Near-Infrared Spectra: Specific Molecules
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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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Near infrared spectra specific molecules chad trujillo gemini observatory

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

- 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


Near infrared spectra specific molecules chad trujillo gemini observatory

Theorists

Observers


Near infrared spectra specific molecules chad trujillo gemini observatory

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


Near infrared spectra specific molecules chad trujillo gemini observatory

Why the near-infrared?

1998 Cruikshank et al.


Near infrared spectra specific molecules chad trujillo gemini observatory

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?


Near infrared spectra specific molecules chad trujillo gemini observatory

Detections (water ice)

Example:

2003 EL61

can be crudely

fit with

100% water ice

and nothing else

(Trujillo et al.

submitted)


Near infrared spectra specific molecules chad trujillo gemini observatory

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?


Near infrared spectra specific molecules chad trujillo gemini observatory

Detections (methane ice)

2003UB313 can

be crudely fit

with 100% pure

methane ice

and nothing

else

(Brown et al. 2005)


Near infrared spectra specific molecules chad trujillo gemini observatory

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?


Near infrared spectra specific molecules chad trujillo gemini observatory

Detections (other)

2003EL61 as

water ice only


Near infrared spectra specific molecules chad trujillo gemini observatory

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.


Near infrared spectra specific molecules chad trujillo gemini observatory

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


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Water ice

detection

requires

S/N~20

for a

3 sigma

detection

of 100%

pure ice

Really want

S/N~40


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Crystalline

water ice

detection

requires

S/N~40

for a

3 sigma

detection

of 100%

pure ice

Really want

S/N~80


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Estimate

of surface

fraction

to 10% for

water ice

requires

S/N~200


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Estimate

of temp

for water

requires

S/N~500


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Methane ice

detection

requires

S/N~20

for a

3 sigma

detection

of 100%

pure ice

Really want

S/N~40


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Estimate

of surface

fraction

to 10% for

pure

methane

requires

S/N~200


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Estimate

of temp

for methane

requires

S/N~200


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Methanol

detection

requires

S/N~70

for a

3 sigma

detection

of 100%

pure ice

Really want

S/N~140


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation

Ammonia

detection

requires

S/N~125

for a

3 sigma

detection

of 100%

pure ice

Really want

S/N~250


Near infrared spectra specific molecules chad trujillo gemini observatory

Simulation Summary

S/NIce

40water/methane detection

80xwater detection

200methanol/ammonia detection

200water/methane fraction to 10%

500water/methane temp, N2/CO/CO2/Ethane limits

water:7/16EL61,Q.,O.,AW197,DE9,TO66,TX300

methane:3/15FY9,UB313,Sedna

xwater:4/4EL61,Q.,O.,TO66,AW197?,DE9?

mthnl/NH3:2/4Q.=NH3:H2O,VE95=methanol

Ethane:1/1FY9

temp:0/1?

N2/CO/CO2:0/1

No CH4/H2O:6/15CS29,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


Near infrared spectra specific molecules chad trujillo gemini observatory

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?


Near infrared spectra specific molecules chad trujillo gemini observatory

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


Near infrared spectra specific molecules chad trujillo gemini observatory

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


Near infrared spectra specific molecules chad trujillo gemini observatory

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.


Near infrared spectra specific molecules chad trujillo gemini observatory

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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