J/ApJ/850/194 Equivalent widths of 8 DIBs for 186 O & B stars (Fan+, 2017)
The behavior of selected diffuse interstellar bands with molecular fraction in
diffuse atomic and molecular clouds.
Fan H., Welty D.E., York D.G., Sonnentrucker P., Dahlstrom J.A., Baskes N.,
Friedman S.D., Hobbs L.M., Jiang Z., Rachford B., Snow T.P., Sherman R.,
Zhao G.
<Astrophys. J., 850, 194 (2017)>
=2017ApJ...850..194F 2017ApJ...850..194F
ADC_Keywords: Stars, B-type; Stars, O; Spectral types; Equivalent widths;
Interstellar medium; Spectra, optical
Keywords: dust, extinction ; ISM: clouds ; ISM: lines and bands ; ISM: molecules
Abstract:
We study the behavior of eight diffuse interstellar bands (DIBs) in
different interstellar environments, as characterized by the fraction
of hydrogen in molecular form (fH2), with comparisons to the
corresponding behavior of various known atomic and molecular species.
The equivalent widths of the five "normal" DIBs
(λλ5780.5, 5797.1, 6196.0, 6283.8, and 6613.6),
normalized to EB-V, show a "lambda-shaped" behavior: they increase
at low fH2, peak at fH2∼0.3, and then decrease. The similarly
normalized column densities of Ca, Ca+, Ti+, and CH+ also decline for
fH2>0.3. In contrast, the normalized column densities of Na, K, CH,
CN, and CO increase monotonically with fH2, and the trends exhibited
by the three C2 DIBs (λλ4726.8, 4963.9, and 4984.8)
lie between those two general behaviors. These trends with fH2 are
accompanied by cosmic scatter, the dispersion at any given fH2 being
significantly larger than the individual errors of measurement. The
lambda-shaped trends suggest the balance between creation and
destruction of the DIB carriers differs dramatically between diffuse
atomic and diffuse molecular clouds; additional processes aside from
ionization and shielding are needed to explain those observed trends.
Except for several special cases, the highest
Wλ(5780)/Wλ(5797) ratios, characterizing the so-called
"sigma-zeta effect," occur only at fH2<0.2. We propose a sequence of
DIBs based on trends in their pair-wise strength ratios with
increasing fH2. In order of increasing environmental density, we
find the λ6283.8 and λ5780.5 DIBs, the λ6196.0
DIB, the λ6613.6 DIB, the λ5797.1 DIB, and the C2 DIBs.
Description:
Most of the spectra were obtained with the ARC echelle spectrograph
(ARCES) on the 3.5m telescope at Apache Point Observatory (APO);
wavelength range between 3500Å and 11000Å, and the resolving
power is 33000.
Eight of our stars were observed with the Magellan Inamori Kyocera
Echelle (MIKE) on the Clay Telescope at Las Campanas Observatory,
Chile, with wavelength coverage between 3200Å and 10000Å. The
effective resolving power is about 45600 in the blue and 36000 in
the red for these spectra.
Another five spectra are from the archive of the Fiberfed Extended
Range Optical Spectrograph (FEROS) mounted on the ESO 1.52m telescope
at La Silla observatory, Chile, which has a resolving power of 48000
and wavelength coverage between 3560Å and 9200Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 189 186 Spectral types and values of E(B-V), N(H), N(H2),
fH2, and EWs of the eight diffuse interstellar
bands (DIBs) for 186 O and B stars
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See also:
J/ApJS/147/61 : Interstellar Ca I absorption (Welty+, 2003)
J/A+A/414/949 : H2, CH, CO column densities (Weselak+ 2004)
J/MNRAS/358/563 : Diffuse Interstellar Bands in 49 stars (Megier+, 2005)
J/ApJ/705/32 : Diffuse interstellar bands from HD 183143 (Hobbs+, 2009)
J/ApJ/700/1299 : Gas-phase element depletions in the ISM (Jenkins, 2009)
J/ApJ/711/1236 : Equivalent width of H2 from FUSE (Jensen+, 2010)
J/ApJ/708/1628 : Diffuse interstellar bands. IV. (McCall+, 2010)
J/MNRAS/404/1321 : TiII in Milky way and Magellanic clouds (Welty+, 2010)
J/ApJ/733/91 : Diffuse interstellar band equivalent widths (Xiang+, 2011)
J/A+A/544/A136 : Diffuse Interstellar Bands in 150 stars (Raimond+, 2012)
J/MNRAS/423/725 : Survey of diffuse interstellar bands (Bondar, 2012)
J/A+A/555/A25 : Equivalent widths of DIBs (Puspitarini+, 2013)
J/ApJ/774/72 : Measurements of 19 DIBs (Kos+, 2013)
J/ApJS/225/19 : DIBs measurements from SDSS-III APOGEE (Elyajouri+, 2016)
J/A+A/606/A76 : The ESO DIBs Large Exploration Survey (Cox+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star name
13- 21 A9 --- SpT MK spectral type
23- 27 F5.2 mag E(B-V) [0/3.4] Reddening, E(B-V)
29- 32 F4.2 mag e_E(B-V) [0.01/0.1]? Uncertainty in E(B-V)
36- 36 A1 --- l_N(H) Limit flag on N(H)
38- 42 F5.2 [cm-2] N(H) [19.4/22]? Log Column density, H
44- 47 F4.2 [cm-2] e_N(H) [0.04/0.3]? Uncertainty in N(H)
49- 49 A1 --- f_N(H) Flag on N(H) (1)
51- 51 A1 --- l_N(H2) Limit flag on N(H2)
53- 57 F5.2 [cm-2] N(H2) [14.5/21.5]? Log Column density, H2
59- 62 F4.2 [cm-2] e_N(H2) [0.01/0.4]? Uncertainty in N(H2)
64- 64 A1 --- f_N(H2) Flag on N(H2) (1)
66- 66 A1 --- l_fH2 Limit flag on fH2
68- 74 F7.5 --- fH2 ? Fraction of hydrogen in molecular form
76- 79 F4.2 --- e_fH2 [0/0.3]? Uncertainty in fH2
81- 81 A1 --- l_W(4727) Limit flag on W(4727)
83- 87 F5.1 10-4nm W(4727) [4.7/343]? Equivalent width, 4727Å (2)
89- 92 F4.1 10-4nm e_W(4727) [0.5/15.2]? Uncertainty in W(4727)
94- 94 A1 --- f_W(4727) Flag on W(4727) (1)
96- 96 A1 --- l_W(4963) Limit flag on W(4963)
98-101 F4.1 10-4nm W(4963) [0.6/68.5]? Equivalent width, 4963Å (2)
103-105 F3.1 10-4nm e_W(4963) [0.1/2.6]? Uncertainty in W(4963)
107-107 A1 --- f_W(4963) Flag on W(4963) (1)
109-109 A1 --- l_W(4984) Limit flag on W(4984)
111-114 F4.1 10-4nm W(4984) [0.4/32.7]? Equivalent width, 4984Å (2)
116-118 F3.1 10-4nm e_W(4984) [0.1/2.1]? Uncertainty in W(4984)
120-120 A1 --- l_W(5780) Limit flag on W(5780)
122-126 F5.1 10-4nm W(5780) [4/891.2]? Equivalent width, 5780Å (2)
128-131 F4.1 10-4nm e_W(5780) [0.8/11.2]? Uncertainty in W(5780)
133-133 A1 --- f_W(5780) Flag on W(5780) (1)
135-135 A1 --- l_W(5797) Limit flag on W(5797)
137-141 F5.1 10-4nm W(5797) [2/356]? Equivalent width, 5797Å (2)
143-145 F3.1 10-4nm e_W(5797) [0.1/4.3]? Uncertainty in W(5797)
147-147 A1 --- f_W(5797) Flag on W(5797)(1)
149-149 A1 --- l_W(6196) Limit flag on W(6196)
151-155 F5.1 10-4nm W(6196) [0.5/106.4]? Equivalent width, 6196Å (2)
157-159 F3.1 10-4nm e_W(6196) [0.1/2]? Uncertainty in W(6196)
161-161 A1 --- l_W(6284) Limit flag on W(6284)
163-168 F6.1 10-4nm W(6284) [7/2287]? Equivalent width, 6284Å (2)
170-173 F4.1 10-4nm e_W(6284) [0.9/30.7]? Uncertainty in W(6284)
175-175 A1 --- f_W(6284) Flag on W(6284) (1)
177-177 A1 --- l_W(6613) Limit flag on W(6613)
179-183 F5.1 10-4nm W(6613) [0.9/427.4]? Equivalent width, 6613Å (2)
185-187 F3.1 10-4nm e_W(6613) [0.2/3.7]? Uncertainty in W(6613)
189-189 A1 --- f_W(6613) Flag on W(6613) (1)
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Note (1): Measurement flags as follows:
b = Column density calculated using surrogates, see Section 3.1;
c = Possible stellar contamination;
d = The profile of the 5797.1A DIB corrected from stellar contamination.
Note (2): in milli-angstrom units.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Jul-2018