### Ultra-Compact Dwarfs and stellar streams : astrophysics @arXiv

Title : NGC 3628-UCD1 : A possible omega centauri analog embedded in a stellar stream.

Let me give you a bit of an introduction in the first place. Stellar streams are streams of stars around a central galaxy, streams assumed to be filled with left over stars from a galaxy merger between a minor galaxy and said central galaxy. In this case, NGC 3628 is the central galaxy and the newly discovered UCD1 is proposed to be a remnant of such a merger-interaction. Also, FYI UCDs stands for Ultra-Compact Dwarfs.

Moving on, as the authors mention in the second section, they were observing the galaxy NGC 3628 and it's associated stellar stream in 2009 when they discovered a bigger object/clump seemingly embedded in the stellar stream. They finally got around to observing the clump in 2014 (what i'm going to take away from this is the fact that there aren't enough grad students to reduce/analyze all the data being acquired so yeah, maybe I'll find a grad position somewhere! :D).

The authors then go on to describe the observations they conducted, photometry and spectroscopy, of UCD1. Based on photometry, they estimate the distance to the clump, proving that the clump is in fact present in the stellar stream and isn't an artifact in our line of sight (because only multi-band photometry or spectroscopy can tell us 3D information, visually we only see 2D information in astronomy). Using spectroscopy, the authors estimate the metallicity of the clump, it's velocity and velocity dispersion. Further, using photometry of the stellar stream, they estimate what the mass of a progenitor galaxy would've been if the clump UCD1 was in fact a remnant from a galaxy merger. The authors also estimate the size and mass of the progenitor galaxy from the stellar stream and UCD1 mass.

On a different note, the first thing that I noticed with the paper was the fact that Dr. David Martinez-Delgado was involved with the work, whose research I followed earlier last year. His work on tidal streams of stars around host galaxies is really interesting and his use of small to medium sized telescopes to obtain deep pictures (very long exposures) is inspiring. Dwarf galaxies are an interesting part of astronomy now-a-days and are becoming easier to detect and study because we're able push down the minimum observable magnitude limit for dwarf galaxies. Studies of tidal streams and dwarf galaxies are definitely things to look out for because these are exciting times!