Asteroid Distributions in the Ecliptic

TL;DR

This study analyzes the distribution, size, and albedo of main belt asteroids across different ecliptic latitudes using optical and infrared data, revealing new asteroid discoveries and variations in asteroid properties with latitude.

Contribution

It provides the first estimates of km-sized asteroid albedos in the middle and outer belts using Spitzer data and compares optical and infrared asteroid density distributions.

Findings

Discovered 58 new asteroids in optical data and 41 in Spitzer fields.

Found consistent power law slopes of asteroid counts across latitude bins.

Detected no low albedo asteroids in Spitzer FLS fields, but they are common in SWIRE fields.

Abstract

We present analysis of the asteroid surface density distribution of main belt asteroids (mean perihelion $\Delta \simeq 2.404$ AU) in five ecliptic latitude fields, $-17 \gtsimeq \beta(\degr) \ltsimeq +15$, derived from deep \textit{Large Binocular Telescope} (LBT) $V-$band (85% completeness limit $V = 21.3$ mag) and \textit{Spitzer Space Telescope} IRAC 8.0 \micron (80% completeness limit $\sim 103 \mu$Jy) fields enabling us to probe the 0.5--1.0 km diameter asteroid population. We discovered 58 new asteroids in the optical survey as well as 41 new bodies in the \textit{Spitzer} fields. The derived power law slopes of the number of asteroids per square degree are similar within each $\sim 5$\degr{} ecliptic latitude bin with a mean value of $ -0.111 \pm 0.077$. For the 23 known asteroids detected in all four IRAC channels mean albedos range from $0.24 \pm 0.07$ to $0.10 \pm 0.05$. No low albedo asteroids ($p_{V}$ $\ltsimeq$ 0.1) were detected in the \textit{Spitzer} FLS fields, whereas in the SWIRE fields they are frequent. The SWIRE data clearly samples asteroids in the middle and outer belts providing the first estimates of these km-sized asteroids' albedos. Our observed asteroid number densities at optical wavelengths are generally consistent with those derived from the Standard Asteroid Model within the ecliptic plane. However, we find an over density at $\beta \gtsimeq 5$\degr{} in our optical fields, while the infrared number densities are under dense by factors of 2 to 3 at all ecliptic latitudes.