This page will briefly describe how to use this tool to calculate the average ISM ratio, and produce results for the concentration of two radioactive isotopes, and then compute the ratio of the concentration of one isotope to another within the three phases of the interstellar medium. All of the results will be displayed in tabular form.
While using the tool, click on any blue link to learn more about a particular subject. For the particular example in this tutorial, we use the default values for each of the text fields. Once you gain familiarity with the tool, however, feel free to choose other values to see how your results change.
Species 1
After clicking the 'Launch Three Phase ISM Tool' button located on the main tool page, the three phase ism tool will open in a separate window as shown in the image below.
In this panel, you enter information about the first species that you are interested in. You must enter the chemical symbol, the mass number, and the half life of the species in years. In this case, we have entered Al for the chemical symbol of aluminum, 26 for aluminum-26's mass number, and 7.16e5 for aluminum-26's half life.
Once your data on species 1 is entered properly, click 'next' in order to proceed to the next step.
Species 2
In this panel, you enter your information about the second species that you are interested in. You must enter the chemical symbol, the mass number, and the half life of the species in years. In this case, we have entered Al for the chemical symbol of aluminum, 27 for aluminum-27's mass number, and Stable for aluminum-27's half life since aluminum-27 is stable against nuclear decay.
Once your data on species 2 is entered properly, click 'next' in order to proceed to the next step.
Chemical Evolution
In this panel, you enter the chemical evolution parameters. These parameters are the age of the Galactic disk in years, the timescale Delta for infall of metal-poor gas to build up the disk, and k, an integer describing the family of infall functions. In this example, we have chosen a Galactic disk age of 1010 years, a Delta of 2.0x108 years, and an infall parameter k of 3.
After you have entered in chemical evolution information, click next to enter your production ratio.
Production Ratio
'Production Ratio' is the ratio of the amount of species 1 produced in its principal production site to the amount of species 2 produced in its principal production site. In the present example, we use a value of 4x10-3, a typical value derived from stellar evolution models for the production ratio of 26Al to 27Al.
After you have entered in the Production Ratio, click next to enter the masses of the three phases.
Masses of Phases
The 'Masses of Phases' are broken down into three different input fields for the following reasons. The first input field is for the mass value of phase 1 (the cold molecular cloud phase) in the three phase model. The second input field is the mass value of phase 2 (the large HI cloud phase), and the final input field is the mass value of phase 3 (the warm ISM phase). Enter each of the three phase masses. Be sure to use the same mass unit for each phase. In this example, we choose 30% of the mass of the interstellar medium to be in phase 1, 30% to be in phase 2, and 40% in phase 3.
When you have entered in these values click next to enter in the mixtime values.
Mixtime Values
In the last panel, you enter in the mixing times between phases 1 and 2 (Time 1) and 2 and 3 (Time 2). These mixing time values have units of years. In the present case, we choose 107 years for both mixing times.
Calculate Results
After you have entered the mixing times between the phases, click on Calculate Results. This will pop up a new window with the results of your calculation.
This is the result of the calculation, that is, the window that opens when you click Calculate Results.
Interpret Your Results
If you have not already done so, click on the result link above. The pop-up window giving your results shows your input values on the left of the panel. These correspond to the values you entered in the panels. Your results are in the right side of the panel. The first output panel shows that the average 26Al/27Al abundance ratio in the interstellar medium is 1.619852x10-6 for the input parameters we have chosen. This is the abundance ratio averaged over all three phases.
The second output table shows the ratio of the concentration of 26Al and 27Al in the three phases to their average concentration throughout the interstellar medium. Thus, for 26Al, the concentration in phase 1 is only a fraction 0.01886 of the average interstellar medium concentration. This makes sense because fresh 26Al is introduced in the model into phase 3. This fresh 26Al must then work its way via phase 2 into phase 1 on 107 year timescales. This means the 26Al decays during this transport and must have a lower concentration in phase 1 than in the other two phases. By contrast, 27Al is uniformly distributed in the three phases since it is stable.
The third output table shows the 26Al/27Al abundance ratio in the each of the three phases for the input parameters we have chosen. We see that the abundance ratio in phase 1 is 3.0558x10-8. This is lower than the average ISM abundance ratio of 1.61985x10-6, which makes sense because the concentration of 26Al in phase 1 is less than the average concentration due to decay during transport among the phases. We note that the abundance ratio in phase 3 is higher than in phase 1 since the relative concentration of 26Al is highest in phase 3.
Changing Input
With the default calculation results available in the pop-up window, you may now change any of the input to see the effect. It is best to leave the new results window in place. Go back to the Three Phase ISM Tool and change any of the input. Then go to the Mix Time Values panel and click Calculate Results again. This should place the new result into the same results window. You may use the back and forward buttons to compare the two calculations.
For example, if you leave all input quantities at their default values but change the mix times Time 1 and Time 2 to both be 1.0e8 instead of 1.0e7, you will get different results from the previous calculation.
Here are the changed results. Note that, if you kept the previous results browser window open when you click the changed results link, you can compare the results of the two calculations with different mixing times by using the back and forward buttons in the results browser window.
