2025/12/01 by G. Girardi, Girardi, G., A. Grazian +257
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries
paper · pdf · doi:10.48550/arxiv.2512.01489
openalex publication_date 2025/12/01 · openalex created_date 2025/12/03 · openalex updated_date 2026/07/30
Our comprehension of the history of star formation at z>3 relies on rest-frame UV observations, yet this selection misses the most dusty and massive sources, yielding an incomplete census at early times. Infrared facilities such as Spitzer and the James Webb Space Telescope have revealed a hidden population at z=3-6 with extreme red colours, named HIEROs (HST-to-IRAC extremely red objects), identified by the criterion HE-ch2>2.25. Recently, Euclid Early Release Observations (ERO) have made it possible to further study such objects by comparing Euclid data with ancillary Spitzer/IRAC imaging. We investigate a 232 arcmin2 area in the Perseus field using VIS and NISP photometry, complemented by the four Spitzer channels and ground-based MegaCam bands (u, g, r, \rm Hα, i, z). Applying the colour cut yields 121 HIEROs; after removing globular clusters, brown dwarfs, and unreliable cases through visual inspection of multiband cutouts, we obtain a final sample of 42 robust HIEROs. Photometric redshifts and physical properties are estimated with the SED-fitting code Bagpipes. From the resulting zphot and M_* values, we compute the galaxy stellar mass function at 3.5