2003AJ....126.1888K

We have performed optical imaging observations of the dark cloud L1251 at multiple wavelengths, B, V, R, and I, using the 105 cm Schmidt telescope at the Kiso Observatory, Japan. The cloud has a cometary shape with a dense ``head'' showing star formation activity and a relatively diffuse ``tail'' without any signs of star formation. We derived extinction maps of A_Band A_Vwith a star count method, and also revealed the color excess (E_B-V_, E_V-R_, and E_V-I_) distributions. On the basis of the color excess measurements we derived the distribution of the ratio of total to selective extinction R_Vover the cloud using an empirical relation between R_Vand A_λ/A_Vreported by Cardelli et al. In the tail of the cloud, R_Vhas a uniform value of ∼3.2, close to that often found in the diffuse interstellar medium (∼3.1), while higher values of R_V=4-6 are found in the dense head. Since R_Vis closely related to the size of dust grains, the high R_V-values are most likely to represent the growth of dust grains in the dense star-forming head of the cloud.