The Galactic Center in Color: Measuring Extinction with High-Proper-Motion Stars

Abstract

The Milky Way's central parsec is a highly extinguished region with a population of high-proper-motion stars. We have tracked 145 stars for $\sim$10 years at wavelengths between 1 and 4 microns to analyze extinction effects in color-magnitude space. Approximately $30\%$ of this sample dims and reddens over the course of years, likely from the motion of sources relative to an inhomogeneous screen of dust. We correct previous measurements of the intrinsic variability fraction for differential extinction effects, resulting in a reduced stellar variability fraction of $34\%$. The extinction variability sub-sample shows that the extinguishing material has sub-arcsecond scales, much smaller variations than previously reported. The observed extinction events imply a typical cross-section of 500 AU and a density of around $3\times 10^{4}atoms/c{\mathrm{m}}^3$ for the extinguishing material, which are consistent with measurements of filamentary dust and gas at the Galactic Center. Furthermore, given that the stars showing extinction variability tend to be more highly reddened than the rest of the sample, the extinction changes are likely due to material localized to the Galactic Center region. We estimate the relative extinction between 1 and 4 microns as, ${\mathrm{A}}_{\mathrm{H}}:{\mathrm{A}}_{{\mathrm{K}}^{\prime }}:{\mathrm{A}}_{{\mathrm{L}}^{\prime }}=1.67\pm 0.05:1:0.69\pm 0.03$. Our measurement of extinction at longer wavelengths -- L' (3.8 $\mu$m) -- is inconsistent with recent estimations of the integrated extinction towards the central parsec. One interpretation of this difference is that the dust variations this experiment is sensitive to -- which are local to the Galactic Center -- are dominated by grains of larger radius than the foreground.

49 pages, 30 figures, accepted for publication in The Astronomical Journal

References in corpus (15)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function
• First proper motions of thin dust filaments at the Galactic Center
• SPISEA: A Python-Based Simple Stellar Population Synthesis Code for Star Clusters
• The Post-Periapse Evolution of Galactic Center Source G1: The second case of a resolved tidal interaction with a supermassive black hole
• Revisiting the Impact of Dust Production from Carbon-Rich Wolf-Rayet Binaries
• The Galactic Center: An Improved Astrometric Reference Frame for Stellar Orbits around the Supermassive Black Hole
• The Galactic Center: Improved Relative Astrometry for Velocities, Accelerations, and Orbits near the Supermassive Black Hole
• Variable dust emission by WC type Wolf-Rayet stars observed in the NEOWISE-R survey
• Colliding Winds in and around the Stellar Group IRS 13E at the Galactic Center
• The Swansong of the Galactic Center Source X7: An Extreme Example of Tidal Evolution near the Supermassive Black Hole
• Mid-infrared extinction and fresh silicate dust towards the Galactic Center
• Tidal Distortion of the Envelope of an AGB Star IRS 3 near Sgr A*

Cited by in corpus (2)

• Mid-infrared extinction toward the Galactic center
• RR Lyrae stars with variable mean magnitudes