Tidal Streams in the Local Group and Beyond by Heidi Jo Newberg & Jeffrey L. Carlin

Author:Heidi Jo Newberg & Jeffrey L. Carlin
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

5.2.3.2 Arifyanto and Fuchs

In the same year as Helmi et al. were mining the Geneva-Copenhagen survey , a group in Germany (Arifyanto and Fuchs 2006) were searching for accretion debris in a sample of 742 stars based on a catalogue from Carney et al. (1994). This resulted in the detection of a number of streams, but none are believed to be due to accretion; three had been previously identified (Hyades -Pleiades , Hercules and Arcturus ; discussed above) and there was a new discovery, again not conclusively extragalactic in origin (Ramya et al. 2012).

However, despite not identifying any bone-fide accretion remnants, this paper warrants discussion here for its approach to identify nearby streams. Using a Keplerian approximation for orbits developed by Dekker (1976), Arifyanto and Fuchs (2006) determine proxies for the total angular momentum and eccentricity, along with a third parameter corresponding to the inclination of the orbit (see Klement 2010 for a review of this method). They argue that this three dimensional space is ideal for dissecting velocity space, as evidenced by their success at finding the above disk streams. This method is simple to apply and unlike the previous APL approach does not require orbits to be calculated, but it is not perfect as it relies on the aforementioned Keplerian approximation that only holds for spherical potentials . Despite these drawbacks it has proved a popular approach that has been used by numerous authors, mainly by employing the proxy for the eccentricity (). Although the approximations behind this proxy break down for high eccentricities, overdensities should remain coherent, and so the simplicity of this approach has resulted in its widespread use.

Another early paper to adopt this technique was Dettbarn et al. (2007), who analysed the sample of Beers et al. (2000) and found a number of candidate halo streams, including existing groups (such as the Helmi stream) and some new ones (named S1, S2, and S3).

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