Astronomy Physics - Apparent Magnitudes

In summary, the WIYN 3.5m telescope has a multi-object spectrograph called "Hydra" with 100 independently deployable fibers that can be placed over a 1 degree field of view. The spectrograph can only view a range of 100nm at a time and the detected cluster of galaxies has a redshift of z~0.01 and spans less than one degree on the sky. To carry out observations, one must predict the apparent magnitudes of the three brightest galaxies in the cluster and the number of galaxies that are 3 magnitudes fainter than the brightest galaxy. This can be done by understanding the relationship between apparent and absolute magnitudes, the types of galaxies usually found in a cluster, and the
  • #1
Rahzizzle
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Homework Statement


The WIYN 3.5m telescope has a multi-object spectrograph called “Hydra.” The instrument has 100 independently deployable fibers that can be placed anywhere over a 1 degree field of view (FoV). Assume the FoV is a circle one degree in diameter. You can get a spectrum through each fiber, but the spectrograph will only allow you to look at 100nm at a time (e.g. 400nm-500nm). Assume you have detected a cluster of galaxies at a redshift of z~0.01. Your initial estimate is that the cluster spans a bit less than one degree on the sky.

Question : In order to carry out some observations you’ll first want to predict what the apparent magnitudes of the three brightest galaxies to be. You also need to predict how many galaxies you expect to see that are 3 magnitudes fainter than the brightest galaxy in the cluster.


I have absolutely no idea where to start, this is a weird question.
 
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  • #2
Its a bit ambiguously worded, you really don't know what the 3 brightest members of cluster are until you look at it, but. . .

Part A: Well, what is the relationship between the apparent and absolute magnitudes of objects. What types of galaxies are usually the brightest members of a cluster? Aside from the brightest members of a cluster, what are the next brightest types of galaxies in general? I

Part B: What is the distribution of galaxy luminosities? I.E. google "galaxy luminosity function" or look it up in your book. Its not a gaussian at all, but for example, if it were, then how could you calculate the number of galaxies between say m=18 and m=20 if it was a gaussian distribution centered at m=17 and [tex]\sigma[/tex]=1 mag?
 

1. What is the definition of apparent magnitude in astronomy physics?

Apparent magnitude is a measure of the brightness of a celestial object as seen from Earth. It is based on a logarithmic scale, where lower numbers indicate brighter objects and higher numbers indicate fainter objects.

2. How is apparent magnitude different from absolute magnitude?

Apparent magnitude is a measure of how bright an object appears to be from Earth, while absolute magnitude is a measure of how bright an object would appear if it were located at a standard distance of 10 parsecs (32.6 light years) away from Earth.

3. What factors can affect the apparent magnitude of a celestial object?

The apparent magnitude of a celestial object can be affected by its distance from Earth, its size and luminosity, and any intervening objects that may block or scatter its light. Atmospheric conditions, such as light pollution or clouds, can also impact apparent magnitude.

4. How is the apparent magnitude of a star measured?

The apparent magnitude of a star is measured using a photometer, which compares the brightness of the star to a standard reference star. The measurement is then adjusted for the star's distance from Earth to determine its apparent magnitude.

5. What is the significance of apparent magnitude in astronomy?

Apparent magnitude is an important tool for astronomers as it allows them to compare the brightness of different celestial objects and track changes in their brightness over time. It also helps determine the distance of objects in the universe and provides insights into their physical properties.

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