A Search for HI in Elliptical Galaxies with Nuclear Radio Sources

Extract

Many searches have been made in the last few years for 21 cm emission from neutral hydrogen in elliptical galaxies. Emission has been detected in several galaxies, which have 10⁸ to 10⁹ M_⊙ of HI (for H_○ = 100 km s⁻¹Mpc⁻¹). Upper limits between 10⁶ and 10⁹ M_⊙ have been set for the HI mass in about 40 other galaxies. Why most E galaxies have so little gas, and why some few have detectable gas, remains a matter of great interest. Two of the galaxies with large HI mass, NGC 1052 and 4278, are known to have powerful nuclear continuum radio sources (P₂₃₈₀ ∼ 10²² WHz⁻¹). Since both of these attributes are fairly rare among elliptical galaxies, their coexistence in these galaxies is not likely to have occurred by chance. We have therefore observed twelve other elliptical galaxies with nuclear radio power P₂₃₈₀ > 10²² WHz⁻¹ at Arecibo Observatory, to determine whether a large mass of HI is a necessary auxillary to nuclear continuum emission.