# e1s - Exam 1 Solutions Lots of partial credit given so give...

This preview shows pages 1–2. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Exam # 1 Solutions Lots of partial credit given, so give at least a qualitative answer to each item. Some useful constants are given at the end of the exam. 1. Extensive spectral observations often show two peaks in high excitation emis- sion molecular line profiles from star-forming molecular globules, and the blue peak is usually stronger than the red peak. 1.1. With equations or diagrams, indicate how a double-line spectral line could be formed in this situation. In a star-forming globule, material is infalling. A double line profile could be formed only if a given radial velocity could originate from two different parts of the cloud. If the infalling velocity and density both varied inversely with radius, you would get a situation that a line-of-sight through the cloud, off-center, would traverse first a red-shifted region of low intensity, then a red-shifted region of high intensity, then a blue-shifted region of high intensity and finally a blue-shifted region of low intensity. At the cloud’s midpoint, there is no Doppler shift because there is no component of the cloud’s velocity along the line-of-sight. This could produce a line with two peaks: one red-shifted and one blue-shifted. 1.2. In order to obtain double-line spectral lines, how should the infall velocity behave with radius? A necessary condition is that the infall velocity vary inversely with radius. In this case, a line of sight contains two points with the same radial velocity from the observers viewpoint. Example: v ( r ) = v /r . If R is the distance from the cloud center to the line-of-sight through r , and z from the line θ = 0 to r , a point in the cloud at position r,θ satisfies z = r sin θ . Then the component of the cloud’s velocity along the line-of-sight is v r = v ( r )sin θ . Solving for r = ( v /v r )sin θ which is double-valued as θ goes between 0 and π/ 2....
View Full Document

{[ snackBarMessage ]}

### Page1 / 4

e1s - Exam 1 Solutions Lots of partial credit given so give...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online