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Using Subaru/Suprime-Cam wide-field imaging and both Keck/ESI and LBT/MODSspectroscopy, we identify and characterize a compact star cluster, which weterm NGC 3628-UCD1, embedded in a stellar stream around the spiral galaxy NGC3628. The size and luminosity of UCD1 are similar to $\omega$ Cen, the mostluminous Milky Way globular cluster, which has long been suspected to be thestripped remnant of an accreted dwarf galaxy. The object has a magnitude of$i=19.3$ mag (${\rm L}_{\rm i}=1.4\times10^{6}~{\rm L}_{\odot}$). UCD1 ismarginally resolved in our ground-based imaging, with a half-light radius of$\sim10$ pc. We measure an integrated brightness for the stellar stream of$i=13.1$ mag, with $(g-i)=1.0$. This would correspond to an accreted dwarfgalaxy with an approximate luminosity of ${\rm L}_i\sim4.1\times10^{8}~{\rmL}_{\odot}$. Spectral analysis reveals that UCD1 has an age of $6.6$ Gyr ,$[\rm{Z}/\rm{H}]=-0.75$, an $[{\alpha}/\rm{Fe}]=-0.10$. We propose that UCD1 isan example of an $\omega$ Cen-like star cluster possibly forming from thenucleus of an infalling dwarf galaxy, demonstrating that at least some of themassive star cluster population may be created through tidal stripping.

NGC 3628-UCD1: A possible $\omega$ Cen Analog Embedded in a Stellar Stream