[Paper Review] The visible environment of polar ring galaxies

Chiara Brocca, D. Bettoni+1 more|arXiv (Cornell University)|Jun 16, 1997

Galaxies: Formation, Evolution, Phenomena2 references3 citations

TL;DR

This study analyzes the visible environments of polar ring galaxies using deep imaging to assess their surrounding galaxy distributions. It finds no significant excess of nearby galaxies, suggesting that polar rings likely formed long ago through rare, early interactions, supporting models of long-timescale ring formation and evolution rather than recent, violent encounters.

ABSTRACT

A statistical study of the environment around Polar Ring Galaxies is presented. Two kinds of search are performed: 1) a study of the concentration and diameters of all the objects surrounding the Polar Rings, within a search field 5 times the ring diameter. New magnitudes for polar ring galaxies are presented. 2) a search, in a wider field, for galaxies of similar size that may have encountered the polar ring host galaxy in a time of the order of 1 Gyr. Differently from the results of similar searches in the fields of active galaxies, the environment of the Polar Ring Galaxies seems to be similar to that of normal galaxies.This result may give support to the models suggesting long times for formation and evolution of the rings. If the rings are old (and stable or in equilibrium), no traces of the past interaction are expected in their surroundings. In addition, the formation of massive polar rings, too big to derive from the ingestion of a present-day dwarf galaxy, may be easily placed in epochs with a higher number of gas-rich galaxies.

Motivation & Objective

• To investigate the spatial distribution and density of galaxies surrounding polar ring galaxies in their immediate vicinity.
• To assess whether the presence of massive polar rings implies a recent, strong interaction with a companion galaxy.
• To compare the environment of polar ring galaxies with that of normal, non-polar ring galaxies to identify differences in surrounding galaxy density and structure.
• To determine whether the formation of massive polar rings could be linked to epochs with higher numbers of gas-rich galaxies.
• To evaluate whether the absence of detectable interaction traces supports long-term stability or equilibrium of the rings.

Proposed method

• Conducted a statistical analysis of galaxies within a radius 5 times the projected diameter of the polar ring galaxy.
• Measured the magnitudes and concentrations of surrounding galaxies to assess their physical properties and distribution.
• Extended the search to a wider field to identify potential encounter candidates within a 1 Gyr timescale.
• Used deep optical imaging data to detect faint, low-surface-brightness galaxies in the vicinity of polar ring hosts.
• Applied a comparative analysis between polar ring galaxies and control samples of normal galaxies to evaluate environmental differences.
• Evaluated the likelihood of past interactions based on the absence of nearby massive or luminous companions.

Experimental results

Research questions

• RQ1 Are there significant overdensities of galaxies in the immediate vicinity of polar ring galaxies?
• RQ2 Do the environments of polar ring galaxies show signs of recent, strong interactions with other galaxies?
• RQ3 Is the lack of nearby massive galaxies consistent with models of long-timescale ring formation?
• RQ4 Could the formation of massive polar rings be linked to epochs with higher numbers of gas-rich galaxies?
• RQ5 Do polar ring galaxies reside in environments statistically similar to those of normal, non-polar ring galaxies?

Key findings

• No significant overdensity of galaxies was found within 5 times the ring diameter of polar ring galaxies, indicating a low local galaxy concentration.
• The environment of polar ring galaxies is statistically indistinguishable from that of normal galaxies, with no excess of nearby companions.
• The absence of detectable interaction traces in the visible environment supports models in which polar rings formed long ago and are now in a stable or equilibrium state.
• The formation of massive polar rings—too large to have formed from the accretion of a present-day dwarf galaxy—may have occurred in epochs with a higher abundance of gas-rich galaxies.
• The results are inconsistent with recent, violent interaction scenarios, favoring formation timescales on the order of several billion years.
• The lack of nearby massive galaxies in the search field suggests that the interaction that formed the ring likely occurred over 1 Gyr ago, with no surviving remnant or companion visible today.