Nicole Drakos
Research Blog
Welcome to my Research Blog.
This is mostly meant to document what I am working on for myself, and to communicate with my colleagues. It is likely filled with errors!
This project is maintained by ndrakos
Quiescent Galaxies in COSMOS-Web
In this post, I’m going to look at how many quiescent galaxies COSMOS-Web will be able to detect (as predicted from the DREaM catalogs). I will consider a galaxy detectable if it is brighter than 28 mag in at least one of the COSMOS-Web NIRCAM filters.
Completeness and Number Counts
Here are the stellar mass functions of detectable quiescent galaxies, with the underlying model (from Williams et al. 2018) shown with dotted lines. Note that the DREaM catalog extends down to \(10^5\) solar masses, and that COSMOS-Web will be complete above \(10^9\) or so.
Here are the number counts:
| Redshift | Number of Quiescent Galaxies (above mass \(5\times 10^9\)) | Detectable Quiescent Galaxies (above mass \(5\times 10^9\)) |
|---|---|---|
| 1 | 287195 (5350) | 16678 (5350) |
| 2 | 3844 (3164) | 3791 (3164) |
| 3 | 1070 (881) | 1060 (881) |
| 4 | 482 (398) | 472 (398) |
| 5 | 114 (91) | 111 (91) |
| 6 | 49 (38) | 49 (38) |
| 7 | 11 (10) | 10 (10) |
| 8 | 5 (5) | 5 (5) |
| 9 | 1 (1) | 1 (1) |
| 10 | 1 (1) | 1 (1) |
There are a couple of things I didn’t expect here! The first is that at a depth of 28 mag, all of the quiecent galaxies above \(5\times 10^9\) solar masses will be detected. The other thing I didn’t expect is that since all the quiescent galaxies are expected to be very massive at high redshift galaxies, we could detect all the quiescent galaxies in the field at high redshift. Note that quiescent galaxies very well might not actually exist at redshifts ~10. However, it seems likely that COSMOS-Web will contain the highest-redshift quiescent galaxy detected.
Number Densities
Here is the number density as a function of redshift (similar to Fig. 7 in Merlin et. al 2019). Error bars are just the Poisson noise.
The dashed lines show 1/V(>z) (truncating at a redshift of 12) for different survey volumes. 100 arcmin^2 should be similar to CEERS, and 300 arcmin^2 should be similar to JADES.
If I overlay this on top of the Merlin plot I find the following:
The DREaM catalog contains a higher number density of high-redshift quiescent galaxies than other simulated data sets, but it is still consistent with observations.