ALBEDOS OF SMALL HILDA GROUP ASTEROIDS AS REVEALED BY<i>SPITZER</i>

Ryan, Erin L.; Woodward, C. E.

doi:10.1088/0004-6256/141/6/186

Cited by 12 publications

(9 citation statements)

References 37 publications

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“…The visible spectral and photometric data are matched to the near-infrared reflectance spectra at 0.75 and 0.913 (Sloan z-band)μm, respectively. The absolute reflectivity level is set by the average visible (0.55 μm) geometric albedo: 0.04 (Ryan & Woodward 2011). Figure 2 shows the average reflectivity spectra of LR and R Hildas, along with analogous data for Trojans taken from Emery et al (2011) andTakir &Emery (2012).…”

Section: Comparison With Jupiter Trojansmentioning

confidence: 99%

“…b Diameters are calculated from the listed absolute magnitudes (Hv) assuming pv = 0.04 (Ryan & Woodward 2011).…”

Section: Notesmentioning

confidence: 99%

“…The general compositional outline for these asteroids posits a mixture of water ice, anhydrous silicates, and organics (e.g., Vilas et al 1994;Emery & Brown 2004;Yang & Jewitt 2007). Observational studies of Hildas have hitherto revealed largely featureless, reddish spectra in the optical and near-infrared (Dahlgren & Lagerkvist 1995;Dahlgren et al 1997;Takir & Emery 2012) and very low albedos averaging around 4% (Ryan & Woodward 2011). Taxonomically, Hildas are predominantly D-and P-type asteroids, with a small fraction of C-type objects (Grav et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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0.7–2.5 μm Spectra of Hilda Asteroids

Wong

Brown

Emery

2017

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The Hilda asteroids are primitive bodies in resonance with Jupiter whose origin and physical properties are not well understood. Current models posit that these asteroids formed in the outer solar system and were scattered along with the Jupiter Trojans into their present-day positions during a chaotic episode of dynamical restructuring. In order to explore the surface composition of these enigmatic objects in comparison with an analogous study of Trojans, we present new near-infrared spectra (0.7-2.5 μm) of 25 Hilda asteroids. No discernible absorption features are apparent in the data. Synthesizing the bimodalities in optical color and infrared reflectivity reported in previous studies, we classify 26 of the 28 Hildas in our spectral sample into the so-called less-red and red sub-populations and find that the two sub-populations have distinct average spectral shapes. Combining our results with visible spectra, we find that Trojans and Hildas possess similar overall spectral shapes, suggesting that the two minor body populations share a common progenitor population. A more detailed examination reveals that while the red Trojans and Hildas have nearly identical spectra, less-red Hildas are systematically bluer in the visible and redder in the near-infrared than less-red Trojans, indicating a putative broad, shallow absorption feature between 0.5 and 1.0μm. We argue that the less-red and red objects found in both Hildas and Trojans represent two distinct surface chemistries and attribute the small discrepancy between less-red Hildas and Trojans to the difference in surface temperatures between the two regions.

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Section: Comparison With Jupiter Trojansmentioning

confidence: 99%

“…b Diameters are calculated from the listed absolute magnitudes (Hv) assuming pv = 0.04 (Ryan & Woodward 2011).…”

Section: Notesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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0.7–2.5 μm Spectra of Hilda Asteroids

Wong

Brown

Emery

2017

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“…Objects in both populations share the general characteristics of flat, featureless optical and near-infrared spectra with reddish colors (e.g., Dahlgren & Lagerkvist 1995;Dotto et al 2006;Fornasier et al 2007;Marsset et al 2014) and similar, very low albedos (e.g., Fernández et al 2003Fernández et al , 2009Ryan & Woodward 2011). In addition, both Hildas and Trojans are notable in having a bimodal color distribution.…”

Section: Introductionmentioning

confidence: 98%

The Color–magnitude Distribution of Hilda Asteroids: Comparison With Jupiter Trojans

Wong

Brown

2017

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Current models of solar system evolution posit that the asteroid populations in resonance with Jupiter are comprised of objects scattered inward from the outer solar system during a period of dynamical instability. In this paper, we present a new analysis of the absolute magnitude and optical color distribution of Hilda asteroids, which lie in 3:2 mean-motion resonance with Jupiter, with the goal of comparing the bulk properties with previously published results from an analogous study of Jupiter Trojans. We report an updated power-law fit of the Hilda magnitude distribution through H = 14. Using photometric data listed in the Sloan Moving Object Catalog, we confirm the previously reported strong bimodality in visible spectral slope distribution, indicative of two subpopulations with differing surface compositions. When considering collisional families separately, we find that collisional fragments follow a unimodal color distribution with spectral slope values consistent with the bluer of the two subpopulations. The color distributions of Hildas and Trojans are comparable and consistent with a scenario in which the color bimodality in both populations developed prior to emplacement into their present-day locations. We propose that the shallower magnitude distribution of the Hildas is a result of an initially much larger Hilda population, which was subsequently depleted as smaller bodies were preferentially ejected from the narrow 3:2 resonance via collisions. Altogether, these observations provide a strong case supporting a common origin for Hildas and Trojans as predicted by current dynamical instability theories of solar system evolution.

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“…Thermal infrared survey observations by the Infrared Astronomical Satellite (IRAS), the Wide-field Infrared Survey Explorer (WISE), AKARI and the Spitzer Space Telescope resulted in estimates of diameters and albedos for thousands of asteroids (e.g., Tedesco et al, 2002;Mainzer et al, 2011a,b;Masiero et al, 2011;Usui et al, 2011;Ryan and Woodward, 2011). They used the absolute magnitude values from the asteroid orbit catalogs MPCORB 2 or AstOrb.…”

Section: Introductionmentioning

confidence: 99%