Noemie El-Bez-Sebastien

arXiv2026

Primitive asteroids in the main belt, Cybele, and Hilda populations from Gaia DR3

Primitive asteroids include C-, P-, and D-classes, known to be dark and having spectra mostly featureless. They differ in the spectral slope, which ranges from moderate values for C-types, and progressively increases in P- and D-types, the latter being the reddest. While C- and P-types are commonly observed in the asteroid main belt, D-types are commonly found further from the Sun, in the Cybele, Hilda, and Jupiter Trojans regions, and very few are reported in the main belt. This study aims at characterizing the abundance of primordial and red asteroids, belonging to the P-, D-, and Z-classes in the Mahlke et al. (2022) taxonomy, in the 2-5.2 AU region using the third data release by the Gaia mission spectral catalog, which includes more than 60000 spectrophotometric data of asteroids. We have applied the following methodology to identify primordial asteroids in the catalog: 1) selection of objects with signal to noise ratio greater than 20; 2) albedo value less than 12%; 3) chi-squared fit to automatically identify potential D-, Z-, and P-types using Bus-DeMeo and Mahlke taxonomy; 4) visual inspection of every spectrum to confirm the taxonomic classification. Referring to Mahlke taxonomy, we have found 318 new D-types across the main belt, as well as 124 Z-types, and is in agreement with theoretical estimations. We computed the spectral slope in the visible range (0.55 - 0.81 μm). We also have identified 265 P-types in the main belt. For the Cybele and Hilda asteroids, we characterize the taxonomic class of all the bodies with SNR higher than 20 in the Gaia catalog, for a total sample of 193 and 180 asteroids, respectively.

astro-ph.EP↗

arXiv2025

Jupiter Trojans spectrophotometry using Gaia DR3 catalog

We present the spectral characterization of Jupiter Trojans using data from the Gaia mission DR3 spectral catalog (320 spectra of good quality) and from the literature. Gaia spectrophotometry is available in 16 spectrophotometric points covering the 0.33-1.08 $μ$m range. The final dataset includes 519 Trojans, 291 in the leading swarm (L4) and 228 in the trailing swarm (L5), which we classified using the Bus-Demeo and Mahlke classification schemes. The Trojan population is dominated by featureless asteroids with red spectral slopes belonging to the D-type, and an important fraction ($\sim$ 40\%) belong to the Z-class (in Mahlke taxonomy), characterized by very red slopes. The L4 swarm shows a higher spectral variability and a higher amount, by a factor of 2, of less spectrally red asteroids belonging to the C, P, and X classes, mainly associated with families members. Once excluding peculiar families members the two swarms have very similar average slope and albedo values (7.86 $\pm$ 0.15\% and 7.35 $\pm$0.15\% for the L4 and L5 swarms, respectively). This points toward a common origin of the bodies of the two swarms, likely from the Transneptunian region. We do not observe a spectral color bi-modality distribution, conversely to the results previously reported in the literature. The spectral slope distribution, peaked at 9-11 \%/1000 Å, it is very narrow compared to that of Transneptunian objects (TNOs) or cometary nuclei. Trojans visible spectral slopes match those of the less red TNOs, and lack of extremely red and organic rich bodies. We suggest that the Jupiter Trojans might have been captured by Jupiter from the Centaurs and scattered disk population, and that the lack of extremely red objects among Trojans is due to removal of the organic-rich crust through the sublimation of volatiles and collisions as TNOs migrated inward in the Solar System.

astro-ph.EP↗