Le Brun, V.; Belladitta, S.; Momcheva, I.; Stern, D.; Wolf, J.; Ezziati, M.; Mortlock, D. J.; Humphrey, A.; Smart, R. L.; Casewell, S. L.; Pérez-Garrido, A.; Goldman, B.; Martín, E. L.; Mohandasan, A.; Reylé, C.; Dominguez-Tagle, C.; Copin, Y.; Lusso, E.; Matsuoka, Y.; Mccarthy, K.; Ricci, F.; Rix, H. -W.; Rottgering, H. J. A.; Schindler, J. -T.; Weaver, J. R.; Allaoui, A.; Bedrine, T.; Castellano, M.; Chabaud, P. -Y.; Daste, G.; Dufresne, F.; Gracia-Carpio, J.; Kümmel, M.; Moresco, M.; Scodeggio, M.; Surace, C.; Vibert, D.; Balestra, A.; Bonnefoi, A.; Caillat, A.; Cogato, F.; Costille, A.; Dusini, S.; Ferriol, S.; Franceschi, E.; Gillard, W.; Jahnke, K.; Le Mignant, D.; Ligori, S.; Medinaceli, E.; Morgante, G.; Passalacqua, F.; Paterson, K.; Pires, S.; Sirignano, C.; Andika, I. T.; Atek, H.; Barrado, D.; Bisogni, S.; Conselice, C. J.; Dannerbauer, H.; Decarli, R.; Dole, H.; Dupuy, T.; Feltre, A.; Fotopoulou, S.; Gillis, B.; Lopez, X. Lopez; Onoue, M.; Rodighiero, G.; Sedighi, N.; Shankar, F.; Siudek, M.; Spinoglio, L.; Vergani, D.; Vietri, G.; Walter, F.; Zamorani, G.; Zapatero Osorio, M. R.; Zhang, J. -Y.; Bethermin, M.; Aghanim, N.; Altieri, B.; Amara, A.; Andreon, S.; Baccigalupi, C.; Baldi, M.; Bardelli, S.; Basset, A.; Battaglia, P.; Biviano, A.; Bonchi, A.; Bonino, D.; Branchini, E.; Brescia, M.; Brinchmann, J.; Camera, S.; Capobianco, V.; Carbone, C.; Carretero, J.; Casas, S.; Castignani, G.; Cavuoti, S.; Cimatti, A.; Colodro-Conde, C.; Congedo, G.; Conversi, L.; Courbin, F.; Courtois, H. M.; Cropper, M.; Cuby, J. -G.; Da Silva, A.; Degaudenzi, H.; De Lucia, G.; Giorgio, A. M. Di; Dolding, C.; Dubath, F.; Duncan, C. A. J.; Dupac, X.; Ealet, A.; Farina, M.; Faustini, F.; Fourmanoit, N.; Frailis, M.; Galeotta, S.; George, K.; Giocoli, C.; Granett, B. R.; Grazian, A.; Grupp, F.; Guzzo, L.; Haugan, S. V. H.; Hoar, J.; Hoekstra, H.; Holmes, W.; Hook, I.; Hormuth, F.; Hornstrup, A.; Hudelot, P.; Jhabvala, M.; Joachimi, B.; Keihänen, E.; Kermiche, S.; Kubik, B.; Kuijken, K.; Kunz, M.; Kurki-Suonio, H.; Lilje, P. B.; Lindholm, V.; Lloro, I.; Mainetti, G.; Maino, D.; Maiorano, E.; Mansutti, O.; Marggraf, O.; Markovic, K.; Martinelli, M.; Martinet, N.; Marulli, F.; Massey, R.; Mei, S.; Mellier, Y.; Meneghetti, M.; Merlin, E.; Meylan, G.; Mora, A.; Moscardini, L.; Neissner, C.; Niemi, S. -M.; Nightingale, J. W.; Padilla, C.; Paltani, S.; Pasian, F.; Pedersen, K.; Percival, W. J.; Pettorino, V.; Polenta, G.; Poncet, M.; Popa, L. A.; Pozzetti, L.; Raison, F.; Rebolo, R.; Renzi, A.; Rhodes, J.; Riccio, G.; Romelli, E.; Roncarelli, M.; Rossetti, E.; Saglia, R.; Sakr, Z.; Sapone, D.; Sartoris, B.; Schewtschenko, J. A.; Schirmer, M.; Schneider, P.; Schrabback, T.; Secroun, A.; Sefusatti, E.; Seidel, G.; Seiffert, M.; Serrano, S.; Sirri, G.; Stanco, L.; Steinwagner, J.; Tallada-Crespí, P.; Taylor, A. N.; Teplitz, H. I.; Tereno, I.; Toft, S.; Toledo-Moreo, R.; Torradeflot, F.; Tutusaus, I.; Valenziano, L.; Valiviita, J.; Vassallo, T.; Verdoes Kleijn, G.; Veropalumbo, A.; Wang, Y.; Weller, J.; Zerbi, F. M.; Zucca, E.; Bolzonella, M.; Burigana, C.; Cabanac, R.; Gabarra, L.; Scottez, V.; Viel, M.; Scott, D.

doi:10.1093/mnras/staf1274

We demonstrate the potential of Euclid 's slitless spectroscopy to discover high-redshift ( z>5 ) quasars and their main photometric contaminant, ultracool dwarfs. Sensitive infrared spectroscopy from space is able to efficiently identify both populations, as demonstrated by Euclid Near-Infrared Spectrometer and Photometer Red Grism (NISP RGE ) spectra of the newly discovered z=5.404 quasar EUCL J181530.01 + 652054.0, as well as several ultracool dwarfs in the Euclid Deep Field North and the Euclid Early Release Observation field Abell 2764. The ultracool dwarfs were identified by cross-correlating their spectra with templates. The quasar was identified by its strong and broad CIII] and MgII emission lines in the NISP RGE 1206–1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP BGE ) 926–1366 nm spectrum confirms CIV and CIII] emission. NISP RGE can find bright quasars at z≈5.5 and z≳7 , redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01 + 652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array ( L144=4.0×1025 W Hz −1 ). The quasar has a bolometric luminosity of 3×1012L⊙ and is powered by a 3.4×109M⊙ black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the ≈ 20 deg 2 surveyed. This finding highlights the potential and effectiveness of NISP spectroscopy in identifying rare, luminous high-redshift quasars, previewing the census of these sources that Euclid's slitless spectroscopy will deliver over about 14000 deg 2 of the sky.

Euclid: the potential of slitless infrared spectroscopy: a z = 5.4 quasar and new ultracool dwarfs / Bañados, E., Le Brun, V., Belladitta, S., Momcheva, I., Stern, D., Wolf, J., Ezziati, M., Mortlock, D.J., Humphrey, A., Smart, R.L., Casewell, S.L., Pérez-Garrido, A., Goldman, B., Martín, E.L., Mohandasan, A., Reylé, C., Dominguez-Tagle, C., Copin, Y., Lusso, E., Matsuoka, Y., et al.. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 542:2(2025), pp. 1088-1102. [10.1093/mnras/staf1274]