The Orbit and Size-Frequency Distribution of Long Period Comets Observed by Pan-STARRS1

Abstract

We introduce a new technique to estimate the comet nuclear size frequency distribution (SFD) that combines a cometary activity model with a survey simulation and apply it to 150 long period comets (LPC) detected by the Pan-STARRS1 near-Earth object survey. The debiased LPC size-frequency distribution is in agreement with previous estimates for large comets with nuclear diameter $>\sim 1$~km but we measure a significant drop in the SFD slope for small objects with diameters $<1$~km and approaching only $100$~m diameter. Large objects have a slope ${\alpha }_{big}=0.72\pm 0.09(stat.)\pm 0.15(sys.)$ while small objects behave as ${\alpha }_{small}=0.07\pm 0.03(stat.)\pm 0.09(sys.)$ where the SFD is $\propto 10^{\alpha H_N}$ and $H_N$ represents the cometary nuclear absolute magnitude. The total number of LPCs that are $>1$~km diameter and have perihelia $q<10$~au is $0.46\pm 0.15\times 10^9$ while there are only $2.4\pm 0.5(stat.)\pm 2(sys.)\times 10^9$ objects with diameters $>100$~m due to the shallow slope of the SFD for diameters $<1$~m. We estimate that the total number of `potentially active' objects with diameters $\ge 1$~km in the Oort cloud, objects that would be defined as LPCs if their perihelia evolved to $<10$~au, is $(1.5\pm 1)\times 10^{12}$ with a combined mass of $1.3\pm 0.9M_{Earth}$. The debiased LPC orbit distribution is broadly in agreement with expectations from contemporary dynamical models but there are discrepancies that could point towards a future ability to disentangle the relative importance of stellar perturbations and galactic tides in producing the LPC population.

accepted for publication in Icarus

References in corpus (12)

• Evidence of fast pebble growth near condensation fronts in the HL Tau protoplanetary disk
• Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles
• Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength
• Interstellar Interloper 1I/2017 U1: Observations from the NOT and WIYN Telescopes
• An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets
• Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 'Oumuamua
• CO in distantly active comets
• The Main-Belt Comets: The Pan-STARRS1 Perspective
• Oort spike comets with large perihelion distances
• CO-Driven Activity in Comet C/2017 K2 (PANSTARRS)
• High-fidelity Simulations of the Near-Earth Object Search Performance of the Large Synoptic Survey Telescope
• The size-frequency distribution of H>13 NEOs and ARM targets detected by Pan-STARRS1

Cited by in corpus (3)

• Initial characterization of interstellar comet 2I/Borisov
• Visible and near-infrared observations of interstellar comet 2I/Borisov with the 10.4-m GTC and the 3.6-m TNG telescopes
• Retrograde orbits excess among observable interstellar objects