# Smoothed Particle Inference: A Kilo-Parametric Method for X-ray Galaxy Cluster Modeling

## Abstract

We propose an ambitious new method that models the intracluster medium in clusters of galaxies as a set of X-ray emitting smoothed particles of plasma. Each smoothed particle is described by a handful of parameters including temperature, location, size, and elemental abundances. Hundreds to thousands of these particles are used to construct a model cluster of galaxies, with the appropriate complexity estimated from the data quality. This model is then compared iteratively with X-ray data in the form of adaptively binned photon lists via a two-sample likelihood statistic and iterated via Markov Chain Monte Carlo. The complex cluster model is propagated through the X-ray instrument response using direct sampling Monte Carlo methods. Using this approach the method can reproduce many of the features observed in the X-ray emission in a less assumption-dependent way that traditional analyses, and it allows for a more detailed characterization of the density, temperature, and metal abundance structure of clusters. Multi-instrument X-ray analyses and simultaneous X-ray, Sunyaev-Zeldovich (SZ), and lensing analyses are a straight-forward extension of this methodology. Significant challenges still exist in understanding the degeneracy in these models and the statistical noise induced by the complexity of the models.

- Authors:

- Publication Date:

- Research Org.:
- Stanford Linear Accelerator Center (SLAC)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 878813

- Report Number(s):
- SLAC-PUB-11376

astro-ph/0507613; TRN: US0602601

- DOE Contract Number:
- AC02-76SF00515

- Resource Type:
- Technical Report

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ABUNDANCE; CLUSTER MODEL; GALAXIES; GALAXY CLUSTERS; MONTE CARLO METHOD; PHOTONS; PLASMA; SAMPLING; SIMULATION; STATISTICS; Astrophysics,ASTRO

### Citation Formats

```
Peterson, John R, Marshall, P J, /KIPAC, Menlo Park, Andersson, K, and /Stockholm U. /SLAC.
```*Smoothed Particle Inference: A Kilo-Parametric Method for X-ray Galaxy Cluster Modeling*. United States: N. p., 2005.
Web. doi:10.2172/878813.

```
Peterson, John R, Marshall, P J, /KIPAC, Menlo Park, Andersson, K, & /Stockholm U. /SLAC.
```*Smoothed Particle Inference: A Kilo-Parametric Method for X-ray Galaxy Cluster Modeling*. United States. doi:10.2172/878813.

```
Peterson, John R, Marshall, P J, /KIPAC, Menlo Park, Andersson, K, and /Stockholm U. /SLAC. Fri .
"Smoothed Particle Inference: A Kilo-Parametric Method for X-ray Galaxy Cluster Modeling". United States. doi:10.2172/878813. https://www.osti.gov/servlets/purl/878813.
```

```
@article{osti_878813,
```

title = {Smoothed Particle Inference: A Kilo-Parametric Method for X-ray Galaxy Cluster Modeling},

author = {Peterson, John R and Marshall, P J and /KIPAC, Menlo Park and Andersson, K and /Stockholm U. /SLAC},

abstractNote = {We propose an ambitious new method that models the intracluster medium in clusters of galaxies as a set of X-ray emitting smoothed particles of plasma. Each smoothed particle is described by a handful of parameters including temperature, location, size, and elemental abundances. Hundreds to thousands of these particles are used to construct a model cluster of galaxies, with the appropriate complexity estimated from the data quality. This model is then compared iteratively with X-ray data in the form of adaptively binned photon lists via a two-sample likelihood statistic and iterated via Markov Chain Monte Carlo. The complex cluster model is propagated through the X-ray instrument response using direct sampling Monte Carlo methods. Using this approach the method can reproduce many of the features observed in the X-ray emission in a less assumption-dependent way that traditional analyses, and it allows for a more detailed characterization of the density, temperature, and metal abundance structure of clusters. Multi-instrument X-ray analyses and simultaneous X-ray, Sunyaev-Zeldovich (SZ), and lensing analyses are a straight-forward extension of this methodology. Significant challenges still exist in understanding the degeneracy in these models and the statistical noise induced by the complexity of the models.},

doi = {10.2172/878813},

journal = {},

number = ,

volume = ,

place = {United States},

year = {2005},

month = {8}

}