1,184 research outputs found
Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
(Abridged) We derive the structure of the Galactic stellar Warp and Flare
using 2MASS RC and RGB stars, selected at mean heliocentric distances of 3, 7
and 17 kpc.
Our results are: (i) a clear stellar warp signature is derived for the 3
selected rings; (ii) the derived stellar warp is consistent (both in amplitude
and phase-angle) with that for the Galactic interstellar dust and HI gas; (iii)
the Sun seems not to fall on the line of nodes. The stellar warp phase-angle
orientation (+15 degrees) is close to the orientation angle of the Galactic bar
and this produces an asymmetric warp for the inner rings; (iv) a
Northern/Southern warp symmetry is observed only for the ring at 17 kpc; (v)
treating a mixture of thin and thick disk populations we trace the disk flaring
and derive a constant scale-height (~0.65 kpc) within R(GC)~15 kpc. Further
out, the disk flaring increase gradually reaching a mean scale-height of ~1.5
kpc at R(GC)~23 kpc; and (vi) these results provide further robust evidence
that there is no disk radial truncation at R(GC)~14 kpc.
In the particular case of the Canis Major over-density we confirm its
coincidence with the Southern stellar maximum warp occurring near l=240. We
present evidence to conclude that all observed parameters (e.g. number density,
radial velocities, proper motion etc) of CMa are consistent with it being a
normal Milky Way outer-disk population, thereby leaving no justification for a
more complex interpretations of its origin. The present analysis does not
provide a conclusive test of the structure or origin of the Monoceros Ring.
Nevertheless, we show that a warped flared Milky Way contributes significantly
at the locations of the Monoceros Ring.Comment: 25 pages, 22 figures, accepted for publication in A&A. A higher
resolution pdf file is available at
http://wwwuser.oat.ts.astro.it/zaggia/public_html/warp
Design, synthesis and biological activity of selective hCAs inhibitors based on 2-(benzylsulfinyl)benzoic acid scaffold
A large library of derivatives based on the scaffold of 2-(benzylsulfinyl)benzoic acid were synthesised and tested as atypical inhibitors against four different isoforms of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). The exploration of the chemical space around the main functional groups led to the discovery of selective hCA IX inhibitors in the micromolar/nanomolar range, thus establishing robust structure-activity relationships within this versatile scaffold. HPLC separation of some selected chiral compounds and biological evaluation of the corresponding enantiomers was performed along with molecular modelling studies on the most active derivatives
Intra- and extra-cellular excretion of carboxylates
Carboxylates, such as malate and citrate, are widely acknowledged to have a central role in plant metabolism. They are involved in the production of energy and its storage as well as contributing to the cellular osmolyte pool and participating in the regulation of cellular pH. As we discuss here, recent research has demonstrated the functional importance of carboxylate excretion into the soil, apoplast and vacuole, particular with respect to the regulation of stomatal and root function
Relative Frequencies of Blue Stragglers in Galactic Globular Clusters: Constraints for the Formation Mechanisms
We discuss the main properties of the Galactic globular cluster (GC) blue
straggler stars (BSS), as inferred from our new catalog containing nearly 3000
BSS. The catalog has been extracted from the photometrically homogeneous V vs.
(B-V) color-magnitude diagrams (CMD) of 56 GCs, based on WFPC2 images of their
central cores. In our analysis we used consistent relative distances based on
the same photometry and calibration. The number of BSS has been normalized to
obtain relative frequencies (F_{BSS}) and specific densities (N_S) using
different stellar populations extracted from the CMD. The cluster F_{BSS} is
significantly smaller than the relative frequency of field BSS. We find a
significant anti-correlation between the BSS relative frequency in a cluster
and its total absolute luminosity (mass). There is no statistically significant
trend between the BSS frequency and the expected collision rate. F_{BSS} does
not depend on other cluster parameters, apart from a mild dependence on the
central density. PCC clusters act like normal clusters as far as the BSS
frequency is concerned. We also show that the BSS luminosity function for the
most luminous clusters is significantly different, with a brighter peak and
extending to brighter luminosities than in the less luminous clusters. These
results imply that the efficiency of BSS production mechanisms and their
relative importance vary with the cluster mass.Comment: 12 pages, 3 figures. accepted for publication in ApJ
HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands
We present the complete photometric database and the color-magnitude diagrams
for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the
F439W and F555W bands. A detailed discussion of the various reduction steps is
also presented, and of the procedures to transform instrumental magnitudes into
both the HST F439W and F555W flight system and the standard Johnson B and V
systems. We also describe the artificial star experiments which have been
performed to derive the star count completeness in all the relevant branches of
the color magnitude diagram. The entire photometric database and the
completeness function will be made available on the Web immediately after the
publication of the present paper.Comment: 21 pages, 77 figures. High resolution version of this paper can be
retrived at http://dipastro.pd.astro.it/globular
Mineralogical characterization of fluorescent grossular garnet var. tsavorite from Merelani Hills, Tanzania
Tsavorite is the trade name for the green vanadium–chromium variety of grossular occurring in the Precambrian terrains in the areas of Merelani Hills (Tanzania) and Tsavo Park (Kenya) which are by far the most important source of gem grade specimens of tsavorite used for high jewellery. The tsavorite crystals from Merelani Hills exhibit a pink-red and yellow fluorescence when irradiated by common portable UV lamp, an unusual phenomenon among members of the garnet group. The electron density map calculated from the diffraction data and plotted against a grossular standard shows that an excess of negative charge is clearly pinpointed in the crystallographic site occupied by Al3+. The bulk elemental analysis shows that the most represented end-member, besides grossular, is the vanadium-bearing goldmanite garnet (3.82–4.08 mol %). The fluorometry with an excitation beam at 408 nm indicates a complex emission pattern with the most intense emissions at 701 and 716 nm and subordinately at 592 nm. The colour perception is dominated by the emission yellow band at 592 nm while the contribution of the red band modulates the colour ranging from bright orange to pink-red. The attribution of the emission at 592 nm is related to Mn2+ while the emissions at 701 and 716 nm could be related to the chromium content and/or to a possible fraction of vanadium as V2+. Because of the characteristic colour perceived under UV light, the use of a common led lamp can be useful as a diagnostic tool to easily identify tsavorite
- …