A. P. Sarma et al. 2005 The Astronomical Journal 130 2566 doi:10.1086/497637
A. P. Sarma1, E. Momjian2, T. H. Troland3 and R. M. Crutcher4
Show affiliationsWe present Very Large Array (VLA) observations of 21 cm H I absorption in the high-velocity (HV) system toward the external galaxy NGC 1275 (Per A). The primary motivation for our observations is to examine whether the only existing (single-dish) detection of the magnetic field in an external galaxy will stand up to independent scrutiny with an interferometer. The H I absorption profile in the HV system toward NGC 1275 has a number of velocity components. In this paper, we focus on the prominent narrow component at 8114 km s-1, in which we have detected the Zeeman effect. The measured line-of-sight magnetic field is Blos = -21.5 ± 6.5 μG. Within the errors, this is consistent with the single-dish detection. A weighted average of the single-dish and VLA detections gives a value for the line-of-sight magnetic field of Blos = -10.7 ± 3.2 μG. The derived ratio of total internal kinetic energy to gravitational energy suggests that the clouds responsible for H I absorption are likely not gravitationally bound. The ratio of magnetic energy to total internal kinetic energy indicates that magnetic effects are likely dominant in these clouds. Finally, the measured ratio of mass to magnetic flux is found to be much lower than the critical value, indicating that the observed H I absorbing clouds are significantly subcritical. This agrees with a recent study of H I absorbing clouds in the cold neutral medium of our Galaxy, thereby extending an important result for Galactic clouds to an extragalactic case.
galaxies: active; galaxies: individual (NGC 1275); galaxies: ISM; galaxies: magnetic fields; radio lines: galaxies
Issue 6 (2005 December)
Received 2005 April 5, accepted for publication 2005 August 30
A. P. Sarma et al. 2005 The Astronomical Journal 130 2566
Mathew Bligh et al 2008 J. Micromech. Microeng. 18 055007
Kuang-Sheng Hong et al 2006 J. Micromech. Microeng. 16 1660
A R Prasanna and Subhendra Mohanty 2003 Class. Quantum Grav. 20 3023
T Skoskiewicz et al 1974 J. Phys. C: Solid State Phys. 7 2670
M Van den Nest et al 2007 New J. Phys. 9 204
Mark Alford and Krishna Rajagopal JHEP06(2002)031
M J Aitken 1999 Rep. Prog. Phys. 62 1333
Gong Yi-Min et al 2008 Chinese Phys. B 17 1130
Josep M Pons 2003 Class. Quantum Grav. 20 3279