J/ApJ/733/91 Diffuse interstellar band equivalent widths (Xiang+, 2011)
A tale of two mysteries in interstellar astrophysics: the 2175 Å extinction
bump and diffuse interstellar bands.
Xiang F.Y., Li A., Zhong J.X.
<Astrophys. J., 733, 91 (2011)>
=2011ApJ...733...91X 2011ApJ...733...91X
ADC_Keywords: Interstellar medium ; Equivalent widths
Keywords: dust, extinction - ISM: lines and bands - ISM: molecules
Abstract:
The diffuse interstellar bands (DIBs) are ubiquitous absorption
spectral features arising from the tenuous material in the space
between stars -the interstellar medium (ISM). Since their first
detection nearly nine decades ago, over 400 DIBs have been observed in
the visible and near-infrared wavelength range in both the Milky Way
and external galaxies, both nearby and distant. However, the identity
of the species responsible for these bands remains as one of the most
enigmatic mysteries in astrophysics. An equally mysterious
interstellar spectral signature is the 2175Å extinction bump, the
strongest absorption feature observed in the ISM. Its carrier also
remains unclear since its first detection 46 years ago. Polycyclic
aromatic hydrocarbon (PAH) molecules have long been proposed as a
candidate for DIBs as their electronic transitions occur in the
wavelength range where DIBs are often found. In recent years, the
2175Å extinction bump is also often attributed to the π-π*
transition in PAHs. If PAHs are indeed responsible for both the
2175Å extinction feature and DIBs, their strengths may correlate.
We perform an extensive literature search for lines of sight for which
both the 2175Å extinction feature and DIBs have been measured.
Unfortunately, we found no correlation between the strength of the
2175Å feature and the equivalent widths of the strongest DIBs. A
possible explanation might be that DIBs are produced by small free
gas-phase PAH molecules and ions, while the 2175Å bump is mainly
from large PAHs or PAH clusters in condensed phase so that there is no
tight correlation between DIBs and the 2175Å bump.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 97 84 The 2175Å extinction bump strengths (W2175)
and DIB equivalent widths (WDIB) for 84
interstellar sightlines
table3.dat 87 797 Sources for the equivalent widths of the 5707,
5780, 5797, 6203, 6284, and 6614 DIBs
table4.dat 104 385 Sources for the equivalent widths of the
6195/6996, 6269/6270, and 6376/6379 DIBs
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See also:
III/148 : Interstellar lines catalogue (Garcia 1991)
II/135 : Suppl. to Diffuse Interstellar Band Measurements (Guarinos 1988)
II/149 : Diffuse Interstellar Band Measurements (Snow+ 1977)
J/ApJ/708/1628 : Diffuse interstellar bands. IV. (McCall+, 2010)
J/ApJ/705/32 : Diffuse interstellar bands from HD 183143 (Hobbs+, 2009)
J/MNRAS/358/563 : Diffuse Interstellar Bands in 49 stars (Megier+, 2005)
J/A+A/429/559 : Diffuse Interstellar Bands in NGC 1448 (Sollerman+, 2005)
J/A+A/414/949 : Interstellar bands and H2, CH, CO column densities (Weselak+
2004)
J/AN/324/219 : Extinction of OB stars (Wegner, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Star HD or BD name
9- 12 F4.2 mag E(B-V) Interstellar reddening E(B-V) (1)
14- 17 F4.2 --- Rv ? Total-to-selective extinction ratio
(RV=AV/E(B-V); AV= V-band extinction)
19- 22 F4.2 --- e_Rv ? Rv uncertainty
24 I1 --- r_Rv ? Rv reference (2)
26- 29 F4.2 um-2 c3 Parameter c3 that relates to the strength
of the bump
31 I1 --- r_c3 c3 reference (2)
33- 36 F4.2 um-1 gamma Band width γ (extinction parameter)
38 I1 --- r_gamma Gamma reference (2)
40- 43 F4.2 um-1 W2175 W2175/E(B-V) (3)
45- 49 F5.1 0.1pm W5707 ? 5707 equivalent width in milliÅ (1)
51- 55 F5.1 0.1pm W5780 5780 equivalent width in milliÅ (1)
57- 61 F5.1 0.1pm W5797 ? 5797 equivalent width in milliÅ (1)
63- 66 F4.1 0.1pm W6195 ? 6195/6196 equivalent width in milliÅ (1)
68- 72 F5.1 0.1pm W6203 ? 6203 equivalent width in milliÅ (1)
74- 78 F5.1 0.1pm W6269 ? 6269/6270 equivalent width in milliÅ (1)
80- 85 F6.1 0.1pm W6284 ? 6284 equivalent width in milliÅ (1)
87- 91 F5.1 0.1pm W6376 ? 6376/6379 equivalent width in milliÅ (1)
93- 97 F5.1 0.1pm W6614 ? 6614 equivalent width in milliÅ (1)
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Note (1): Sources for E(B-V) and WDIB are
* Dorschner et al. (1977A&A....58..201D 1977A&A....58..201D),
* Herbig (1975ApJ...196..129H 1975ApJ...196..129H, 1993ApJ...407..142H 1993ApJ...407..142H, 2000ApJ...542..334H 2000ApJ...542..334H),
* Seab & Snow (1984ApJ...277..200S 1984ApJ...277..200S),
* Benvenuti & Porceddu (1989A&A...223..329B 1989A&A...223..329B),
* Desert et al. (1995A&A...303..223D 1995A&A...303..223D),
* Sonnentrucker al. (1997A&A...327.1215S 1997A&A...327.1215S),
* Snow et al. (2002ApJ...573..670S 2002ApJ...573..670S),
* Wszolek & Godlowski (2003MNRAS.338..990W 2003MNRAS.338..990W),
* Thorburn+ (2003ApJ...584..339T 2003ApJ...584..339T),
* Galazutdinov et al. (2004MNRAS.355..169G 2004MNRAS.355..169G),
* Megier et al. (2005, Cat. J/MNRAS/358/563),
* Cox et al. (2007A&A...465..899C 2007A&A...465..899C),
* Hobbs+ (2008ApJ...680.1256H 2008ApJ...680.1256H, 2009, Cat. J/ApJ/705/32),
* McCall et al. (2010, Cat. J/ApJ/708/1628),
* Friedman et al. (2011ApJ...727...33F 2011ApJ...727...33F).
See Appendix and Tables 3 and 4 for details on how we obtain the DIB
equivalent widths adopted here.
Note (2): Sources as follows:
1 = Wegner (2003, Cat. J/AN/324/219),
2 = Geminale (2006, PhD thesis, Universita degli Studi di Padova);
3 = Jenniskens & Greenberg (1993A&A...274..439J 1993A&A...274..439J),
4 = Fitzpatrick & Massa (2005AJ....130.1127F 2005AJ....130.1127F),
5 = Whittet et al. (2004ApJ...602..291W 2004ApJ...602..291W),
6 = Fitzpatrick & Massa (1990ApJS...72..163F 1990ApJS...72..163F),
7 = Lewis et al. (2005ApJ...619..357L 2005ApJ...619..357L),
8 = Sofia et al. (2005ApJ...625..167S 2005ApJ...625..167S).
Note (3): We use the black shaded area (W2175/E(B-V)=πc3/2γ)
above the "linear background extinction" in the Fitzpatrick & Massa
(FM90; 1990ApJS...72..163F 1990ApJS...72..163F) decomposition scheme as a measure of the
strength of the 2175Å extinction bump (normalized by E(B-V)).
See section 1.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm DIB [5707/6614] DIB wavelength identification; in
Angstroms
6- 12 A7 --- Star [2905/+631964] Stellar HD or BD ID
14- 17 F4.2 mag E(B-V) [0.05/1.28] E(B-V)
19- 22 F4.2 um-1 W2175 The 2175 equivalent width divided by E(B-V)
24- 29 F6.1 0.1pm W ? Equivalent width of DIB (in milliÅ)
31- 35 F5.1 0.1pm e_W ? Uncertainty in W (in milliÅ)
37 A1 --- q_W [AX] Adopt/Reject code (G1)
39- 60 A22 --- Aut Author's name for Ref
62- 80 A19 --- Ref Bibcode of source reference
82- 87 F6.1 0.1pm Wado [5/1888]? Adopted equivalent width of DIB (in
milli-Angstroms)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm DIB1 DIBs pair wavelength identification; in Å
5 A1 --- --- [/]
6- 9 I4 0.1nm DIB2 DIBs pair wavelength identification; in Å
11- 17 A7 --- Star [2905/+631964] Stellar HD or BD ID
19- 22 F4.2 mag E(B-V) [0.05/1.28] E(B-V)
24- 27 F4.2 um-1 W2175 The 2175 equivalent width divided by E(B-V)
29 A1 --- l_W1 Limit flag on W1
30- 34 F5.1 0.1pm W1 ? Equivalent width of 1st DIB in pair (in mÅ)
36- 39 F4.1 0.1pm e_W1 ? Uncertainty in W1 (in milliÅ)
41 A1 --- q_W1 [AX] Adopt/Reject code for 1st DIB in pair (G1)
43- 48 F6.1 0.1pm W2 ? Equivalent width of 2nd DIB in pair (in mÅ)
50- 53 F4.1 0.1pm e_W2 ? Uncertainty in W2 (in milliÅ)
55 A1 --- q_W2 [AX] Adopt/Reject code for 2nd DIB in pair (G1)
57- 78 A22 --- Aut Author's name for Ref
80- 98 A19 --- Ref Bibcode of source reference
100-104 F5.1 0.1pm Wado [2.5/246.9]? Adopted DIB equivalent
widths (in milli-Angstroms)
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Global notes:
Note (G1): Those adopted for deriving the "mean" equivalent widths used in
this work are denoted by "A" (otherwise by "X").
See Appendix for details.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 12-Nov-2012