Reddening and polarimetric studies toward IC 1805

Near IR and (V-I) photometry is presented for probable members in the cluster IC 1805. From a color-difference analysis, the ratio of total to selective absorption R(v), is found to be uniform across the cluster and calculated to be 3.1 + or - 0.1. Assuming a distance modulus to the Hyades of 3.3 mag, a distance to IC 1805 of 2.4 + or - 0.1 kpc is obtained by employing several ZAMS fitting calibrations. The resultant C-M diagram contains both MS and ZAMS B type stars, implying that massive star formation in the cluster was a continuous process. Photometric and spectroscopic data for foreground stars toward the cluster indicate that at least two-thirds of the reddening of the cluster is due to the general interstellar material (IM). Multicolor polarimetric measurements are also presented for 24 probable cluster members and for 49 foreground objects. It is concluded that the visual polarization across the local galactic spiral arm is 5 percent, and that the size distribution of grains within IC 1805 is similar to that in the foreground region. After correcting for foreground IM, the residual intracluster polarization indicates that the cluster may be located near a Parker (1966) magnetic well with field strength similar to that of the foreground IM.

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