The influence of particle background on galaxy cluster observations of the EP-FXT

Many X-ray astronomical observatories are dedicated to observing cosmic phenomena such as galaxy clusters, which inevitably involves the influence of background. When observing the universe, there are mainly two types of background: the cosmic X-ray background and the particle background, known as non-X-ray background. Understanding the variation of the particle background is crucial for the observations made by the Einstein Probe (EP) satellite.

In order to simulate the observation effects of EP-FXT, this paper utilized fixed-point observation data obtained from eROSITA’s Performance Verification phase and Filter Wheel Closed data to construct a background model. Subsequently, based on the eROSITA background model, an EP-FXT background model was established. Due to the different orbits, the particle background of eROSITA is about seven times that of EP-FXT. Based on this, a comparison was made between the high-particle-background model and the low-particle-background model in the observation of galaxy clusters.

The results indicate that, without systematic errors, a high background leads to a 20% increase in the errors of the fitting parameter.

The impact of systematic errors is more pronounced in observations with high particle backgrounds. Additionally, the low particle background demonstrates clear advantages in the fitting of temperature and metallicity parameters, with this advantage becoming more significant as the temperature and metallicity increase.