Volume 653, September 2021
|Number of page(s)||15|
|Section||Galactic structure, stellar clusters and populations|
|Published online||03 September 2021|
Distance and extinction to the Milky Way spiral arms along the Galactic centre line of sight
Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
2 Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
Accepted: 28 May 2021
Context. The position of the Sun inside the disc of the Milky Way significantly hampers the study of the spiral arm structure given the high amount of dust and gas along the line of sight, and the overall structure of this disc has therefore not yet been fully characterised.
Aims. We aim to analyse the spiral arms in the line of sight towards the Galactic centre (GC) in order to determine their distance, extinction, and stellar population.
Methods. We use the GALACTICNUCLEUS survey, a JHKs high-angular-resolution photometric catalogue (0.2″) for the innermost regions of the Galaxy. We fitted simple synthetic colour-magnitude models to our data via χ2 minimisation. We computed the distance and extinction to the detected spiral arms. We also analysed the extinction curve and the relative extinction between the detected features. Finally, we studied extinction-corrected Ks luminosity functions (KLFs) to study the stellar populations present in the second and third spiral arm features.
Results. We determined the mean distances to the spiral arms: d1 = 1.6 ± 0.2 kpc, d2 = 2.6 ± 0.2 kpc, d3 = 3.9 ± 0.3 kpc, and d4 = 4.5 ± 0.2 kpc, and the mean extinctions: AH1 = 0.35 ± 0.08 mag, AH2 = 0.77 ± 0.08 mag, AH3 = 1.68 ± 0.08 mag, and AH4 = 2.30 ± 0.08 mag. We analysed the extinction curve in the near-infrared for the stars in the spiral arms and find mean values of AJ/AH = 1.89 ± 0.11 and AH/AKs = 1.86 ± 0.11, in agreement with the results obtained for the GC. This implies that the shape of the extinction curve does not depend on distance or absolute extinction. We also built extinction maps for each spiral arm and find them to be homogeneous and that they might correspond to independent extinction layers. Finally, analysing the KLFs from the second and third spiral arms, we find that they have similar stellar populations. We obtain two main episodes of star formation: > 6 Gyr (∼60 − 70% of the stellar mass), and 1.5 − 4 Gyr (∼20 − 30% of the stellar mass), compatible with previous work. We also detect recent star formation at a lower level (∼10%) for the third spiral arm.
Key words: Galaxy: disk / Galaxy: center / Galaxy: structure / dust / extinction / stars: formation
© F. Nogueras-Lara et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.