Extinction ratios in the inner Galaxy as revealed by the VVV survey

Javier Alonso-García, Dante Minniti, Márcio Catelan, Rodrigo Contreras Ramos, Oscar A. Gonzalez, Maren Hempel, Philip W. Lucas, Roberto K. Saito, Elena Valenti, Manuela Zoccali

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Interstellar extinction towards the Galactic Center is large and significantly differential. Its reddening and dimming effects in red clump stars in the Galactic Bulge can be exploited to better constrain the extinction law towards the innermost Galaxy. By virtue of a deep and complete catalog of more than 30 million objets at $|l|\le2.7\deg$ and $|b|\le1.55\deg$ obtained from VVV survey observations, we apply the red clump method to infer the selective-to-total extinction ratios in the $Z$, $Y$, $J$, $H$ and $K_s$ broadband near-infrared filters. The measured values are smaller than previously reported, and are not constant, with mean values, e.g., $A_{K_S}/E(J-K_s)=0.428\pm0.005\pm0.04$ and $A_{K_S}/E(H-K_s)=1.104\pm0.022\pm0.2$. We also obtain a ratio $A_Z$:$A_Y$:$A_J$:$A_H$:$A_{K_S}$ of 7.74:5.38:3.30:1.88:1.0, implying extinction towards the Galactic Center to follow a distribution as a function of wavelength steeper than previously reported, consistent with a power law $A_{\lambda}\propto{\lambda}^{-2.47}$ in the near-infrared.
Original languageEnglish
Article numberL13
JournalAstrophysical Journal Letters
Issue number1
Early online date25 Oct 2017
Publication statusPublished - 1 Nov 2017


  • astro-ph.GA
  • astro-ph.SR


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