1. Weeding the Astrophysical Garden Using Complete Experimental Spectra
James P. McMillan, Christopher F. Neese, Satyakumar Nagarajan and Frank C. De Lucia
Half a Decade of ALMA: Cosmic Dawns Transformed
September 20, 2016
Indian Wells, CA

2. The problem of the ‘Weeds’
6 Weeds found in the Hot Core of Orion KL
Each Weed:
Dense lab spectra,
100s – 1000s of lines
Difficult to predict,
100s – 1000s of unpredicted spectral lines.
Many unpredicted lines are of non-trival intensity
Fortman et al. J.Mol.Spectrosc 280:11 (2012)

3. The problem of the ‘Weeds’
CH3CH2CN
CH3CN
CH2CHCN
Goldsmith, P., Bergin, T., De Lucia, F. C., et al. 2006, Report from the Workshop on Laboratory Spectroscopy in Support of Herschel, SOFIA, and ALMA (Pasadena, CA: California Institute of Technology)
Lines from perturbed excited vibrational states are difficult to predict
CH3OH
HCOOCH3
CH3CHO
CH3OCH3

4. The problem of the ‘Weeds’
Incomplete Methyl Formate Predictions
Each Weed:
Dense lab spectra,
100s – 1000s of lines
Difficult to predict,
100s – 1000s of unpredicted spectral lines.
Many unpredicted lines are of non-trival intensity
McMillan et al. ApJ 823:1 (2016)

5. Acquiring the Intensity Calibrated Complete Experimental Spectrum (CES)
10 Heaters
Sample
Transmitter
THz Source
Detector
6 meters
Butterfly Valve
Steps:
0 𝑡ℎ : Contamination
1 𝑠𝑡 : Pressure vs. Doppler Broadening
2 𝑛𝑑 : Acquire CES
K per scan; 1578 scans
Local Thermodynamic Equilibrium

6. The Point-by-point Technique
Doppler Broadened Naperian Absorbance:
A(ν) =(1− 𝑒 − ℎ𝜈 𝑘𝑇 )( 𝑛𝐿 𝑄 )𝑆 𝑒 − 𝐸 𝑙 𝑘𝑇 𝐾 𝑇 𝑒 −ln 2 ( ν− 𝜈 0 𝛿𝜈 ) 2
A(ν) =(1− 𝑒 − ℎ𝜈 𝑘𝑇 )( 𝑛𝐿 𝑄 ) 𝑆 𝑒 − 𝐸 𝑙 𝑘𝑇 𝐾 𝑇
Doppler width:
More constants:
𝛿ν= ν 𝑜 2 𝑁 𝑎 𝑘 𝑙𝑛(2) 𝑀 𝑐 𝑇 = W ν 𝑜 𝑇
K = 𝑊( 8 𝜋 3 3𝑐ℎ ln 2 𝜋 )
𝐸 𝑙 = 𝐸 𝑙 +𝑘 ln 𝑊 2 (1− ν ν 𝑜 ) 2

7. The Point-by-point Technique
Doppler Broadened Naperian Absorbance:
A(ν) =(1− 𝑒 − ℎ𝜈 𝑘𝑇 )( 𝑛𝐿 𝑄 )𝑆 𝑒 − 𝐸 𝑙 𝑘𝑇 𝐾 𝑇 𝑒 −ln 2 ( ν− 𝜈 0 𝛿𝜈 ) 2
A(ν) =(1− 𝑒 − ℎ𝜈 𝑘𝑇 )( 𝑛𝐿 𝑄 ) 𝑆 𝑒 − 𝐸 𝑙 𝑘𝑇 𝐾 𝑇
Reduces to the familiar form
Doppler width:
More constants:
𝛿ν= ν 𝑜 2 𝑁 𝑎 𝑘 𝑙𝑛(2) 𝑀 𝑐 𝑇 = W ν 𝑜 𝑇
K = 𝑊( 8 𝜋 3 3𝑐ℎ ln 2 𝜋 )
𝐸 𝑙 = 𝐸 𝑙 +𝑘 ln 𝑊 2 (1− ν ν 𝑜 ) 2

8. The Point-by-point Technique
Input
Output
Calibrate T and nL/Q
𝐴 𝑝𝑒𝑎𝑘 =(1− 𝑒 − ℎν 𝑘𝑇 )(𝑆)( 𝑛𝐿 𝑄 ) 𝑒 − 𝐸 𝑙 𝑘𝑇 𝐾 𝑇
Fit a single scan; multiple lines
Generate 𝐸 𝑙 and 𝑆
Fit a single frequency bin; all scans
A(ν) =(1− 𝑒 − ℎ𝜈 𝑘𝑇 )( 𝑛𝐿 𝑄 ) 𝑆 𝑒 − 𝐸 𝑙 𝑘𝑇 𝐾 𝑇
Doppler width:
More constants:
𝛿ν= ν 𝑜 2 𝑁 𝑎 𝑘 𝑙𝑛(2) 𝑀 𝑐 𝑇 = W ν 𝑜 𝑇
K = 𝑊( 8 𝜋 3 3𝑐ℎ ln 2 𝜋 )
𝐸 𝑙 = 𝐸 𝑙 +𝑘 ln 𝑊 2 (1− ν ν 𝑜 ) 2

9. The Point-by-point Technique
Predicts Complete Experimental Spectrum
1.) Simply Download the table of 𝑆 and 𝐸 𝑙 .
2.) Choose your temperature
and plot!
A(ν) =(1− 𝑒 − ℎ𝜈 𝑘𝑇 )( 𝑛𝐿 𝑄 ) 𝑆 𝑒 − 𝐸 𝑙 𝑘𝑇 𝐾 𝑇
McMillan et al. ApJ 823:1 (2016)
Doppler width:
More constants:
𝛿ν= ν 𝑜 2 𝑁 𝑎 𝑘 𝑙𝑛(2) 𝑀 𝑐 𝑇 = W ν 𝑜 𝑇
K = 𝑊( 8 𝜋 3 3𝑐ℎ ln 2 𝜋 )
𝐸 𝑙 = 𝐸 𝑙 +𝑘 ln 𝑊 2 (1− ν ν 𝑜 ) 2

10. Astrophysical Analysis
CH3CN In The Orion KL Hot Core
Steps:
1.) Generate a complete experimental spectrum
2.) Convolve spectra with astrophysical line shape
3.) Adjust for column density
Fortman et al. J.Mol.Spectrosc 280:11 (2012)
190K (LTE) Methyl Cyanide (CH3CN)
ALMA

11. Astrophysical Analysis
CH3CH2CN & CH2CHCN
vs Orion Hot Core
190K - Ethyl Cyanide (CH3CH2CN)
190K - Vinyl Cyanide (CH2CHCN)
ALMA
CH313CN & Terrestrial
vs Orion Hot Core
190K - 13C Methyl Cyanide
190K - Terrestrial Methyl Cyanide
ALMA
Fortman et al. J.Mol.Spectrosc 280:11-20 (2012)

12. Astrophysical Analysis
Recover Temperature and Density Profiles
Methyl Cyanide in the Orion Hot Core
This new, velocity class based work, is featured on our poster!
Still simulates to the accuracy of ALMA!

13. Laboratory Work Overview
210 – 270 Band
Point-by-point
Published ?
Ethyl Cyanide
Complete
ApJ 725: (2010)
Vinyl Cyanide
ApJ 737:20 (2011)
Methanol
ApJ 795:56 (2014)
Methyl Formate
ApJ 823:1 (2016)
Methyl Cyanide
Draft in progress
Dimethyl Ether
In Progress No
Acetaldehyde

14. Laboratory Work Overview
210 – 270 Band
Point-by-point
Published ?
Ethyl Cyanide
Complete
ApJ 725: (2010)
Vinyl Cyanide
ApJ 737:20 (2011)
Methanol
ApJ 795:56 (2014)
Methyl Formate
ApJ 823:1 (2016)
Methyl Cyanide
Draft in progress
Dimethyl Ether
In Progress No
Acetaldehyde

15. Laboratory Work Overview
210 – 270 Band
Point-by-point
Published ?
Ethyl Cyanide
Complete
ApJ 725: (2010)
Vinyl Cyanide
ApJ 737:20 (2011)
Methanol
ApJ 795:56 (2014)
Methyl Formate
ApJ 823:1 (2016)
Methyl Cyanide
Draft in progress
Dimethyl Ether
In Progress No
Acetaldehyde

16. Laboratory Work Overview
550 – 650 Band
Point-by-point
Published ?
Ethyl Cyanide
Complete
ApJ 714: (2010)
Methanol
ApJ 782:2 (2014)
Acetaldehyde
Sample too old, to be redone
No, but over 500 assignments made
Methyl Cyanide
Line shape issues, to be redone
No, presented at the 2013 ISMS

17. Summary Simulation is spectrally complete
Includes unanalyzed excited states
Format available both as a line list catalog and in the point-by-point
Shown that our results can be used for astronomy