Metalicity configuration in dat.10 input file

[matg41]

Hello
I am using your wonderful program to simulate open star clusters. One issue I encountered is that in a region I investigated, two clusters with different origins and metallicities are merging together. Is there a way to provide the algorithm with a dat.10 file that includes an estimated metallicity for each star?
Thank you for your attention. Feel free to let me know if you need any further adjustments!

[FrancescoFlammini]

Dear matg41,

thanks for using our code. Unluckily, our code has a single metallicity for all the stars in the cluster. We are working on a version that will do that in the future but as of now, this is still not supported in the main version.

I leave the issue open in case you have any further questions.

Best regards,
Francesco

[matg41]

@FrancescoFlammini Thank you for your response.
I have a few additional questions regarding the parameters in the input file. Should I ask them here or start a new topic?
Thank you,
Mohammad

[FrancescoFlammini]

Hi @matg41 just use this one no problem!

[matg41]

I'm preparing to start a simulation based on real-world data gathered from Gaia DR3. I have the current values for the cluster. I'm wondering about the following:

1. Is it acceptable to create the dat.10 file using the current data and start the simulation from there?
2. Should the initial condition and data in dat.10 represent the cluster's state when it was first formed, rather than its current state?

I'd appreciate any guidance on how to properly set up the initial conditions for this simulation using the Gaia DR3 data.
Thank you!
Mohammad

[kaiwu-astro]

Hi Mohammad, I think the answers to these questions largely depend on your research goal.

1. in which aspect "acceptable"? Always remember the chaotic nature of N-Body problems. It is extremely hard to preciously predict the positions/velocities of all stars after some time. Also note that all physical quantities from Gaia observation come with an uncertainly. They again make the chaos pronounce. The valuable information lies in statistical quantities, such as lagrangian radii of the cluster.
2. again, it largely depends on your research question. If you want to know how this star cluster is formed, then maybe the initial condition should be a baby cluster. If you want to know the future, then observation may be good; but again, be careful what quantites you want to study.

For more info about N-body simulation, take a look at Spurzem & Kamlah 2023 https://ui.adsabs.harvard.edu/abs/2023LRCA....9....3S/abstract
You may also want to look at how we study clusters which to some extent resemble NGC 4372: https://ui.adsabs.harvard.edu/abs/2016MNRAS.458.1450W/abstract

Feel free to ask more. Regards, Kai

[matg41]

Hello dear participants, I am currently trying to determine the appropriate inputs for the &XTRNL0 configuration when kz(14) = 3 for a cluster located within the Milky Way, for which I have known position and velocity data. I would like to confirm whether the following inputs appear appropriate based on the latest version of the document available on Overleaf:

GMG: 1.5E12
DISK: 8.5E10
A: 5.5
B: 0.25
VCIRC: 220
RCIRC: 7.5
GMB: 1.8E10
AR: 0.22
GAM: 0.5
RG: (l, b, ?)
VG: (v1, v2, v3)
MP: Mass of the cluster
AP: Half-mass radius / 1.3
MPDOT: ?
TDELAY: ?

Additionally, I was unable to find any resources to calculate the third element of RG (if it requires a third element), as well as MPDOT and TDELAY. Any guidance or references on these parameters would be greatly appreciated. Thank you for your assistance!

[FrancescoFlammini]

Dear @matg41 ,

sorry for the late response. The 3 terms are directly connected to the initial conditions of your choice

RG Initial position; DISK+VCIRC=0, VG(3)=0: A(1+E)=RG(1), E=RG(2)
MPDOT Decay time for gas expulsion (MP = MP0/(1 + MPDOT*(T-TD))
TDELAY Delay time for starting gas expulsion (T > TDELAY)

The latter two simply depend on the decay time for your gas in the external potential model. It depends on several factors, and from a dynamical point of view it shouldn't have much impact. You have to wonder how gas is important there (especially in terms of star cluster age).

For the RG, you can see it depends simply on the coordinates you chose for your system. It is your "z" coordinate. If you leave the space empty in the input file, the code will automatically pick the default value (which should be 0 for all your issued parameters).

Best regards and sorry for the late answer,
Francesco