Debiased orbit and absolutemagnitude distributions for nearEarth objects
Abstract
The debiased absolutemagnitude and orbit distributions as well as source regions for nearEarth objects (NEOs) provide a fundamental frame of reference for studies of individual NEOs and more complex populationlevel questions. We present a new fourdimensional model of the NEO population that describes debiased steadystate distributions of semimajor axis, eccentricity, inclination, and absolute magnitude H in the range 17 < H < 25. The modeling approach improves upon the methodology originally developed by Bottke et al. (2000, Science 288, 21902194) in that it is, for example, based on more realistic orbit distributions and uses sourcespecific absolutemagnitude distributions that allow for a powerlaw slope that varies with H. We divide the main asteroid belt into six different entrance routes or regions (ER) to the NEO region: the ν_{6}, 3:1J, 5:2J and 2:1J resonance complexes as well as Hungarias and Phocaeas. In addition we include the Jupiterfamily comets as the primary cometary source of NEOs. We calibrate the model against NEO detections by Catalina Sky Surveys' stations 703 and G96 during 20052012, and utilize the complementary nature of these two systems to quantify the systematic uncertainties associated to the resulting model. We find that the (fitted) H distributions have significant differences, although most of them show a minimum powerlaw slope at H ∼ 20. As a consequence of the differences between the ERspecific H distributions we find significant variations in, for example, the NEO orbit distribution, average lifetime, and the relative contribution of different ERs as a function of H. The most important ERs are the ν_{6} and 3:1J resonance complexes with JFCs contributing a few percent of NEOs on average. A significant contribution from the Hungaria group leads to notable changes compared to the predictions by Bottke et al. in, for example, the orbit distribution and average lifetime of NEOs. We predict that there are 962_{56}^{+52} (802_{42}^{+48} ×10^{3}) NEOs with H < 17.75 (H < 25) and these numbers are in agreement with the most recent estimates found in the literature (the uncertainty estimates only account for the random component). Based on our model we find that relative shares between different NEO groups (Amor, Apollo, Aten, Atira, Vatira) are (39.4,54.4,3.5,1.2,0.3)%, respectively, for the considered H range and that these ratios have a negligible dependence on H. Finally, we find an agreement between our estimate for the rate of Earth impacts by NEOs and recent estimates in the literature, but there remains a potentially significant discrepancy in the frequency of Tunguskasized and Chelyabinsksized impacts.
 Publication:

Icarus
 Pub Date:
 September 2018
 DOI:
 10.1016/j.icarus.2018.04.018
 arXiv:
 arXiv:1804.10265
 Bibcode:
 2018Icar..312..181G
 Keywords:

 NearEarth objects;
 Asteroids;
 Dynamics;
 Comets;
 Resonances;
 Orbital;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 33 pages, 28 figures, accepted for publication in Icarus