Cannibalization and Rebirth in the NGC5387 System. I. The Stellar Stream
  & Star Forming Region
  We have identified a low surface brightness stellar stream from visual
inspection of SDSS imaging for the edge-on, spiral galaxy NGC5387. A blue
overdensity was also identified in SDSS coincident with the stream intersection
with the NGC5387 disk. The overdensity was also detected in the GALEX Deep
Imaging Survey and found to contribute 38% of the total FUV integrated flux
from NGC5387, which suggests that the region is actively forming stars. Deeper
imaging was acquired with the Vatican Advanced Technology Telescope (VATT) in
the B, V, and R filters that confirmed the presence of both the stellar stream
and the blue overdensity. Analysis of the VATT photometry indicates the stellar
stream is red in color, B-V = 0.7, and has a stellar mass of 6x10^8
M$_{\odot}$, which implies a merger ratio of 1:50. Assessment of the stream
morphology suggests that the merger event has a circular radius, R~16 kpc, the
stream formed in ~400 Myr, and the progenitor had a total mass of ~2x10
M$_{\odot}$. Spectroscopy from LBT+MODS1 was used to determine that the blue
overdensity is at the same redshift as NGC5387, consists of young stellar
populations (~10 Myr), is metal-poor (12 + log(O/H) = 8.03), and forming stars
at an enhanced rate (~1-3 M$_{\odot}$/year) given its total stellar mass
(2x10^7 M$_{\odot}$). Several interpretations are posited to explain these
observational data, of which the most likely are (i) that the blue overdensity
is a region of enhanced star formation in the outer disk of NGC5387 induced by
the minor accretion event, and (ii) that the blue overdensity is the progenitor
of the stellar stream undergoing a period of enhanced star formation as a
result of its interaction with NGC5387. Confirmation and theoretical
exploration of these scenarios are presented in a companion paper.
