Neutral hydrogen in the galaxy l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 25

Neutral hydrogen in the Galaxy PowerPoint PPT Presentation


Neutral hydrogen in the Galaxy. Neutral hydrogen in the Galaxy. HII regions. Orion nebula Triangulum nebula . Interstellar extinction law. Dust in the Eagle nebula. Dust: reddening in colour-colour plot. Calculating E(B-V) from colour-colour plot.

Related searches for Neutral hydrogen in the Galaxy

Download Presentation

Neutral hydrogen in the Galaxy

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Neutral hydrogen in the galaxy l.jpg

Neutral hydrogen in the Galaxy


Neutral hydrogen in the galaxy2 l.jpg

Neutral hydrogen in the Galaxy


Hii regions l.jpg

HII regions

Orion nebula Triangulum nebula


Interstellar extinction law l.jpg

Interstellar extinction law


Dust in the eagle nebula l.jpg

Dust in the Eagle nebula


Dust reddening in colour colour plot l.jpg

Dust: reddening in colour-colour plot


Calculating e b v from colour colour plot l.jpg

Calculating E(B-V) from colour-colour plot

Consider observations of a set of stars in the (U-B) vs (B-V)

plane. The reddening vector will have a specific direction:

which for Aλ 1/λ gives

Using this, any star can be de-reddened back to the stellar

locus, allowing both E(B-V) and spectral type to be determined


Atmospheric extinction l.jpg

Atmospheric Extinction


Hii regions9 l.jpg

HII regions

Orion nebula Triangulum nebula


Hii region spectra l.jpg

HII region spectra

Different HII regions can have very different ratios of emission line strengths.


Temperature diagnostics l.jpg

Temperature diagnostics


Oiii diagnostic temperatures l.jpg

OIII diagnostic temperatures


Nebula temperatures l.jpg

Nebula temperatures

(T/104)0.25 exp(-39000/Te) = 2.5x10-7 T*


The cooling curve l.jpg

The Cooling Curve

Volume emissivity ε = Λ(T) nH2


Density diagnostics l.jpg

Density diagnostics


Shocks in the interstellar medium l.jpg

Shocks in the interstellar medium


Discussion question l.jpg

Discussion Question

What would happen if the piston were moved faster

than the sound speed of the gas?

What properties would you expect to be conserved

for material passing through the shock discontinuity?

(With what complications?)


Supernovae 1a as standard candles for cosmology l.jpg

Supernovae 1A as standard candles for cosmology

  • Light-curve stretch correlates with luminosity

  • Correcting for this gives distances accurate to ~5%


Isothermal shocks l.jpg

Isothermal Shocks


Shocks in the interstellar medium20 l.jpg

Shocks in the interstellar medium


The cooling curve21 l.jpg

The Cooling Curve

Volume emissivity ε = Λ(T) nH2


Course summary l.jpg

Course Summary

1. Observational Astronomy

- Quantifying light (flux density, intensity)

- Magnitude system (m = m0 - 2.5 log10f)

- Measuring distances (parallax)

- Luminosities, absolute magnitudes

- Stars as black bodies (L=4πR2Teff4)

- Stellar classification (OBAFGKM)

- Hertzsprung-Russell (colour-magnitude) diagram

- Astronomical co-ordinates (Right ascension, Declination)


Course summary23 l.jpg

Course Summary

2. Main sequence stars

- Energy generation (nuclear fusion; tunnelling; pp/CNO)

- Escape of light from a star (random walk diffusion process)

- Equations of stellar structure (mass continuity, hydrostatic equilibrium, energy generation and radiative diffusion)

- Simple solutions (dimensionless variables)

- Explained observed main sequence properties (e.g. LM≈3).

- Complication: convection

- Upper and lower limits of the main sequence: radiation pressure (Eddington luminosity), and degeneracy pressure


Course summary24 l.jpg

Course Summary

3. Degenerate stars

- Later stages of stellar evolution (red giants etc; briefly)

- Electron degeneracy pressure

- Accurately with 6D density of states

- Roughly, using the uncertainty principal

- Fermi momentum

- Maximum mass for White Dwarfs (Chandrasekhar limit)

- Sizes, densities and ages of White Dwarfs

- Neutron stars and black holes


Course summary25 l.jpg

Course Summary

4. The interstellar medium

- Its effect on starlight (extinction and reddening)

- Photo-ionisation by stars, giving HII regions

- Radiative recombination, and the Strömgren radius

- Temperatures and densities from emission line ratios

- Propagation of perturbations: sound waves

- Shocks: derived conditions of the step-change

- Supernova shocks: feed metals back in to new star formation


  • Login