Photometric distances to young stars in the inner Galactic disk. I. The L = 314${}^o$ direction

Abstract

The spiral structure of the Milky Way is nowadays receiving renewed attention thanks to the combined efforts of observational campaigns in different wavelength regimes, from the optical to the radio. We start in the paper the exploration of a number of key sectors in the inner Milky Way, where the spiral structure is still poorly known. We search for density enhancements of young stars that might plausibly be associated with spiral structure. To this aim we collect sufficiently wide-field UBVI photometry. The intensive usage of U-band photometry ensures robust determination of reddening and hence distance for stars of spectral type earlier than A0, which are well-known spiral arm tracers. The fields we use are large enough to include in most cases well-studied Galactic clusters, which we use as bench-marks to assess the quality and standardisation of the data, and to validate our method. We focus in this paper on the line of sight to the Galactic longitude l= 314${}^o$. First of all, we made exhaustive tests to show that our data-set is in the standard system, and calibrated our method using the two open clusters NGC 5617 and Pismis 19 which happen to be in the field, and for which we found estimates of the basic parameters in full agreement with the literature. We then applied the method to the general field stars and detected signatures of three different groups of stars, evenly distributed across the field of view, at 1.5${}_{-0.2}^{+0.5}$, 2.5${}_{-0.5}^{+0.3}$, and 5.1${}_{-1.1}^{+1.5}$ kpc, respectively. These distances are compatible with the location of the nowadays commonly accepted description of the Carina-Sagittarius and Scutum-Crux arms, at heliocentric distance of $\sim$ 2 an 5 kpc,

23 pages, 13 eps figure, in press in Astronomy and Astrophysics

References in corpus (6)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• Water maser motions in W3(OH) and a determination of its distance
• Spiral structure in the outer Galactic disk. I. The Third Galactic Quadrant
• Spiral structure of the Third Galactic Quadrant and the solution to the Canis Major debate
• The population in the background of open clusters: Tracer of the Norma-Cygnus arm
• Searching for spiral features in the outer Galactic disk. The field towards WR38 and WR38a

Cited by in corpus (7)

• The Skeleton of the Milky Way
• Binary open clusters in the Milky Way: photometric and spectroscopic analysis of NGC 5617 and Trumpler 22
• The thickening of the thin disk in the third Galactic quadrant
• Anchors for the Cosmic Distance Scale: the Cepheid QZ Normae in the Open Cluster NGC 6067
• Strengthening the Open Cluster Distance Scale via VVV Photometry
• A new look at Sco OB1 association with Gaia DR2
• Photometric distances to young stars in the inner galactic disk