Morphology, dynamics, and star formation in the Cone Nebula and NGC2264
Several questions about the star formation process are still debated. For instance, we know that stars form from the gravitational contraction of clouds of gas and dust, called “molecular clouds,” since they are mainly made of molecular hydrogen. Mainly thanks to observations from the Herschel satellite, we also know that most star formation occurs in long filaments embedded in these clouds. However, it is still not clear whether this is a rapid process dominated by turbulence or a slow process where magnetic fields and phenomena such as ambipolar diffusion play an important role. Furthermore, we still have to properly account for the effects due to the environment and the feedback provided by the stars formed inside the clouds, mainly the most massive ones.
In this field, an important role is played by nearby star-forming regions to the Sun. In these regions, it is possible to take a complete census of young stars, ranging from the most massive ones down to the smallest brown dwarfs. However, nearby regions do not offer the same diversity of star-forming environments as more distant regions do. The two most representative nearby star-forming regions are the Orion Molecular Cloud, located about 1500 light years from us, and the Cone Nebula, located approximately 2400 light years away.
The team of researchers, led by astronomer E. Flaccomio (INAF – Astronomical Observatory of Palermo), recently published a new study on the Cone Nebula and its cluster, NGC2264. The study is based on a selection of young stars associated with the nebula across a 2.5-degree wide region (for comparison, the full Moon’s angular diameter is about 0.5 degrees), obtained by combining data in X-rays, optical, and infrared bands. The use of data covering such a wide range of the electromagnetic spectrum is necessary due to the peculiar properties of young stars. For instance, young stars are characterized by intense magnetic activity that makes them shine in X-rays thousands of times more than old stars. Additionally, most young stars are surrounded by a disk of gas and cold dust, called “protoplanetary disks,” which emit in the infrared and millimetric bands. Young stars are also characterized by a peculiar variability of their emission and, being part of their parental cluster, by a coherent dynamics. Thanks to this multiband approach, the authors have identified 2257 young stars associated with the Cone Nebula and NGC2264.
The authors have identified four new sub-regions within the Cone Nebula that have different ages and stellar populations, including a very young region that is still embedded in the parental cloud. The analysis of the dynamics of these young stars has revealed evidence of expansion and rotation throughout the entire region. Additionally, the study found the existence of two gravitationally collapsing filaments, whose collision may have triggered the star formation in the southern region of the nebula. The first episodes of star formation in the Cone Nebula occurred approximately 4 million years ago. The study has been described in the paper titled: “Spatial and dynamical structure of the NGC 2264 star-forming region“, which recently appeared on the Astronomy & Astrophysics journal. Among the authors are G. Micela, S. Sciortino, L. Prisinzano, M. G. Guarcello, R. Bonito and I. Pillitteri of INAF – Astronomical Observatory of Palermo, along with G. Peres of the University of Palermo.
The figure (click here to view the entire image) displays a DSS2 image of the region surrounding the Cone Nebula and NGC2264. The arrows indicate the position of the star S Mon (spectral class O7) and the Cone Nebula itself. The orange and blue shaded areas indicate the regions observed with Chandra and XMM-Newton, respectively. The orange squares mark the CoRoT fields, while the yellow circles indicate the positions of the two previously known sub-regions within the Cone Nebula. The polygons define the newly identified regions.
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