The start of the Sagittarius spiral arm(Sagittarius origin) and the start of the Norma spiral arm(Norma origin): model-computer and observed arm tangents at galactic longitudes −20° <l< +23°

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DOIResolve DOI: http://doi.org/10.3847/0004-6256/151/3/55
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TypeArticle
Journal titleThe Astronomical Journal
ISSN1538-3881
Volume151
Issue3
Article number55
Pages116
SubjectSpiral galaxies; Disk galaxy; Galaxy structure; General ISM; ISM structure; Statistical methods
AbstractHere, we fitted a four-arm spiral model to the more accurate data on global arm pitch angle and arm longitude tangents to get the start of each spiral arm near the galactic nucleus. We find that the tangent to the "start of the Sagittarius" spiral arm (arm middle) is at l = −17° ± 0°.5, while the tangent to the "start of the Norma" spiral arm (arm middle) is at l = +20° ± 0°.5. Earlier, we published a compilation of observations and analysis of the tangent to each spiral arm tracer from longitudes +23° to +340°; in this paper we cover the arm tracers in the remaining longitudes +340 (=−20°) to +23°. Our model arm tangents are confirmed through the recent observed masers data (at the arm's inner edge). Observed arm tracers in the inner Galaxy show an offset from the mid arm; this was also found elsewhere in the Milky Way disk. In addition, we collated the observed tangents to the so-called 3 kpc arm features; statistically they are found to be near l = −18° ± 2° and near l = +21° ± 2°, after excluding misidentified spiral arms. We find that the model-computed arm tangents in the inner Galaxy are spatially coincident with the mean longitude of the observed tangents to the 3 kpc arm features (same galactic longitudes, within the errors). These spatial similarities may be suggestive of a contiguous space.
Publication date
PublisherIOP Publishing
LanguageEnglish
AffiliationNational Science Infrastructure; National Research Council Canada
Peer reviewedYes
NPARC number23000075
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Record identifier697adf80-8f2c-404f-906b-7e72ce416a46
Record created2016-06-01
Record modified2016-06-01
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