Albedos of Small Hilda Group Asteroids as Revealed by Spitzer

Abstract

We present thermal 24 $\mu$m observations from the \textit{Spitzer Space Telescope} of 62 Hilda asteroid group members with diameters ranging from 3 to 12 kilometers. Measurements of the thermal emission when combined with reported absolute magnitudes allow us to constrain the albedo and diameter of each object. From our \textit{Spitzer} sample, we find the mean geometric albedo, $p_V=$ 0.07 $\pm$ 0.05 for small (D $<$ 10 km) Hilda group asteroids. This value of $p_V$ is greater than and spans a larger range in albedo space than the mean albedo of large (D $\gtrsim$ 10 km) Hilda group asteroids which is $p_V=$ 0.04 $\pm$ 0.01. Though this difference may be attributed to space weathering, the small Hilda group population reportedly displays greater taxonomic range from C-, D- and X-type whose albedo distributions are commensurate with the range of determined albedos. We discuss the derived Hilda size-frequency distribution, color-color space, and geometric albedo for our survey sample in the context of the expected migration induced "seeding" of the Hilda asteroid group with outer solar system proto-planetesimals as outlined in the "Nice" formalism.

34 pages, 6 figures. Submitted to Astronomical Journal

References in corpus (9)

• Origin of the Structure of the Kuiper Belt during a Dynamical Instability in the Orbits of Uranus and Neptune
• Thermal inertia of near-Earth asteroids and implications for the magnitude of the Yarkovsky effect
• High Albedos of Low Inclination Classical Kuiper Belt Objects
• Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. III. An Asteroid-based Calibration of MIPS at 160 microns
• Thermal inertia of main belt asteroids smaller than 100 km from IRAS data
• Rectified Asteroid Albedos and Diameters from IRAS and MSX
• Asteroid families in the first order resonances with Jupiter
• Albedos of Main-Belt Comets 133P/Elst-Pizarro and 176P/LINEAR
• Albedos of Small Jovian Trojans

Cited by in corpus (5)

• WISE/NEOWISE Observations of the Hilda Population: Preliminary Results
• PRIMASS visits Hilda and Cybele groups
• The color-magnitude distribution of Hilda asteroids: Comparison with Jupiter Trojans
• Size Distribution of Small Hilda Asteroids
• $0.7-2.5\mu$m spectra of Hilda asteroids