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New satellite galaxies in the halo of nearby spiral galaxy NGC 4631 are noted by superimposed boxes. The insert image displays the full stellar stream extending below and above the Whale galaxy. The picture was produced by combining deep white-light images obtained at the Remote Observatories of the Southern Alps with images from the Blackbird Remote Observatory.
The insert image was produced by combining the larger image with exposures taken through a 40cm corrected newtonian telescope, a FLI ML16803 and Astrodon E-series filters. Exposure times: 385 minutes Luminance, 250 minutes Red, 250 minutes Green and 250 minutes Blue (All 1X1)
Image copyright ©2011- 2015 R Jay GaBany
Insert image copyright ©2015 Karel Teuwen and R. Jay GaBany
The southern portion of the stellar stream, extending to the lower left, and new satellite galaxies in the halo of nearby spiral galaxy NGC 4631 were detected in deep integrated-light images from the Black Bird Remote Observatory. Mouse over the picture for an annoted version of the image.
This image was produced with a RCOS half meter telescope, Apogee Alta U16M camera and Astrodon E-Series filters. Exposure times: 1,065 minutes Luminance, 120 minutes Red, 120 minutes Green, 120 minutes Blue (All 1X1)
Image copyright ©2011- 2015 R Jay GaBany
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Discovery of a stellar tidal stream and new satellite galaxies around the Whale galaxy, NGC 4631
We report the discovery of a stellar tidal stream in the halo of the familiar Whale galaxy (NGC4631), a nearby edge-on spiral interacting with NGC4656, also known as the Hockey Stick galaxy. The stream has two components: a bridge-like feature extended between NGC4631 and NGC4656 and an overdensity with extended features on the opposite side of the NGC4631 disk. The orientation of the southern portion of the stream relative to the orientations of NGC4631 and NGC4656 is not consistent with an origin from interaction between these two spirals, and is more likely debris from a minor merger with a former dwarf satellite.
The stellar tidal features can be qualitatively reproduced by an N -body model that predicts the tidal disruption of a single, massive dwarf satellite on a moderately eccentric orbit around NGC 4631 over approximately 3.5 Gyr (billion years).
Our deep images also detected the presence of two overdensities. Their morphology is consistent with that of faint, extended dwarf galaxy satellites of NGC 4631. A third galactic satellite candidate was subsequently confirmed in a separate investigation conducted by B. Javanmardi, D. Martinez-Delgado, et al.
Download the full resolution version of the scientific paper (PDF)
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