J/ApJS/207/7 Modeling Galactic extinction with dust and PAH (Mulas+, 2013)
Modeling galactic extinction with dust and "Real" polycyclic aromatic
hydrocarbons.
Mulas G., Zonca A., Casu S., Cecchi-Pestellini C.
<Astrophys. J. Suppl. Ser., 207, 7 (2013)>
=2013ApJS..207....7M 2013ApJS..207....7M
ADC_Keywords: Interstellar medium ; Models ; Abundances
Keywords: dust, extinction - ISM: abundances - ultraviolet: ISM
Abstract:
We investigate the remarkable apparent variety of galactic extinction
curves by modeling extinction profiles with core-mantle grains and a
collection of single polycyclic aromatic hydrocarbons. Our aim is to
translate a synthetic description of dust into physically
well-grounded building blocks through the analysis of a statistically
relevant sample of different extinction curves. All different flavors
of observed extinction curves, ranging from the average galactic
extinction curve to virtually "bumpless" profiles, can be described by
the present model. We prove that a mixture of a relatively small
number (54 species in 4 charge states each) of polycyclic aromatic
hydrocarbons can reproduce the features of the extinction curve in the
ultraviolet, dismissing an old objection to the contribution of
polycyclic aromatic hydrocarbons to the interstellar extinction curve.
Despite the large number of free parameters (at most the 54x4 column
densities of each species in each ionization state included in the
molecular ensemble plus the 9 parameters defining the physical
properties of classical particles), we can strongly constrain some
physically relevant properties such as the total number of C atoms in
all species and the mean charge of the mixture. Such properties are
found to be largely independent of the adopted dust model whose
variation provides effects that are orthogonal to those brought about
by the molecular component. Finally, the fitting procedure, together
with some physical sense, suggests (but does not require) the presence
of an additional component of chemically different very small
carbonaceous grains.
Description:
The model being used here includes two main components: a population
of silicate core, carbon-coated dust grains, and a "molecular"
component of free-flying PAHs. The descriptions of these components
are detailed in section 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 245 329 Classical dust component parameters, obtained from
the simplified and detailed models for the average
interstellar extinction curve (ISEC) and for the
lines of sight in Figure 1
table2.dat 162 329 Si and C abundances resulting from the simple and
detailed models for the average interstellar
extinction curve (ISEC) and for the lines of sight
plotted in Figure 1
table3.dat 43 329 Average charges per C atoms and rms dispersions
obtained with the detailed model for the average
interstellar extinction curve (ISEC) and for the
lines of sight in Figure 1
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See also:
J/A+A/527/A109 : Dust and PAH emission SEDs of disk galaxies (Popescu+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- LoS Line of sight identifier
16- 23 F8.6 --- Nd.s Simple model dust normalization factor (1)
25- 32 F8.6 --- e_Nd.s ? Uncertainty in Nd.s (blank if <10-6)
34- 37 F4.2 --- fv.s [0/1] Simple model vacuum fraction of silicate
core
39- 42 F4.2 --- e_fv.s ? Uncertainty in fv.s (blank if <0.01)
44- 47 F4.2 nm w.s Simple model total carbonaceous mantle thickness
49- 52 F4.2 nm e_w.s ? Uncertainty in w.s (blank if <0.01)
54- 57 F4.2 --- fsp2.s Simple model fraction of sp2 (graphitic)
material in the carbonaceous mantle
59- 62 F4.2 --- e_fsp2.s ? Uncertainty in fsp2.s (blank if <0.01)
64- 67 F4.2 nm amin.s Simple model small grain lower limit
69- 72 F4.2 nm e_amin.s ? Uncertainty in amin.s (blank if <0.01)
74- 78 F5.2 nm amax.s Simple model small grain upper limit
80- 83 F4.2 nm e_amax.s ? Uncertainty in amax.s (blank if <0.01)
85- 90 F6.2 nm bmin.s Simple model big grain lower limit
92- 95 F4.2 nm e_bmin.s ? Uncertainty in bmin.s (blank if <0.01)
97-103 F7.2 nm bmax.s Simple model big grain upper limit
105-109 F5.2 nm e_bmax.s ? Uncertainty in bmax.s (blank if <0.01)
111-116 F6.4 --- q.s Simple model power law index q (1)
118-123 F6.4 --- e_q.s ? Uncertainty in q.s (blank if <10-4)
125-127 F3.1 --- chi2.s ? Simple model reduced χ2 (blank if <0.1)
129-137 F9.7 --- Nd.d Detailed model dust normalization factor (1)
139-146 F8.6 --- e_Nd.d ? Uncertainty in Nd (blank if <10-6)
148-151 F4.2 --- fv.d Detailed model vacuum fraction of silicate core
153-156 F4.2 --- e_fv.d ? Uncertainty in fv.d (blank if <0.01)
158-161 F4.2 nm w.d Detailed model total carbonaceous mantle
thickness
163-166 F4.2 nm e_w.d ? Uncertainty in w (blank if <0.01)
168-171 F4.2 --- fsp2.d Detailed model fraction of sp2 (graphitic)
material in the carbonaceous mantle
173-176 F4.2 --- e_fsp2.d ? Uncertainty in fsp2.d (blank if <0.01)
178-182 F5.2 nm amin.d Detailed model small grain miner limit
184-187 F4.2 nm e_amin.d ? Uncertainty in amin.d (blank if <0.01)
189-193 F5.2 nm amax.d Detailed model small grain upper limit
195-199 F5.2 nm e_amax.d ? Uncertainty in amax.d (blank if <0.01)
201-206 F6.2 nm bmin.d Detailed model big grain miner limit
208-212 F5.2 nm e_bmin.d ? Uncertainty in bmin.d (blank if <0.01)
214-220 F7.2 nm bmax.d Detailed model big grain upper limit
222-226 F5.2 nm e_bmax.d ? Uncertainty in bmax.d (blank if <0.01)
228-234 F7.5 --- q.d Detailed.d model power law index
236-241 F6.4 --- e_q.d ? Uncertainty in q.d
243-245 F3.1 --- chi2.d ? Detailed model reduced χ2 (blank if <0.1)
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Note (1): if q is the exponent of the MRN distribution of the grain sizes
(Mathis-Rumpl-Nordsieck, 1977ApJ...217..425M 1977ApJ...217..425M: dN(a)∝a-q),
where a is the size of grains in um, Ne is expressed in umq-3.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- LoS Line of sight identifier
16- 19 F4.1 ppm Si/H1s Small grain Si/H abundance (simple model)
21- 23 F3.1 ppm e_Si/H1s ? Uncertainty in Si/H1s (blank if <0.1)
25- 29 F5.1 ppm Si/H2s Large grain Si/H abundance (simple model)
31- 33 F3.1 ppm e_Si/H2s ? Uncertainty in Si/H2s (blank if <0.1)
35- 39 F5.1 ppm Si/H.s Total grain Si/H abundance (simple model)
41- 43 F3.1 ppm e_Si/H.s ? Uncertainty in Si/H.s (blank if <0.1)
45- 48 F4.1 ppm C/H1s Small grain C/H abundance (simple model)
50- 53 F4.1 ppm e_C/H1s ? Uncertainty in C/H1s (blank if <0.1)
55- 58 F4.1 ppm C/H2s Large grain C/H abundance (simple model)
60- 63 F4.1 ppm e_C/H2s ? Uncertainty in C/H2s (blank if <0.1)
65- 69 F5.1 ppm C/H3s PAH C/H abundance (simple model)
71- 75 F5.1 ppm e_C/H3s ? Uncertainty in C/H3s (blank if <0.1)
77- 81 F5.1 ppm C/H.s Total grain+PAH C/H abundance (simple model)
83- 87 F5.1 ppm e_C/H.s ? Uncertainty in C/H.s (blank if <0.1)
89- 92 F4.1 ppm Si/H1d small grain Si/H abundance (detailed model)
95- 98 F4.1 ppm e_Si/H1d ? Uncertainty in Si/H1d (blank if <0.1)
100-104 F5.1 ppm Si/H2d large grain Si/H abundance (detailed model)
106-109 F4.1 ppm e_Si/H2d ? Uncertainty in Si/H2d (blank if <0.1)
111-115 F5.1 ppm Si/H.d total grain Si/H abundance (detailed model)
117-120 F4.1 ppm e_Si/H.d ? Uncertainty in Si/H.d (blank if <0.1)
122-125 F4.1 ppm C/H1d small grain C/H abundance (detailed model)
127-130 F4.1 ppm e_C/H1d ? Uncertainty in C/H1d (blank if <0.1)
132-135 F4.1 ppm C/H2d large grain C/H abundance (detailed model)
137-140 F4.1 ppm e_C/H2d ? Uncertainty in C/H2d (blank if <0.1)
142-146 F5.1 ppm C/H3d PAH grain C/H abundance (detailed model)
148-151 F4.1 ppm e_C/H3d ? Uncertainty in C/H3d (blank if <0.1)
153-157 F5.1 ppm C/H.d total grain+PAH C/H3d abundance (detailed model)
159-162 F4.1 ppm e_C/H.d ? Uncertainty in C/H.d (blank if <0.1)
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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- 14 A14 --- LoS Line of sight identifier
16- 22 F7.4 --- /Nc Average charge per C atom (in e-)
24- 29 F6.4 --- e_/Nc Uncertainty in /Nc (in e-)
31- 36 F6.4 --- sQ/Nc RMS dispersion in charge per C atom (in e-)
38- 43 F6.4 --- e_sQ/Nc Uncertainty in sQ/Nc (in e-)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Aug-2013