Homework 2019 Cambridge

Bookmark the class web share

Please bookmark the class web share. I have placed documents, PDFs of the lectures, and models, in folders below this site.

Cloudy

Have a laptop to compute models and plot results during the workshop

We want to spend our time thinking about the astronomy rather than the computer science. You need to have a working copy of Cloudy to participate. You should be able to create an input deck using a text editor, run Cloudy, and make plots of the predictions as we go along.

It would be best to bring a laptop to do the simulations and plots locally. This is the best way to participate. The classroom will have Eduroam wifi so logging into a remote machine is possible.

Download and install Cloudy

We will use the current version of Cloudy. Instructions for downloading and installing Cloudy are here. Vital Fernandez created a nice set of videos on how to build and run Cloudy.

Problems?? Search our Yahoo user group to see if others have solved it, and post a question if you don't find help.

You should make it through at least step 5 of the instructions on this site.

When finished you will have an Cloudy executable that can successfully pass its smoke test (run the code with the input having the single command "test").

You should have a script "run" that will read input from "name.in" and produce the "name.out" output file.

Have access to the code's documentation

These are PDF files are located in the docs directory of the Cloudy download, and are also posted in the docs directory of the web share. You should be able to view the Cloudy Quick Start Guide Hazy1 and Hazy2, the documentation files, on your laptop. Please don't print them.

Typos?? If you notice any please let me know by posting to the Yahoo group.

Read the Cloudy Quick Start Guide

This is a short introduction to all of Cloudy. Read it to get an overview of what we will be discussing.

Run the "M16.in" model and plot some results.

We will be considering the famous HST image of M16 throughout the workshop. Here is a recent paper describing the optical spectrum. We will start by making a model of it.

Run the model

You will find the input script for this model in the sims directory of the web share. Several files will be created when you compute the model. The most important is the main output, named "M16.out" if you use our recommended "run" script. Look at the last lines in that file. They should say "Cloudy exited OK". If they don't you have problems and should investigate.

Plot the temperature and ionization structure

We will make lots of plots showing predicted quantities during the workshop. You will need to compute models and create plots while in the class. I use Jeremy Sanders' Veusz program, which is GUI based and very Cloudy friendly. The appendix of the Cloudy Quick Start Guide explains how we use Veusz and I strongly recommend it.

The file "M16.ovr" is the "overview" file that was created when you ran Cloudy. It has lots of information about the physical conditions in the cloud. The first row gives column headers. The remaining rows give properties of the cloud as a function of depth into the cloud. They are tab delimited fields meaning that a tab character separates columns.

Make a plot in which the depth into the cloud is the x-axis and the gas kinetic temperature is the y-axis. The depth in cm is the first column in the overview file. Both axis should be linear. The temperature is the second. Save a copy of the plot in PDF format. Post the plot on our forum.

Next plot the atomic and ionized hydrogen ionizations as a function of depth into the cloud. The depth in cm is the first column, the fraction of hydrogen that is atomic is the seventh column, and the fraction that is ionized is the eighth column. Include both ionization fractions on the same plot. Both axis should be linear.

Plot the entire spectrum of the star and the cloud

This is contained in the file M16.con. The first column is the wavelength in microns. This is the x-axis and the plot should be a base 10 log and have a range from 0.01 to 1000 microns. The spectrum of the incident radiation field, the star, is in column 2. Add this to the pole. Column 7 gives the spectrum of the cloud. Add this to the cloud. Both spectra are specific luminosities in ergs/s and should be plotted as a base 10 log y-axis. Make the axis have a maximum of 1e40 erg/s and minimum of 1e35 erg/s. This gives the emission from the M 16 cloud. Add the spectrum of the star to the plot. This is in column 2.

Plot the optical spectrum of the star and cloud

This is the same as the previous spectrum but change the x-axis to range from 0.35 microns to 0.8 microns.

Plot the emissivity of some strong lines

This emissivity, the emission in various lines, is stored in the M16.ems file. The first column gives the depth into the cloud while the rest give the emissivity, erg cm-3 s-1, in various lines. Plot these as a function of depth. Make both axis linear to better predict what the image shows.