Euclid: Quick Data Release (Q1) – A photometric search for ultracool dwarfs in the Euclid Deep Fields

M. Žerjal; C. Dominguez-Tagle; N. Vitas; N. Sedighi; E. L. Martín; M. R. Zapatero Osorio; J. Olivares; S. Muñoz Torres; S. Tsilia; J.-Y. Zhang; D. Barrado; V. J. S. Béjar; H. Bouy; A. Burgasser; P. Cruz; N. Lodieu; P. Mas Buitrago; N. Phan-Bao; E. Solano; R. Tata; B. Goldman; A. Mohandasan; C. Reylé; R. L. Smart; N. Aghanim; B. Altieri; A. Amara; S. Andreon; N. Auricchio; C. Baccigalupi; M. Baldi; A. Balestra; S. Bardelli; P. Battaglia; A. Biviano; A. Bonchi; E. Branchini; M. Brescia; J. Brinchmann; S. Camera; G. Cañas-Herrera; V. Capobianco; C. Carbone; J. Carretero; S. Casas; M. Castellano; G. Castignani; S. Cavuoti; K. C. Chambers; A. Cimatti; C. Colodro-Conde; G. Congedo; C. J. Conselice; L. Conversi; Y. Copin; F. Courbin; H. M. Courtois; M. Cropper; J.-G. Cuby; A. Da Silva; H. Degaudenzi; G. De Lucia; C. Dolding; H. Dole; M. Douspis; F. Dubath; X. Dupac; S. Dusini; S. Escoffier; M. Farina; F. Faustini; S. Ferriol; S. Fotopoulou; M. Frailis; E. Franceschi; S. Galeotta; K. George; B. Gillis; C. Giocoli; P. Gómez-Alvarez; J. Gracia-Carpio; B. R. Granett; A. Grazian; F. Grupp; S. V. H. Haugan; J. Hoar; W. Holmes; F. Hormuth; A. Hornstrup; K. Jahnke; M. Jhabvala; E. Keihänen; S. Kermiche; A. Kiessling; B. Kubik; K. Kuijken; M. Kümmel; M. Kunz; H. Kurki-Suonio; Q. Le Boulc’h; A. M. C. Le Brun; S. Ligori; P. B. Lilje; V. Lindholm; I. Lloro; G. Mainetti; D. Maino; E. Maiorano; O. Mansutti; O. Marggraf; M. Martinelli; N. Martinet; F. Marulli; R. Massey; E. Medinaceli; S. Mei; Y. Mellier; 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; L. Pozzetti; F. Raison; R. Rebolo; A. Renzi; J. Rhodes; G. Riccio; E. Romelli; M. Roncarelli; R. Saglia; Z. Sakr; D. Sapone; B. Sartoris; J. A. Schewtschenko; M. Schirmer; P. Schneider; A. Secroun; G. Seidel; M. Seiffert; S. Serrano; P. Simon; C. Sirignano; G. Sirri; L. Stanco; J. Steinwagner; P. Tallada-Crespí; A. N. Taylor; I. Tereno; S. Toft; R. Toledo-Moreo; F. Torradeflot; A. Tsyganov; I. Tutusaus; L. Valenziano; J. Valiviita; T. Vassallo; G. Verdoes Kleijn; A. Veropalumbo; Y. Wang; J. Weller; A. Zacchei; G. Zamorani; F. M. Zerbi; E. Zucca; J. Martín-Fleitas; V. Scottez

doi:10.1051/0004-6361/202556980

Euclid: Quick Data Release (Q1) – A photometric search for ultracool dwarfs in the Euclid Deep Fields

M. Žerjal
, C. Dominguez-Tagle
, N. Vitas
, N. Sedighi
, E. L. Martín
, M. R. Zapatero Osorio
, J. Olivares
, S. Muñoz Torres
, S. Tsilia
, J.-Y. Zhang
, D. Barrado
, V. J. S. Béjar
, H. Bouy
, A. Burgasser
, P. Cruz
, N. Lodieu
, P. Mas Buitrago
, N. Phan-Bao
, E. Solano
, R. Tata

B. Goldman, A. Mohandasan, C. Reylé, R. L. Smart, N. Aghanim, B. Altieri, A. Amara, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, A. Bonchi, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, J.-G. Cuby, A. Da Silva, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, M. Douspis, F. Dubath, X. Dupac, S. Dusini, S. Escoffier, M. Farina, F. Faustini, S. Ferriol, S. Fotopoulou, M. Frailis, E. Franceschi, S. Galeotta, K. George, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, B. R. Granett, A. Grazian, F. Grupp, S. V. H. Haugan, J. Hoar, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, K. Kuijken, M. Kümmel, M. Kunz, H. Kurki-Suonio, Q. Le Boulc’h, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. Massey, E. Medinaceli, S. Mei, Y. Mellier, 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, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, J. A. Schewtschenko, M. Schirmer, P. Schneider, A. Secroun, G. Seidel, M. Seiffert, S. Serrano, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, A. Tsyganov, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, J. Martín-Fleitas, V. Scottez

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Abstract

We present a catalogue of 5306 new ultracool dwarf (UCD) candidates in the three Euclid Deep Fields in the Q1 data release. They range from late M to late T dwarfs, and include 1200 L and T dwarfs. A total of 546 objects have been spectroscopically confirmed, including 329 L dwarfs and 26 T dwarfs. We also provide empirical Euclid colours as a function of spectral type. Our UCD selection criteria are based only on colour (I_E − Y_E > 2.5). The combined requirement for optical detection and a stringent signal-to-noise ratio threshold ensure a high purity of the sample, but at the expense of completeness, especially for T dwarfs. The detections range from magnitudes 19 and 24 in the near-infrared bands, and extend down to 26 in the optical band. We discuss Euclid’s capability to identify UCD candidates based on its photometric passbands. The average surface density of detected UCDs on the sky is approximately 100 objects per deg², including 20 L and T dwarfs per deg². This leads to an expectation of at least 1.4 million UCDs in the final data release of the Euclid Wide Survey, including at least 300 000 L dwarfs, and more than 2600 T dwarfs, using the strict selection criteria from this work.

Original language	English
Article number	A37
Journal	Astronomy and Astrophysics
Volume	711
Number of pages	17
ISSN	0004-6361
DOIs	https://doi.org/10.1051/0004-6361/202556980
Publication status	Published - 2026

Bibliographical note

This paper is published on behalf of the Euclid Consortium.

Keywords

Catalogs
Brown dwarfs

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Žerjal, M., Dominguez-Tagle, C., Vitas, N., Sedighi, N., Martín, E. L., Zapatero Osorio, M. R., Olivares, J., Muñoz Torres, S., Tsilia, S., Zhang, J.-Y., Barrado, D., Béjar, V. J. S., Bouy, H., Burgasser, A., Cruz, P., Lodieu, N., Mas Buitrago, P., Phan-Bao, N., Solano, E., ... Scottez, V. (2026). Euclid: Quick Data Release (Q1) – A photometric search for ultracool dwarfs in the Euclid Deep Fields. Astronomy and Astrophysics, 711, Article A37. https://doi.org/10.1051/0004-6361/202556980

@article{5a72bee85f8e4033974dc41ea2df3fa4,

title = "Euclid: Quick Data Release (Q1) {\textendash} A photometric search for ultracool dwarfs in the Euclid Deep Fields",

abstract = "We present a catalogue of 5306 new ultracool dwarf (UCD) candidates in the three Euclid Deep Fields in the Q1 data release. They range from late M to late T dwarfs, and include 1200 L and T dwarfs. A total of 546 objects have been spectroscopically confirmed, including 329 L dwarfs and 26 T dwarfs. We also provide empirical Euclid colours as a function of spectral type. Our UCD selection criteria are based only on colour (IE − YE > 2.5). The combined requirement for optical detection and a stringent signal-to-noise ratio threshold ensure a high purity of the sample, but at the expense of completeness, especially for T dwarfs. The detections range from magnitudes 19 and 24 in the near-infrared bands, and extend down to 26 in the optical band. We discuss Euclid{\textquoteright}s capability to identify UCD candidates based on its photometric passbands. The average surface density of detected UCDs on the sky is approximately 100 objects per deg2, including 20 L and T dwarfs per deg2. This leads to an expectation of at least 1.4 million UCDs in the final data release of the Euclid Wide Survey, including at least 300 000 L dwarfs, and more than 2600 T dwarfs, using the strict selection criteria from this work.",

keywords = "Catalogs, Brown dwarfs",

author = "M. {\v Z}erjal and C. Dominguez-Tagle and N. Vitas and N. Sedighi and Mart{\'i}n, \{E. L.\} and \{Zapatero Osorio\}, \{M. R.\} and J. Olivares and \{Mu{\~n}oz Torres\}, S. and S. Tsilia and J.-Y. Zhang and D. Barrado and B{\'e}jar, \{V. J. S.\} and H. Bouy and A. Burgasser and P. Cruz and N. Lodieu and \{Mas Buitrago\}, P. and N. Phan-Bao and E. Solano and R. Tata and B. Goldman and A. Mohandasan and C. Reyl{\'e} and Smart, \{R. L.\} and N. Aghanim and B. Altieri and A. Amara and S. Andreon and N. Auricchio and C. Baccigalupi and M. Baldi and A. Balestra and S. Bardelli and P. Battaglia and A. Biviano and A. Bonchi and E. Branchini and M. Brescia and J. Brinchmann and S. Camera and G. Ca{\~n}as-Herrera and V. Capobianco and C. Carbone and J. Carretero and S. Casas and M. Castellano and G. Castignani and S. Cavuoti and Chambers, \{K. C.\} and A. Cimatti and C. Colodro-Conde and G. Congedo and Conselice, \{C. J.\} and L. Conversi and Y. Copin and F. Courbin and Courtois, \{H. M.\} and M. Cropper and J.-G. Cuby and \{Da Silva\}, A. and H. Degaudenzi and \{De Lucia\}, G. and C. Dolding and H. Dole and M. Douspis and F. Dubath and X. Dupac and S. Dusini and S. Escoffier and M. Farina and F. Faustini and S. Ferriol and S. Fotopoulou and M. Frailis and E. Franceschi and S. Galeotta and K. George and B. Gillis and C. Giocoli and P. G{\'o}mez-Alvarez and J. Gracia-Carpio and Granett, \{B. R.\} and A. Grazian and F. Grupp and Haugan, \{S. V. H.\} and J. Hoar and W. Holmes and F. Hormuth and A. Hornstrup and K. Jahnke and M. Jhabvala and E. Keih{\"a}nen and S. Kermiche and A. Kiessling and B. Kubik and K. Kuijken and M. K{\"u}mmel and M. Kunz and H. Kurki-Suonio and \{Le Boulc{\textquoteright}h\}, Q. and \{Le Brun\}, \{A. M. C.\} and S. Ligori 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 M. Martinelli and N. Martinet and F. Marulli and R. Massey and E. Medinaceli and S. Mei and Y. Mellier and M. Meneghetti and E. Merlin and G. Meylan and A. Mora and M. Moresco and L. Moscardini and R. Nakajima and C. Neissner and S.-M. Niemi and C. Padilla and S. Paltani and F. Pasian and K. Pedersen and Percival, \{W. J.\} and V. Pettorino and S. Pires 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 R. Saglia and Z. Sakr and D. Sapone and B. Sartoris and Schewtschenko, \{J. A.\} and M. Schirmer and P. Schneider and A. Secroun and G. Seidel and M. Seiffert and S. Serrano and P. Simon and C. Sirignano and G. Sirri and L. Stanco and J. Steinwagner and P. Tallada-Cresp{\'i} and Taylor, \{A. N.\} and I. Tereno and S. Toft and R. Toledo-Moreo and F. Torradeflot and A. Tsyganov and I. Tutusaus and L. Valenziano and J. Valiviita and T. Vassallo and \{Verdoes Kleijn\}, G. and A. Veropalumbo and Y. Wang and J. Weller and A. Zacchei and G. Zamorani and Zerbi, \{F. M.\} and E. Zucca and J. Mart{\'i}n-Fleitas and V. Scottez",

note = "This paper is published on behalf of the Euclid Consortium.",

year = "2026",

doi = "10.1051/0004-6361/202556980",

language = "English",

volume = "711",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Žerjal, M, Dominguez-Tagle, C, Vitas, N, Sedighi, N, Martín, EL, Zapatero Osorio, MR, Olivares, J, Muñoz Torres, S, Tsilia, S, Zhang, J-Y, Barrado, D, Béjar, VJS, Bouy, H, Burgasser, A, Cruz, P, Lodieu, N, Mas Buitrago, P, Phan-Bao, N, Solano, E, Tata, R, Goldman, B, Mohandasan, A, Reylé, C, Smart, RL, Aghanim, N, Altieri, B, Amara, A, Andreon, S, Auricchio, N, Baccigalupi, C, Baldi, M, Balestra, A, Bardelli, S, Battaglia, P, Biviano, A, Bonchi, A, Branchini, E, Brescia, M, Brinchmann, J, Camera, S, Cañas-Herrera, G, Capobianco, V, Carbone, C, Carretero, J, Casas, S, Castellano, M, Castignani, G, Cavuoti, S, Chambers, KC, Cimatti, A, Colodro-Conde, C, Congedo, G, Conselice, CJ, Conversi, L, Copin, Y, Courbin, F, Courtois, HM, Cropper, M, Cuby, J-G, Da Silva, A, Degaudenzi, H, De Lucia, G, Dolding, C, Dole, H, Douspis, M, Dubath, F, Dupac, X, Dusini, S, Escoffier, S, Farina, M, Faustini, F, Ferriol, S, Fotopoulou, S, Frailis, M, Franceschi, E, Galeotta, S, George, K, Gillis, B, Giocoli, C, Gómez-Alvarez, P, Gracia-Carpio, J, Granett, BR, Grazian, A, Grupp, F, Haugan, SVH, Hoar, J, Holmes, W, Hormuth, F, Hornstrup, A, Jahnke, K, Jhabvala, M, Keihänen, E, Kermiche, S, Kiessling, A, Kubik, B, Kuijken, K, Kümmel, M, Kunz, M, Kurki-Suonio, H, Le Boulc’h, Q, Le Brun, AMC, Ligori, S, Lilje, PB, Lindholm, V, Lloro, I, Mainetti, G, Maino, D, Maiorano, E, Mansutti, O, Marggraf, O, Martinelli, M, Martinet, N, Marulli, F, Massey, R, Medinaceli, E, Mei, S, Mellier, Y, Meneghetti, M, Merlin, E, Meylan, G, Mora, A, Moresco, M, Moscardini, L, Nakajima, R, Neissner, C, Niemi, S-M, Padilla, C, Paltani, S, Pasian, F, Pedersen, K, Percival, WJ, Pettorino, V, Pires, S, Polenta, G, Poncet, M, Popa, LA, Pozzetti, L, Raison, F, Rebolo, R, Renzi, A, Rhodes, J, Riccio, G, Romelli, E, Roncarelli, M, Saglia, R, Sakr, Z, Sapone, D, Sartoris, B, Schewtschenko, JA, Schirmer, M, Schneider, P, Secroun, A, Seidel, G, Seiffert, M, Serrano, S, Simon, P, Sirignano, C, Sirri, G, Stanco, L, Steinwagner, J, Tallada-Crespí, P, Taylor, AN, Tereno, I, Toft, S, Toledo-Moreo, R, Torradeflot, F, Tsyganov, A, Tutusaus, I, Valenziano, L, Valiviita, J, Vassallo, T, Verdoes Kleijn, G, Veropalumbo, A, Wang, Y, Weller, J, Zacchei, A, Zamorani, G, Zerbi, FM, Zucca, E, Martín-Fleitas, J & Scottez, V 2026, 'Euclid: Quick Data Release (Q1) – A photometric search for ultracool dwarfs in the Euclid Deep Fields', Astronomy and Astrophysics, vol. 711, A37. https://doi.org/10.1051/0004-6361/202556980

TY - JOUR

T1 - Euclid: Quick Data Release (Q1) – A photometric search for ultracool dwarfs in the Euclid Deep Fields

AU - Žerjal, M.

AU - Dominguez-Tagle, C.

AU - Vitas, N.

AU - Sedighi, N.

AU - Martín, E. L.

AU - Zapatero Osorio, M. R.

AU - Olivares, J.

AU - Muñoz Torres, S.

AU - Tsilia, S.

AU - Zhang, J.-Y.

AU - Barrado, D.

AU - Béjar, V. J. S.

AU - Bouy, H.

AU - Burgasser, A.

AU - Cruz, P.

AU - Lodieu, N.

AU - Mas Buitrago, P.

AU - Phan-Bao, N.

AU - Solano, E.

AU - Tata, R.

AU - Goldman, B.

AU - Mohandasan, A.

AU - Reylé, C.

AU - Smart, R. L.

AU - Aghanim, N.

AU - Altieri, B.

AU - Amara, A.

AU - Andreon, S.

AU - Auricchio, N.

AU - Baccigalupi, C.

AU - Baldi, M.

AU - Balestra, A.

AU - Bardelli, S.

AU - Battaglia, P.

AU - Biviano, A.

AU - Bonchi, A.

AU - Branchini, E.

AU - Brescia, M.

AU - Brinchmann, J.

AU - Camera, S.

AU - Cañas-Herrera, G.

AU - Capobianco, V.

AU - Carbone, C.

AU - Carretero, J.

AU - Casas, S.

AU - Castellano, M.

AU - Castignani, G.

AU - Cavuoti, S.

AU - Chambers, K. C.

AU - Cimatti, A.

AU - Colodro-Conde, C.

AU - Congedo, G.

AU - Conselice, C. J.

AU - Conversi, L.

AU - Copin, Y.

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 - Dolding, C.

AU - Dole, H.

AU - Douspis, M.

AU - Dubath, F.

AU - Dupac, X.

AU - Dusini, S.

AU - Escoffier, S.

AU - Farina, M.

AU - Faustini, F.

AU - Ferriol, S.

AU - Fotopoulou, S.

AU - Frailis, M.

AU - Franceschi, E.

AU - Galeotta, S.

AU - George, K.

AU - Gillis, B.

AU - Giocoli, C.

AU - Gómez-Alvarez, P.

AU - Gracia-Carpio, J.

AU - Granett, B. R.

AU - Grazian, A.

AU - Grupp, F.

AU - Haugan, S. V. H.

AU - Hoar, J.

AU - Holmes, W.

AU - Hormuth, F.

AU - Hornstrup, A.

AU - Jahnke, K.

AU - Jhabvala, M.

AU - Keihänen, E.

AU - Kermiche, S.

AU - Kiessling, A.

AU - Kubik, B.

AU - Kuijken, K.

AU - Kümmel, M.

AU - Kunz, M.

AU - Kurki-Suonio, H.

AU - Le Boulc’h, Q.

AU - Le Brun, A. M. C.

AU - Ligori, S.

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 - Martinelli, M.

AU - Martinet, N.

AU - Marulli, F.

AU - Massey, R.

AU - Medinaceli, E.

AU - Mei, S.

AU - Mellier, Y.

AU - Meneghetti, M.

AU - Merlin, E.

AU - Meylan, G.

AU - Mora, A.

AU - Moresco, M.

AU - Moscardini, L.

AU - Nakajima, R.

AU - Neissner, C.

AU - Niemi, S.-M.

AU - Padilla, C.

AU - Paltani, S.

AU - Pasian, F.

AU - Pedersen, K.

AU - Percival, W. J.

AU - Pettorino, V.

AU - Pires, S.

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 - Saglia, R.

AU - Sakr, Z.

AU - Sapone, D.

AU - Sartoris, B.

AU - Schewtschenko, J. A.

AU - Schirmer, M.

AU - Schneider, P.

AU - Secroun, A.

AU - Seidel, G.

AU - Seiffert, M.

AU - Serrano, S.

AU - Simon, P.

AU - Sirignano, C.

AU - Sirri, G.

AU - Stanco, L.

AU - Steinwagner, J.

AU - Tallada-Crespí, P.

AU - Taylor, A. N.

AU - Tereno, I.

AU - Toft, S.

AU - Toledo-Moreo, R.

AU - Torradeflot, F.

AU - Tsyganov, A.

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 - Zacchei, A.

AU - Zamorani, G.

AU - Zerbi, F. M.

AU - Zucca, E.

AU - Martín-Fleitas, J.

AU - Scottez, V.

N1 - This paper is published on behalf of the Euclid Consortium.

PY - 2026

Y1 - 2026

N2 - We present a catalogue of 5306 new ultracool dwarf (UCD) candidates in the three Euclid Deep Fields in the Q1 data release. They range from late M to late T dwarfs, and include 1200 L and T dwarfs. A total of 546 objects have been spectroscopically confirmed, including 329 L dwarfs and 26 T dwarfs. We also provide empirical Euclid colours as a function of spectral type. Our UCD selection criteria are based only on colour (IE − YE > 2.5). The combined requirement for optical detection and a stringent signal-to-noise ratio threshold ensure a high purity of the sample, but at the expense of completeness, especially for T dwarfs. The detections range from magnitudes 19 and 24 in the near-infrared bands, and extend down to 26 in the optical band. We discuss Euclid’s capability to identify UCD candidates based on its photometric passbands. The average surface density of detected UCDs on the sky is approximately 100 objects per deg2, including 20 L and T dwarfs per deg2. This leads to an expectation of at least 1.4 million UCDs in the final data release of the Euclid Wide Survey, including at least 300 000 L dwarfs, and more than 2600 T dwarfs, using the strict selection criteria from this work.

AB - We present a catalogue of 5306 new ultracool dwarf (UCD) candidates in the three Euclid Deep Fields in the Q1 data release. They range from late M to late T dwarfs, and include 1200 L and T dwarfs. A total of 546 objects have been spectroscopically confirmed, including 329 L dwarfs and 26 T dwarfs. We also provide empirical Euclid colours as a function of spectral type. Our UCD selection criteria are based only on colour (IE − YE > 2.5). The combined requirement for optical detection and a stringent signal-to-noise ratio threshold ensure a high purity of the sample, but at the expense of completeness, especially for T dwarfs. The detections range from magnitudes 19 and 24 in the near-infrared bands, and extend down to 26 in the optical band. We discuss Euclid’s capability to identify UCD candidates based on its photometric passbands. The average surface density of detected UCDs on the sky is approximately 100 objects per deg2, including 20 L and T dwarfs per deg2. This leads to an expectation of at least 1.4 million UCDs in the final data release of the Euclid Wide Survey, including at least 300 000 L dwarfs, and more than 2600 T dwarfs, using the strict selection criteria from this work.

KW - Catalogs

KW - Brown dwarfs

U2 - 10.1051/0004-6361/202556980

DO - 10.1051/0004-6361/202556980

M3 - Journal article

SN - 0004-6361

VL - 711

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A37

ER -

Euclid: Quick Data Release (Q1) – A photometric search for ultracool dwarfs in the Euclid Deep Fields

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