This composite image was produced by combining exposures from the Vatican Advanced Technology Telescope (VATT), using the VATT4k imager; data from the GALEX Deep Imaging Survey and images from the Sloan Digital Sky Survey Data Release 9. Image preparation by R. Jay GaBany.

Image copyright 2014 R Jay GaBany

Cannibalization and rebirth in the NCG 5387 system

NGC 5387

In the hierarchical galaxy formation paradigm, also known as the Standard Model or Lambda Cold Dark Matter (LCDM), the haloes of Milky Way sized galaxies were built by the assimilation of less massive galaxies through minor accretion events. During their merger, satellite galaxies can become tidally disrupted due gravitational forces that cause some stars to be pulled into long streams.

Computer simulations of minor accretion events within the LCDM context predict stellar streams can assume a variety of morphologies that are determined by their orbital parameters: "great circles" from circular orbits (see NGC 5709); "umbrellas" (see NGC 4651) and "shells" (see NGC 3521) from radial orbits and "mixed" morphologies from old mergers of various orbital types.

Similar modeling that tracks the build-up of material in halos suggests the distribution of tidal debris within the haloes of galaxies similar to the Mikly Way are based on their accretion history- more specifically, the number, mass, and timing of individual accretions.

In contrast to detailed predictions from computer simulations, the observational portrait of minor accretion events is far from complete, owing primarily to the inherent difficulty of detecting tidal features due to their extremely low surface brightness.

In this paper, we present the case of the NGC 5387 system- a spiral galaxy identified to be in the rare state of an ongoing satellite accretion event based on imaging from the Sloan Digital Sky Survey Data Release 9, the Vatican Advanced Technology Telescope (VATT) and the Galaxy Evolution Explorer (GALEX) Deep Imaging Survey. The event has two notable features:
  • a stellar stream and
  • a blue overdensity that represents either a region of enhanced star formation in the outer disk of NGC 5387 induced by the minor accretion event or the progenitor of the stellar stream experiencing enhanced star formation.

Read the full .pdf documentation.

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