From the Sun, a look at the edge of each spiral arm in our Milky Way (seen tangentially, along the line of sight) can yield numerous insights. Using different arm tracers (dust, masers, synchrotron emission, CO gas, open star clusters), we observe here for the first time an age gradient (about 12 ± 2 Myrs/kpc), much as predicted by the density wave theory. This implies that the arm tracers are leaving the dust lane at a relative speed of about 81 ± 10 km/s. We then compare with recent optical data obtained from the Gaia satellite, pertaining to the spiral arms.
KeywordsAstrophysicsGalaxyMilky WaySpiral Arms
Kounkel, M., Covey, K. and Stassun, K. (2020) Untangling the Galaxy: II. Structure within 3 kpc. Astronomical Journal, 160, Article No. 279. https://doi.org/10.3847/1538-3881/abc0e6
Khoperskov, S., Gerhard, O., Di Matteo, P., Haywood, M., Katz, D., Khrapov, S., et al. (2020) Hic Sunt Dracones: Cartography of the Milky Way Spiral Arms and Bar Resonances with Gaia Data Release 2. Astronomy & Astrophysics, 634, Article No. L8. https://doi.org/10.1051/0004-6361/201936645
Cantat-Gaudin, T., Anders, F., Castro-Ginard, A., Jordi, C., Romero-Gómez, M., Soubiran, C., et al. (2020) Painting a Portrait of the Galactic Disk with Its Stellar clusters. Astronomy & Astrophysics, 640, Article No. A1. https://doi.org/10.1051/0004-6361/202038192
Vallée, J.P. (2005) The Spiral Arms and Interarm Separation of the Milky Way: An Updated Statistical Study. Astronomical Journal, 130, 569-575. https://doi.org/10.1086/431744
Abuter, R., Amorim, A., Bauböck, M., Berge, J.P., Bonnet, H., Brandner, W., et al. (2019) A Geometric Distance Measurement to the Galactic Center Black Hole with 0.3% Uncertainty. Astronomy & Astrophysics, 625, Article No. L10. https://doi.org/10.1051/0004-6361/201935656
Vallée, J.P. (2015) Different Studies of the Global Pitch Angle of the Milky Way’s Spiral Arms. Monthly Notices of the Royal Astronomical Society, 450, 4277-4284. https://doi.org/10.1093/mnras/stv862
Vallée, J.P. (2017) The Norma Spiral Arm: Large-Scale Pitch Angle. Astrophysics and Space Science, 362, Article No. 173. https://doi.org/10.1007/s10509-017-3145-5
Vallée, J.P. (2016) The Start of the Sagittarius Spiral Arm (Sagittarius Origin) and the Start of the Norma Spiral Arm (Norma Origin): Model-Computed and Observed Arm Tangents at Galactic Longitudes -20° https://doi.org/10.3847/0004-6256/151/3/55
Vallée, J.P. (2017) A Guided Map to the Spiral Arms in the Galactic Disk of the Milky Way. Astronomical Review, 13, 113-146. https://doi.org/10.1080/21672857.2017.1379459
Drimmel, R. and Poggio, E. (2018) On the Solar Velocity. Research Notes AAS, 2, Article No. 210. https://doi.org/10.3847/2515-5172/aaef8b
Vallée, J.P. (2021) A Low Density Wave’s Spiral Pattern Speed, from the Tracer Separations (Age Gradient) across a Spiral Arm in the Milky Way. Monthly Notices of the Royal Astronomical Society, 506, 523-530. https://doi.org/10.1093/mnras/stab1679
Nitschai, M.S., Eilers, A.-C., Neumayer, N., Cappellari, M. and Rix, H.-W. (2021) Dynamical Model of the Milky Way Using APOGEE and Gaia Data. Astrophysical Journal, 916, Article No. 112. https://doi.org/10.3847/1538-4357/ac04b5
Gilmore, G. (2018) Gaia: 3-Dimensional Census of the Milky Way Galaxy. Contem-porary Physics, 59, 155-173. https://doi.org/10.1080/00107514.2018.1439700
Xu, Y., Liu, C., Tian, H., Newberg, H.J., Laporte, C.F.P., Zhang, B., et al. (2020) Exploring the Perturbed Milky Way Disk and the Substructures of the Outer Disk. Astrophysical Journal, 905, Article No. 6. https://doi.org/10.3847/1538-4357/abc2cb
Bennett, M. and Bovy, J. (2021) Did Sgr Cause the Vertical Waves in the Solar Neighbourhood? Monthly Notices of the Royal Astronomical Society, 503, 376-393. https://doi.org/10.1093/mnras/stab524
Petersen, M. and Penarrubia, J. (2021) Detection of the Milky Way Reflex Motion Due to the Large Magellanic Cloud Infall. Nature Astronomy, 5, 251-255. https://doi.org/10.1038/s41550-020-01254-3
Li, H. and Widrow, L. (2021) The Stellar Distribution Function and Local Vertical Potential from Gaia DR2. Monthly Notices of the Royal Astronomical Society, 503, 1586-1598. https://doi.org/10.1093/mnras/stab574
Sysoliatina, K. and Just, A. (2021) Towards a Fully Consistent Milky Way Disk Model: IV. The Impact of GAIA DR2 and APOGEE. Astronomy & Astrophysics, 647, Article No. A39. https://doi.org/10.1051/0004-6361/202038840
Bland-Hawthorn, J. and Tepper-Garcia, T. (2021) Galactic Seismology: The Evolving “Phase Spiral” after the Sagittarius Dwarf Impact. Monthly Notices of the Royal Astronomical Society, 504, 3168-3186. https://doi.org/10.1093/mnras/stab704
Katz, D., Antoja, T., Romero-Gomez, M., Drimmel, R., Reylé, C., Seabroke, G.M., et al. (2018) Gaia Data Release 2. Mapping the Milky Way Disk Kinematics. Astronomy & Astrophysics, 616, Article No. A11. https://doi.org/10.1051/0004-6361/201832865
Lopez-Corredoira, M., Garzon, F., Wang, H.-F., Sylos Labini, F., Nagy, R., Chrobáková, Ž., et al. (2020) Gaia-DR2 Extended Kinematical Maps. Part II: Dynamics in the Galactic Disk Explaining Radial and Vertical Velocities. Astronomy & Astrophysics, 634, Article No. A66. https://doi.org/10.1051/0004-6361/201936711
Antoja, T., Helmi, A., Romero-Gomez, M., Katz, D., Babusiaux, C., Drimmel, R., et al. (2018) A Dynamically Young and Perturbed Milky Way Disk. Nature, 561, 360-362. https://doi.org/10.1038/s41586-018-0510-7
Laporte, C., Minchev, I., Johnston, K. and Gomez, F. (2019) Footprints of the Sagittarius Dwarf Galaxy in the Gaia Data Set. Monthly Notices of the Royal Astronomical Society, 485, 3134-3152. https://doi.org/10.1093/mnras/stz583
Bland-Hawthorn, J., Sharma, S., Tepper-Garcia, T., Binney, J., Freeman, K.C., Hayden, M.R., et al. (2018) The GALAH Survey and Gaia DR2: Dissecting the Stellar Disc’s Phase Space by Age, Action, Chemistry and Location. Monthly Notices of the Royal Astronomical Society, 486, 1167-1191. https://doi.org/10.1093/mnras/stz217
Ibata, R., Gilmore, G. and Irwin, M.J. (1994) A Dwarf Satellite Galaxy in Sagittarius. Nature, 370, 194-196. https://doi.org/10.1038/370194a0
Vallée, J.P. (2018) Meta-Analysis from Different Tracers of the Small Local Arm around the Sun—Extent, Shape, Pitch, Origin. Astrophysics and Space Science volume, 363, Article No. 243. https://doi.org/10.1007/s10509-018-3463-2
Anders, F., Cantat-Gaudin, T., Quadrino-Lodoso, I., Gieles, M., Jordi, C., Castro-Ginard, A., et al. (2021) The Star Cluster Age Function in the Galacticdisk with Gaia DR2. Astronomy & Astrophysics, 645, Article No. L2. https://doi.org/10.1051/0004-6361/202038532
Poggio, E., Drimmel, R., Cantat-Gaudin, T., Ramos, P., Ripepi, V., Zari, E., et al. (2021) Galactic Spiral Structure Revealed by GAIA EDR3. Astronomy & Astrophysics, 651, Article No. L104. https://doi.org/10.1051/0004-6361/202140687
Vallée, J.P. (2002) Metastudy of the Spiral Structure of Our Home Galaxy. Astrophysical Journal, 566, 261-266. https://doi.org/10.1086/337988
Vallée, J.P. (2020) Statistics on 24 Spiral Galaxies, Having Different Observed Arm Locations, Using Different Arm Tracers. New Astronomy, 76, Article ID: 101337. https://doi.org/10.1016/j.newast.2019.101337
Dobbs, C. and Baba, J. (2014). Dawes Review 4: Spiral Structures in Disk Galaxies. Publications of the Astronomical Society of Australia, 31, Article No. e035. https://doi.org/10.1017/pasa.2014.31
Pettitt, A., Dobbs, C., Baba, J., Colombo, D., Duarte-Cabral, A., Egusa, F., et al. (2020) How Do Different Spiral Arm Models Impact the ISM and GMC Population? Monthly Notices of the Royal Astronomical Society, 498, 1159-1174. https://doi.org/10.1093/mnras/staa2242
Shu, F.H. (2016) Six Decades of Spiral Density Wave Theory. Annual Review of Astronomy and Astrophysics, 54, 667-724. https://doi.org/10.1146/annurev-astro-081915-023426
Roberts, W.W. (1975) Theoretical Aspects of Galactic Research. Vistas in Astronomy, 19, 91-109. https://doi.org/10.1016/0083-6656(75)90008-2
Lin, C.C. and Shu, F.H. (1964) On the Spiral Structure of Disk Galaxies. Astrophysical Journal, 140, 646-655. https://doi.org/10.1086/147955
Gittins, D.M. and Clarke, C.J. (2004) Constraining Corotation from Shocks in Tightly Wound Spiral Galaxies. Monthly Notices of the Royal Astronomical Society, 349, 909-921. https://doi.org/10.1111/j.1365-2966.2004.07560.x
Vallée, J.P. (2014) The Spiral Arms of the Milky Way: The Relative Location of Each Different Arm Tracer, within a Typical Spiral Arm Width. Astronomical Journal, 148, Article No. 5. https://doi.org/10.1088/0004-6256/148/1/5
Vallée, J.P. (2017) Recent Advances in the Determination of Some Galactic Constants in the Milky Way. Astrophysics and Space Science, 362, Article No. 79. https://doi.org/10.1007/s10509-017-3058-3