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| EPoS Contribution |
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Unveiling the Dynamics of the Barnard 59 Star-Forming Clump
Elena Redaelli MPE, Munich, DE | |
| Barnard 59 (B59) is an irregularly shape, massive clump located at the western end of the Pipe Nebula, a filamentary molecular cloud. B59 is the only place where star formation is active, with ~20 young stellar objects associated to it. Our team has investigated the source using ammonia data acquired as part of the Green Bank Ammonia Survey (GAS). The spectral analysis allowed us to analyze the physical properties of B59, such as its kinematics, density, and temperature structure. The source contains a dense log[N(NH3)cm-2]>14.4) and cold (T~11K) region whose velocity dispersion (~0.18km/s) is comparable to the sonic speed (~0.20 km/s at 10K). However, we observe a variation in the kinematics at the positions of some of the YSOs, in particular the Class 0/I BHB07-11 (B11) source, which is the youngest object in the cluster, and it is known to power a bipolar outflow. Our spectral analysis is sensitive to the protostellar feedback. It shows that in the vicinity of B11, the kinetic temperature rises to T~16-18K and linewidths are broader. In addition, we measured the level of the non-thermal turbulence in the source. The coherent core shows the lowest values of the non-thermal velocity dispersion (σNT), with subsonic gas motions (σNT/Cs ~0.55). At its edges a sharp transition to supersonic motions is visible, and the ratio reaches its highest values towards B11. The protostellar feedback observed in our line data is consistent with a SED analysis of the dust thermal continuum emission of the region as seen with Herschel/SPIRE data, from which we derived dust temperature and H₂ column density. The YSO is embedded in a dense and warm (Tdust~20K) envelope, heated up by the protostar activity. We also computed a virial index of α=0.43 for the source, which means it is gravitationally bound, subvirial and should be contracting. Since that no hints of fragmentation or infall motions are reported in the literature, we propose that the magnetic field could be an extra source of support against the core self gravity, since the Pipe is an highly magnetized environment. Future polarimetric observations, combined with further molecular line data, will allow us to investigate this proposition. | |
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| Caption: σNT/Cs map in B59. The dashed lines show ammonia column density contours, and the solid one represents the transition from subsonic to supersonic motions (σNT/Cs=1). The markers show the positions of the known YSOs, divided by evolutionary stage: Class 0/I, cyan hexagon. Class I, orange triangles. Class I/II, green stars. Class II: magenta circles. B11, the youngest source in the sample, is found in the region where the ratio reaches its highest values, highlighting the protostellar feedback caused by this object. | |
| Collaborators: F.O. Alves, MPE, DE P. Caselli, MPE, DE J.E. Pineda, MPE, DE The Green Bank Ammonia Survey (GAS) |
Key publication
Suggested Session: Cores |