Kinematical and Photometric Deconstruction of the UGC 694-IC 412 System: Evidence for a Line-of-Sight Projection

TL;DR

This paper demonstrates that the apparent interaction between galaxies UGC 694 and IC 412 is a line-of-sight projection, confirmed by kinematic and photometric analysis showing they are at vastly different distances.

Contribution

The study provides a comprehensive kinematical and photometric analysis that conclusively shows the galaxies are not interacting but are aligned by chance along the line of sight.

Findings

UGC 694 and IC 412 are separated by approximately 123.5 Mpc.

The velocity difference between the galaxies is about 8372 km/s.

Morphological disturbances in UGC 694 are likely due to internal processes, not interaction.

Abstract

This study re-evaluates the previously assumed interaction between the galaxy pair UGC 694 and IC 412 through a combined kinematical and photometric approach. While morphological features such as tidal bridges have been visually identified in past surveys, our quantitative analysis using SDSS DR16 kinematical data reveals a significant radial velocity offset of approximately 8372 km/s. UGC 694 exhibits a heliocentric velocity of 12683 +/- 34 km/s, placing it at a distance of approximately 188 Mpc, whereas IC 412 is located in the foreground at approximately 62 Mpc with a velocity of 4311 +/- 46 km/s. This vast spatial separation of approximately 123.5 Mpc confirms that the perceived proximity is a line-of-sight projection effect rather than a physical gravitational encounter. Furthermore, we utilize differential photometry to analyze the structural asymmetry and color distribution of UGC 694. Our photometric findings suggest that the galaxy's disturbed morphology is not a result of a tidal encounter with IC 412, but likely originates from internal evolutionary processes or minor mergers with undetected companions. This work emphasizes the critical role of multi-wavelength validation in classifying interacting systems to avoid misinterpretation due to projection effects.