GALACTICNUCLEUS: A high-angular-resolution JHKs imaging survey of the Galactic centre III. Evidence for wavelength dependence of the extinction curve in the near-infrared

Abstract

The characterisation of the extinction curve in the near infrared (NIR) is fundamental to analyse the structure and stellar population of the Galactic centre (GC), whose analysis is hampered by the extreme interstellar extinction ($A_V\sim 30$ mag) that varies on arc-second scales. Recent studies indicate that the behaviour of the extinction curve might be more complex than previously assumed, pointing towards a variation of the extinction curve as a function of wavelength. We aim at analysing the variations of the extinction index, $\alpha$, with wavelength, line-of-sight, and absolute extinction, extending previous analysis to a larger area of the innermost regions of the Galaxy. We analysed the whole GALACTICNUCLEUS survey, a high-angular resolution ($\sim 0.2^{\prime \prime }$) $JH{K}_s$ NIR survey specially designed to observe the GC in unprecedented detail. It covers a region of $\sim 6000$\,pc${}^2$, comprising fields in the nuclear stellar disc, the inner bulge, and the transition region between them. We applied two independent methods based on red clump (RC) stars to constrain the extinction curve and analysed its variation superseding previous studies. We used more than 165,000 RC stars and increased significantly the size of the regions analysed to confirm that the extinction curve varies with the wavelength. We estimated a difference $\Delta \alpha =0.21\pm 0.07$ between the obtained extinction indices, ${\alpha }_{JH}=2.44\pm 0.05$ and ${\alpha }_{H{K}_s}=2.23\pm 0.05$. We also concluded that there is no significant variation of the extinction curve with wavelength, with the line-of-sight or the absolute extinction. Finally, we computed the ratios between extinctions, $A_J/A_H=1.87\pm 0.03$ and $A_H/A_{K_s}=1.84\pm 0.03$, consistent with all the regions of the GALACTICNUCLEUS catalogue.

10 pages, 8 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (8)

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• The complex, variable near infrared extinction towards the Nuclear Bulge
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Cited by in corpus (10)

• GALACTICNUCLEUS: A high-angular-resolution $JH{K}_s$ imaging survey of the Galactic centre. IV. Extinction maps and de-reddened photometry
• The nuclear star cluster and nuclear stellar disc of the Milky Way: Different stellar population and star formation history
• Distance to three molecular clouds in the central molecular zone
• Evidence of an age gradient along the line of sight in the nuclear stellar disc of the Milky Way
• Kinematic data rebuild the Nuclear star cluster as the most metal rich region of the Galaxy
• Radio observations of massive stars in the Galactic centre: The Arches Cluster
• The Arches cluster revisited: IV. Observational constraints on the binary properties of very massive stars
• A new distance to the Brick, the dense molecular cloud G0.253+0.016
• Detecting hot stars in the Galactic centre with combined near- and mid-infrared photometry
• Distance and extinction to the Milky Way spiral arms along the Galactic centre line of sight