A search for late-type brown dwarfs in the Euclid Quick Data Release 1

TL;DR

This study identifies and characterizes 15 mid-to-late T dwarf candidates in the Euclid dataset, demonstrating Euclid's potential to discover ultracool substellar objects beyond current survey capabilities.

Contribution

First identification of ultracool dwarf candidates in Euclid data using combined photometric and spectroscopic analysis, including discovery of new objects without prior literature.

Findings

15 T dwarf candidates identified and validated

8 newly discovered ultracool dwarfs with no previous records

Euclid survey shows promise for ultracool dwarf discovery beyond existing surveys

Abstract

We present the identification and characterization of 15 mid-to-late T dwarf candidates in the Euclid Quick Release 1 (Q1) dataset, based on a combined photometric and spectroscopic analysis. Candidates were initially selected via color-based cuts in the Euclid $Y_E - J_E$ and $J_E - H_E$ color-color space, targeting the region occupied by ultracool dwarfs in synthetic photometry from the Sanghi et al. (2024) sample. From an initial pool of 38,845 sources, we extracted low-resolution near-infrared spectra from the Euclid NISP instrument and applied a two-stage validation procedure that included spectral template fitting followed by visual inspection. Eight of the 15 validated candidates are newly identified objects with no prior literature association. We examined their morphological and photometric properties and compared them with established spectral standards. Photometric distances were derived using band-averaged distance modulus estimates. We discuss the limitations and promise of the Euclid survey for ultracool dwarf studies, and demonstrate the potential for discovering substellar populations beyond the reach of current wide-field surveys.