[Paper Review] Interaction of Galaxies with the ICM

J. H. van Gorkom|arXiv (Cornell University)|Aug 12, 2003

Astronomy and Astrophysical Research3 citations

TL;DR

This paper establishes that ram pressure stripping by the intracluster medium (ICM) is a dominant mechanism for transforming disk galaxies in clusters, causing hydrogen deficiency, truncated gas disks, and suppressed star formation. Hydrodynamical simulations and multiwavelength observations confirm that ICM interactions explain observed trends in H I morphology, kinematics, and star formation suppression out to two Abell radii.

ABSTRACT

In recent years a wealth of data and detailed hydrodynamical simulations have appeared that show the effects of interactions between the ICM and galaxies. Single dish observations show that cluster galaxies are deficient in their HI content out to 2 Abell radii. The deficient galaxies tend to be on radial orbits. Imaging of the HI distribution in individual galaxies shows a remarkable trend of HI extent with location in the cluster. These trends can be reproduced in simulations of ram pressure stripping by the ICM using SPH and 3D hydro-codes. Detailed imaging of individual galaxies shows in some caes undisturbed old stellar disks, truncated gas disks that are much smaller than the stellar disks, asymmetric extraplanar gas in the center and enhanced central star formation. These phenomena have all been predicted by hydrodynamical simulations. Optical imaging and spectroscopic surveys show that small HI disks go together with truncated star forming disks, that HI deficiency correlates with suppressed star formation rates and that the spatial extent of HI deficiency in clusters is matched by or even surpassed by the extent of reduced star formation rates. Recent volume limited HI imaging surveys of clusters in the local universe show that most gas rich galaxies are located in groups and subclumps, that yet have to fall into the clusters. In these groups we see much evidence for interactions between gas rich galaxies.

Motivation & Objective

• To determine the role of the intracluster medium (ICM) in transforming disk galaxies within galaxy clusters.
• To assess whether ram pressure stripping explains observed hydrogen deficiency and morphological changes in cluster galaxies.
• To evaluate the relative importance of ICM interactions versus gravitational interactions in shaping galaxy evolution in clusters.
• To link observational trends in H I distribution and star formation with hydrodynamical simulations of ICM-galaxy interactions.
• To investigate the spatial extent and dynamical triggers of ICM-induced environmental effects, including the role of cluster substructures and infall trajectories.

Proposed method

• Utilized hydrodynamical simulations with SPH and full 3D hydro-codes to model ram pressure stripping of galactic ISM by the ICM.
• Compared simulation outputs with multiwavelength observations, including single-dish and synthesis imaging of H I in Virgo and Coma clusters.
• Analyzed optical imaging and spectroscopic surveys to correlate H I deficiency with star formation rate suppression.
• Employed volume-limited H I surveys to map the spatial distribution of gas-rich galaxies relative to cluster substructures and infall regions.
• Integrated kinematic data from H I observations to constrain simulation parameters and validate predicted gas morphologies.
• Evaluated the impact of cluster dynamics—such as subcluster mergers and bulk ICM motions—on the reach and efficiency of ram pressure stripping.

Experimental results

Research questions

• RQ1 To what extent does ram pressure stripping by the ICM explain the observed hydrogen deficiency and truncated gas disks in cluster galaxies?
• RQ2 How do the spatial distributions of H I deficiency and suppressed star formation correlate with cluster-centric radius and orbital dynamics?
• RQ3 What is the relative contribution of ICM interactions versus gravitational interactions (e.g., in groups) to galaxy transformation in cluster environments?
• RQ4 Can hydrodynamical simulations reproduce the observed morphological and kinematic features of gas-poor, non-star-forming disk galaxies in clusters?
• RQ5 How does the dynamical state of a cluster (e.g., merging subclusters) influence the spatial extent and effectiveness of ICM-induced stripping?

Key findings

• H I deficiency in cluster galaxies extends out to approximately two Abell radii, with the most deficient galaxies on radial orbits, consistent with ram pressure stripping during infall.
• Detailed H I imaging reveals truncated gas disks and asymmetric extraplanar gas in individual galaxies, features predicted by hydrodynamical simulations of ram pressure stripping.
• Star formation rates are suppressed in H I-deficient galaxies, with the extent of suppression matching or exceeding the spatial extent of H I deficiency, indicating a strong causal link.
• Gas-rich galaxies are predominantly found in low-velocity dispersion groups and subclumps on the outskirts of clusters, suggesting that pre-infall interactions may play a major role in galaxy transformation.
• Observations show that galaxies in these outer groups exhibit strong H I distortions and interactions, indicating that environmental effects begin well before entry into the dense ICM.
• The reach of ICM effects—extending to 2 R_A—may be enhanced in dynamically active clusters with bulk motions and shocks, explaining why stripping is observed far from the cluster core.