Spitzer Thermal Radiometry of TNOs

John Stansberry

Will Grundy

John Spencer

Mike Brown

Dale Cruikshank

Overview

Spitzer TNO projects and sample Multiband Imaging Photometer for Spitzer (MIPS)

– Characteristics– Data processing

Data and Results for Particular Objects– 2003 UB313, Sedna, 2005 FY9, Huya– Binaries 1999 TC36, 1998 SM165

Summary

Some other Spitzer results at this conference– Lellouch et al. (Pluto thermal lightcurve)– Grundy et al. (Classical TNO albedos)– Emery et al. (3-10um reflectance)– Bauer et al. (coma of Echeclus)– Spencer et al. (Density of 1998 SM165) (poster)

Spitzer TNO Radiometry Summary

Total GTO – Cycle 2 Sample: 64 TNOs, 13 Centaurs (a < 30AU) Cruikshank/Rieke – “Bright” TNOs and Centaurs (GTO, 2003)

– 13 Centaurs, 31 TNOs– 14 detected at both 24 & 70um with good SNR– TNO Albedos 10% (5% - 20%)– Centaur Albedos 5% (2.5% - 7%)– Beaming parameters ~ 0.7 – 1.8 : thermal inertia important

M. Brown – Icy Planetoids (Cycle 1-2, 2004-2005)– 13 TNOs, ~ ½ detected at both 24 & 70um with good SNR– SEDs consistent with bright and dark terrains for largest objects

W. Grundy – Classical-Belt TNOs (Cycle 1, 2004)– 15 TNOs, 8 - 10 detected– See Grundy et al. Talk

J. Spencer – Binary TNOs (Cycle 1-2, 2004-2005)– 5 targets, 2 detected– See Spencer et al. Poster

Final GTO – Cycle 2 Tally Likely to be ~24 TNOs, 10 Centaurs, 5 Binaries– Cycle 3 (2006) will add ~12 TNOs, 8 Centaurs, 1 Binary

Spitzer Sample: Orbital Elements

MIPS Overview

Multiband Imaging Photometer for SIRTF Spitzer– 24, 70 and 160 micron channels– IFOV 5’x5’, 2.5’x5’, 5’x1’– Arrays operate at 5K, telescope at 5 – 10K

24um (23.68 m , 6.5 beam)– 128 x 128 InSb array– Faint limit ~30 Jy (moving targets only)

70um (71.42 m , 20 beam)– 32 x 32 Ge:Ga photoconductor array– 1/2 of the array suffers from high noise due to cabling issues– Faint limit ~1-2 mJy

160um (156 m, 40 beam)– 20 x 2 stressed Ge:Ga photoconductor array– 5 dead pixels (contiguous) due to cabling issue– Faint limit ~90 mJy – only useful for Pluto…

Ge:Ga Data

Responsivity is not constant for Ge:Ga detectors

Calibration sources track the changing responsivity

– Cal. sources flashed every ~100sec during data taking

– 10 sky images between cal. images

– Responsivity of each pixel determined by interpolation of cal. sources

70um response vs. time, ground test

The MIPS Calibration

24um: Repeatability is better than 1%(Absolute calibration good to 4%: Stars)

160um: Absolute calibration good to 12% (Asteroids)(Repeatability is better than 10%)

70um: Absolute calibration good to 8% (Stars)(Repeatability is better than 7%)

Gordon et al. 2006, in prep. Engelbracht et al. 2006, in prep.

Stansberry et al. 2006, in prep.

Data Massage (24m)

Orcus/2004 DW @ 24um, M. Brown data

Typical mosaic with effects ofscattered light and Latents

Same mosaic aftercorrection

subtract divide

Super-Sky Mosaics (24m)

Individual Visits

NaN out the Source, Coadd in SkyCoordinates

Super-Sky Image

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Straight Mosaic Sky Subtracted

Sedna

Spitzer’s first Director’s proposal fora Solar System object (M. Brown):2003 VB12 / Sedna

1 month past end of commissioning (2004-1-28)

70um, 2500sec exposure

Sedna

40 mJy background source

Sedna

Sky Subtracted Images

1 = 0.7 mJy 5.2 1.2 mJy

Sedna: Size and Albedo

Adopt 2 mJy as upper limit– Best image gives 0.7 mJy,

1- noise @ 70um Size depends on Sedna’s

thermal state (fast- or slow-rotator)– Likely to favor fast-rotator

(43K TBB at 90 AU) Featureless spectrumTrujillo et al 2005

– Not a planetoid: D < 2000 km, pV > 12%

Lack of volatile ices– Low albedo: pV < 30%, D >

1200kmSTM limit

ILM limit

(ILM)

(STM)

2003 UB313

• August 2005

• 2 4000 sec 24um exposures

• 2 5000 sec 70um exposures

24um, 8000 sec super-sky

2003 UB313

1st Visit, sky subtracted 2nd Visit, sky subtracted

1 noise < 0.01 mJy/beam

0.03 mJy source

2003 UB313

1 noise 0.75 mJy/beamAdopt 2.5 mJy for Xena

70um normal and sky-subtracted images, both epochs.

2003 UB313: Size and Albedo

Neither the STM nor Fast-Rotator seem todescribe the spectrum of 03UB313…

1.2mm data from Bertoldi et al.24um data plotted incorrectly:Should be 0.03 mJy.

2003 UB313: Size and Albedo

UB313 is complex– Volatile ices

– Extreme seasonal cycle

– Pluto/Triton good analogs Simple thermal models don’t

fit 2-Terrain model comes close

– Diameter < about 2600km

– pV > about 70%

New, better data expected soon

2005 FY9

24um: 800 sec70um: 400 sec

2005 FY9

Volatile ices suggest complex surface 2-terrain model required to fit thermal data

– Diameter ~1600 km

– pV ~ 80%

1999 TC36

1998 SM165: = 0.5 g/cc (Spencer’s poster)2003 FX128, 2000 CR46 (Centaurs) in the works.

2003 EL61: = 3 0.3 g/cc

Results To Date

TNO Albedos and DiametersSpitzer and ISO

Object H_v S (%/100nm) p_v (%) D (km) STM eta p_v (%) D (km) ref.(15789) 1993 SC 7.31 35.6 3.5 (2.2 - 5.1) 398 (227 - 508) t(15874) 1996 TL66 5.46 0.13 > 1.8 < 958 t(15875) 1996 TP66 7.42 26.5 1.1 (0.8 - 1.5) 406 (347 - 406) 2.5 (2.3 - 2.9) s(47171) 1999 TC36 5.37 35.2 7.9 (5.8 - 11) 405 (350 - 470)* 1.2 (1.0 - 1.4) 5 (4 - 6) 609 (562 - 702) s,a(29981) 1999 TD10 9.10 10.4 5.3 (3.8 - 7.8) 88 ( 73 - 104) 1.3 (1.0 - 1.6) s

8.64 6.5 98 1.5 e(55565) 2002 AW197 3.62 22.0 12 (8.8 - 18) 734 (599 - 857 1.2 (1.0 - 1.4) 9 (7 - 11) 977 (890 - 1152) s,m(28978) Ixion 4.04 22.9 19 (11. - 37) 480 (344 - 632) 0.6 (0.4 - 0.9) > 15 < 804 s,a(38628) Huya 5.10 22.2 6.6 (5.0 - 8.9) 500 (431 - 575 1 (0.9 - 1.2) > 8 < 540 s,a(20000) Varuna 3.94 23.9 14 (8.0 - 23) 586 (457 - 776) 1.6 (1.2 - 2.3) 6 (4 - 8) 1016 (915 - 1218) s,j

7 (4 - 10) 914 (810 - 1122) l(90377) Sedna > 12 < 1900(50000) Quaoar 2.7 28.2 8.7 1300 1.8 s(90482) Orcus 2.3 20 1000 1.2 s(55637) 2002 UX25 3.6 7.4 900 1.4 s(90568) 2004 GV9 3.68 11 700 1.8 s2003 EL61 -0.26 -1.90 55 - 75 1000 - 1600 s2003 UB313 -1.1 0.0 > 70 < 2600 60 (45 - 75) 3000 (2600-3400) s,b2005 FY9 0.1 11.3 70 - 90 1250 - 1650 s

Method

Pluto 11.3 61 (51 - 71) 2290 (2198 - 2382)Charon -1.85 37 (35 - 39) 1242 (1200 - 1284)Triton 1.99 75 (72 - 78) 2707 (2705 - 2709)(19308) 1996 TO66 4.77 1.13 > 2.7 < 899 sub-mm limit a,g(19521) Chaos 4.95 25.4 > 3.3 < 744 sub-mm limit a,g(24835) 1995 SM55 4.58 2.05 > 5.3 < 700 sub-mm limit a,g(26308) 1998 SM165 6.38 27.8 9.1 (5.2 - 13) 238 (184 - 292) binary m4,g*(47171) 1999 TC36 5.39 35.2 14 (7.9 - 20) 302 (233 - 370) binary m4,g*(50000) Quaoar 2.74 28.2 10 (4.8 - 9.0) 1260 (1070 - 1450) imaging b2(55636) 2002 TX300 3.47 -0.96 > 15 < 693 sub-mm limit or,g(58534) 1997 CQ29 7.38 23.5 23 (13 - 32) 77 (60 - 95) binary m4,n,g(66652) 1999 RZ253 6.03 28.7 16 (9.3 - 23) 170 (131 - 208) binary n,g(84522) 2002 TC302 4.94 0.0 > 5.1 < 1211 sub-mm limit a,g(88611) 2001 QT297 7.01 24.5 5.6 (3.2 - 8.0)) 168 (130 - 206) binary os,g(90377) Sedna 1.20 35.9 > 8.5 < 1800 imaging b41998 WW31 7.76 0.48 6.0 (3.4 - 8.6) 152 (117 - 186) binary v,g2001 QC298 7.69 4.25 2.5 (1.4 - 3.5) 244 (189 - 299) binary m4,g*2003 EL61 -0.26 -1.90 65 (60 - 73) 2050 (1960 - 2500) shape, rotation r*2003 UB313 -1.1 0.0 86 (79 - 93) 2400 (2300 - 2500) imaging b5a: Altenhoff et al., 2004 g: Grundy et al., 2005 m4: Margot et al., 2004 r: Rabinowitz et al., 2005b2: Brown and Trujillo, 2002 j: Jewit et al., 2001 n: Noll et al., 2004 s: Spitzerb4: Brown and Trujillo, 2004 l: Lellouch et al., 2002 os: Osip et al., 2003 t: Thomas et al.b: Bertoldi et al., 2006 m2: Margot et al., 2002 or: Ortiz et al., 2004 v: Veillet et al., 2002b5: Brown et al. 2006e: Emery and Cruikshank, 2006*: Objects also have radiometric sizes and albedos.

RADIOMETRY

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