Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997mnras.289..948o&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 289, Issue 4, pp. 948-954.
Astronomy and Astrophysics
Astronomy
7
Ism: Kinematics And Dynamics, Ism: Molecules, Globular Clusters: Individual: Omicroncen, Globular Clusters: Individual: 47Tuc, Radio Lines: Ism
Scientific paper
We present the results of a ^12CO J=1-->0 millimetre emission-line study towards the central regions of the globular clusters omicronCen and 47Tuc. Towards the long-period variable V42 in omicronCen, a CO emission line is detected at a signal-to-noise ratio of about 5 and a radial velocity of -31 km s^-1 with respect to the systemic velocity of the cluster v_omicronCen. The emission is characterized by a full-width at half-maximum FWHM=2.2km s^-1 and a peak antenna temperature T*_A~75mK. Its possible origin within the cluster from circumstellar material, or from foreground gas unrelated to the cluster, is discussed. In addition, CO emission is detected at two positions towards the extended IRAS source X1323-472, blueshifted by about 40 km s^-1 relative to v_omicronCen, with a width Deltav=3.2km s^-1 and a peak antenna temperature T*_A~40mK. The spatial distribution of the emission appears to be clumped within the instrumental beam, rather than uniform and diffuse. The CO velocity agrees with that of an H i 21-cm emission feature seen towards that position. Both the CO and H i emission probably arise from a foreground, high-velocity cloud in the northern extension of the Magellanic Stream. In 47Tuc we detected two narrow lines symmetrically redshifted and blueshifted by 34 km s^-1 from the systemic velocity of 47Tuc. The emission occurs in a region which possibly contains an X-ray bow shock, supposed to arise from the interaction of the cluster with the hot halo medium. The CO lines are characterized by a FWHM of 2.0 km s^-1 and a peak antenna temperature T*_A~60mK. The origin of the CO emission may arise from a bow shock in the intracluster gas.
Ferraro Francesco R.
Fusi Pecci Flavio
Gredel Roland
Origlia Livia
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