HD 204827, the C2, C3 rich sightline

The C2 Diffuse Interstellar Bands

Takeshi Oka

Department of Astronomy and AstrophysicsAnd Department of Chemistry

The Enrico Fermi Institute, University of Chicago

J. A. Thorburn, L. M. Hobbs, T. Oka, D. E. Welty, D. G. York B. J. McCall, S. D. Friedman, P. Sonnentrucker, T. P. Snow

ApJ 584, 339-356 (2003)

Carbon in space, Lago di Como, May 23, 2006

T. Oka, Thorburn, J. A., McCall, B. J., S. D. Friedman,L. M. Hobbs, P.Sonnentrucker, D. E. Welty, D. G. York

ApJ 582, 823-829 (2003)

HD 204827, the C2, C3 rich sightline

William Huggins, Comet Tebbutt, 1881

1942

1951 Alex Douglas C3

1966 IVR The Douglas effect

1975 HCCCCCN,

1977-8 HCCCCCCCN, HCCCCCCCCCN

Origin of diffuse interstellar linesNature, 269 130 (1977) Alex Douglas

Cn

Proc. R. Soc. London, A. 34, 148 (1881)4050 Å

• J. A. Thorburn, L. M. Hobbs, T. Oka, D. E. Welty, D. G. York, B. J. McCall, S. D. Friedman, P. Sonnentrucker, T. P. Snow

• Apache Point Observatory 3.5-meter• 3,800–10,000 Å ; / ~ 38,000 (8 km/s)• 53 stars, 0.11<E(B-V)<1.99, S/N > 800 at 5780 Å

Systematic observations of DIBs

HD 183143 versus HD 204827

E(B-V)= 1.27 1.11

C2 C3

N(C2) < 6 1012 cm-2

= 440 1012 cm-2

High discrimination

N(CH) = 50 1012 cm-2

= 80 1012 cm-2

Poor discrimination

C2 richC2 poor

C2 rich

C2 poor

C2 DIBs

Minority

Weak and sharp

Diffuse Interstellar Bands

W(DIB) versus N(C2)

4984.82 År = 0.857

5418.92 År = 0.905

C2 DIBs Non-C2 DIBs

5780.59 År = 0.305

6397.39 År = 0.416

)]([

)(log

)6196(

)(log 2

VBEN

CN

W

XW

C2 DIBs

λ(Å) Δλ(Å) r(C2) r(C3) Note

4363.81 0.50 0.623 0.559

4734.77 0.39 0.797 0.795

4963.88 0.73 0.757 0.668

4969.14 0.79 0.856 0.640

4979.61 0.47 0.762 0.734

4984.79 0.50 0.857 0.593

5170.57 0.44 0.634 0.413

5176.04 0.69 0.843 0.687

5418.87 0.85 0.905 0.693

5512.68 0.57 0.684 0.431

5541.87 0.45 0.742 0.576

5546.48 0.53 0.802 0.787

5762.76 0.48

5769.16 0.49 0.749 0.565

5793.22 0.71

6729.25 0.44 0.782 0.782

21.3 cm-1

20.9 cm-1

20.4cm-1

15.0 cm-1

19.1 cm-1

Doublet Lines

The Doublets

4963.99

4969.24

4979.64

4984.82

5170.57

5176.04

5541.87

5546.48

5762.76

5769.16

21.3 cm-1

20.9 cm-1

20.4 cm-1

15.0 cm-1

19.1 cm-1

Π

Π

Π

Σ

HC3 HC5 HC6 HC7 HC8 C3- C7

- A (cm-1) 14.4 23.7 -15.1 26.2 -19.3 26.6 27.4

λ (Å) Δ

4.03.83.82.41.82.23.12.81.61.01.11.01.52.01.3

Tex

22 K

34 K

26 K

Π←Σ

3 106 s

Is / Iw

A

HD 204827HD 147889HD 172028

Or inverted

C2-rich HD 204827Hot HD 34078

T = 301 K

T = 40.6 K

C2 rich

C2 poor

C2 DIBs

Minority

Weak ans sharp

Keck Adamkovics, Blake and McCall

1.006

1.004

1.002

1.000

0.998

0.996

0.994

0.992

517951785177517651755174

2( )

8B

T

B = 365 MHz for T = 100 K 182 MHz 200 K 122 MHx 300 K

B = 564.00 MHz HC7N 290.52 MHz HC9N 169.06 MHz HC11N

2.60 cm-1

Summary

DIBs which correlate well with C2 and C3 C2 DIB

HD 204827, Minority, Weak and sharp

Doublet structure suggests spin-orbit splitting Linear carbon chain molecule

Relatively high density ?

DIBs for high temperature medium HD 34078

Rotational structure B n 8 – 12?

Big question: C2, C3 C2 DIB or C2 DIB C2, C3?

HD 34078

T = 301 K

HD 204827

T = 40.6 K

C3

Adamkovics, Blake, McCall RA 06

The high temperature sightline HD 34078

R head