Radio Galaxy Classification: #Tags, Not Boxes

Lawrence Rudnick

doi:10.3390/galaxies9040085

Abstract

After six decades of studying radio galaxies, we are now delightfully overwhelmed by their exponentially expanding numbers and the complexity of their structures. Similarly, the methods we use to classify radio galaxies have exploded, often resulting in conflicting terminology, ambiguous classifications, and historical schemes that may or may not match our current physical understanding. After discussions with more than 100 radio astronomers over the last several years and listening to their ideas and aspirations, I propose that we reconceptualize the classification of radio galaxies. Instead of trying to place them into “boxes”, we should assign them #tags, a system that is easy to understand and apply, that is flexible and evolving, and that can accommodate conflicting ideas with respect to what is relevant and important. Here, I outline the basis of such a #tag system; the rest is up to the community.

Highlights

IntroductionWhy do we classify radio galaxies, or any objects for that matter? I observe three main benefits to classification in general:
Why do we classify radio galaxies, or any objects for that matter? I observe three main benefits to classification in general: Citation: Rudnick, L
Could we find a group of astronomers to decide on what a dying radio galaxy is? Often, objects do not fit nicely into the boxes we have defined—ADS lists 230 articles with “hybrid,”

Summary

Introduction

Why do we classify radio galaxies, or any objects for that matter? I observe three main benefits to classification in general:. Why do we classify radio galaxies, or any objects for that matter? We group together objects with very different physical origins (e.g., the broad variety of “X-shaped” radio galaxies), confounding studies that look for correlations and or that develop physical models, etc. Other classes can be combined, e.g., a source can be in both the FRI and narrow-angle tail classes These multiple uses and the lack of a clear definition for many of the classes can result in confusion and, worse, can result in scientifically inconsistent results from different studies. Other measured quantities, such as polarization information as a function of wavelength or.

Tag Example

Conclusions