1. On Deuterated Polycyclic Aromatic Hydrocarbons in Space
杨雪娟 (XTU)
Collabrators：李爱根 (MU), R. Glaser (MU)
星际物理与化学（昆明 2018）

2. Origin of Deuterium
Spallation; Pregalactic Cosmic Rays; Shock Waves; Hot explosions; Disrupted NSs；×
Big Bang Nucleosynthesis (BBN) √
Epstein+, 1976, Nature

3. of Cosmological Interests
(D/H)prim  Cosmological parameters & Baryon–photon ratio  baryonic density of the Universe.
The amount of deuterium in a galaxy  Cosmic nucleosynthesis & chemical evolution of the galaxy；
Comparing the primordial and Galactic deuterium abundances  Discriminating among different Galactic chemical evolution models；

4. Primordial D abundance
Measure using gas clouds that are seen in absorption against the light of an unrelated background light source (typically, a quasar) (Adams 1976).
(D/H)prim ~ ppm (Cooke et al. 2018; Zavarigin et al. 2018)
Measure from the analysis of CMB observation data.
(D/H)prim ~ 27 ppm (Cyburt et al. 2003; Coc et al. 2004; Dunkley et al. 2009)

5. Deuterium in the Local ISM
~83 − 92% of the primordial deuterium at the solar circle.
Very close to the primordial value at low metallicity.
Decreases towards higher metallicity, with very small scatter between D & O abundance.
van der voort+, 2017

6. Deuterium in the Local ISM
The D/H ratio measured from Copernicus, HST, IMAPS & FUSE shows large variations from sightline to sightline through the local ISM (Linsky et al. 2006; 2009).
Linsky 2009

7. D Reduction: Astration
Conversion of D into other elements by nuclear fusion in stars;
Problems:
Regions separated by only a few hundred pc have extremely different star formation histories;  No other evidence of such variations in star formation activity.
Turbulent diffusion has not homogenized the elemental abundances in the gas;  Turbulent mixing is expected to be effective at mixing gas over length scales of hundreds of pc on 109 yr time scales.

8. Problem with Astration
The expected associated variations of O/H is not observed.
No anticorrelation of O-D abundance:
Not astration;
Other process!
Draine 2006

9. Depletion of D: Role of Dust
Carbonaceous grains & PAHs are a possible reposi- tory of missing D:
Carbonaceous interstellar grains could incorporate enough deuterium atoms to substantially reduce the D abundance in the gas phase.
Variations of (D/H)gas  Variations of D sequestered in dust grains from one sightline to another.
Draine 2006

10. Kinetics of Deuteration
Draine 2006
Doney+ 2016

11. DPAH: Spectral Features
× 1.36
DPAH
HPAH
Hudgins (2004)

12. DPAH: Observations Orion Bar M17 Detection of deuterated-PAHs
in Orion Bar & M17 PDRs.
Peeters et al. (2004)

13. DPAH: Observations
IRAS
NGC 3603
W17b
Doney et al. (2016)

14. DPAH: Observations
W51 M8 G
Doney et al. (2016)

15. DPAH: Observations
6/41 Galactic HII regions show deuterated-PAH emission.
Doney et al. (2016)

16. DPAH: Observations No evidence of large amount of deuterated PAHs
Onaka et al. (2015)

17. DPAH: Our Work
Modeling DPAH Emission (Draine & Li 2001; Draine & Li 2007 )
T=3500K, 6000K, 10000K, 22000K, MMP83
Goal: A database of DPAH spectra

18. A4.4/A3.3 : Calculated Molecules

19. A4.4/A3.3 : Calculated Molecules

20. D1-PAH Spectra
C-D bending
C-D stretch

21. D1-PAH Spectra
C-D bending
C-D stretch

22. Full Deuterated PAH Spectra
C-D bending
C-D stretch

23. D1-PAH Results: A4.4 & A3.3

24. D1-PAH Results: A4.4/A3.3

25. Summary
Deuterium synthesis and depletion is of great importance and interests;
Carbonaceous dust grains and PAHs could be a repository of the cosmic D, and a reason for different D/H abundance observed along different lines of sight;
A systematic theoretical study of deuterated PAHs is urgent, and with our study one can get the D abundance easily from the observed C-D vibrational features.
Thank you!