Euclid: Disky titans -- surprisingly high star formation activity and gas content in two brightest group galaxies at z∼0.75
Year: 2026
Type: article
Abstract: We present the discovery of two disky titans in the first data release of the satellite Euclid . These sources are massive (M_*>10^ 11 , M_⊙ ) star-forming ̊m SFR ∼ 20 , M_⊙, ̊m yr ^ -1 $) disks located in strong over-dense environments at intermediate redshifts (z ). Their existence is puzzling, given the abundance of passive, bulge-dominated sources commonly found at the centre of groups and clusters at low redshifts. First, our analysis shows that these objects are located in massive groups (M_ They represent a small fraction of the massive galaxies in over-dense regions (just four candidates in over 20, ^2 deg analysed in this study ̊m h 13.8 , M_⊙), where rapid accretion of cold gas should be prevented by the formation of a static hot halo. Despite this, a millimetre follow-up with NOEMA shows significant cold gas reservoirs (M_ ̊m H_2 10.3 , M_⊙) within these sources. Second, our morphological analysis indicates a massive, passive bulge in these galaxies. This bulge is expected to stabilise the disk against fragmentation, thereby suppressing further star formation. However, these sources lie on the Schmidt--Kennicutt relation or even slightly above. Building on these observations, we propose a scenario where these disky titans are the product of a merger-induced rejuvenation episode, in which the most massive galaxy in a group accretes cold gas from another member and briefly restarts star formation. Such a scenario is supported by a comparison with the TNG300 simulation and easily explains the persistence of star formation activity in massive galaxies in over-dense environments as temporary stages of more complex evolution. More generally, our study showcases the ability of Euclid to find rare objects, thanks to the unprecedented statistic offered by its surveys and the scientific potential residing in the synergy between and other facilities observing at longer wavelengths. Euclid
Source: Astronomy and Astrophysics
Authors: F. Gentile, E. Daddi, D. Elbaz, A. Enia, F. Vito, P.-A. Duc, M. Franco, H. Fu, R. Giuffrida, D. Roberts, F. Shankar, S. Lu, P. Awad, J-B. Billand, M. Baes, L. Bisigello, E. Duran-Camacho, G. Castignani, O. Cucciati, G. De Lucia, C. D'Eugenio, D. Donevski, M. Fossati, M. Fumagalli, R. Gobat, C. Gruppioni, M. Magliocchetti, B. Magnelli, G. Papini, L. Pozzetti, V. Sangalli, J. G. Sorce, L. Spinoglio, V. Strazzullo, M. Tarrasse, G. Toni, G. Zamorani, J. Lewis, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, H. Degaudenzi, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. Gwyn, S. V. H. Haugan, H. Hoekstra, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Melchior, 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, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, H. J. A. Rottgering, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, P. Schneider, T. Schrabback, A. Secroun, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, J. Skottfelt, L. Stanco, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, F. M. Zerbi, E. Zucca, M. Sereno
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: National Aeronautics and Space Administration, European Space Agency, European Commission, Agence Nationale de la Recherche, Magyar Tudományos Akadémia, Agenzia Spaziale Italiana, Conseil Régional, Île-de-France, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, National Astronomical Observatory of Japan, Agenția Spațială Română, Norsk Romsenter, Gauss Centre for Supercomputing, Fundação para a Ciência e a Tecnologia, Innovate UK
OpenAlex ID: W7214767260
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