Extinction law in the range 0.4-4.8 $\mu$m and the 8620 $\mathring{A}$ DIB towards the stellar cluster Westerlund 1

Abstract

The young stellar cluster Westerlund 1 (Wd 1: $l$=339.6${}^{\circ }$, b=$-$0.4${}^{\circ }$) is one of the most massive in the local Universe, but accurate parameters are pending on better determination of its extinction and distance. Based on our photometry and data collected from other sources, we have derived a reddening law for the cluster line-of-sight representative of the Galactic Plane (-5${}^{\circ }<$b$<$+5${}^{\circ }$) in the window 0.4-4.8 $\mu$m: The power law exponent $\alpha$=2.13$\pm$0.08 is much steeper than those published a decade ago (1.6-1.8) and our index $R_V$=2.50$\pm$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 $A_{Ks}$=0.74$\pm$0.08 ($A_V$=11.40$\pm$ 2.40) is substantially smaller than previous results(0.91-1.13), part of which ($A_{Ks}$=0.63 or $A_V$=9.66) is from the ISM. The extinction in front of the cluster spans a range of $\Delta A_V\sim$8.7\,mag 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 $\mathring{A}$ (the "GAIA DIB") for Wd 1 cluster members and derived the relation $A_{Ks}$=0.612 $EW$ $-$ 0.191 $E{W}^2$. This extends the Munari et al. (2008) relation, valid for $E_{B-V}$ $<$ 1, to the non-linear regime ($A_V$ $>$ 4).

arXiv commentto appear in MNRAS, 16 pages, 22 figures

References in corpus (37)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• Correcting for the Effects of Interstellar Extinction
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• The Wavelength Dependence of Interstellar Extinction from 1.25 to 8.0 microns Using GLIMPSE Data
• An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-Through-UV Curve Morphology
• Hi-GAL: the Herschel infrared Galactic Plane Survey
• Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
• Infrared Extinction Toward Nearby Star-Forming Regions
• Interstellar Extinction Law toward the Galactic Center III: J, H, Ks bands in the 2MASS and the MKO systems, and 3.6, 4.5, 5.8, 8.0 micron in the Spitzer/IRAC system
• On the massive stellar population of the Super Star Cluster Westerlund 1
• Line derived infrared extinction towards the Galactic Center
• Interstellar Extinction Law in the J, H, and Ks Bands toward the Galactic Center
• Galactocentric Distance With the OGLE and Hipparcos Red Clump Stars
• The Optical-Infrared Extinction Curve and its Variation in the Milky Way
• Modelling the Galactic Bar Using Red Clump Giants
• A census of the Wolf-Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy
• Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands
• An Analysis of the Shapes of Interstellar Extinction Curves. VI. The Near-IR Extinction Law
• Interstellar Extinction Curve Variations Toward the Inner Milky Way: A Challenge to Observational Cosmology
• Extinction Map of the Galactic center: OGLE-II Galactic bulge fields
• The population of OB supergiants in the starburst cluster Westerlund 1
• Lifting the Dusty Veil II: A Large-Scale Study of the Galactic Infrared Extinction Law
• The Slope of the Near Infrared Extinction Law
• Mass segregation and elongation of the starburst cluster Westerlund 1
• Diffuse interstellar bands in RAVE Survey spectra
• The Starburst Cluster Westerlund 1: The Initial Mass Function and Mass Segregation
• The complex, variable near infrared extinction towards the Nuclear Bulge
• Clump Distance to the Magellanic Clouds and Anomalous Colors in the Galactic Bulge
• A VLT/FLAMES survey for massive binaries in Westerlund 1: I. first observations of luminous evolved stars
• Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1
• Radio emission from the massive stars in the Galactic Super Star Cluster Westerlund 1
• A large scale extinction map of the Galactic Anticenter from 2MASS
• Variations of the Selective Extinction Across the Galactic Bulge - Implications for the Galactic Bar
• A Near-Infrared Imaging Survey of Coalsack Globule 2
• The little-studied cluster Berkeley 90. II. The foreground ISM
• Marginal likelihoods of distances and extinctions to stars: computation and compact representation
• Infrared extinction in the Inner Milky Way through the red clump giants

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