Using classical Cepheids to study the far side of the Milky Way disk. II. The spiral structure in the first and fourth Galactic quadrants

Aims. Classical Cepheids provide the foundation for the empirical extragalactic distance ladder. Milky Way Cepheids are the only stars in this class accessible to trigonometric parallax measurements. However, the parallaxes of Cepheids from the second Gaia data release (GDR2) are affected by systematics because of the absence of chromaticity correction, and occasionally by saturation. Methods. As a proxy for the parallaxes of 36 Galactic Cepheids, we adopt either the GDR2 parallaxes of their spatially resolved companions or the GDR2 parallax of their host open cluster. This novel approach allows us to bypass the systematics on the GDR2 Cepheids parallaxes that is induced by saturation and variability. We adopt a GDR2 parallax zero-point (ZP) of −0.046 mas with an uncertainty of 0.015 mas that covers most of the recent estimates. Results. We present new Galactic calibrations of the Leavitt law in the V, J, H, KS, and Wesenheit WH bands. We compare our results with previous calibrations based on non-Gaia measurements and compute a revised value for the Hubble constant anchored to Milky Way Cepheids. Conclusions. From an initial Hubble constant of 76.18 ± 2.37 km s−1 Mpc−1 based on parallax measurements without Gaia, we derive a revised value by adopting companion and average cluster parallaxes in place of direct Cepheid parallaxes, and we find H0 = 72.8 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 when all Cepheids are considered and H0 = 73.0 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 for fundamental mode pulsators only.

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Similarities between Hurricanes and Galaxies: A Short Review

10.20944/preprints202110.0402.v1 ◽

2021 ◽

Author(s):

Jim Henry ◽

Mesut Yurukcu ◽

George Nnanna

Keyword(s):

Milky Way ◽

Spiral Galaxies ◽

Spiral Structure ◽

Fibonacci Numbers ◽

Short Review ◽

Review Article ◽

Double Spiral ◽

Natural Pattern

Universe created with the fundamental laws of science. Nature is lazy and needs to form with the least possible to be perfect. A natural pattern, such as pinecones, sunflowers, pineapples, and cacti, has a double spiral structure. Once we look at these plants' centers, we will see the seeds line up in spirals shape. The number of spirals whirling in each direction will give us the Fibonacci numbers. We can give more examples representing these natural patterns; however, one example is unique and remarkable. The similarities between spiral galaxies- Milky Way and hurricanes. Are they similar in every property or just in shape and rotational movements? What are the similarities between them? This short review article will try to find these questions' answers by reviewing some literature articles. The first part of this article gave some information about hurricanes and galaxies. The second of this article focused on the comparison between hurricanes and galaxies. Finally, we will conclude the article with our remarks.

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The galactic structure and the appearance of the Milky Way

Symposium - International Astronomical Union ◽

10.1017/s0074180900000590 ◽

1970 ◽

Vol 38 ◽

pp. 222-224

Author(s):

E. D. Pavlovskaya ◽

A. S. Sharov

Keyword(s):

Spatial Distribution ◽

Surface Brightness ◽

Milky Way ◽

Spiral Structure ◽

Galactic Structure ◽

Interstellar Matter

The appearance of the Milky Way for an observer situated within our Galaxy is determined by the spatial distribution of stars and absorbing interstellar matter. Hence it may be hoped that the study of the surface brightness of the Milky Way permits to derive the spiral structure of our Galaxy.

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Local stellar distribution and galactic spiral structure

Symposium - International Astronomical Union ◽

10.1017/s007418090000053x ◽

1970 ◽

Vol 38 ◽

pp. 189-198 ◽

Cited By ~ 1

Author(s):

S. W. McCuskey

Keyword(s):

Spiral Structure ◽

The Sun ◽

Long Period ◽

Classical Cepheids ◽

Galactic Clusters ◽

The Galaxy ◽

Galactic Spiral Structure ◽

Ob Associations ◽

Galactic Spiral ◽

Spiral Arm

Aside from the well-known spiral arm tracers such as the OB associations, young galactic clusters, WR stars and possibly the long-period classical cepheids, the more common stars in the neighborhood of the sun within 2 kpc show little or no relationship to the local spiral structure of the galaxy.

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Magnetic Fields and Spiral Structure

Symposium - International Astronomical Union ◽

10.1017/s0074180900032745 ◽

1983 ◽

Vol 100 ◽

pp. 159-160 ◽

Cited By ~ 2

Author(s):

R. Beck

Keyword(s):

Star Formation ◽

Magnetic Fields ◽

Milky Way ◽

Spiral Structure ◽

Radio Continuum ◽

Continuum Emission ◽

Radio Telescopes ◽

Evolution Of Galaxies ◽

Structure Strength ◽

Spiral Structures

Interstellar magnetic fields are known to be a constraint for star formation, but their influence on the formation of spiral structures and the evolution of galaxies is generally neglected. Structure, strength and degree of uniformity of interstellar magnetic fields can be determined by measuring the linearly polarised radio continuum emission at several frequencies (e.g. Beck, 1982). Results for 7 galaxies observed until now with the Effelsberg and Westerbork radio telescopes are given in the table. The Milky Way is also included for comparison.

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The spiral structure of our Milky Way

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313000665 ◽

2012 ◽

Vol 8 (S292) ◽

pp. 106-106

Author(s):

L. G. Hou ◽

J. L. Han

Keyword(s):

Milky Way ◽

Spiral Structure ◽

Hii Regions ◽

Giant Molecular Clouds ◽

Constant Weight ◽

Spiral Arms ◽

Flat Rotation Curve ◽

Methanol Masers ◽

The Masses ◽

Excitation Parameters

AbstractThe spiral structure of our Milky Way has not yet been well outlined. HII regions, giant molecular clouds (GMCs) and 6.7-GHz methanol masers are primary tracers for spiral arms. We collect and update the database of these tracers which has been used in Hou et al. (2009) for the spiral arms.The new database consists of ∼ 2000 HII regions, ∼ 1300 GMCs and ∼ 800 methanol masers (6.7 GHz). If the photometric or trigonometric distance for any tracer is available from the literature, we will adopt it. Otherwise, we have to use the kinematic distance. We modify the VLSR according to the newly determined solar motions (U0 = 10.27 km s−1, V0 = 15.32 km s−1 and W0 = 7.74 km s−1, Schönrich et al. 2010), then calculate the kinematic distances with a flat rotation curve (R0 = 8.3 kpc, θ0 = 239 km s−1, Brunthaler et al. 2011). Very important step is that we weight tracers according to the excitation parameters of HII regions or the masses of GMCs, and a constant weight for masers. All three kinds of tracers are used together to outline the spiral structure (Fig. 1). A contour and gray map is constructed after we made a Gaussian extension for the tracers with the amplitude of weighting parameter.

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The Spiral Structure of the Southern Milky Way

Publications of the Astronomical Society of the Pacific ◽

10.1086/127914 ◽

1963 ◽

Vol 75 ◽

pp. 103 ◽

Cited By ~ 4

Author(s):

John B. Whiteoak

Keyword(s):

Milky Way ◽

Spiral Structure

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Application of the Density-Wave Theory to the Spiral Structure of the Milky way System. III. Magnetic Field: Large-Scale Hydromagnetic Shock Formation

The Astrophysical Journal ◽

10.1086/150592 ◽

1970 ◽

Vol 161 ◽

pp. 887 ◽

Cited By ~ 52

Author(s):

William W., Jr. Roberts ◽

C. Yuan

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Milky Way ◽

Spiral Structure ◽

Density Wave ◽

Wave Theory ◽

Shock Formation ◽

Density Wave Theory

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Distribution and kinematics of 26Al in the Galactic disc

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2125 ◽

2020 ◽

Vol 497 (2) ◽

pp. 2442-2454 ◽

Cited By ~ 2

Author(s):

Yusuke Fujimoto ◽

Mark R Krumholz ◽

Shu-ichiro Inutsuka

Keyword(s):

Star Formation ◽

Milky Way ◽

Spiral Structure ◽

Rotation Speed ◽

Scale Height ◽

Stellar Winds ◽

Galactic Disc ◽

Stellar Feedback ◽

Self Gravity ◽

Solar Position

ABSTRACT 26Al is a short-lived radioactive isotope thought to be injected into the interstellar medium (ISM) by massive stellar winds and supernovae (SNe). However, all-sky maps of 26Al emission show a distribution with a much larger scale height and faster rotation speed than either massive stars or the cold ISM. We investigate the origin of this discrepancy using an N-body + hydrodynamics simulation of a Milky-Way-like galaxy, self-consistently including self-gravity, star formation, stellar feedback, and 26Al production. We find no evidence that the Milky Way’s spiral structure explains the 26Al anomaly. Stars and the 26Al bubbles they produce form along spiral arms, but, because our simulation produces material arms that arise spontaneously rather than propagating arms forced by an external potential, star formation occurs at arm centres rather than leading edges. As a result, we find a scale height and rotation speed for 26Al similar to that of the cold ISM. However, we also show that a synthetic 26Al emission map produced for a possible Solar position at the edge of a large 26Al bubble recovers many of the major qualitative features of the observed 26Al sky. This suggests that the observed anomalous 26Al distribution is the product of foreground emission from the 26Al produced by a nearby, recent SN.

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