Using classical Cepheids to study the far side of the Milky Way disk. II. The spiral structure in the first and fourth Galactic quadrants

Abstract

In an effort to improve our understanding of the spiral arm structure of the Milky Way, we use Classical Cepheids (CCs) to increase the number of young tracers on the far side of the Galactic disk with accurately determined distances. We use a sample of 30 CCs, discovered using near-infrared photometry from the VISTA Variables in the Vía Láctea survey (VVV) and classified based on their radial velocities and metallicities. We combine them with another 20 CCs from the literature for which VVV photometry is available. The compiled sample of CCs with homogeneously computed distances based on VVV infrared photometry was employed as a proof of concept to trace the spiral structure in the poorly explored far side of the disk. Although the use of CCs has some caveats, these variables are currently the only available young tracers in the far side disk for which a numerous sample with accurate distances can be obtained. Therefore, a larger sample could allow us to make a significant step forward in our understanding of the Milky Way disk as a whole. We present preliminary evidence that CCs favor: a spiral arm model with two main arms (Perseus and Scutum-Centaurus) branching out into four arms at galactocentric distances, $R_{\mathrm{GC}}\gtrsim 5-6\mathrm{kpc}$; the extension of the Scutum-Centaurus arm behind the Galactic center; a possible connection between the Perseus arm and the Norma tangency direction. The current sample of CCs in the far side of the Galaxy are in the mid-plane, arguing against the presence of a severely warped disk at small Galactocentric distances ($R_{\mathrm{GC}}\lesssim 12\mathrm{kpc}$) in the studied area. The discovery and characterization of CCs at near-IR wavelengths appears to be a promising tool to complement studies based on other spiral arm tracers and extend them to the far side of our Galaxy.

10 pages, 6 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (21)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• Dawes Review 4: Spiral Structures in Disc Galaxies
• On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk
• Dark matter in the Milky Way, II. the HI gas distribution as a tracer of the gravitational potential
• The VMC Survey. XXV. The 3D structure of the Small Magellanic Cloud from Classical Cepheids
• The local spiral structure of the Milky Way
• A Possible Extension of the Scutum-Centaurus Arm into the Outer Second Quadrant
• Mapping Spiral Structure on the far side of the Milky Way
• The spiral pattern rotation speed of the Galaxy and the corotation radius with GAIA DR2
• Cepheid Variables in the Flared Outer Disk of our Galaxy
• The panchromatic view of the Magellanic Clouds from Classical Cepheids. I. Distance, Reddening and Geometry of the Large Magellanic Cloud disk
• The Galactic spiral structure as revealed by O- and early B-type stars
• Tracing the Spiral Structure of the Outer Milky Way with Dense Atomic Hydrogen Gas
• Constraining Dust Extinction Properties via the VVV Survey
• Using classical Cepheids to study the far side of the Milky Way disk: I. Spectroscopic classification and the metallicity gradient
• Constraining the pitch angle of the Galactic spiral arms in the Milky Way
• Parallaxes for star forming regions in the inner Perseus spiral arm
• Young stars as tracers of a barred-spiral Milky Way
• Updated theoretical Period-Age and Period-Age-Color relations for Galactic Classical Cepheids: an application to the Gaia DR2 sample
• VVV WIN 1733$-$3349: a low extinction window to probe the far side of the Milky Way bulge

Cited by in corpus (8)

• What Does the Milky Way Look Like?
• Tracing the Milky Way warp and spiral arms with classical Cepheids
• A new and homogeneous metallicity scale for Galactic classical Cepheids II. The abundance of iron and alpha elements
• Open clusters housing classical Cepheids in Gaia DR3
• Constraints on the history of Galactic spiral arms revealed by Gaia GSP-Spec alpha-elements
• The Observed Age Gradient in the Milky Way -- as a Test for theories of spiral arm structure
• Unveiling VVV/WISE Mira variables on the far side of the Galactic disk: Distances, kinematics and a new extinction law
• Modeling the vertical distribution of the Milky Way's flat subsystem objects