548 research outputs found
SMA Observations of W3(OH) Complex: Physical and Chemical Differentiation between W3(HO) and W3(OH)
We report on the Submillimeter Array (SMA) observations of molecular lines at
270 GHz toward W3(OH) and W3(HO) complex. Although previous observations
already resolved the W3(HO) into two or three sub-components, the physical
and chemical properties of the two sources are not well constrained. Our SMA
observations clearly resolved W3(OH) and W3(HO) continuum cores. Taking the
advantage of the line fitting tool XCLASS, we identified and modeled a rich
molecular spectrum in this complex, including multiple CHCN and CHOH
transitions in both cores. HDO, CHCN, OCS, and vibrationally
excited lines of HCN, CHCN, and CHOCHO were only detected in
W3(HO). We calculate gas temperatures and column densities for both cores.
The results show that W3(HO) has higher gas temperatures, and larger
column densities than W3(OH) as previously observed, suggesting physical and
chemical differences between the two cores. We compare the molecular abundances
in W3(HO) to those in the Sgr B2(N) hot core, the Orion KL hot core and the
Orion Compact Ridge, and discuss the chemical origin of specific species. An
east-west velocity gradient is seen in W3(HO), and the extension is
consistent with the bipolar outflow orientation traced by water masers and
radio jets. A north-south velocity gradient across W3(OH) is also observed.
However, with current observations we can not assure if the velocity gradients
are caused by rotation, outflow or radial velocity differences of the
sub-components in W3(OH).Comment: Accepted by Ap
Experimental and theoretical characterization of the Zn - Zn bond in [Zn2(η5-C5Me5)2]
The existence and characterization of a bond between the Zn atoms in the recently synthesized complex [Zn2(5-C5Me5)2], as well as between Zn and ligand C atoms is firmly based on neutron diffraction and low-temperature X-ray synchrotron diffraction experiments. The multipolar analysis of the experimental electron density and its topological analysis by means of the Atoms in Molecules (AIM) approach reveals details of the Zn - Zn bond, such as its open-shell intermediate character (the results are consistent with a typical metal-metal single bond), as well as many other topological properties of the compound. Experimental results are also compared with theoretical ab initio calculations of the DFT (density functional theory) and MP2 (Mller-Plesset perturbation theory) electron densities, giving a coherent view of the bonding in the complex. For instance, charges calculated from the AIM approach applied to the atomic basin of each Zn atom are, on average, +0.72 e from both the experimental and the theoretical electron density, showing a moderate charge transfer from the metal, confirmed by the calculated topological indexes.Ministerio de Educación y Ciencia MAT2006-0199
Protostellar cores in Sagittarius B2 N and M
We present 500 AU and 700 AU resolution 1 mm and 3 mm ALMA observations,
respectively, of protostellar cores in protoclusters Sagittarius B2 (Sgr B2)
North (N) and Main (M), parts of the most actively star-forming cloud in our
Galaxy. Previous lower resolution (5000 AU) 3 mm observations of this region
detected 150 sources inferred to be young stellar objects (YSOs) with
. With a tenfold increase in resolution, we detect 371
sources at 3 mm and 218 sources in the smaller field of view at 1 mm. The
sources seen at low resolution are observed to fragment into an average of two
objects. About a third of the observed sources fragment. Most of the sources we
report are marginally resolved and are at least partially optically thick. We
determine that the observed sources are most consistent with Stage 0/I YSOs,
i.e., rotationally supported disks with an active protostar and an envelope,
that are warmer than those observed in the solar neighborhood. We report
source-counting-based inferred stellar mass and the star formation rate of the
cloud: 2800, 0.0038 yr for Sgr
B2 N and 6900, 0.0093 yr for Sgr
B2 M respectively.Comment: 31 pages, 18 figures. Accepted for publication in ApJ (September 15,
2023
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