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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
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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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)
Note (1): Sources for E(B-V) and WDIB are * Dorschner et al. (1977A&A....58..201D), * Herbig (1975ApJ...196..129H, 1993ApJ...407..142H, 2000ApJ...542..334H), * Seab & Snow (1984ApJ...277..200S), * Benvenuti & Porceddu (1989A&A...223..329B), * Desert et al. (1995A&A...303..223D), * Sonnentrucker al. (1997A&A...327.1215S), * Snow et al. (2002ApJ...573..670S), * Wszolek & Godlowski (2003MNRAS.338..990W), * Thorburn+ (2003ApJ...584..339T), * Galazutdinov et al. (2004MNRAS.355..169G), * Megier et al. (2005, Cat. J/MNRAS/358/563), * Cox et al. (2007A&A...465..899C), * Hobbs+ (2008ApJ...680.1256H, 2009, Cat. J/ApJ/705/32), * McCall et al. (2010, Cat. J/ApJ/708/1628), * Friedman et al. (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), 4 = Fitzpatrick & Massa (2005AJ....130.1127F), 5 = Whittet et al. (2004ApJ...602..291W), 6 = Fitzpatrick & Massa (1990ApJS...72..163F), 7 = Lewis et al. (2005ApJ...619..357L), 8 = Sofia et al. (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) decomposition scheme as a measure of the strength of the 2175Å extinction bump (normalized by E(B-V)). See section 1.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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)
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
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)
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.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 12-Nov-2012
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