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Near-Infrared Spectra: Specific Molecules Chad Trujillo (Gemini Observatory)

Near-Infrared Spectra: Specific Molecules Chad Trujillo (Gemini Observatory). Introduction Part 1: Background - Why ices and why the near-infrared? - Detections on KBOs and KBO analogues: Water, Methane, and other molecules Part 2: How to end an Easter egg hunt

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Near-Infrared Spectra: Specific Molecules Chad Trujillo (Gemini Observatory)

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  1. Near-Infrared Spectra: Specific Molecules Chad Trujillo (Gemini Observatory)

  2. Introduction Part 1: Background - Why ices and why the near-infrared? - Detections on KBOs and KBO analogues: Water, Methane, and other molecules Part 2: How to end an Easter egg hunt - For the first time, we can count the bright KBOs - Required signal for detection and physical interest - List of KBOs that have been well-studied - List of KBOs we can (reasonably) study - Summary of population-wide spectroscopic results correcting for signal to noise bias

  3. Theorists Observers

  4. Why the near-infrared? There are two reasons to study KBOs: 1) Dynamics of an old (but not primordial) population 2) Ices - tracer of pristine thermal history - possible geologic effects - sensitive to ion bombardment - reservoir for atmosphere - very difficult to study in other solar system populations due to thermal alteration - compositions can constrain models (i.e. Nice, etc.) - very deep transitions in the near-infrared - almost completely neutral in the visible

  5. Why the near-infrared? 1998 Cruikshank et al.

  6. Detections (water ice) 2003 EL61, Orcus, Quaoar, 1996 TO66, 1999 DE9, 2002 AW197, 2002 TX300?, Charon, Phoebe, Triton -Where signal/resolution allow, crystalline water ice seen. -Crystalline water ice may have a lifetime shorter than the age of the solar system -Transition shape is somewhat sensitive to temperature -All have 0.1 < e < 0.2 except Quaoar (0.035) and DE9 (0.4) -But, what is the fraction of KBOs with water, really?

  7. Detections (water ice) Example: 2003 EL61 can be crudely fit with 100% water ice and nothing else (Trujillo et al. submitted)

  8. Detections (methane ice) 2003 UB313, 2005 FY9, Sedna, Pluto, Triton -Methane has a high vapor pressure -It may only be present on the largest bodies -Has been found to be pure (2003 UB313) as well as dissolved in N2 (Pluto) -Line position is sensitive to temperature and environment -But, what is the fraction of KBOs with methane, really?

  9. Detections (methane ice) 2003UB313 can be crudely fit with 100% pure methane ice and nothing else (Brown et al. 2005)

  10. Detections (other) Ammonia hydrate: Quaoar, Charon Cyanides: Phoebe, 2003 EL61? Methanol: VE95, Pholus Nitrogen: Pluto, Triton CO: Pluto, Triton CO2: Phoebe, Triton Ethane: 2005FY9 Propane: 2005FY9? -But, what is the fraction of KBOs, really?

  11. Detections (other) 2003EL61 as water ice only

  12. Detections (other) 2003EL61 as water ice + HCN. This is not an HCN detection, since there are no transitions seen. Note 2.35um drop, which is seen in other bodies and may be triple-CN.

  13. Simulation Made a simple monte-carlo simulation of ice observations: -Model near-infrared spectral observations comparing science goal to control spectrum -Assume albedo is unknown and neutral material may be present in control spectrum -Simulated H and K, but found that signal requirements are similar for both. -Want to determine the required signal-to-noise ratios (S/N) for detection / non-detection -Relate this to S/N achievable at large (8m – 10m) telescopes

  14. Simulation Water ice detection requires S/N~20 for a 3 sigma detection of 100% pure ice Really want S/N~40

  15. Simulation Crystalline water ice detection requires S/N~40 for a 3 sigma detection of 100% pure ice Really want S/N~80

  16. Simulation Estimate of surface fraction to 10% for water ice requires S/N~200

  17. Simulation Estimate of temp for water requires S/N~500

  18. Simulation Methane ice detection requires S/N~20 for a 3 sigma detection of 100% pure ice Really want S/N~40

  19. Simulation Estimate of surface fraction to 10% for pure methane requires S/N~200

  20. Simulation Estimate of temp for methane requires S/N~200

  21. Simulation Methanol detection requires S/N~70 for a 3 sigma detection of 100% pure ice Really want S/N~140

  22. Simulation Ammonia detection requires S/N~125 for a 3 sigma detection of 100% pure ice Really want S/N~250

  23. Simulation Summary S/N Ice 40 water/methane detection 80 xwater detection 200 methanol/ammonia detection 200 water/methane fraction to 10% 500 water/methane temp, N2/CO/CO2/Ethane limits water: 7/16 EL61,Q.,O.,AW197,DE9,TO66,TX300 methane: 3/15 FY9,UB313,Sedna xwater: 4/4 EL61,Q.,O.,TO66,AW197?,DE9? mthnl/NH3: 2/4 Q.=NH3:H2O,VE95=methanol Ethane: 1/1 FY9 temp: 0/1? N2/CO/CO2: 0/1 No CH4/H2O: 6/15 CS29,TL66,GN171,WR106,Huya,Ixion Pluto: Methane, N2, CO, Ethane? Charon: xwater, NH3, NH3:H2O Triton: Methane, N2, CO, CO2, 13CO Phoebe: xwater, CO2, OH, CH, CN, Fe2+, metal-OH, phyllosilicate

  24. What's Left? Combining all our resources in an international collaboration, we can probably get about 15 nights / year of 8m – 10m telescope time ~ 70 hours / year of integration time ~ 200 hours over next 3 years Much more time than this is wasted every year outside the solar system. Assume Keck=VLT=Gemini: S/N~100 in 1 hour for a K=18 object What can we do?

  25. What's Left? The 7 brightest KBOs have at least S/N=80 completed There are about 8 KBOs left that are “easy” H2O/CH4 detections

  26. What's Left? These have S/N~250 These have S/N~100 About 4 of these have S/N~50 About 4 of these have S/N~40

  27. What's Left? The Good News: - There are about 40 KBOs left that could use 8 hours of exposure time, 8 of which could use 1 hour for marginal results - About 25 KBOs could be observed by an international team of collaborators using the world's largest telescopes. - Such an effort would produce ~8 X/H2O detections, ~5 CH4 detections, a few temperatures, a few good N2/CO limits, tripling our knowledge of KBO surfaces The Bad News: - Don't bother observing any of the brightest 15 KBOs unless you spend at least 4 hours of exposure time on a 8m – 10m telescope in good conditions.

  28. Your Results So Far... After taking into account S/N issues: For KBOs -100% (4) of water ice is crystalline -44% (7/16) of KBOs show water ice -50% (2/4) of KBOs show ammonia hydrate or methanol -20% (3/15) of KBOs show methane ice -Only the biggest KBOs have methane ice, is this physical or small number statistics? -Only 1 KBO has been observed deeply enough to detect N2/CO/CO2/Ethane (FY9, Ethane only) -40% (6/15) of KBOs are featureless -No clear correlation between surface and orbital parameters -Results are similar with inclusion of KBO analogues (Pluto,Charon,etc.) Tips for observers: -Don't repeat objects that are already done! -Observe in good conditions and at low airmass! -Take high (80-100) S/N spectra!

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