EDP Sciences
Free access
Volume 425, Number 1, October I 2004
Page(s) 133 - 141
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20047059

A&A 425, 133-141 (2004)
DOI: 10.1051/0004-6361:20047059

Star count analysis of the interstellar matter in the region of L1251

L. G. Balázs1, P. Ábrahám1, M. Kun1, J. Kelemen1 and L. V. Tóth2, 3

1  Konkoly Observatory of the Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary
2  Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
3  Eötvös Loránd University of Sciences, Dept. of Astronomy, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary

(Received 12 January 2004 / Accepted 26 April 2004)

We studied the ISM distribution in and around the star forming cloud L1251 with optical star counts. A careful calculation with a maximum likelihood based statistical approach resulted in B, V, R, I extinction distributions from the star count maps. A distance of $330\pm 30$ pc was derived. The extinction maps revealed an elongated dense cloud with a bow shock at its eastern side. We estimated a Mach number of $M\approx2$ for the bow shock. A variation of the apparent dust properties is detected, i.e. the RV=AV/EB-V total to selective extinction ratio varies from 3 to 5.5, peaking at the densest part of L1251. The spatial structure of the head of L1251 is well modelled with a Schuster-sphere (i.e. n=5 polytropic sphere). The observed radial distribution of mass fits the model with high accuracy out to 2.5 pc distance from the assumed center. Unexpectedly, the distribution of NH 3 1.3 cm line widths is also well matched by the Schuster solution even in the tail of the cloud. Since the elongated head-tail structure of L1251 is far from the spherical symmetry the good fit of the linewidths in the tail makes it reasonable to assume that the present cloud structure has been formed by isothermal contraction.

Key words: ISM: individual object: L1251

SIMBAD Objects

© ESO 2004