Thermal properties, sizes, and size distribution of Jupiter-family cometary nuclei

    Authors

    Y. R. Fernandez; M. S. Kelley; P. L. Lamy; I. Toth; O. Groussin; C. M. Lisse; M. F. A'Hearn; J. M. Bauer; H. Campins; A. Fitzsimmons; J. Licandro; S. C. Lowry; K. J. Meech; J. Pittichova; W. T. Reach; C. Snodgrass;H. A. Weaver

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    Abbreviated Journal Title

    Icarus

    Keywords

    Comets, Nucleus; Comets, Dust; Infrared observations; SPITZER-SPACE-TELESCOPE; SHORT-PERIOD COMETS; NEAR-EARTH ASTEROIDS; KUIPER-BELT OBJECTS; DEEP-IMPACT; CCD PHOTOMETRY; ENSEMBLE PROPERTIES; RADAR OBSERVATIONS; DISTANT COMETS; 103P/HARTLEY 2; Astronomy & Astrophysics

    Abstract

    We present results from SEPPCoN, an on-going Survey of the Ensemble Physical Properties of Cometary Nuclei. In this report we discuss mid-infrared measurements of the thermal emission from 89 nuclei of Jupiter-family comets (JFCs). All data were obtained in 2006 and 2007 using imaging capabilities of the Spitzer Space Telescope. The comets were typically 4-5 AU from the Sun when observed and most showed only a point-source with little or no extended emission from dust. For those comets showing dust, we used image processing to photometrically extract the nuclei. For all 89 comets, we present new effective radii, and for 57 comets we present beaming parameters. Thus our survey provides the largest compilation of radiometrically-derived physical properties of nuclei to date. We have six main conclusions: (a) The average beaming parameter of the JFC population is 1.03 +/- 0.11, consistent with unity; coupled with the large distance of the nuclei from the Sun, this indicates that most nuclei have Tempel 1-like thermal inertia. Only two of the 57 nuclei had outlying values (in a statistical sense) of infrared beaming. (b) The known JFC population is not complete even at 3 km radius, and even for comets that approach to similar to 2 AU from the Sun and so ought to be more discoverable. Several recently-discovered comets in our survey have small perihelia and large (above similar to 2 km) radii. (c) With our radii, we derive an independent estimate of the JFC nuclear cumulative size distribution (CSD), and we find that it has a power-law slope of around -1.9, with the exact value depending on the bounds in radius. (d) This power-law is close to that derived by others from visible-wavelength observations that assume a fixed geometric albedo, suggesting that there is no strong dependence of geometric albedo with radius. (e) The observed CSD shows a hint of structure with an excess of comets with radii 3-6 km. (f) Our CSD is consistent with the idea that the intrinsic size distribution of the JFC population is not a simple power-law and lacks many sub-kilometer objects. (C) 2013 Elsevier Inc. All rights reserved.

    Journal Title

    Icarus

    Volume

    226

    Issue/Number

    1

    Publication Date

    1-1-2013

    Document Type

    Article

    Language

    English

    First Page

    1138

    Last Page

    1170

    WOS Identifier

    WOS:000324720200089

    ISSN

    0019-1035

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