Mike's Astronomy Page

I'm a graduate student in Astronomy and I am currently working with Michele Trenti (at the Space Telescope Science Institute), Cole Miller, and Doug Hamilton (here at UMD) simulating gravitational interactions between stars and stellar remnants in the dense setting of globular star clusters. For now, all that's posted here are files from my research that will probably not be of any interest to you unless you have a disproportionately large interest in Astronomy. Otherwise, I recommend that you go find some other part of the page to look at...

Current Work:

I'm currently simulating clusters of stars of varying mass sizes with and without an intermediate mass black hole in the center of the cluster. The simulations are started with a King potential with varying values of the constant W_0, and some are run in the presence of an external tidal field. I have divided the page into the different groups of runs I have done in order to make it easier to handle.
Take me to:
16k runs
New 8k runs
Old 8k runs
Things before summer 2007

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The 16k runs
Because of the greatly increased expense for higher N computations, there are fewer of these than there are of the 8K runs. Currently, there are only 5, all of which are run with 16384 individual stars, with a King potential with W_0 = 7.0, in the presence of an external tidal field, as would happen as a globular cluster orbits a galaxy. We varied the initial IMF, using a Salpeter distribution for 1/2 of the runs, and a Miller & Scalo IMF for the other 1/2. We select the stars from the mass range 0.2-100 M_sun, then apply mass loss to those stars above the turnoff mass, 0.8 M_sun here. We then add an IMBH to 1/2 of the runs. So far, we have the following plots to analyze the data:
Plot 1 - A histogram of the average masses in radial bins, calculated using only two spatial dimensions (since that's all we can see on the sky). The black plot is the beginning of the simulation, red is ~1/4 of the way through, blue is 1/2, and green is at the end.
Plot 2 - A histogram of the slope of the local mass function in different radial bins, with the same color code as in plot 1.

Run #1 - Salpeter IMF, no IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #2 - Salpeter IMF, IMBH - This run really doesn't have an IMBH since it was ejected from the system at very early time. So... you'll notice that it behaves virtually as if it never had one.
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #2 (take 2) - This one actually has an IMBH.
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #3 - Miller and Scalo IMF, no IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #4 - Miller and Scalo IMF, IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #5 - Old model of stellar evolution from Michele's Previous Research, no IMBH, but 10% binaries initially
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Combined Plots: Plot 3 - A plot of the difference between the slope of the local mass function in the center vs. the slope 1/2 way out. The black points are all runs without an IMBH and the red points are with, and the filled points are from Miller & Scalo runs while the open ones are from Salpeter:
.ps .pdf

Plot 3a - Same as plot 3, but averaged over the 5 surrounding points:
.ps .pdf

Plot 4 - Same thing as plot 3, except this time the difference in average mass:
.ps .pdf

Plot 4a - Same as plot 4, but averaged over the 5 surrounding points:
.ps .pdf

Plot 5 - A plot of the average radius of different bins of the mass, the top plot for the 16k salpeter, the bottom for 16k salpeter with a BH:
.htm

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New 8k runs
The old 8k runs were run using a different model - these are run using the same model as the 16k runs - just 1/2 the number of particles. There are 6 of these, and all were run with W_0 = 7.0 in the presence of an external tidal field. Half of the runs were done with a Salpeter IMF, while the other half were done with a Miller & Scalo IMF. Two were done without an IMBH, two were done with an IMBH and two with an IMBH of double the mass of the first IMBH. We use the same two plots (for now) as we did in the case of the 16k runs.

Run #1 - Salpeter IMF, no IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #2 (take 1) - Salpeter IMF, normal IMBH. The IMBH was kicked out of this one approximately 10% of the way through, so it also looks like a run without an IMBH, and will be treated as such
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #3 - Salpeter IMF, triple mass IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #4 - Miller & Scalo IMF, no IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #5 - Miller & Scalo IMF, normal IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Run #6 - Miller & Scalo IMF, triple mass IMBH
Plot 1: .ps .pdf
Plot 2: .ps .pdf

Combined plots, permanently missing Run #2, since the BH never stays in the cluster. The green plot is a salpeter IMF run without an IMBH, but that had a very persistent BH-BH binary in it that caused it to look like a BH run.:
Plot 3 - Same as corresponding plot for the 16k runs -
.ps .pdf

Plot 3a - Same as Plot 3, but averaged over 5 neighboring points:
.ps .pdf

Plot 4 - Same as corresponding plot for the 16k runs -
.ps .pdf

Plot 4a - Same as Plot 4, but averaged over 5 neighboring points:
.ps .pdf

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Old 8k runs
Plot 1 = A histogram of the average masses at different radii at the beginning (black line) of the simulation, 1/4 of the way through the simulation (red line), 1/2 way through (blue line) and at the end (green line) of the simulation. The 2-d version of these plots has the radius from the center of the cluster calculated using only two dimensions as it would be on the sky.
Plot 2 = A histogram of the masses within the inner 10% of the cluster at the beginning of the simulation (black) and at the end (red).
Plot 3 = A plot of the evolution of the slope of the mass function as the cluster evolves
Plot 2a = A combination of the final histograms of the masses within the inner 10% of the cluster with (red line) and without (black line) a black hole in the center
Plot 4 = a plot of the internal energy of a cluster comparing no BH (black) vs. BH (red) and in one case an even larger BH (blue).
Plot 5 = The internal energy of a cluster plotted against the number of binaries in the cluster.
Plot 6 = The number of stars in the cluster over time with no BH (black), BH (red), and possibly an even larger BH (blue)
Plot 7 = A plot of the difference between Plot 1 with and without a BH

New plot with 40 points, showing how the difference in average mass between the center of the cluster and the 25h radial percentile of the cluster changes over the course of the simulation:
Isolated Clusters: .pdf .ps
Tidal Clusters: .pdf .ps

Run 1: No BH, W_0 = 7.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 2: BH, W_0 = 7.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 1+2 comparison: W_0 = 7.0, isolated cluster
Plot 2a - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 4 - .pdf .ps
Plot 5 - .pdf .ps
Plot 6 - .pdf .ps

Plot 7 - 2-d: .pdf .ps

Run 3: No BH, W_0 = 5.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 4: BH, W_0 = 5.0, isolated cluster. I was not able to obtain the snapshot at 500 nb6 time units, so that is absent from Plot 1.
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - Coming Soon

Run 3+4 comparison: W_0 = 5.0, isolated cluster
Plot 2a - 3-d: .pdf .ps 2-d: .pdf .ps

Run 5: No BH, W_0 = 11.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 6: BH, W_0 = 11.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 5+6 comparison: W_0 = 11.0, isolated cluster
Plot 2a - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 6 - .pdf .ps

Run 7: No BH, W_0 = 3.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 8: BH, W_0 = 3.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 7+8 comparison: W_0 = 3.0, isolated cluaster
Plot 2a - 2-d: .pdf .ps
Plot 6 - .pdf .ps

Run 9: No BH, W_0 = 7.0, tidal field
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 10: BH, W_0 = 7.0, tidal field
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 9+10 comparison: W_0 = 7.0, tidal field
Plot 2a - 2-d: .pdf .ps
Plot 4 - .pdf .ps
Plot 6 - .pdf .ps

Run 11: No BH, W_0 = 5.0, tidal field. The green is 1500 nb6 times units, because the simulation doesn't make it all the way to the end. Plot 2 is done at 1000 nb6 time units instead of at the end because so few particles were left at the end.
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 12: BH, W_0 = 5.0, tidal field. Details of the plots the same as Run 11.
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 11+12 comparison: W_0 = 5.0, tidal field, same details as Run 11.
Plot 2a - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 6 - .pdf .ps

Run 13: No BH, W_0 = 11.0, tidal field
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 14: BH, W_0 = 11.0, tidal field
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 13+14 comparison: W_0 = 11.0, tidal field
Plot 2a - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 4 - .pdf .ps
Plot 6 - .pdf .ps

Run 15: No BH, W_0 = 3.0, tidal field

Run 16: BH, W_0 = 3.0, tidal field

Run 15+16 Comparison: W_0 = 3.0, tidal field
Plot 6 - .pdf .ps

Run 17: BH of double mass, W_0 = 7.0, isolated cluster
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 18: BH of double mass, W_0 = 7.0, tidal field
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 3 - .pdf .ps

Run 19: W_0 = 7.0, isolated cluster, Miller&Scalo IMF
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps

Run 20: W_0 = 7.0, isolated cluster, Miller&Scalo IMF, BH
Plot 1 - 3-d: .pdf .ps 2-d: .pdf .ps
Plot 2 - 3-d: .pdf .ps 2-d: .pdf .ps

Run 19+20 Comparison: W_0 = 7.0, isolated cluster, Miller&Scalo IMF
Plot 2a - 2-d: .pdf .ps

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Spring 2007 and Before:
Mike's 2nd Year Project Paper .pdf .doc

Below is a list of calculations that are important to my project:
Why we can make disrupted stars disappear without changing anything .pdf .ps

Take me back to:
Mike's Home Page