Stellar mass loss and the intracluster medium in Galactic globular clusters: a deep radio survey for H i and OH

Abstract

We present the results of a survey, the deepest to date, for H i emission at 21 cm and OH emission at 18 cm (lines at 1612, 1665, 1667 and 1720 MHz) in the direction towards the Galactic globular clusters M15, M2, NGC6934, NGC7006 and Pal13. The aim is to measure the amount of hydrogen in the intra-cluster medium (ICM), and to find OH masers in the circumstellar envelopes of globular cluster red giants. We present a tentative detection of 0.3 M⊙ of neutral hydrogen in M15 and possible detections of neutral hydrogen in M2 and Pal13. We derive upper limits to the neutral hydrogen content of NGC6934 and NGC7006. No OH emission is detected. We also present deep H i data of the northern tip of the Magellanic Stream behind Pal13.