Transcript The Spiral Structure of the Milky Way

Radio Astronomy And The
Spiral Structure Of The Milky
Way
Jess Broderick
Supervisor: Dr George Warr
Outline
Overview of the spiral arm structure of
the Milky Way.
 Using radio astronomy to detect the
spiral structure.
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The Spiral Arm Structure Of The
Milky Way
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Optical spiral tracers: O & B type stars,
open star clusters, emission nebulae (HII)
regions.
Optical observations limited in effectiveness
due to clouds of interstellar dust.
Solution: Use radio wavelengths to study
the spiral structure, eg. 21 cm line of neutral
hydrogen.
Using Radio Astronomy To Detect
The Spiral Structure
Mapping The Spiral Arms Of The
Milky Way
Starting point: Map the intensity of
neutral hydrogen along the Galactic
plane for various Galactic longitudes.
 As a result of this procedure, it has
been shown that the neutral hydrogen
appears to be concentrated in the spiral
arms of the Milky Way.
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B. Burke et. al., An Introduction To Radio Astronomy.
Uncertainties Involved In Detecting
The Spiral Structure Using Radio
Astronomy
Assuming circular model of rotation of
gas.
 Range of phenomena near the Galactic
plane.
 Ambiguity in the overall flux density
profile.
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H. Karttunen et. al., Fundamental Astronomy.
Sun
Galactic Centre
Intensity
Radial Velocity
Conclusion
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Radio observations can be used to provide a
more comprehensive analysis of the Milky
Way’s spiral structure than optical
observations allow.
Uncertainties involved in interpreting the
neutral hydrogen flux density profiles.
It can be concluded that 21 cm hydrogen
observations do indeed indicate spiral
structure on a large scale in the Galactic
plane.