Studies of the Magellanic Clouds: II. Dimensions and structure of the Small Cloud
Abstract
Star counts to m = 14.3 and i6.o in and around the Small Cloud indicate a maximum major axis of not less than = 7 kpc. The total numbers of stars brighter than mpg = 14.3 (M = -4.4), corrected for foreground, is about 500, of which half are located within an area of 4.5 square degrees around the centroid C' of the distribution (1h oo , -72?5, 1950) located nearly to the north-east of the geometrical center C of the axial bar (oh 51=, -73?I). From long-exposure photographs and the counts to m = o6.o evidence is presented that, when allowance is made for the disturbance introduced by the asymmetrical prominence stretching toward the Large Cloud, the Small Cloud is a tilted, flattened system with the same basic pattern of spiral structure as in the Large Cloud. Excluding the prominence the total numbers of stars brighter than mpg = 16.0 (M = -2.7) within the main system is about 10,000. From a dis- cussion of the gradient of the luminosity function in various parts of the system it appears that in the core of the system around C" (oh48 , - 73?5) the population type differs significantly from that around C'. The inclination of the equa- torial plane of the system on the line of sight is estimated at 30 , the major axis being in position angle An analysis of Harvard data on cepheids does not indicate clearly which is the nearer part of the minor axis, but is not inconsistent with the assumption that the main spiral arm is trailing in the rotation.
- Publication:
-
The Astronomical Journal
- Pub Date:
- July 1955
- DOI:
- 10.1086/107218
- Bibcode:
- 1955AJ.....60..219D