Gaia-DR2 distance to the W3 Complex in the Perseus Arm

Abstract

The Perseus Arm is the closest Galactic spiral arm from the Sun, offering an excellent opportunity to study in detail its stellar population. However, its distance has been controversial with discrepancies by a factor of two. Kinematic distances are in the range 3.9-4.2 kpc as compared to 1.9-2.3 kpc from spectrophotometric and trigonometric parallaxes, reinforcing previous claims that this arm exhibits peculiar velocities. We used the astrometric information of a sample of 31 OB stars from the star-forming W3 Complex to identify another 37 W3 members and to derive its distance from their Gaia-DR2 parallaxes with improved accuracy. The Gaia-DR2 distance to the W3 Complex,2.14${}_{-0.07}^{+0.08}$ kpc, coincides with the previous stellar distances of $\sim$ 2 kpc. The Gaia-DR2 parallaxes tentatively show differential distances for different parts of the W3 Complex: W3 Main, located to the NE direction, is at 2.30${}_{-0.16}^{+0.19}$ kpc, the W3 Cluster (IC 1795), in the central region of the complex, is at 2.17${}_{-0.11}^{+0.12}$ kpc, and W3(OH) is at 2.00${}_{-0.23}^{+0.29}$ kpc to the SW direction. The W3 Cluster is the oldest region, indicating that it triggered the formation of the other two star-forming regions located at the edges of an expanding shell around the cluster.

14 pages, 8 figures, accepted for publication in Monthly Notes of the Royal Astronomical Society in May 21th, 2019

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• Interaction between the Supernova Remnant HB 3 and the Nearby Star-Forming Region W3
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• Hunting for the elusive methylene radical
• A Multi-Epoch Study of Radio Continuum Emission from MassiveProtostars
• The Detection of Deuterated Water in the Large Magellanic Cloud with ALMA
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• Evolution of magnetized hub-filament systems: Comparing the observed properties of W3(OH), W3 Main, and S 106
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• SOFIA Polarization Spectrum of Three Star-Forming Clouds
• Measurement of Cosmic-Ray Density in the Spiral Arms toward Galactic Anticenter
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