Decoding NGC 7252 as a blue elliptical galaxy
First author: Koshy George
Elliptical galaxies with blue optical colours and significant star formation are hypothesised to be major merger remnants of gas rich spiral galaxies or normal elliptical galaxies with a sudden burst of star formation. We present here a scenario where blue elliptical galaxies identified from shallow imaging surveys may fail to recover faint features indicative of a past merger activity using a nearby major merger remnant. Based on deep optical imaging data of a post merger galaxy, NGC 7252, we demonstrate that the galaxy can appear as an elliptical galaxy if observed at higher redshifts. The main body and the low-surface brightness merger features found at the outskirts of the galaxy are blue in optical g-r colour map. We argue that the higher redshift blue elliptical galaxies discovered in surveys as shallow as the SDSS or DECaLS may be advanced mergers with their defining tidal features falling below the detection limits of the surveys. This should be taken into consideration during the morphological classification of such systems in future and ongoing surveys.