ossos: the missing small members of the haumea …the ossos rejectability of each size distribution...

OSSOS: THE MISSING SMALL

MEMBERS OF THE HAUMEA FAMILY

Rosemary E. Pike

Darin Ragozzine, Benjamin Proudfoot, Steven Maggard, Mike Alexandersen, OSSOS Core

SMALL BODIES IN THE SOLAR SYSTEM

NASA

Asteroid Belt

Kuiper Belt (TNOs)

STUDYING SMALL BODIES

• Orbital Distribution

• Size Distribution

• Surface Properties

• Formation Location

• Composition

• Collisional History

OSSOS: THE MISSING SMALL MEMBERS OF THE HAUMEA FAMILY

• How do we discover small bodies in the Solar System?

• What are ‘Families’ and how are they created?

• What can we learn from the family members discovered in OSSOS and its related surveys?

• The next step- a large survey to discover thousands of TNOs on Subaru.

the largest fully tracked survey ever made

836 TNOs

first 85: Bannister et al. (2016)arXiv: 1511.02895rest: Bannister et al., in prep

• 948 detected TNOs• 838 characterized TNOs (brighter than limits)• only 2 lost in tracking. • Minor Planet Center has 1083 multi-opposition TNOs• LSST will detect more TNOs but not fainter.

TNO DISCOVERY SURVEYS

2018

CFEPS Hilat Alexandersen 2016

Discoveries on CFHT•Canada-France Ecliptic Plane Survey: 400 degrees2

•CFEPS High Latitude Survey: 701 degrees2

•Alexandersen: 32 degrees2

•OSSOS: 155 degrees2


836 TNOs



Characterized TNO

DetectionsCFEPS: 169HiLat: 24

Alexandersen: 77OSSOS: 836


2018

(This is about 30% of all known TNOs!)



836 TNOs



Many other Science Results!•11 OSSOS + 3 Col-OSSOS Science papers published

•Col-OSSOS: Colours of the Outer Solar System Origins Survey (grJ using Gemini GMOS, u using CFHT MegaPrime)

•2:1 colors using LBT


2018


TNO DISCOVERIES

Video: Stephen Gwyn, OSSOS

COLLISIONAL FAMILIES

• Common in the Asteroid belt

• Share proper orbital elements

NASA

ASTEROID FAMILIES

• Cluster in a/i/e space

• Parker et al. 2008 combined the SDSS colors and proper orbital elements to identify 37 families with at least 100 members

• ~50% of the asteroids in the sample are family members

Parker et al. 2008

FAMILY CHARACTERISTICS

• Orbital Distribution

• Surface Property Distribution

• Size/H-magnitude distribution

Shankman et al. (2013)

WHAT ABOUT THE KUIPER BELT?• Although the Kuiper belt has

considerably more bodies, it is significantly less dense

• Many efforts have focused on discovering TNO families

• Only one family discovered to date: Associated with the dwarf planet HaumeaYoutube: V101Science

HAUMEA FAMILY• Haumea family was identified by Brown et. al 2007

• Includes objects with similar orbits and neutral colors/water-ice surfaces

• Models for formation include graze and merge, catastrophic collision, satellite collision

• Updated identification of Haumea family members based on ejection velocity was done by Proudfoot & Ragozzine (in review) on the MPC TNOs.

Proudfoot & Ragozzine (Accepted to AJ)

Family Distribution Models

What is the size distribution of the Haumea family?This is dependent on the formation event!

OSSOS HAUMEA FAMILY CANDIDATES

Dynamical classifications: Proudfoot & Ragozzine

(accepted to AJ)

∆v =37 m/s

∆v =155 m/s

∆v =158 m/sOSSOS

Alexandersen

HiLat/CFEPS

Pike et al. (in Review)

ISOTROPIC VS GRAZE AND MERGE MODELS

OSSOS XVI THE MISSING SMALL MEMBERS OF THE HAUMEA FAMILY 1

Supplementary Figure 1. Comparison of Isotropic and Graze and Merge models. The Isotropic and Graze and Merge (G & M) orbital models11

were assigned H-magnitudes based on a single slope distribution with ↵ = 0.0, ↵ = 0.3, and ↵ = 0.9 (green). These models were biased usingthe survey simulator, and the biased Isotropic (blue) and Graze and Merge (red) do not produce significantly different biased H-distributions.

• The different models have different a/e/i distributions, but more detections are required to differentiate these using a survey like OSSOS.

• A different model test is required.Pike et al. (in Review)

TESTING LITERATURE H-DISTRIBUTIONS

• Tested Single Slope, Knee, and Divot size distributions

• For the Knee and Divot, we adjusted the transition magnitude 2-2.5 magnitudes brighter because of the high albedos of these objects

• The AD test was used to determine the rejectability of the size distributions

XX

XX


BRIGHT-END H-DISTRIBUTION• We identified the Haumea

family candidates in the MPC with Pan-STARRS w-band photometry

• We assumed a uniform survey depth for the w-band of 22.5*

• The AD test rules out α>0.8 and strongly favors α≤0.4

*Lin et al. 2016 Pike et al. (in Review)6 objects : ∆v <160 m/s

★No evidence for a size distribution transition★Favor single slopes 0.2≤α≤0.4

POPULATION ESTIMATE


THE MISSING SMALL MEMBERS OF THE HAUMEA FAMILY 11

Table 2. H-distribution Model Parameters and Rejectability

Source H-Distribution ↵bright ↵faint Hr-transition c OSSOS �v <100 m s-1 OSSOS �v <160 m s-1 PanSTARRS

Type Rejectable AD Results AD Results

Fraser et al. (2014, hot) Knee 0.87 0.2 5.2 – 0.8% 3.7% –

Lawler et al. (2018a, scattering) Knee 0.9 0.4 5.2 – 0.7% 3.7% –

Shankman et al. (2013, scattering) Divot 0.8 0.5 6.1 5.6 21% 60% –

Gladman et al. (2012, resonant) Single Slope 0.9 – – – 2.0% 4.1% 2.9%

(Other) Single Slope 0.8 – – – 15% 4.3% 6%

Single Slope 0.7 – – – 6.4% 41% 23%

Single Slope 0.6 – – – 10% 60% 20%

Single Slope 0.5 – – – 16% 95% 30%

Single Slope 0.4 – – – 18% 95% 73%

Single Slope 0.3 – – – 34% 60% 69%

Single Slope 0.2 – – – 38% 34% 79%

Single Slope 0.1 – – – 51% 25% 74%

Single Slope 0.0 – – – 59% 2.9% 35%

Note. The Source column indicates where a particular slope was published and which population was studied to measure this slope. The different H-distributionsare defined by their slopes ↵ as in equation 2. The broken size distributions utilize two slopes, a transition point Hr-transition, and can use a contrast c in the case ofa divot size distribution (see Shankman et al. 2013, 2016). The OSSOS rejectability of each size distribution gives the percentage of biased detections with largerH-magnitudes than the OSSOS detections, entries in bold are rejectable; the bold AD results are rejectable at 2�. The AD statistic was also used to determinerejectability of the different slopes compared to the PanSTARRS detections, bold indicates that slope is rejected at 2�.

Table 3. Population Estimates and Implied Mass of Ejected Fragments in units of Haumea’s mass

Population Estimate Implied Ejected Mass [% of Haumea]

Slope �v <100 m s-1 �v <100 m s-1 �v <160 m s-1 �v <160 m s-1 �v <100 m s-1 �v <160 m s-1

↵ 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 9.5

0.7 455+1830-431 2+6

-2 1698+2923-1515 6+10

-5 – –

0.6 326+1301-308 3+10

-3 1307+2254-1105 10+17

-8 0.7% 1.5%

0.5 253+934-240 5+16

-5 840+1558-725 14+27

-12 0.4% 1.3%

0.4 178+709-166 7+28

-6 596+1164-530 23+46

-21 0.5% 1.8%

0.3 119+502-110 11+45

-10 446+717-387 39+63

-34 0.8% 2.9%

0.2 82+344-73 16+69

-14 326+469-282 65+93

-56 1.1% 4.5%

0.1 57+269-51 25+120

-23 253+309-210 113+138

-94 1.6% 7.0%

The uncertainty on the population estimate is 2�, calculated by running the survey simulator 2,000 separate times until 1 (for �v <100 m s-1) or 3 (for �v <160m s-1) objects are detected. The median value is quoted as the population estimate, and the central 95% of the values are bounded by the 2� uncertainties. TheHr < 6 is calculated by scaling the fainter population estimate using the input H-distribution model. Assuming an albedo of 0.85, Hr = 3.5 corresponds to adiameter of 288 km, Hr = 6 corresponds to a diameter of 91 km and Hr = 9.5 is a diameter of 18 km. Proudfoot & Ragozzine (2018) have identified 22 candidatefamily members with 3.95< HV < 6.45 for �v < 160 m s-1 and 7 candidate family members for �v < 100 m s-1. The estimates which do not produce enoughfamily members to explain the known objects are indicated in bold. This excludes some of the steepest slopes, and is another indication that the H-distributionmust be shallow.










Single Slope 0.7 – – – 6.4% 41% 23%

Single Slope 0.6 – – – 10% 60% 20%

Single Slope 0.5 – – – 16% 95% 30%

Single Slope 0.4 – – – 18% 95% 73%

Single Slope 0.3 – – – 34% 60% 69%

Single Slope 0.2 – – – 38% 34% 79%

Single Slope 0.1 – – – 51% 25% 74%

Single Slope 0.0 – – – 59% 2.9% 35%





↵ 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 9.5

0.7 455+1830-431 2+6

-2 1698+2923-1515 6+10

-5 – –

0.6 326+1301-308 3+10

-3 1307+2254-1105 10+17

-8 0.7% 1.5%

0.5 253+934-240 5+16

-5 840+1558-725 14+27

-12 0.4% 1.3%

0.4 178+709-166 7+28

-6 596+1164-530 23+46

-21 0.5% 1.8%

0.3 119+502-110 11+45

-10 446+717-387 39+63

-34 0.8% 2.9%

0.2 82+344-73 16+69

-14 326+469-282 65+93

-56 1.1% 4.5%

0.1 57+269-51 25+120

-23 253+309-210 113+138

-94 1.6% 7.0%


Combine:

• orbital distribution models (Proudfoot & Ragozzine submitted)

• Single slope size distribution

• OSSOS Detections

• OSSOS Characterization

Population Estimate and Total Mass Estimate

HAUMEA FAMILY POPULATION

Pike et al. (in Review)7 known 22 known

Table 3: Population Estimates and Implied Mass of Ejected Fragments


Slope �v <100 m s�1 �v <100 m s�1 �v <160 m s�1 �v <160 m s�1 �v <100 m s�1 �v <160 m s�1

↵ 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 9.5

0.6 310+1236�293

3+10�3

1242+2139�914

10+17�7

0.7% 1.4%

0.5 295+1087�279

6+19�6

978+1304�725

16+31�14

0.86% 1.9%

0.4 201+801�187

8+32�7

673+1006�520

27+40�21

1.0% 2.5%

0.3 116+491�107

11+44�10

436+762�321

39+63�34

1.2% 3.2%

0.2 81+341�72

16+68�14

323+550�247

64+92�55

1.5% 4.9%

0.1 53+250�47

23+111�21

235+373�188

104+128�87

1.9% 6.9%

0.0 37+209�35

15+87�14

169+278�133

70+46�15

2.3% 8.9%

The uncertainty on the population estimate is 2�, calculated by running the survey simulator 2,000 separate

times until 1 (for �v <100 m s�1) or 3 (for �v <160 m s�1) objects are detected. The median value is

quoted as the population estimate, and the central 95% of the values are bounded by the 2� uncertainties.

The Hr < 6 is calculated by scaling the fainter population estimate using the input H-distribution model.

Assuming an albedo of 0.85–0.48, Hr = 3.5 corresponds to a diameter of 288–383 km, Hr = 6 corresponds

to a diameter of 91–121 km, and Hr = 9.5 is a diameter of 18–24 km. There are 22 candidate family

members with 3.95< HV < 6.45 for �v <160 m s�1 and 7 candidate family members for �v <100 m s�111.

T All of the slopes shown here produce a number of detections consistent with the known Haumea family

members.

25

THE FOSSIL SURVEYFormation of the Outer Solar System: an Icy Legacy

• Mike Alexandersen• Chan-Kao Chang • Ying-Tung Chen • Young-Jun Choi• Wesley Fraser • Paula Granados• Youngmin JeongAhn • Jianghui Ji• JJ Kavelaars• Myung-Jin Kim• Samantha Lawler • Matthew Lehner • Jian Li

• Zhong-Yi Lin • Hong-Kyu Moon • Surhud More • Marco Munoz• Keiji Ohtsuki • Rosemary Pike• Seitaro Urakawa • Shiang-Yu Wang • Fumi Yoshida • Haibin Zhao • Ji-Lin Zhou• Lying Zhou• Hui Zhang

THE NEXT GENERATION TNO+JT SURVEY• Effective TNO discovery and tracking strategies from the

previous OSSOS+ surveys

• Large field of view and increased sensitivity of HSC on Subaru.

• Results in a limiting magnitude of mr~26 and a survey area of 176 square degrees!

• We hope to complement our survey effort with observations from other facilities, including u-band color observations from CFHT.

The FOSSIL Survey will detect 2-4 times more TNOs than are currently

known! NAOJ

FOSSIL: PRIMARY SCIENCE CASES

• Plutino Size Distribution: How does the size distribution of Plutinos (3:2) change at small sizes? FOSSIL will robustly measure the number of smaller Plutinos by targeting the regions where they are most detectable. The number of small Plutinos probes their collisional history, formation density, and formation conditions.

• Jovian Trojans: Where were the JTs formed and how did they become co-orbitals? FOSSIL will target both the L4 and L5 JT cloud to measure the size distribution, colors, and light-curves of a large sample of JTs. This will constrain the origin and evolution of JTs and the role of Jupiter’s migration in the early Solar System.

• High-inclination and high-perihelion Objects: What is the population size and distribution of high-i and high-q objects? FOSSIL will use a large and deep survey including off-ecliptic blocks to detect these objects. Their distribution is indicative of the migration of the giant planets and the presence of any undiscovered planets.

• Colors of Resonant TNOs: Which surface types are most common in the resonances, and does this vary depending on the resonance location? FOSSIL will specifically target the 3:2, 5:3, 7:4, 2:1, and 5:2 which trapped objects from different formation locations during planetary migration. The color distribution within the resonances constrains the composition of the proto-planetesimal disk.

We study several subpopulations of small bodies to answer fundamental questions about the Solar System. How did the Solar System form and

evolve? How did the giant planets migrate? How did the planetesimals and planets form?

We have many secondary science goals, including the discovery of Haumea family members (which are high-inclination). The total survey area is

larger than OSSOS and ~1.5 magnitudes deeper, so we should detect 5-10 family members (and NOT more).

SURVEY DESIGN

RESULTS FROM OSSOS+• The Haumea family H-distribution is best characterized by a single slope 0.2≤α≤0.4.• Catastrophic collision (0.7≤α≤0.9, Leinhardt et al. 2012) are excluded.• Shallow slopes are consistent with Graze and Merge scenarios (but the orbital

distribution of Haumea family members are not consistent with current Graze and merge scenarios).

• For a single slope size distribution α=0.3, an isotropic model of the Haumea family orbital distribution, and 3 detections with ∆v<160 m/s, the OSSOS Ensemble Surveys determine:

• Population: Objects with diameters >91 km• Implied Ejected Mass: 3% Haumea’s mass

• As the next step forward in understanding the formation and evolution of the solar system, we have proposed the FOSSIL survey on Subaru.










Single Slope 0.7 – – – 6.4% 41% 23%

Single Slope 0.6 – – – 10% 60% 20%

Single Slope 0.5 – – – 16% 95% 30%

Single Slope 0.4 – – – 18% 95% 73%

Single Slope 0.3 – – – 34% 60% 69%

Single Slope 0.2 – – – 38% 34% 79%

Single Slope 0.1 – – – 51% 25% 74%

Single Slope 0.0 – – – 59% 2.9% 35%





↵ 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 6 3.5 < Hr < 9.5 3.5 < Hr < 9.5

0.7 455+1830-431 2+6

-2 1698+2923-1515 6+10

-5 – –

0.6 326+1301-308 3+10

-3 1307+2254-1105 10+17

-8 0.7% 1.5%

0.5 253+934-240 5+16

-5 840+1558-725 14+27

-12 0.4% 1.3%

0.4 178+709-166 7+28

-6 596+1164-530 23+46

-21 0.5% 1.8%

0.3 119+502-110 11+45

-10 446+717-387 39+63

-34 0.8% 2.9%

0.2 82+344-73 16+69

-14 326+469-282 65+93

-56 1.1% 4.5%

0.1 57+269-51 25+120

-23 253+309-210 113+138

-94 1.6% 7.0%


ossos: the missing small members of the haumea …the ossos rejectability of each size distribution...

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