1,863 research outputs found
Internal Kinematics of Luminous Compact Blue Galaxies
We describe the dynamical properties which may be inferred from HST/STIS
spectroscopic observations of luminous compact blue galaxies (LCBGs) between
0.1<z<0.7. While the sample is homogeneous in blue rest-frame color, small size
and line-width, and high surface-brightness, their detailed morphology is
eclectic. Here we determine the amplitude of rotation versus random, or
disturbed motions of the ionized gas. This information affirms the accuracy of
dynamical mass and M/L estimates from Keck integrated line-widths, and hence
also the predictions of the photometric fading of these unusual galaxies. The
resolved kinematics indicates this small subset of LCBGs are dynamically hot,
and unlikely to be embedded in disk systems.Comment: To appear in "Starbursts: from 30 Doradus to Lyman Break Galaxies"
2005, eds. R. de Grijs and R. M. Gonzalez Delgado (Kluwer
Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution
We present C and O abundances in the Magellanic Clouds derived from deep
spectra of HII regions. The data have been taken with the Ultraviolet-Visual
Echelle Spectrograph at the 8.2-m VLT. The sample comprises 5 HII regions in
the Large Magellanic Cloud (LMC) and 4 in the Small Magellanic Cloud (SMC). We
measure pure recombination lines (RLs) of CII and OII in all the objects,
permitting to derive the abundance discrepancy factors (ADFs) for O^2+, as well
as their O/H, C/H and C/O ratios. We compare the ADFs with those of other HII
regions in different galaxies. The results suggest a possible metallicity
dependence of the ADF for the low-metallicity objects, but more uncertain for
high-metallicity objects. We compare nebular and B-type stellar abundances and
we find that the stellar abundances agree better with the nebular ones derived
from collisionally excited lines (CELs). Comparing these results with other
galaxies we observe that stellar abundances seem to agree better with the
nebular ones derived from CELs in low-metallicity environments and from RLs in
high-metallicity environments. The C/H, O/H and C/O ratios show almost flat
radial gradients, in contrast with the spiral galaxies where such gradients are
negative. We explore the chemical evolution analysing C/O vs. O/H and comparing
with the results of HII regions in other galaxies. The LMC seems to show a
similar chemical evolution to the external zones of small spiral galaxies and
the SMC behaves as a typical star-forming dwarf galaxy.Comment: Accepted for publication in MNRAS, 17 pages, 11 figures, 8 table
Generation of decoherence-free displaced squeezed states of radiation fields and a squeezed reservoir for atoms in cavity QED
We present a way to engineer an effective anti-Jaynes-Cumming and a
Jaynes-Cumming interaction between an atomic system and a single cavity mode
and show how to employ it in reservoir engineering processes. To construct the
effective Hamiltonian, we analyse considered the interaction of an atomic
system in a \{Lambda} configuration, driven by classical fields, with a single
cavity mode. With this interaction, we firstly show how to generate a
decoherence-free displaced squeezed state for the cavity field. In our scheme,
an atomic beam works as a reservoir for the radiation field trapped inside the
cavity, as employed recently by S. Pielawa et al. [Phys. Rev. Lett. 98, 240401
(2007)] to generate an Einstein-Podolsky-Rosen entangled radiation state in
high-Q resonators. In our scheme, all the atoms have to be prepared in the
ground state and, as in the cited article, neither atomic detection nor precise
interaction times between the atoms and the cavity mode are required. From this
same interaction, we can also generate an ideal squeezed reservoir for atomic
systems. For this purpose we have to assume, besides the engineered atom-field
interaction, a strong decay of the cavity field (i.e., the cavity decay must be
much stronger than the effective atom-field coupling). With this scheme, some
interesting effects in the dynamics of an atom in a squeezed reservoir could be
tested
Maternal Hypercholesterolemia in Gestational Diabetes and the Association with Placental Endothelial Dysfunction
Hierarchical TiN-Supported TsFDH Nanobiocatalyst for CO2 Reduction to Formate
The electrochemical reduction of CO2 to value-added products like formate represents a promising technology for the valorization of carbon dioxide. We propose a proof-of-concept bioelectrochemical system (BES) for the reduction of CO2 to formate. For the first time, our device employs a nanostructured titanium nitride (TiN) support for the immobilization of a formate dehydrogenase (FDH) enzyme. The hierarchical TiN nanostructured support exhibits high surface area and wide pore size distribution, achieving high catalytic loading, and is characterized by higher conductivity than other oxide-based supports employed for FDHs immobilization. We select the oxygen-tolerant FDH from Thiobacillus sp. KNK65MA (TsFDH) as enzymatic catalyst, which selectively reduces CO2 to formate. We identify an optimal TiN morphology for the enzyme immobilisation through enzymatic assay, reaching a catalyst loading of 59 μg cm−2 of specifically-adsorbed TsFDH and achieving a complete saturation of the anchoring sites available on the surface. We evaluate the electrochemical CO2 reduction performance of the TiN/TsFDH system, achieving a remarkable HCOO− Faradaic efficiency up to 76 %, a maximum formate yield of 44.1 μmol mg−1FDH h−1 and high stability. Our results show the technological feasibility of BES devices employing novel, nanostructured TiN-based supports, representing an important step in the optimization of these devices
3D Spectroscopy of Local Luminous Compact Blue Galaxies: Kinematics of NGC 7673
The kinematic properties of the ionized gas of local Luminous Compact Blue
Galaxy (LCBG) NGC 7673 are presented using three dimensional data taken with
the PPAK integral field unit at the 3.5-m telescope in the Centro Astron\'omico
Hispano Alem\'an. Our data reveal an asymmetric rotating velocity field with a
peak to peak difference of 60 km s. The kinematic centre is found to be
at the position of a central velocity width maximum ( km
s), which is consistent with the position of the luminosity-weighted
centroid of the entire galaxy. The position angle of the minor rotation axis is
168 as measured from the orientation of the velocity field contours.
At least two decoupled kinematic components are found. The first one is compact
and coincides with the position of the second most active star formation region
(clump B). The second one is extended and does not have a clear optical
counterpart. No evidence of active galactic nuclei activity or supernovae
galactic winds powering any of these two components has been found. Our data,
however, show evidence in support of a previously proposed minor merger
scenario in which a dwarf galaxy, tentatively identified with clump B, is
falling into NGC 7673. and triggers the starburst. Finally, it is shown that
the dynamical mass of this galaxy may be severely underestimated when using the
derived rotation curve or the integrated velocity width, under the assumption
of virialization.Comment: Accepted for publication by MNRAS. The paper contains 10 figures and
2 table
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