J/A+A/688/A111 NGC 3603 stacked nebular spectrum (Rogers+, 2024)
Spectral characterisation of the extinction properties of NGC 3603 using
JWST NIRSpec.
Rogers C., Brandl B., De Marchi G.
<Astron. Astrophys. 688, A111 (2024)>
=2024A&A...688A.111R 2024A&A...688A.111R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Spectra, infrared
Keywords: dust, extinction - HII regions -ISM: lines and bands
Abstract:
A necessary ingredient in understanding the star formation history of
a young cluster is knowledge of the extinction towards the region.
This has typically been done by making use of the colour-difference
method with photometry, or similar methods utilising the colour-colour
diagram. These approaches rely on adopting an extinction law with a
given total-to-selective extinction ratio R(V), or determining a value
of R(V) through empirical relationships. They also rely upon accurate
spectral classification, reliable stellar isochrones, and separating
field stars from genuine cluster members.
The colour excess E(B-V) can be independently determined by
studying the decrements of the recombination lines produced by the
nebular gas. Having access to many recombination lines from the same
spectral series removes the need of adopting an extinction curve.
Rather, different extinction curves can be trialled and the most
appropriate one selected based on a minimum chi2 procedure.
Using the Micro-Shutter Assembly (MSA) on board the Near InfraRed
Spectrograph (NIRSpec), multi-object spectroscopy was performed,
yielding 600 nebular spectra from the Galactic massive star formation
region NGC 3603. The recombination line intensity ratios were used to
determine independent values of E(B-V). A series of extinction curves
were trialled ranging from R(V)=2 to R(V)=8. The appropriate value of
R(V) was adopted based on the minimum 2 procedure.
The extinction characteristics of NGC 3603 are similar to other
Galactic HII regions like Orion, as well as starburst regions such 30
Doradus in the Large Magellanic Cloud, in that we find a relatively
large value of R(V)=4.8±1.06, larger than the Galactic average of
3.1. We find a typical value of E(B-V)=0.64±0.27, significantly
lower than values determined in previous studies. We also present a
stacked nebular spectrum with a typical continuum S/N=70. This
spectrum highlights the recombination lines of the HII region, several
s-process elements such as KrIII and SeIV, and molecular H2 emission
lines. This high S/N spectrum can act as a helpful template for
identifying nebular emission lines.
Using ratios of hydrogen recombination lines, we calculated the value
of R(V), E(B-V) and A(V) for > 200 lines of sight across NGC
3603. An extinction curve with a typical value R(V)=4.8±1.06 is
required to explain the colour excess observed in the nebular spectra.
This corresponds to a typical E(B-V)=0.64±0.27. This is
significantly lower than what has been found in previous extinction
studies of NGC 3603.
Description:
Normalised stacked nebular infrared spectrum for NGC 3603,
created by combining and averaging all of the usable nebular
spectra together.
Objects:
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RA (2000) DE Designation(s)
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11 15 10.80 -61 15 32.3 NGC 3603 = BRAN 348B
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spec.dat 49 3817 NGC 3603 normalised stacked nebular infrared spectrum
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See also:
J/MNRAS/368/253 : Faint emission lines in M16, M20, NGC 3603
(Garcia-Rojas+, 2006)
J/ApJ/675/1319 : Infrared photometry of NGC 3603 (Harayama+, 2008)
J/ApJ/799/100 : Herschel FIR observations of NGC3603 (Di Cecco+, 2015)
Byte-by-byte Description of file: spec.dat
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Bytes Format Units Label Explanations
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1- 24 E24.18 um lambda Wavelength
26- 49 E24.18 --- Flux Flux in arbitrary units
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Acknowledgements:
Ciaran Rogers, rogers(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 05-Jun-2024