J/MNRAS/433/2075 Asteroid families identification (Carruba+, 2013)
A multi-domain approach to asteroid families identification
Carruba V., Domingos R.C., Nesvorny D., Roig F., Huaman M.E., Souami D.
<Mon. Not. R. Astron. Soc. 433, 2075 (2013)>
=2013MNRAS.433.2075C 2013MNRAS.433.2075C
ADC_Keywords: Minor planets
Keywords: Asteroids
Abstract:
It has been shown that large families are not limited to what found by
hierarchical clustering methods (HCM) in the domain of proper elements
(a,e,sin(i)), that seems to be biased to find compact, relatively
young clusters, but that there exists an extended population of
objects with similar taxonomy and geometric albedo, that can extend
to much larger regions in proper elements and frequencies domains: the
family "halo". Numerical simulations can be used to provide estimates
of the age of the family halo, that can then be compared with ages of
the family obtained with other methods. Determining a good estimate of
the possible orbital extension of a family halo is therefore quite
important, if one is interested in determining its age and, possibly,
the original ejection velocity field. Previous works have identified
families halos by an analysis in proper elements domains, or by using
Sloan Digital Sky Survey-Moving Object Catalog data, fourth release
(SDSS-MOC4) multi-band photometry to infer the asteroid taxonomy, or
by a combination of the two methods. The limited number of asteroids
for which geometric albedo was known until recently discouraged in the
past the extensive use of this additional parameter, which is however
of great importance in identifying an asteroid taxonomy. The new
availability of geometric albedo data from the Wide-field Infrared
Survey Explorer (WISE) mission for about 100,000 asteroids
significantly increased the sample of objects for which such
information, with some errors, is now known.
In this work we proposed a new method to identify families halos in a
multi-domain space composed by proper elements, SDSS-MOC4 (a, i-z)
colors, and WISE geometric albedo for the whole main belt (and the
Hungaria and Cybele orbital regions). Assuming that most families were
created by the breakup of an undifferentiated parent body, they are
expected to be homogeneous in colors and albedo. The new method is
quite effective in determining objects belonging to a family halo,
with low percentages of likely interlopers, and results that are quite
consistent in term of taxonomy and geometric albedo of the halo
members.
Description:
Asteroid families are groups of asteroids that are supposed to have a
common origin in the collisional event that shattered the parent body.
They are usually determined by identifying clusters of objects close
in proper elements domain (a,e,sin(i)). The Hierarchical Clustering
Method (HCM hereafter) as described by Bendjoya and Zappala (2002,
"Asteroids III", Univ. of Arizona Press, Tucson, 613) operates by
identifying all objects that are closer than a given distance (cutoff)
with respect to at least one other member of a family.
If an object is closer than this distance, it is associated to the
dynamical family, and the procedure is repeated until no new family
members are found. For small values of the cutoff only the objects
closest in proper element domain are identified as family members: the
family ``core''. At larger cutoff one is able to identify objects
that, while still belonging to the collisional group, may have
dynamically evolved since the family formation and drifted apart from
the core: the family ``halo''. One problem in obtaining a good
determination of a family halo is however the presence of objects in
the orbital region of the halo that might not be, for taxonomical
reasons, associated with the local family: the interlopers.
To minimize the presence of interlopers, in this work we proposed to
identify asteroid families in a multi-domain composed by asteroid
proper elements a, e, sin(i), Sloan Digital Sky Survey Moving Object
Catalog, fourth release (SDSS-MOC4), a* and i-z colors, and Wide-field
Infrared Survey Explorer (WISE) geometric albedo pV. By also taking
account of taxonomically related information such as the Sloan colors
and the WISE albedo, we considerably reduced the number of identified
interlopers in the given asteroid family, also improving the quality
of its orbital identification. Our results are given in this data-base
for each of the families identified in Carruba et al. (2013). Each
file families.dat is named after the first eight digits of the given
family, and is reported in the format: # of family member, asteroid
identification, a, e, sin(i), n, g, s, H, Ly, pV, a*, i-z, where n is
the proper mean-motion, g and s are the precession frequencies of the
argument of pericenter and longitude of the node, H is the absolute
magnitude, and Ly is the Lyapunov exponent. We refer the reader to
Carruba et al. (2013A&A...550A..85C 2013A&A...550A..85C) for the details of the method and
for a list of identified asteroid families.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
families.dat 53 62 List of the families
asteroids.dat 176 4565 Asteroid families identification
families/* . 62 List of the members of each family
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See also:
B/astorb : Orbits of Minor Planets (Bowell+ 2013)
http://www.feg.unesp.br/~vcarruba/HALOS/Halos.html : author's latest version
Byte-by-byte Description of file: families.dat
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Bytes Format Units Label Explanations
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1 I1 --- R [1/5] Number of the the orbital region (1)
3- 19 A17 --- Region Name of the orbital region (1)
23- 28 I6 --- Planet Number of the representative asteroid
30- 44 A15 --- Family Name of the family
46- 53 A8 --- File Name of the corresponding file (without
extension), in the "families" subdirectory.
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Note (1): There are 5 regions: "Inner main belt" (1), "Central main belt" (2),
"Outer main belt" (3), "Cybele region" (4), or "Hungaria region" (5)
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Byte-by-byte Description of file: families/* asteroids.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
4- 6 I3 --- FM Family membership number
11- 16 I6 --- ID Asteroid identification, such as 4 for Vesta
17 A1 --- --- [.]
23- 31 F9.7 AU a Asteroid proper semi-major axis
32- 33 A2 --- --- [0]
39- 47 F9.7 --- e [0/1] Asteroid proper eccentricity
48- 49 A2 --- --- [0]
54- 63 F10.7 --- sin(i) [0/1] Sine of asteroid proper inclination
64- 65 A2 --- --- [0]
68- 78 F11.6 deg/yr N Asteroid proper mean motion
79- 81 A3 --- --- [0]
84- 94 F11.6 arcsec/yr G Asteroid proper frequency of precession
of the pericenter
95- 97 A3 --- --- [0]
100-110 F11.6 arcsec/yr S Asteroid proper frequency of precession
of the node
111-113 A3 --- --- [0]
119-123 F5.2 mag H Asteroid absolute magnitude
128-133 F6.2 yr-1 Ly Asteroid Lyapunov exponent
136-142 F7.4 --- pV Asteroid WISE geometric albedo
145-151 F7.4 --- e_pV Error on geometric albedo
157-164 F8.5 mag a* Asteroid SDSS-MOC4 a* color, defined from
SDSS colors: C1(g-r)+C2(r-i)+C3
169-176 F8.5 mag i-z Asteroid SDSS-MOC4 i-z colors
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History:
Prepared by Valerio Carruba [UNESP, Brazil]
(End) Valerio Carruba [UNESP/Brazil], Francois Ochsenbien [CDS] 03-May-2013