7 research outputs found
CARMA Large Area Star Formation Survey: Structure and Kinematics of Dense Gas in Serpens Main
We present observations of N2H+(1-0), HCO+(1-0), and HCN(1-0) toward the
Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey
(CLASSy). We mapped 150 square arcminutes of Serpens Main with an angular
resolution of 7 arcsecs. The gas emission is concentrated in two subclusters
(the NW and SE subclusters). The SE subcluster has more prominent filamentary
structures and more complicated kinematics compared to the NW subcluster. The
majority of gas in the two subclusters has subsonic to sonic velocity
dispersions. We applied a dendrogram technique with N2H+(1-0) to study the gas
structures; the SE subcluster has a higher degree of hierarchy than the NW
subcluster. Combining the dendrogram and line fitting analyses reveals two
distinct relations: a flat relation between nonthermal velocity dispersion and
size, and a positive correlation between variation in velocity centroids and
size. The two relations imply a characteristic depth of 0.15 pc for the cloud.
Furthermore, we have identified six filaments in the SE subcluster. These
filaments have lengths of 0.2 pc and widths of 0.03 pc, which is smaller than a
characteristic width of 0.1 pc suggested by Herschel observations. The
filaments can be classified into two types based on their properties. The first
type, located in the northeast of the SE subcluster, has larger velocity
gradients, smaller masses, and nearly critical mass-per-unit-length ratios. The
other type, located in the southwest of the SE subcluster, has the opposite
properties. Several YSOs are formed along two filaments which have
supercritical mass per unit length ratios, while filaments with nearly critical
mass-per-unit-length ratios are not associated with YSOs, suggesting that stars
are formed on gravitationally unstable filaments.Comment: Accepted to ApJ. 38 pages, 16 figures, 5 table
A Search For X-Ray Emission From Colliding Magnetospheres In Young Eccentric Stellar Binaries
Among young binary stars whose magnetospheres are expected to collide, only two systems have been observed near periastron in the X-ray band: the low-mass DQ Tau and the older and more massive HD 152404. Both exhibit elevated levels of X-ray emission at periastron. Our goal is to determine whether colliding magnetospheres in young high-eccentricity binaries commonly produce elevated average levels of X-ray activity. This work is based on Chandra snapshots of multiple periastron and non-periastron passages in four nearby young eccentric binaries (Parenago 523, RX J1622.7-2325 Nw, UZ Tau E, and HD 152404). We find that for the merged sample of all four binaries the current X-ray data show an increasing average X-ray flux near periastron (at a ∼2.5-sigma level). Further comparison of these data with the X-ray properties of hundreds of young stars in the Orion Nebula Cluster, produced by the Chandra Orion Ultradeep Project (COUP), indicates that the X-ray emission from the merged sample of our binaries cannot be explained within the framework of the COUP-like X-ray activity. However, due to the inhomogeneities of the merged binary sample and the relatively low statistical significance of the detected flux increase, these findings are regarded as tentative only. More data are needed to prove that the flux increase is real and is related to the processes of colliding magnetospheres