J/MNRAS/463/2653 8620 DIB equivalent width and extinction (Damineli+, 2016)
Extinction law in the range 0.4-4.8 micron and the 8620Å DIB towards the
stellar cluster Westerlund 1.
Damineli A., Almeida L.A., Blum R.D., Damineli D.S.C., Navarete F.,
Rubinho M.S., Teodoro M.
<Mon. Not. R. Astron. Soc. 463, 2653 (2016)>
=2016MNRAS.463.2653D 2016MNRAS.463.2653D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, photometry ; Photometry, CCD
Keywords: dust, extinction - ISM:lines and bands -
open clusters and associations: individual: Westerlund 1
Abstract:
The young stellar cluster Westerlund 1 (Wd 1: l=339.6, b=-0.4) is one
of the most massive in the local Universe, but accurate parameters are
pending on better determination of its extinction and distance. Based
on our photometry and data collected from other sources, we have
derived a reddening law for the cluster line-of-sight representative
of the Galactic plane (-5°<b<+5°) in the window 0.4-4.8um. The
power-law exponent alpha=2.13±0.08 is much steeper than those
published a decade ago (1.6-1.8) and our index RV=2.50±0.04 also
differs from them, but in very good agreement with recent works based
on deep surveys in the inner Galaxy. As a consequence, the total
extinction AKs=0.74±0.08 (AV=11.40±2.40) is substantially
smaller than previous results (0.91-1.13), part of which (AKs=0.63
or AV=9.66) is from the interstellar medium. The extinction in front
of the cluster spans a range of AV∼8.7 with a gradient increasing from
SW to NE across the cluster face, following the same general trend of
warm dust distribution. The map of the J-Ks colour index also shows a
trend of reddening in this direction. We measured the equivalent width
of the diffuse interstellar band at 8620 A (the 'GAIA DIB') for Wd 1
cluster members and derived the relation AKs=0.612EW-0.191EW2.
This extends the Munari et al. relation, valid for E(B-V)<1, to the
non-linear regime (AV>4).
Description:
Photometry in the optical, near-infrared and mid-infrared windows in a
10x10 arcmin field around the stellar cluster Westerlund 1 is analyzed
to derive an extinction law. Cluster members and Red Clump stars are
used,spanning a range of 17 magnitudes in Ks. Photometry in the
passbands were not simultaneous and span a period of about 6 years.
Since the sample comprises more than 24000 stars, variability is not
an important source of errors. Equivalent widths of the 8620Å DIB
in medium-high resolution spectra have been measured to extend its
relation to extinction larger than the regime it was shown to have a
linear behaviour.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 43 110 8620EW, AKs and AV for 110 stars
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See also:
J/A+AS/127/423 : VI photometry of Westerlund 1 and 2 (Piatti+ 1998)
J/AJ/133/2696 : BVRI light curves of Westerlund 1 stars (Bonanos, 2007)
J/A+A/477/147 : X-ray sources in Westerlund 1 (Clark+, 2008)
J/AJ/145/46 : UBVIc photometry in Westerlund 1 (Lim+, 2013)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Name of the star
14- 18 F5.3 0.1nm EW8620 ? Equivalent width of the 8620Å DIB
20- 23 F4.2 mag AKs Extinction in the AKs band
25- 29 F5.2 mag AV ? Extinction in the AV band
31- 42 A12 --- Observ Observatory/program/note
43 A1 --- Flag [*] Excess emission (1)
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Note (1): * indicates contamination by hot dust.
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Acknowledgements:
Augusto Damineli, augusto.damineli(at)iag.usp.br
(End) Augusto Damineli [IAGUSP, Brazil], Patricia Vannier [CDS] 03-Nov-2016