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Measuring the Abundance of Sub-kilometer-sized Kuiper Belt Objects Using Stellar Occultations

Schlichting, Hilke E. and Ofek, Eran O. and Sari, Re'em and Nelan, Edmund P. and Gal-Yam, Avishay and Wenz, Michael and Muirhead, Philip and Javanfar, Nikta and Livio, Mario (2012) Measuring the Abundance of Sub-kilometer-sized Kuiper Belt Objects Using Stellar Occultations. Astrophysical Journal, 761 (2). Art. No. 150. ISSN 0004-637X.

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We present here the analysis of about 19,500 new star hours of low ecliptic latitude observations (|b| ≤ 20°) obtained by the Hubble Space Telescope's Fine Guidance Sensors over a time span of more than nine years, which is in addition to the ~12, 000 star hours previously analyzed by Schlichting et al. Our search for stellar occultations by small Kuiper Belt Objects (KBOs) yielded one new candidate event corresponding to a body with a 530 ± 70 m radius at a distance of about 40 AU. Using bootstrap simulations, we estimate a probability of ≈5% that this event is due to random statistical fluctuations within the new data set. Combining this new event with the single KBO occultation reported by Schlichting et al. we arrive at the following results: (1) the ecliptic latitudes of 6º.6 and 14º.4 of the two events are consistent with the observed inclination distribution of larger, 100-km-sized KBOs. (2) Assuming that small, sub-kilometer-sized KBOs have the same ecliptic latitude distribution as their larger counterparts, we find an ecliptic surface density of KBOs with radii larger than 250 m of N(r > 250 m) = 1.1^(+1.5)_(–0.7) × 10^7 deg^(–2); if sub-kilometer-sized KBOs have instead a uniform ecliptic latitude distribution for –20° < b < 20° then N(r > 250 m) = 4.4^(+5.8)_(–2.8) × 10^6 deg^(–2). This is the best measurement of the surface density of sub-kilometer-sized KBOs to date. (3) Assuming the KBO size distribution can be well described by a single power law given by N(> r) ∝ r^(1–q) , where N(> r) is the number of KBOs with radii greater than r, and q is the power-law index, we find q = 3.8 ± 0.2 and q = 3.6 ± 0.2 for a KBO ecliptic latitude distribution that follows the observed distribution for larger, 100-km-sized KBOs and a uniform KBO ecliptic latitude distribution for –20° < b < 20°, respectively. (4) Regardless of the exact power law, our results suggest that small KBOs are numerous enough to satisfy the required supply rate for the Jupiter family comets. (5) We can rule out a single power law below the break with q > 4.0 at 2σ, confirming a strong deficit of sub-kilometer-sized KBOs compared to a population extrapolated from objects with r > 45 km. This suggests that small KBOs are undergoing collisional erosion and that the Kuiper Belt is a true analog to the dust producing debris disks observed around other stars.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ofek, Eran O.0000-0002-6786-8774
Sari, Re'em0000-0002-1084-3656
Gal-Yam, Avishay0000-0002-3653-5598
Muirhead, Philip0000-0002-0638-8822
Additional Information:© 2012 American Astronomical Society. Received 2012 August 30; accepted 2012 October 29; published 2012 December 4. We thank Dr. Evan Kirby for analyzing and fitting the guide star spectrum. For H.S. support for this work was provided by NASA through Hubble Fellowship Grant No.HST-HF-51281.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contact NAS 5-26555. R.S. acknowledges support by an ERC grant, a Packard Fellowship, and HST Grant No. HST-AR-12154.08-A. E.O.O. is incumbent of the Arye Dissentshik career development chair and is grateful for support by a grant from the Israeli Ministry of Science and for support from the The Helen Kimmel Center for Planetary Science.
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF-51281.01-A
European Research Council (ERC)UNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Ministry of Science (Israel)UNSPECIFIED
Helen Kimmel Center for Planetary ScienceUNSPECIFIED
Subject Keywords:comets: general; Kuiper Belt: general; methods: observational; occultations; planets and satellites: formation; techniques: photometric
Issue or Number:2
Record Number:CaltechAUTHORS:20130111-150720147
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Official Citation:Measuring the Abundance of Sub-kilometer-sized Kuiper Belt Objects Using Stellar Occultations Hilke E. Schlichting et al. 2012 ApJ 761 150
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36333
Deposited By: Ruth Sustaita
Deposited On:11 Jan 2013 23:34
Last Modified:03 Mar 2020 13:01

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