CHUN-HAO TO PRO
I am a cosmologist!
*chto@uchicago.edu
Cosmological constraints from joint analyses of clusters, galaxies, and weak lensing
Chun-Hao To*, DES cluster working group
Galaxy Cluster physics
Dark Matter Halo
~
5\times 10^{14} M_\odot
Red galaxies
~ 2% of the mass
Hot gas
~ 10% of the mass
Nihar Dalal's talk
Cosmology
Galaxy physics
Baryonic feedback
Yang+03, Lin&Mohr04, More+16,
Kravstov+18, Shin+19, To+20 (APJ 897,15), ... many more
Vikhlinin+06, Eckert+16,
To+24 (JCAP 2024, 037), Dalal+25, Kovac+25, Siegel+25, ...many more
Clusters
Dark Matter Halo:
Rare peaks in the density field.
250 Mpc/h
Cluster Cosmology
Dark Matter Halo:
Rare peaks in the density field.
Abundances are exponentially sensitive to the amount of structure.
More structures
Bahcall 95, Wang&Steinhardt 98, Borgani+ 01, Allen+ 03, Vikhlinin+ 09, DeHann+16, To+ 21, Bocquet+24,... many more
Invisible
Cluster Cosmology
Text
Cluster mass
Cluster Cosmology
Bocquet+24 (SPT), Ghirardina+24 (eROSITA), Mantz+14 (WtG),... many many more
Cluster Cosmology
~6500 clusters found in DES Y1
Cluster Cosmology
DES+20
Photo-z uncertainty at z=0.2 ~= 100 Mpc/h
- Optical clusters have 20-30 % contributions from line-of-sight galaxies.
- Modeling these components (and their impact on the weak lensing profile) is essential for unbiased cluster cosmology.
To+21 (MNRAS 502,4093) , Lee+22, Wu+22, Zhang+23, and many more
How should we proceed?
How should we proceed?
- Clusters are really part of the large-scale structure.
How should we proceed?
-
Clusters are really part of the large-scale structure.
- Analyze clusters in the same way as galaxies.
Why do we want to make it even more complicated?
Why do we want to make it even more complicated?
Adding more data makes modeling simpler:
- Focusing on large scales where we can model the data perturbatively (>0.2 Mpc/h vs >8 Mpc/h).
- Self-calibrating projection effects.
- Easily integrated into joint analyses.
Reanalysis of DES-Y1 data
Large-scale only reanalysis
DES-Y1 clusters
To&Krause+ 21 (PRL, 126, 141301)
DES Y1
DES Y3 (>16k clusters)
DES Y3 clusters are unique
Merloni+24, Kornoelje+25, DES+25, see also ACTDESHSC Collaboration+25 (ACT DR6)
[SPT deep]
Y3 cluster cosmology are challenging due to high S/N
- 19 astrophysical parameters describing the connection of measurements and matter fluctuations (linear galaxy bias, intrinsic alignments, mass—observable relations, and projection effects)
- 12 observational parameters describing observational systematics (photometric redshift and shear measurement)
DES standard!
To+25 (PRD, 112, 063537)
Exhaustively test possible systematics
Title Text
Subtitle
Simulations (Cardinal, To+24, APJ,961,59) to test cluster finding algorithm.
To+25 (PRD, 112, 063537)
Cosmological constraints from DES-Y3 assuimg model.
\Lambda \rm{CDM}
DES cluster
In addition to the 9 modeling tests, we pass an additional 9 null tests.
We unblind!
DES+25 (PRD accepted)
DES cluster
Cosmology constraints (50% improvements relative to DES-Y1):
S_8=0.864\pm 0.04
\Omega_{\rm{m}}=0.27^{+0.02}_{-0.03}
DES+25 (PRD accepted)
Multiwavelength cluster
| Detection | red galaxy | Gas | Gas |
| Mass and redshift | low mass high z | high mass | low z |
| Analysis | Large-scale | Small-scale | Small-scale |
eRASS1
SPT
DES
DES+25 (PRD accepted)
DES internal consistency
Posterior Predictive Distribution (PPD) with a criteria PPD (d1|d2)>0.01.
P(cosmic shear | CL+GC, ΛCDM) = 0.04> 0.01
P(cosmic shear + galaxy-galaxy lensing| CL+GC) = 0.07>0.01
DES+25
DES+25 (PRD accepted)
All probes combined
DES joint analyses of clusters, galaxies, and weak lensing (CL+3x2pt):
S_8=0.81\pm 0.02
\Omega_{\rm{m}}=0.27^{+0.02}_{-0.03}
24% improvements compared to 3x2pt.
DES+25
DES+25 (PRD accepted)
DES+25
Under CDM
- The matter density of the universe from CL+3x2pt is consistent with DES and DESI BAO.
- But is 2.04 lower than DES-Y5 SN.
\Lambda
\sigma
DES+25 (PRD accepted)
Actively analyze full DES data
Actively analyze full DES data
Extending the model to test evolving dark energy.
w0-waCDM model
Stay tuned for the new Y6 constraints!
DES Y1
DES Y1 reanalysis
Clusters as individual objects
Clusters as part of large-scale structure
cosmo25
By CHUN-HAO TO
