A low density wave's spiral pattern speed, from the tracer separations (age gradient) across a spiral arm in the Milky Way

Vallée, J. P.

doi:10.1093/mnras/stab1679

Cited by 10 publications

(4 citation statements)

References 43 publications

(24 reference statements)

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“…This value of 152 km/s is the linear pattern speed of the density wave, which applies at the solar orbit, so the required angular pattern speed is 152/ 8.1 = 18.8 km/s/kpc.. Near a Galactic radius of 8.1 kpc, that angular pattern speed value near 19 km/s/kpc is in the range suggested by various authors, e.g. [20], and implies a galactic co-rotation radius of 233/18.8 = 12.4 ±1 kpc.…”

Section: Figure 3 a Typical Cross-section Of A Spiral Arm Running Ove...mentioning

confidence: 65%

Kinematic Structure of the Milky Way Galaxy, Near the Spiral Arm Tangents

Vallée¹

2022

IJAA

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We compare the observed radial velocity of different arm tracers, taken near the tangent to a spiral arm. A slight difference is predicted by the density wave theory, given the shock predicted at the entrance to the inner spiral arm. In many of these spiral arms, the observed velocity offset confirms the prediction of the density wave theory (with a separation between the maser velocity and the CO gas peak velocity, of about 20 km/s)-when the observed offset is bigger than the error estimates.

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Section: Figure 3 a Typical Cross-section Of A Spiral Arm Running Ove...mentioning

confidence: 65%

Kinematic Structure of the Milky Way Galaxy, Near the Spiral Arm Tangents

Vallée¹

2022

IJAA

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“…Another important application of the results obtained relates to our own Galaxy. Shaviv (2003) summarised the Ω p measurements for MW in their Table 3, where the measurements are clearly concentrated in two sets with average about 22-26 km/s/kpc and 14 km/s/kpc (see also Bobylev & Bajkova 2022;Vallée 2021;Naoz & Shaviv 2007). Given that RC of Galaxy to a first approximation is flat here (Russeil et al 2017), we obtained ≈ 1.7, namely, MW show signs of the ongoing coupling between patterns as found in Font et al (2014).…”

Section: Discussion Additional Notes and Conclusionmentioning

confidence: 65%

Resonance coupling in spiral arms

Marchuk

2024

A&A

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To address questions about the physical nature and origin of spiral arms in galaxies, it is necessary to measure their dynamical properties, such as the angular speed, $ p $, or the corotation radius. Observations suggest that galaxies may contain several independent spiral patterns simultaneously. It was shown that so-called non-linear resonance coupling plays an important role in such systems. We aim to identify cases of independent spiral patterns for galaxies with a flat rotation curve and to investigate what relative pattern velocities, $ out p in p $, they might have for all possible cases of coupling between the main resonances. We solved equations for the main resonance positions (1:1, 2:1, 4:1) and estimated the ratio upvarpi of the corotation radii for two subsequent patterns. For six close galaxies with flat rotation curves, we collected the measurements of the corotation radii in the literature, using at least three different methods in each case for credibility. We found at least two independent spiral patterns for each galaxy and measured the upvarpi ratios. We found upvarpi ratios for all possible cases for the main resonances. For three cases, we obtained $ indicating that it would be difficult to fit two or even more spiral patterns in the disc. These ratios have been used to derive the wind-up time for spirals, estimated to be several galactic rotations. We find that three pairs of coupling cases, including those that have been vastly acknowledged in galaxies, namely, $ OLR_ in =CR_ out CR_ in =IUHR_ out $, have very close upvarpi ratios; hence, they ought to be found simultaneously, as observed. We find a strongly confirmed apparent resonance coupling for six galaxies and we show that the observed upvarpi is in agreement with theory. In two of them, we identified a previously unreported form of simultaneous coupling, namely, $ OLR_ in =OUHR_ out OUHR_ in =CR_ out $. This result was also predicted from the proximity of upvarpi .

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“…At the Sun's location, this represents an "angular velocity" for the material (gas and stars) of about 28.8 km/s/kpc (=233/8.1). This value is different than the spiral pattern speed, nearer 17 km/s/kpc [11]. Observations show that the gas and stars move at the same speed, in their roughly circular orbit, around the Galactic Center.…”

Section: Velocity/kinematical Mapping the Galactic Diskmentioning

confidence: 67%

“…At what angular speed does the "spiral pattern" rotate? Various variants of the density wave theory put it between 15 and 20 km/s/kpc (Table 2 in [38]), Vallée [11]). Multiplying by the Sun's distance to the Galactic Center, one finds its linear velocity to be about 145 km/sec.…”

Section: Theories On Sustained Spiral Structurementioning

confidence: 99%

Arm Tangents and the Spiral Structure of the Milky Way—The Age Gradient

Vallée¹

2021

IJAA

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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.

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A low density wave's spiral pattern speed, from the tracer separations (age gradient) across a spiral arm in the Milky Way

Cited by 10 publications

References 43 publications

Kinematic Structure of the Milky Way Galaxy, Near the Spiral Arm Tangents

Kinematic Structure of the Milky Way Galaxy, Near the Spiral Arm Tangents

Resonance coupling in spiral arms

Arm Tangents and the Spiral Structure of the Milky Way—The Age Gradient

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