Interarm islands in the Milky Way – the one near the Cygnus spiral arm

Vallée, J. P.

doi:10.1093/mnras/staa758

Cited by 6 publications

(3 citation statements)

References 68 publications

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“…With NIR deep imaging, we identified one cluster in each region, having 73 and 89 cluster members in S207 and S208, respectively, with a mass detection limit of 0.1 M ⊙ for S207 and ∼0.2 M ⊙ for S208. From the K-band luminosity function (KLF) fitting of the clusters, S207 and S208 are likely to be located at D = 4 kpc from the Sun, which suggests that two regions are located in the interarm region between the Cygnus and Perseus arms (Vallée 2020). The fitting also suggested that S207 is at the end of the embedded cluster phase (∼2-3 Myr), while the S208 cluster is very young (∼0.5 Myr).…”

Section: Introductionmentioning

confidence: 95%

Low-metallicity Young Clusters in the Outer Galaxy. III. Sh 2-127

Yasui

Kobayashi

Saito

et al. 2021

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In deep near-infrared imaging of the low-metallicity ([O/H] = −0.7 dex) H II region Sh 2-127 (S127) with Subaru/MOIRCS, we detected two young clusters with 413 members (S127A) in a slightly extended H II region and another with 338 members (S127B) in a compact H II region. The limiting magnitude was K = 21.3 mag (10σ), corresponding to a mass detection limit of ∼0.2 M ⊙ . These clusters are an order of magnitude larger than previously studied young low-metallicity clusters and larger than the majority of solar neighborhood young clusters. Fits to the K-band luminosity functions indicate very young cluster ages of 0.5 Myr for S127A and 0.1-0.5 Myr for S127B, consistent with the large extinction (up to A V ≃ 20 mag) from thick molecular clouds and the presence of a compact H II region and class I source candidates, and suggest that the initial mass function (IMF) of the low-metallicity clusters is indistinguishable from typical solar neighborhood IMFs. Disk fractions of 28% ± 3% for S127A and 40% ± 4% for S127B are significantly lower than those of similarly aged solar neighborhood clusters (∼50%-60%). The disk fraction for S127B is higher than those of previously studied low-metallicity clusters (<30 %), probably due to S127B's age. This suggests that a large fraction of very young stars in low-metallicity environments have disks, but the disks are lost on a very short timescale. These results are consistent with our previous studies of low-metallicity star-forming regions, suggesting that a solar neighborhood IMF and low disk fraction are typical characteristics for low-metallicity regions, regardless of cluster scales.

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Section: Introductionmentioning

confidence: 95%

Low-metallicity Young Clusters in the Outer Galaxy. III. Sh 2-127

Yasui

Kobayashi

Saito

et al. 2021

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“…The question of the possible bending of the Perseus arm is mentioned (Section 4 in [26] suggested 2 arms; in contrario, [27] suggested an interarm island near the Perseus arm). Also,the width of each spiral arm is thus not well defined in Gaia DR3; in contrario, a new multi-tracer approach for defining the spiral arm width was advocated (masers near the Shock front/inner arm versus broad diffuse broad CO gas near the Potential Minimum/outer arm -see [28]).…”

Section: Locations Of Spiral Arms -Complementarity Of Arm Tangents Wi...mentioning

confidence: 99%

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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“…The Sun is located in an interarm, in between two long spiral arms (Sagittarius arm and Perseus arm). Other small interarm islands are known within our Galactic disk (Vallée 2018;Vallée 2020). The magnetic field strength there is not known (too few data).…”

Section: Turbulence Local and Everywherementioning

confidence: 93%

Superposing the Magnetic Spiral Structure of the Milky Way, on the Stellar Spiral Arms—Matching the Unique Galactic Magnetic Field Reversal Zone with Two Galactic Spiral Arm Segments

Vallée¹

2022

IJAA

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To pinpoint the peak location of the synchrotron total intensity emission in a spiral arm, we use a map of the spiralarm locations (from the observed arm tangent). Thus in a typical spiral arm in Galactic Quadrant I, we find the peak of the synchrotron radiation to be located about 220 ± 40 pc away from the inner arm edge (hot dust lane) inside the spiral arm. While most of the galactic disk has a clockwise large-scale magnetic field, we make a statistical analysis to delimitate more precisely the smaller reverse annulus with a counterclockwise galactic magnetic field. We find an annulus width of 2.1 ± 0.3 kpc (measured along the Galactic radius), located from 5.5 to 7.6 kpc from the Galactic Center). The annulus does not overlay with a single spiral arm-it encompasses segments of two different spiral arms. Using a recent delineation of the position of spiral arms, the field-reversed annulus is seen to encompass the Crux-Centaurus arm (in Galactic Quadrant IV) and the Sagittarius arm (in Galactic Quadrant I). Thus the full Sagittarius-Carina arm is composed of: 1) a Sagittarius arm (in Galactic quadrant I) with a counterclockwise magnetic field, and 2) a Carina arm (in Galactic Quadrant IV) with a clockwise magnetic field. Also the full Scutum-Crux-Centaurus arm is composed of: 1) a Scutum arm (in Galactic Quadrant I) with a clockwise magnetic field, and 2) a Crux-Centaurus arm (in Galactic Quadrant IV) with a counterclockwise magnetic field. Arm segments do not all have the same magnetic field direction. For completeness, we display 6 known magnetised advancing supershells around the Sun (within 400 pc), pushing out the interstellar magnetic field.

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Interarm islands in the Milky Way – the one near the Cygnus spiral arm

Cited by 6 publications

References 68 publications

Low-metallicity Young Clusters in the Outer Galaxy. III. Sh 2-127

Low-metallicity Young Clusters in the Outer Galaxy. III. Sh 2-127

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

Superposing the Magnetic Spiral Structure of the Milky Way, on the Stellar Spiral Arms—Matching the Unique Galactic Magnetic Field Reversal Zone with Two Galactic Spiral Arm Segments

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