Searching for intermediate mass black holes: understanding the data first

TL;DR

This paper investigates the challenges in detecting intermediate mass black holes in globular clusters by simulating integral field spectroscopy observations and highlighting biases caused by bright stars.

Contribution

It introduces a method to create realistic mock IFU data from Monte Carlo simulations to understand observational biases in IMBH detection.

Findings

Luminosity-weighted IFU observations are biased by bright stars.

Intrinsic scatter in velocity dispersion measurements can obscure IMBH signatures.

Properly accounting for scatter is crucial for accurate IMBH detection.

Abstract

The detection of intermediate mass black holes (IMBHs) in globular clusters has been hotly debated, with different observational methods delivering different outcomes for the same object. In order to understand these discrepancies, we construct detailed mock integral field spectroscopy (IFU) observations of globular clusters, starting from realistic Monte Carlo cluster simulations. The output is a data cube of spectra in a given field-of-view that can be analyzed in the same manner as real observations and compared to other (resolved) kinematic measurement methods. We show that the main discrepancies arise because the luminosity-weighted IFU observations can be strongly biased by the presence of a few bright stars that introduce a scatter in velocity dispersion measurements of several km/s. We show that this intrinsic scatter can prevent a sound assessment of the central kinematics, and therefore should be fully taken into account to correctly interpret the signature of an IMBH.