J/ApJS/149/157 EMILI line-identification in IC 418 spectrum (Sharpee+, 2003)
Introducing EMILI: computer-aided emission line identification.
Sharpee B., Williams R., Baldwin J.A., van Hoof P.A.M.
<Astrophys. J. Suppl. Ser. 149, 157 (2003)>
=2003ApJS..149..157S 2003ApJS..149..157S
ADC_Keywords: Planetary nebulae ; Spectroscopy
Keywords: line: identification - methods: data analysis -
planetary nebulae: individual (IC 418)
Abstract:
The identification of spectral lines can be a tedious process
requiring the interrogation of large spectroscopic databases, but
it does lend itself to software algorithms that can determine the
characteristics of candidate line identifications. We present here
criteria used for the identification of lines and a logic developed
for a line identification software package called EMILI, which uses
the v2.04 Atomic Line List as the basic line database. EMILI considers
all possible database transitions within the wavelength uncertainties
for observed optical emission lines and computes an approximate
intensity for each candidate line. It searches for other multiplet
members that are expected to be seen with each candidate line, and
rank-orders all of the tentative line identifications for each
observed line based on a set of criteria. When applied to the spectra
of the Orion Nebula and the planetary nebula IC 418, EMILI's
recommended line IDs agree well with those of previous traditional
manual line assignments. The existence of a semiautomated procedure
should give impetus to the study of very high signal-to-noise spectra,
enabling the identification of previously unidentified spectral lines
to be handled with ease and consistency.
Description:
EMILI is a stand-alone FORTRAN code that runs in 510 minutes on any
UNIX, LINUX, or Windows computer that has a suitable FORTRAN compiler.
It is publicly available over the Web at
http://www.pa.msu.edu/astro/software/emili/
with a primer and has the following logical flow:
for each line in a list of unidentified observed lines submitted to
EMILI, a transition database is queried for all transitions within
the immediate wavelength vicinity. A separate list of preidentified
"signature lines" from the same spectrum is used to establish
kinematic and ionization models of the observed object. EMILI
calculates a predicted template flux for all candidate emission lines
considered in the line list based upon these models and upon the
characteristics of each transition. For each candidate transition
in the database EMILI searches the line list to identify other
transitions from the same multiplet. EMILI then ranks each candidate
ID for an observed feature according to wavelength agreement,
strongest relative predicted flux, and the numbers of multiplet
members detected, and it presents the results to the user for final
ID determination.
Objects:
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RA (2000) DE Designation(s)
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05 27 28.2 -12 41 50 IC 418 = PN G215.2-24.2
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 142 1005 EMILI Line Identifications for IC 418
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See also:
J/PASP/106/745 : The Spectrum of IC 418 (Hyung+ 1994)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm OWave Observed wavelength in Angstroms (1)
10- 13 F4.1 km/s FWHM The Full Width at Half Maximum of the line
15- 22 F8.4 --- F*100/Hb Observed intensity relative to Hβ (2)
24- 31 F8.4 --- I*100/Hb De-reddened intensity relative to Hβ (3)
33- 39 F7.1 --- S/N ?=99990.0 Signal to noise of the line (4)
41 A1 --- IDI EMILI IDI value (5)
43 A1 --- V Rank of EMILI IDI value (6)
46- 53 A8 --- Ion Source ion of line
55- 62 F8.3 0.1nm TWave ? Tabulated wavelength of transition (Å)
64 A1 --- f_TWave [:?] Flag on TWave (7)
67- 71 F5.1 km/s DWave ? Difference between OWave and TWave (8)
73- 97 A25 --- Lower Lower level Term/Configuration (9)
99-127 A29 --- Upper Upper level Term/Configuration
129-132 F4.1 --- Jlow ? Lower level J value (10)
134-137 F4.1 --- Jup ? Upper level J value (10)
139-141 A3 --- Multi EMILI multiplet check (11)
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Note (1): Corrected for +68.6km/s nebular proper motion.
Note (2): Where F(Hβ)=1.31*10-11erg/cm3/s.
Note (3): Where F(Hβ)=2.87*10-11erg/cm3/s.
Note (4): 99990.0 = indeterminate S/N.
Note (5): The IDI which we have instituted for EMILI is defined to be
IDI = W + F + M
where W, F, and M take integer values between 0 and 3 according to
the deviations of wavelength, flux, and multiplet components,
respectively, with lower scores being better.
An "*" is IDI>9. No IDI value for manual IDs
Note (6): Rank A,B,C,D where applicable.
The EMILI ID rankings A, B, C, and D refer to the first, second,
third, and fourth highest ranked IDs from the algorithm.
No rank for manual IDs.
Note (7): the symbols mean the following:
? = identification does not have a solid basis and the spectral
feature may be spurious or the line list does not contain the
correct transition for that feature.
: = uncertain identification.
Note (8): DWave = c * (λ-λo)/λ.
Note (9): Coupling schemes used are LS, LK, J1,K.
Note (10): the value J=-9.9 is used for line from blended level.
Note (11): Check statistics for LS coupled levels only;
(A/B) where A is number of lines expected and B the number considered found.
Not used for manual IDs. An "*" indicates A>9.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 17-Nov-2003