Astronomy and Astrophysics, volume 506, 711-727 (2009/11-1)
Star formation history of Canis Major R1. I. Wide-field X-ray study of the young stellar population.
GREGORIO-HETEM J., MONTMERLE T., RODRIGUES C.V., MARCIOTTO E., PREIBISCH T. and ZINNECKER H.
Abstract (from CDS):
The CMa R1 star-forming region contains several compact clusters as well as many young early-B stars. It is associated with a well-known bright rimmed nebula, the nature of which is unclear (fossil HII region or supernova remnant). To help elucidate the nature of the nebula, our goal was to reconstruct the star-formation history of the CMa R1 region, including the previously unknown older, fainter low-mass stellar population, using X-rays. We analyzed images obtained with the ROSAT satellite, covering ∼5 sq. deg. Complementary VRI photometry was performed with the Gemini South telescope. Colour-magnitude and colour-colour diagrams were used in conjunction with pre-main sequence evolutionary tracks to derive the masses and ages of the X-ray sources. The ROSAT images show two distinct clusters. One is associated with the known optical clusters near Z CMa, to which ∼40 members are added. The other, which we name the ``GU CMa'' cluster, is new, and contains ∼60 members. The ROSAT sources are young stars with masses down to M*∼0.5M☉, and ages up to 10Myr. The mass functions of the two clusters are similar, but the GU CMa cluster is older than the cluster around Z CMa by at least a few Myr. Also, the GU CMa cluster is away from any molecular cloud, implying that star formation must have ceased; on the contrary (as already known), star formation is very active in the Z CMa region.
stars: pre-main sequence - X-rays: stars - infrared: stars - ISM: clouds
VizieR on-line data:
<Available at CDS (J/A+A/506/711): tablea1.dat tablea2.dat>
Tables A.1, A.2: [GMR2009] CMaX NN (Nos 1-98). Table 1: [GMR2009] CMaX NNW (Nos 17N, 17S, 55N ,55S). Table 2: [GMR2009] CMaX NN-N, [GMR2009] CmaX NNWN N=17.
Status at CDS
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