J/AJ/152/111 A 2011-2013 survey of trans-Neptunian objects (Alexandersen+, 2016)
A carefully characterized and tracked trans-Neptunian survey: the size
distribution of the plutinos and the number of Neptunian trojans.
Alexandersen M., Gladman B., Kavelaars J.J., Petit J.-M., Gwyn S.D.J.,
Shankman C.J., Pike R.E.
<Astron. J., 152, 111-111 (2016)>
=2016AJ....152..111A 2016AJ....152..111A (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets ; Surveys ; Magnitudes
Keywords: astrometry - Kuiper belt: general - methods: data analysis -
methods: observational - planets and satellites: detection - surveys
Abstract:
The trans-Neptunian objects (TNOs) preserve evidence of planet
building processes in their orbital and size distributions. While all
populations show steep size distributions for large objects, a
relative deficit of Neptunian trojans and scattering objects with
diameters of D<100km has been detected. We investigated this deficit
with a 32 square degree survey, in which we detected 77 TNOs that are
brighter than a limiting r-band magnitude of 24.6. Our plutino sample
(18 objects in 3:2 mean-motion resonance with Neptune) shows a deficit
of D<100km objects, rejecting a single power-law size distribution at
>99% confidence. Combining our survey with the Canada-France Ecliptic
Plane Survey, we perform a detailed analysis of the allowable
parameters for the plutino size distribution, including knees and
divots. We surmise the existence of 9000±3000 plutinos with an
absolute magnitude of Hr≤8.66 and 37000-10000+12000 with
Hr≤10.0 (95% confidence). Our survey also discovered one
temporary Uranian trojan, one temporary Neptunian trojan, and one
stable Neptunian trojan, for which we estimate populations of
110-100+500, 210-200+900, and 150-140+600 with
Hr≤10.0, respectively. All three populations are thus less
numerous than the main belt asteroids (592 asteroids with
Hr≤10.0). With such population sizes, the temporary Neptunian
trojans cannot be previously stable trojans diffusing out of the
resonance now; they must be recently captured Centaurs or scattering
objects. As the bias against the detection of objects grows with
larger semimajor axes, our discovery of three 3:1 resonators and one
4:1 resonator adds to the growing evidence that the high-order
resonances are far more populated than is typically predicted.
Description:
Our survey was designed to obtain 40 sq.deg. of high-cadence sky
coverage near the right ascension (R.A.) of 2hr. Despite the severe
weather and technical problems in 2011 and 2012, we succeeded in
obtaining high-quality observations for 32 sq.deg., thanks to a robust
survey design. The survey was conducted using MegaCam on the
Canada-France-Hawaii Telescope (CFHT) on Maunakea, Hawaii, which was
chosen for its combination of a large field of view (almost
1°*1°) and a 3.58m diameter aperture, providing the best
combination of depth and coverage. Additionally, the queue-operation
of CFHT was crucial for the success of this survey, which required
many observations throughout two semesters, but often only a couple of
hours of observations in a given night.
The on-sky pointings of the survey were chosen to be near Neptune's L4
Lagrange point, where many Neptunian trojans reside and many n:2, n:3,
and n:4 resonances are near pericenter. The survey obtained one
"low-lat" block of 20 sq.deg. (5°*4°) centered near the
ecliptic plane and another "high-lat" block of 12 sq.deg.
(4°*3°) located ∼15° north.
Our survey needed to reach mr∼24.5 to detect objects with Hr∼9.7
at 30au. This depth is more than a magnitude past the reported
transition near Hr∼8.5±0.2.
The discovery observations for each field were a set of three 320s
exposures (plus 40s overhead) separated by ∼1hr ("triplets"); 10
fields could thus obtain discovery images in a three-hour block.
Our fields obtained discovery observations in 2011 and 2012 October.
Our "low-lat" block was divided horizontally into two 10 sq.deg.
sub-blocks obtaining triplets, as described above. The southern half
obtained discovery observations on 2011 October 24 and the northern
half on 2011 October 26, with image qualities mostly in the range
0.5''-0.6''. The high-lat block obtained discovery triplets in 2012
October, with image qualities ranging from 0.5'' to 0.8''. The 2012
October high-lat discovery block was divided vertically into two 6
sq.deg. sub-blocks. The discovery triplets consisted of the six fields
of the sub-block, interspersed with single images ("nailing" images)
of fields from the other sub-block to extend the interval between
subsequent images of the triplets up to near an hour. The western half
obtained discovery observations on 2012 October 20; the eastern half
was observed on 2012 October 21.
Objects were tracked for up to 28 months of total arc.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 282 87 List of all objects detected in our survey
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See also:
B/astorb : Orbits of Minor Planets (Bowell+ 2014)
http://www.minorplanetcenter.net/iau/MPCORB.html : MPC database
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- ID Internal object designation (1)
10- 18 A9 --- OID Old internal designation (2)
20- 26 A7 --- MPC Minor Planet Center (MPC) designation (3)
28- 33 F6.1 d Epoch [5803/6221.9] Epoch (JD-2450000) (4)
35- 40 F6.1 d JD [5858.9/6221.9] Julian Date at discovery
(JD-2450000)
42- 47 F6.3 AU Dist [20/52.7] Heliocentric distance at discovery (r)
49- 53 F5.3 AU e_Dist [0/5.135] Uncertainty in Dist
55- 56 I2 --- Nobs [3/43] Number of astrometric measurements (N)
58- 63 F6.4 yr Time [0.0002/2.4] Arc length: time from first to last
observation (t)
65- 73 F9.6 AU a [19/92.4] Semi-major axis (5)
75- 83 F9.6 AU e_a [0.0009/25] Uncertainty in a (6)
85- 92 F8.6 --- e [0.01/0.62] Eccentricity (5)
94-101 F8.6 --- e_e [0/0.58] Uncertainty in e (6)
103-108 F6.3 deg i [1.2/53.9] Inclination (5)
110-115 F6.3 deg e_i [0/25.4] Uncertainty in i (6)
117-123 F7.3 deg Omega [4.8/358.4] Longitude of ascending node
(Ω) (5)
125-131 F7.3 deg e_Omega [0/303.6] Uncertainty in Omega (6)
133-139 F7.3 deg omega [2.9/352.2] Argument of pericenter (ω) (5)
141-148 F8.3 deg e_omega [0.011/1789] Uncertainty in omega (6)
150-156 F7.3 deg M [0.6/360] Mean anomaly measured at JD epoch (5)
158-163 F6.3 deg e_M [0/34.3] Uncertainty in M (6)
165-169 F5.2 mag [21.5/24.9] Average apparent magnitude in
CFHT/MegaCam r-band (mr) (7)
171-175 F5.3 mag e_ [0/0.262] Uncertainty in rmag
177-181 F5.2 mag rMag [5.58/10.65] Absolute magnitude in CFHT/MegaCam
r-band; phase corrected (Hr) (8)
183-186 F4.2 arcsec/h Motion [2.53/6.27] Rate of motion at discovery
188-192 F5.3 deg alpha [0.034/0.777] Phase angle at discovery (α)
194 I1 --- C [0/1] Characterization flag (1=characterized,
or 0=uncharacterized) (9)
196 A1 --- S [NSI] Security of the classification
(N=not classified, I=insecure, or S=secure)
198-206 A9 --- Class Classification type (classical, detached,
notclass, or resonant)
208 A1 --- f_Class [0NUimo] Additional classification flag
(type of resonant, or type of classical) (10)
210-211 I2 --- P [0/19] P resonance index
213-214 I2 --- Q [0/10] Q resonance index
216-218 I3 deg Cbf [60/180]?=-99 Libration center of best-fit
clone (Cbf) (11)
220-222 I3 deg Cmx [60/180]?=-99 Libration center of max-a
clone (Cmx) (11)
224-226 I3 deg Cmn [60/180]?=-99 Libration center of min-a
clone (Cmn) (11)
228-230 I3 deg Lbf [12/170]?=-99 Libration amplitude of best-fit
clone (Lbf) (11)
232-234 I3 deg Lmx [13/150]?=-99 Libration amplitude of max-a
clone (Lmx) (11)
236-238 I3 deg Lmn [14/164]?=-99 Libration amplitude of min-a
clone (Lmn) (11)
240-242 I3 deg CLK [90/270]?=-99 Lidov-Kozai libration center
(CLK)
244-248 F5.1 deg LLKbf [40/85]?=-99 Lidov-Kozai libration amplitude of
best-fit clone (LLKbf)
250-254 F5.1 deg LLKmx [40/57]?=-99 Lidov-Kozai libration amplitude of
max-a clone (LLKmx)
256-260 F5.1 deg LLKmn [40/83]?=-99 Lidov-Kozai libration amplitude of
min-a clone (LLKmn)
262-268 F7.1 arcsec sigma5 [1.6/13000] Long-axis of on-sky uncertainty
ellipse 5 years after 1st observation
(σ5) (12)
270-274 I5 arcsec sigma10 [8/30000] Long-axis of on-sky uncertainty
ellipse 10 years after 1st observation
(σ10) (12)
276-282 A7 --- Com Comments (13)
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Note (1): The format of the object designation is:
ma = Denotes the survey (first author is Mike Alexandersen);
uma = Uncharacterized object;
l = Indicates the low-lat block. The survey obtained one "low-lat" block
of 20 sq.deg. (5°*4°) centered near the ecliptic plane;
h = Indicates the high-lat block. The survey obtained another "high-lat"
block of 12 sq.deg. (4°*3°) located ∼15° north;
nt = Not tracked object (all but two objects from the characterized sample
were tracked to two-opposition arcs. Ten objects did not achieve
two-opposition arcs, however, eight of these were past our
characterization limit and thus do not affect our scientific
modeling. See Section 3.3 for more details about the tracking).
Note (2): Should not be used, but here for redundance, just in case.
Note (3): Blank when no MPC designation given due to short arc.
Note (4): For which the elements (especially M) were calculated.
Note (5): The J2000 barycentric orbital elements are all given at the Epoch
(Julian date-2450000).
Note (6): The uncertainty for the orbital elements is from the Bernstein &
Khushalani (2000AJ....120.3323B 2000AJ....120.3323B) orbit-fitting code.
Note (7): Measured by the moving-object pipeline, in the discovery triplet (the
discovery observations for each field were a set of three 320s exposures).
Note (8): Calculated from using the appropriate phase-angle corrections.
Note (9): Characterized objects are Trans-Neptunian Objects (TNOs) that are
brighter than a limiting r-band magnitude of 24.6.
Note (10): Additional classification flags are defined as follows:
i = Inner classical (Alexandersen et al. 2014MPEC....V...67A);
m = Main classical (Alexandersen et al. 2014MPEC....V...66A;
Tomatic 2014, MPEC, V71);
o = Outer classical (Alexandersen et al. 2014MPEC....V...69A);
U = Temporarily resonant 1:1 with Uranus (Uranian co-orbital) (Alexandersen
et al. 2013MPEC....F...19A);
N = Neptune resonant.
Note (11): The liberation center Cpq is given for resonances that allow values
other than 180°, while the libration amplitude Lpq is given for all
resonant objects. Objects that are additionally in the Lidov-Kozai
resonance (Kozai 1962AJ.....67..591K 1962AJ.....67..591K; Lidov 1962P&SS....9..719L 1962P&SS....9..719L) also have
the libration center CLK and libration amplitude LLK listed. Cpq,
Lpq, and LLK have values listed for the nominal fit, the Max-a clone
(superscript) and Min-a clone (subscript) used during classification,
because we do not have a good way of estimating the uncertainty on these.
Note (12): Where the first observation was on 2011/10/25.
Note (13): Ratios in brackets means that the object is close to that resonance,
possibly influenced by the proximity.
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 05-Dec-2016