Detection of Ionized Gas in the Globular Cluster 47 Tucanae

By P. Freire, Michael Kramer, Andrew G. Lyne, F. Camilo, R. Manchester, N. N. J. Bank, Columbia, Atnf, Bologna. 2001

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We report the detection of ionized intracluster gas in the globular cluster 47 Tucanae. Pulsars in this cluster with a negative period derivative, which must lie in the distant half of the cluster, have significantly higher measured integrated electron column densities than the pulsars with a positive period derivative. We derive the plasma density within the central few parsecs of the cluster using two different methods that yield consistent values. Our best estimate of ne = 0.067 ± 0.015 cm-3 is about 100 times the free electron density of the interstellar medium in the vicinity of 47 Tucanae, and the ionized gas is probably the dominant component of the intracluster medium.

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Citations in the corpus

• Eight New Millisecond Pulsars in NGC 6440 and NGC 6441 (2007, background): “The congregation 13 The exception is 47 Tucanae (Freire et al. 2001b) where the DM differences between pulsars are predominantly due to gas intrinsic to the GC. 14 See E. M. Standish 1998, JPL Planetary and Lunar Ephemerides, available from http://ssd.jpl.nasa.gov/iau-comm4/de405iom/de405iom.pdf. of”
• The multimessenger picture of compact object encounters: binary mergers versus dynamical collisions (2012, background): “The only globular cluster where gas is clearly detected is 47 Tuc, where the density of ionized gas is of order 0.1 cm−3 (Freire et al. 2001).”
• The Vertical Structure of Warm Ionised Gas in the Milky Way (2008, background): “The DM contribution from the globular cluster itself is expected to be negligible (Freire et al. 2001; Howk et al. 2003).”
• Science with ASKAP (2008, background): “Recent observations of globular clusters have led to the discovery of the fastest spinning pulsar [128], the shortest orbital period of any known radio pulsar [51], an analysis of the surface mass density of globular clusters [103], and the detection of ionised intracluster gas [104].”