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

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

doi:10.1093/mnras/staf1274

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

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

Research output: Contribution to journal › Article › peer-review

Abstract

We demonstrate the potential of Euclid 's slitless spectroscopy to discover high-redshift (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) spectra of the newly discovered quasar EUCL J181530.01652054.0, 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 and emission lines in the NISP 1206-1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP) 926-1366 nm spectrum confirms and emission. NISP can find bright quasars at and, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array (W Hz). The quasar has a bolometric luminosity of and is powered by a black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the 20 deg 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 deg of the sky.

Original language	English
Pages (from-to)	1088-1102
Number of pages	15
Journal	Monthly Notices of the Royal Astronomical Society
Volume	542
Issue number	2
Early online date	4 Aug 2025
DOIs	https://doi.org/10.1093/mnras/staf1274
Publication status	Published - 1 Sept 2025

Keywords

stars: brown dwarfs
quasars: individual: EUCL J181530.01 + 652054.0
stars: individual: EUCL J174429.80 + 672728.1, EUCL J002516.31-491618.5
stars: individual: EUCL J174429.80 + 672728.1
EUCL J002516.31-491618.5

Access to Document

10.1093/mnras/staf1274Licence: CC BY

Final_Version
© The Author(s) 2025.Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 3.43 MBLicence: CC BY

Cite this

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., ... Scott, D. (2025). Euclid: the potential of slitless infrared spectroscopy: a z = 5.4 quasar and new ultracool dwarfs. Monthly Notices of the Royal Astronomical Society, 542(2), 1088-1102. https://doi.org/10.1093/mnras/staf1274

@article{f20b1ead553b4748bba4c18a7a972ad4,

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

abstract = "We demonstrate the potential of Euclid 's slitless spectroscopy to discover high-redshift (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) spectra of the newly discovered quasar EUCL J181530.01652054.0, 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 and emission lines in the NISP 1206-1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP) 926-1366 nm spectrum confirms and emission. NISP can find bright quasars at and, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array (W Hz). The quasar has a bolometric luminosity of and is powered by a black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the 20 deg 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 deg of the sky.",

keywords = "stars: brown dwarfs, quasars: individual: EUCL J181530.01 + 652054.0, stars: individual: EUCL J174429.80 + 672728.1, EUCL J002516.31-491618.5, stars: individual: EUCL J174429.80 + 672728.1, EUCL J002516.31-491618.5",

author = "E Ba{\~n}ados and V Le Brun and S Belladitta and I Momcheva and D Stern and J Wolf and M Ezziati and Mortlock, \{D J\} and A Humphrey and Smart, \{R L\} and Casewell, \{S L\} and A P{\'e}rez-Garrido and B Goldman and Mart{\'i}n, \{E L\} and A Mohandasan and C Reyl{\'e} and C Dominguez-Tagle and Y Copin and E Lusso and Y Matsuoka and K McCarthy and F Ricci and H-W Rix and Rottgering, \{H J A\} and J-T Schindler and Weaver, \{J R\} and A Allaoui and T Bedrine and M Castellano and P-Y Chabaud and G Daste and F Dufresne and J Gracia-Carpio and M K{\"u}mmel and M Moresco and M Scodeggio and C Surace and D Vibert and A Balestra and A Bonnefoi and A Caillat and F Cogato and A Costille and S Dusini and S Ferriol and E Franceschi and W Gillard and K Jahnke and D Le Mignant and S Ligori and E Medinaceli and G Morgante and F Passalacqua and K Paterson and S Pires and C Sirignano and Andika, \{I T\} and H Atek and D Barrado and S Bisogni and Conselice, \{C J\} and H Dannerbauer and R Decarli and H Dole and T Dupuy and A Feltre and S Fotopoulou and B Gillis and Lopez, \{X Lopez\} and M Onoue and G Rodighiero and N Sedighi and F Shankar and M Siudek and L Spinoglio and D Vergani and G Vietri and F Walter and G Zamorani and Zapatero Osorio, \{M R\} and J-Y Zhang and M Bethermin and N Aghanim and B Altieri and A Amara and S Andreon and C Baccigalupi and M Baldi and S Bardelli and A Basset and P Battaglia and A Biviano and A Bonchi and D Bonino and E Branchini and M Brescia and J Brinchmann and S Camera and V Capobianco and C Carbone and J Carretero and S Casas and G Castignani and S Cavuoti and A Cimatti and C Colodro-Conde and G Congedo and L Conversi and F Courbin and Courtois, \{H M\} and M Cropper and J-G Cuby and A Da Silva and H Degaudenzi and G De Lucia and Giorgio, \{A M Di\} and C Dolding and F Dubath and Duncan, \{C A J\} and X Dupac and A Ealet and M Farina and F Faustini and N Fourmanoit and M Frailis and S Galeotta and K George and C Giocoli and Granett, \{B R\} and A Grazian and F Grupp and L Guzzo and Haugan, \{S V H\} and J Hoar and H Hoekstra and W Holmes and I Hook and F Hormuth and A Hornstrup and P Hudelot and M Jhabvala and B Joachimi and E Keih{\"a}nen and S Kermiche and B Kubik and K Kuijken and M Kunz and H Kurki-Suonio and Lilje, \{P B\} and V Lindholm and I Lloro and G Mainetti and D Maino and E Maiorano and O Mansutti and O Marggraf and K Markovic and M Martinelli and N Martinet and F Marulli and R Massey and S Mei and Y Mellier and M Meneghetti and E Merlin and G Meylan and A Mora and L Moscardini and C Neissner and S-M Niemi and Nightingale, \{J W\} and C Padilla and S Paltani and F Pasian and K Pedersen and Percival, \{W J\} and V Pettorino and G Polenta and M Poncet and Popa, \{L A\} and L Pozzetti and F Raison and R Rebolo and A Renzi and J Rhodes and G Riccio and E Romelli and M Roncarelli and E Rossetti and R Saglia and Z Sakr and D Sapone and B Sartoris and Schewtschenko, \{J A\} and M Schirmer and P Schneider and T Schrabback and A Secroun and E Sefusatti and G Seidel and M Seiffert and S Serrano and G Sirri and L Stanco and J Steinwagner and P Tallada-Cresp{\'i} and Taylor, \{A N\} and Teplitz, \{H I\} and I Tereno and S Toft and R Toledo-Moreo and F Torradeflot and I Tutusaus and L Valenziano and J Valiviita and T Vassallo and G Verdoes Kleijn and A Veropalumbo and Y Wang and J Weller and Zerbi, \{F M\} and E Zucca and M Bolzonella and C Burigana and R Cabanac and L Gabarra and V Scottez and M Viel and D Scott",

note = "{\textcopyright} The Author(s) 2025.Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.",

year = "2025",

month = sep,

day = "1",

doi = "10.1093/mnras/staf1274",

language = "English",

volume = "542",

pages = "1088--1102",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press (OUP)",

number = "2",

}

Bañados, E, Le Brun, V, Belladitta, S, Momcheva, I, Stern, D, Wolf, J, Ezziati, M, Mortlock, DJ, Humphrey, A, Smart, RL, Casewell, SL, Pérez-Garrido, A, Goldman, B, Martín, EL, Mohandasan, A, Reylé, C, Dominguez-Tagle, C, Copin, Y, Lusso, E, Matsuoka, Y, McCarthy, K, Ricci, F, Rix, H-W, Rottgering, HJA, Schindler, J-T, Weaver, JR, 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, IT, Atek, H, Barrado, D, Bisogni, S, Conselice, CJ, Dannerbauer, H, Decarli, R, Dole, H, Dupuy, T, Feltre, A, Fotopoulou, S, Gillis, B, Lopez, XL, Onoue, M, Rodighiero, G, Sedighi, N, Shankar, F, Siudek, M, Spinoglio, L, Vergani, D, Vietri, G, Walter, F, Zamorani, G, Zapatero Osorio, MR, 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, HM, Cropper, M, Cuby, J-G, Da Silva, A, Degaudenzi, H, De Lucia, G, Giorgio, AMD, Dolding, C, Dubath, F, Duncan, CAJ, Dupac, X, Ealet, A, Farina, M, Faustini, F, Fourmanoit, N, Frailis, M, Galeotta, S, George, K, Giocoli, C, Granett, BR, Grazian, A, Grupp, F, Guzzo, L, Haugan, SVH, 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, PB, 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, JW, Padilla, C, Paltani, S, Pasian, F, Pedersen, K, Percival, WJ, Pettorino, V, Polenta, G, Poncet, M, Popa, LA, 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, JA, 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, AN, Teplitz, HI, 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, FM, Zucca, E, Bolzonella, M, Burigana, C, Cabanac, R, Gabarra, L, Scottez, V, Viel, M & Scott, D 2025, 'Euclid: the potential of slitless infrared spectroscopy: a z = 5.4 quasar and new ultracool dwarfs', Monthly Notices of the Royal Astronomical Society, vol. 542, no. 2, pp. 1088-1102. https://doi.org/10.1093/mnras/staf1274

TY - JOUR

T1 - Euclid: the potential of slitless infrared spectroscopy: a z = 5.4 quasar and new ultracool dwarfs

AU - Bañados, E

AU - Le Brun, V

AU - Belladitta, S

AU - Momcheva, I

AU - Stern, D

AU - Wolf, J

AU - Ezziati, M

AU - Mortlock, D J

AU - Humphrey, A

AU - Smart, R L

AU - Casewell, S L

AU - Pérez-Garrido, A

AU - Goldman, B

AU - Martín, E L

AU - Mohandasan, A

AU - Reylé, C

AU - Dominguez-Tagle, C

AU - Copin, Y

AU - Lusso, E

AU - Matsuoka, Y

AU - McCarthy, K

AU - Ricci, F

AU - Rix, H-W

AU - Rottgering, H J A

AU - Schindler, J-T

AU - Weaver, J R

AU - Allaoui, A

AU - Bedrine, T

AU - Castellano, M

AU - Chabaud, P-Y

AU - Daste, G

AU - Dufresne, F

AU - Gracia-Carpio, J

AU - Kümmel, M

AU - Moresco, M

AU - Scodeggio, M

AU - Surace, C

AU - Vibert, D

AU - Balestra, A

AU - Bonnefoi, A

AU - Caillat, A

AU - Cogato, F

AU - Costille, A

AU - Dusini, S

AU - Ferriol, S

AU - Franceschi, E

AU - Gillard, W

AU - Jahnke, K

AU - Le Mignant, D

AU - Ligori, S

AU - Medinaceli, E

AU - Morgante, G

AU - Passalacqua, F

AU - Paterson, K

AU - Pires, S

AU - Sirignano, C

AU - Andika, I T

AU - Atek, H

AU - Barrado, D

AU - Bisogni, S

AU - Conselice, C J

AU - Dannerbauer, H

AU - Decarli, R

AU - Dole, H

AU - Dupuy, T

AU - Feltre, A

AU - Fotopoulou, S

AU - Gillis, B

AU - Lopez, X Lopez

AU - Onoue, M

AU - Rodighiero, G

AU - Sedighi, N

AU - Shankar, F

AU - Siudek, M

AU - Spinoglio, L

AU - Vergani, D

AU - Vietri, G

AU - Walter, F

AU - Zamorani, G

AU - Zapatero Osorio, M R

AU - Zhang, J-Y

AU - Bethermin, M

AU - Aghanim, N

AU - Altieri, B

AU - Amara, A

AU - Andreon, S

AU - Baccigalupi, C

AU - Baldi, M

AU - Bardelli, S

AU - Basset, A

AU - Battaglia, P

AU - Biviano, A

AU - Bonchi, A

AU - Bonino, D

AU - Branchini, E

AU - Brescia, M

AU - Brinchmann, J

AU - Camera, S

AU - Capobianco, V

AU - Carbone, C

AU - Carretero, J

AU - Casas, S

AU - Castignani, G

AU - Cavuoti, S

AU - Cimatti, A

AU - Colodro-Conde, C

AU - Congedo, G

AU - Conversi, L

AU - Courbin, F

AU - Courtois, H M

AU - Cropper, M

AU - Cuby, J-G

AU - Da Silva, A

AU - Degaudenzi, H

AU - De Lucia, G

AU - Giorgio, A M Di

AU - Dolding, C

AU - Dubath, F

AU - Duncan, C A J

AU - Dupac, X

AU - Ealet, A

AU - Farina, M

AU - Faustini, F

AU - Fourmanoit, N

AU - Frailis, M

AU - Galeotta, S

AU - George, K

AU - Giocoli, C

AU - Granett, B R

AU - Grazian, A

AU - Grupp, F

AU - Guzzo, L

AU - Haugan, S V H

AU - Hoar, J

AU - Hoekstra, H

AU - Holmes, W

AU - Hook, I

AU - Hormuth, F

AU - Hornstrup, A

AU - Hudelot, P

AU - Jhabvala, M

AU - Joachimi, B

AU - Keihänen, E

AU - Kermiche, S

AU - Kubik, B

AU - Kuijken, K

AU - Kunz, M

AU - Kurki-Suonio, H

AU - Lilje, P B

AU - Lindholm, V

AU - Lloro, I

AU - Mainetti, G

AU - Maino, D

AU - Maiorano, E

AU - Mansutti, O

AU - Marggraf, O

AU - Markovic, K

AU - Martinelli, M

AU - Martinet, N

AU - Marulli, F

AU - Massey, R

AU - Mei, S

AU - Mellier, Y

AU - Meneghetti, M

AU - Merlin, E

AU - Meylan, G

AU - Mora, A

AU - Moscardini, L

AU - Neissner, C

AU - Niemi, S-M

AU - Nightingale, J W

AU - Padilla, C

AU - Paltani, S

AU - Pasian, F

AU - Pedersen, K

AU - Percival, W J

AU - Pettorino, V

AU - Polenta, G

AU - Poncet, M

AU - Popa, L A

AU - Pozzetti, L

AU - Raison, F

AU - Rebolo, R

AU - Renzi, A

AU - Rhodes, J

AU - Riccio, G

AU - Romelli, E

AU - Roncarelli, M

AU - Rossetti, E

AU - Saglia, R

AU - Sakr, Z

AU - Sapone, D

AU - Sartoris, B

AU - Schewtschenko, J A

AU - Schirmer, M

AU - Schneider, P

AU - Schrabback, T

AU - Secroun, A

AU - Sefusatti, E

AU - Seidel, G

AU - Seiffert, M

AU - Serrano, S

AU - Sirri, G

AU - Stanco, L

AU - Steinwagner, J

AU - Tallada-Crespí, P

AU - Taylor, A N

AU - Teplitz, H I

AU - Tereno, I

AU - Toft, S

AU - Toledo-Moreo, R

AU - Torradeflot, F

AU - Tutusaus, I

AU - Valenziano, L

AU - Valiviita, J

AU - Vassallo, T

AU - Verdoes Kleijn, G

AU - Veropalumbo, A

AU - Wang, Y

AU - Weller, J

AU - Zerbi, F M

AU - Zucca, E

AU - Bolzonella, M

AU - Burigana, C

AU - Cabanac, R

AU - Gabarra, L

AU - Scottez, V

AU - Viel, M

AU - Scott, D

N1 - © The Author(s) 2025.Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

PY - 2025/9/1

Y1 - 2025/9/1

N2 - We demonstrate the potential of Euclid 's slitless spectroscopy to discover high-redshift (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) spectra of the newly discovered quasar EUCL J181530.01652054.0, 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 and emission lines in the NISP 1206-1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP) 926-1366 nm spectrum confirms and emission. NISP can find bright quasars at and, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array (W Hz). The quasar has a bolometric luminosity of and is powered by a black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the 20 deg 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 deg of the sky.

AB - We demonstrate the potential of Euclid 's slitless spectroscopy to discover high-redshift (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) spectra of the newly discovered quasar EUCL J181530.01652054.0, 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 and emission lines in the NISP 1206-1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP) 926-1366 nm spectrum confirms and emission. NISP can find bright quasars at and, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array (W Hz). The quasar has a bolometric luminosity of and is powered by a black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the 20 deg 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 deg of the sky.

KW - stars: brown dwarfs

KW - quasars: individual: EUCL J181530.01 + 652054.0

KW - stars: individual: EUCL J174429.80 + 672728.1, EUCL J002516.31-491618.5

KW - stars: individual: EUCL J174429.80 + 672728.1

KW - EUCL J002516.31-491618.5

UR - https://www.scopus.com/pages/publications/105013762690

U2 - 10.1093/mnras/staf1274

DO - 10.1093/mnras/staf1274

M3 - Article

SN - 0035-8711

VL - 542

SP - 1088

EP - 1102

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

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

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