Locating Simulation Predictions for Massive Galaxies
Kelechi Njoku
7 Aug
Hi,
I have been trying to find a way to locate the x, y, and z positions, the halo mass, and the sfr of massive galaxies using the browsable API. I am defining 'massive galaxies" as those that are more massive than 10^9 Msun. I am also limiting my search to galaxies falling in between a redshift range of 5 > z > 3. I have been able to successfully locate the x, y, and z positions, as well as the halo masses and sfr in the redshift range for the provided subhalos.
My confusion lies with:
How to weed out these "massive galaxies".
If the subhalos I am looking at are individual galaxies or are they just empty clumps of dark matter.
I am focusing on galaxies with an SFR of approx. 0 so as to only work with quiescent galaxies. However, with the information I have seen, I can only decipher the halo mass and not the masses of the galaxy within each subhalo. My goal is to collect and analyze all this data on a broad scale.
Please help,
Kelechi Njoku
Dylan Nelson
18 Aug
We often define a "galaxy" as a subhalo with nonzero stellar mass.
It isn't clear if by "more massive than 10^9 Msun" you refer to total halo mass, or stellar mass. I would suggest you should do the latter.
There are many definitions/measurements of stellar mass available, one is e.g. the stellar mass within twice the stellar half mass radius. We commonly use this as a definition of galaxy stellar mass.
In that case, selecting M_star > 1e9 Msun will return galaxies.
I wouldn't call these "massive". Typically, observers would use M_star > 1e11 Msun as a definition of truly massive galaxies.
Some of these will have SFR == 0, or very low values of SFR, and these are all candidates for quiescent galaxies.
Hi,
I have been trying to find a way to locate the x, y, and z positions, the halo mass, and the sfr of massive galaxies using the browsable API. I am defining 'massive galaxies" as those that are more massive than 10^9 Msun. I am also limiting my search to galaxies falling in between a redshift range of 5 > z > 3. I have been able to successfully locate the x, y, and z positions, as well as the halo masses and sfr in the redshift range for the provided subhalos.
My confusion lies with:
I am focusing on galaxies with an SFR of approx. 0 so as to only work with quiescent galaxies. However, with the information I have seen, I can only decipher the halo mass and not the masses of the galaxy within each subhalo. My goal is to collect and analyze all this data on a broad scale.
Please help,
Kelechi Njoku
We often define a "galaxy" as a subhalo with nonzero stellar mass.
It isn't clear if by "more massive than 10^9 Msun" you refer to total halo mass, or stellar mass. I would suggest you should do the latter.
There are many definitions/measurements of stellar mass available, one is e.g. the stellar mass within twice the stellar half mass radius. We commonly use this as a definition of galaxy stellar mass.
In that case, selecting
M_star > 1e9 Msunwill return galaxies.I wouldn't call these "massive". Typically, observers would use
M_star > 1e11 Msunas a definition of truly massive galaxies.Some of these will have
SFR == 0, or very low values of SFR, and these are all candidates for quiescent galaxies.