1,214 research outputs found
The Southern Proper Motion Program IV. The SPM4 Catalog
We present the fourth installment of the Yale/San Juan Southern Proper Motion
Catalog, SPM4. The SPM4 contains absolute proper motions, celestial
coordinates, and (B,V) photometry for over 103 million stars and galaxies
between the south celestial pole and -20 deg declination. The catalog is
roughly complete to V=17.5 and is based on photographic and CCD observations
taken with the Yale Southern Observatory's double-astrograph at Cesco
Observatory in El Leoncito, Argentina. The proper-motion precision, for
well-measured stars, is estimated to be 2 to 3 mas/yr, depending on the type of
second-epoch material. At the bright end, proper motions are on the
International Celestial Reference System by way of Hipparcos Catalog stars,
while the faint end is anchored to the inertial system using external galaxies.
Systematic uncertainties in the absolute proper motions are on the order of 1
mas/yr.Comment: 34 pages, 8 figures, 3 tables; accepted for publication in AJ; note -
modified author list and acknowledgements sectio
Proper Motions in Kapteyn Selected Area 103: A Preliminary Orbit for the Virgo Stellar Stream
We present absolute proper motions in Kapteyn Selected Area (SA) 103. This
field is located 7 degrees west of the center of the Virgo Stellar Stream (VSS,
Duffau et al. 2006), and has a well-defined main sequence representing the
stream. In SA 103 we identify one RR Lyrae star as a member of the VSS
according to its metallicity, radial velocity and distance. VSS candidate
turnoff stars and subgiant stars have proper motions consistent with that of
the RR Lyrae star. The 3D velocity data imply an orbit with a pericenter of 11
kpc and an apocenter of ~90 kpc. Thus, the VSS comprises tidal debris found
near the pericenter of a highly destructive orbit. Examining the six globular
clusters at distances larger than 50 kpc from the Galactic center, and the
proposed orbit of the VSS, we find one tentative association, NGC 2419. We
speculate that NGC 2419 is possibly the nucleus of a disrupted system of which
the VSS is a part.Comment: ApJL accepte
Detection of a Stellar Stream Behind Open Cluster NGC 188: Another Part of the Monoceros Stream
We present results from a WIYN/OPTIC photometric and astrometric survey of
the field of the open cluster NGC 188 ((l,b) = (122.8\arcdeg, 22.5\arcdeg)). We
combine these results with the proper-motion and photometry catalog of Platais
et al. and demonstrate the existence of a stellar overdensity in the background
of NGC 188. The theoretical isochrone fits to the color-magnitude diagram of
the overdensity are consistent with an age between 6 and 10 Gyr and an
intermediately metal poor population ([Fe/H] = -0.5 to -1.0). The distance to
the overdensity is estimated to be between 10.0 and 12.6 kpc. The
proper-motions indicate that the stellar population of the overdensity is
kinematically cold.
The distance estimate and the absolute proper motion of the overdensity agree
reasonably well with the predictions of the Pe\~{n}arrubia et al. model of the
formation of the Monoceros stream. Orbits for this material constructed with
plausible radial-velocity values, indicate that dynamically, this material is
unlikely to belong to the thick disk. Taken together, this evidence suggests
that the newly-found overdensity is part of the Monoceros stream.Comment: accepted by A
CREATIVE POTENTIAL OF RESEARCH AND DEVELOPMENT - A COMPOSITE INDEX OF POTENTIAL SIENTIFIC CREATIVITY
Both Lisbon Council in March 2000 and the one in Barcelona in 2002 represent major turning points in science and research activities at European level. At that time there was a formal recognition that science, technology and innovation, coupled with a quality education is the key to development and long-term competitiveness of European space. Moreover, the decade 2000-2010 was declared as a dedicated to the investment in these sectors, and 2009 was named Year of Creativity and Innovation at European level. In a study in the EU States and candidate countries, whose results were published in 2010, it was noted however that, despite the special attention given lately to these issues, index fund allocations for research and development budgets national level of 2007 is 0.67% on average in the EU (27 countries), compared with Japan (0.68%), South Korea (0.80%) and especially the United States (1.03 %). The purpose of this paper is to identify those factors that influence a nation\'s potential of scientific creativity and to find a way to compare different countries in terms of such potential. If until now many attempts were made to create an index of national or regional creativity, our goal is to narrow the field of creativity to scientific research and to compare the performance / potential of Romania compared to other European Union countries. Among the basic elements which have a direct impact on the potential for innovative scientific development, one can identify investment, human resources and current performance. Based on the above factors, a composite index of scientific creativity potential was developed, which takes into account the three main elements described above: human capital (human resources in science and technology and researchers), financial capital (investment in research and development) and scientific performance (Hirsch Index). Data for the first two were extracted from the Eurostat database for comparisons to be made between countries, while the third one has been estimated by specialized research teams based on data available on Essential Science Indicators (ESI) of Web of Knowledge. The main limit is the level of accuracy in data provided by each nation, and the extent to which such data were estimated, not final. The main benefit is that of identifying the position one country compared to others, but also to find the main factors that placed that country at one level or another in the overall classifications, thus allowing for the development of action plans particularly focused on those elements.research and development,human reources, creative potential, investment in research and development
Chemical Inhomogeneities in the Milky Way Stellar Halo
We have compiled a sample of 699 stars from the recent literature with
detailed chemical abundance information (spanning -4.2 < [Fe/H] < +0.3), and we
compute their space velocities and Galactic orbital parameters. We identify
members of the inner and outer stellar halo populations in our sample based
only on their kinematic properties and then compare the abundance ratios of
these populations as a function of [Fe/H]. In the metallicity range where the
two populations overlap (-2.5 < [Fe/H] < -1.5), the mean [Mg/Fe] of the outer
halo is lower than the inner halo by ~0.1 dex. For [Ni/Fe] and [Ba/Fe], the
star-to-star abundance scatter of the inner halo is consistently smaller than
in the outer halo. The [Na/Fe], [Y/Fe], [Ca/Fe], and [Ti/Fe] ratios of both
populations show similar means and levels of scatter. Our inner halo population
is chemically homogeneous, suggesting that a significant fraction of the Milky
Way stellar halo originated from a well-mixed ISM. In contrast, our outer halo
population is chemically diverse, suggesting that another significant fraction
of the Milky Way stellar halo formed in remote regions where chemical
enrichment was dominated by local supernova events. We find no abundance trends
with maximum radial distance from the Galactic center or maximum vertical
distance from the Galactic disk. We also find no common kinematic signature for
groups of metal-poor stars with peculiar abundance patters, such as the
alpha-poor stars or stars showing unique neutron-capture enrichment patterns.
Several stars and dSph systems with unique abundance patterns spend the
majority of their time in the distant regions of the Milky Way stellar halo,
suggesting that the true outer halo of the Galaxy may have little resemblance
to the local stellar halo.Comment: Accepted for publication in AJ. Full tables available upon reques
A proper motion study of the globular cluster M55
We have derived the absolute proper motion (PM) of the globular cluster M55
using a large set of CCD images collected with the du Pont telescope between
1997 and 2008. We find (PM_RA*cos(DEC), PM_DEC) = (-3.31 +/- 0.10, -9.14 +/-
0.15) mas/yr relative to background galaxies. Membership status was determined
for 16 945 stars with 14<V<21 from the central part of the cluster. The PM
catalogue includes 52 variables of which 43 are probable members of M55. This
sample is dominated by pulsating blue straggler stars but also includes 5
eclipsing binaries, three of which are main sequence objects. The survey also
identified several candidate blue, yellow and red straggler stars belonging to
the cluster. We detected 15 likely members of the Sgr dSph galaxy located
behind M55. The average PM for these stars was measured to be (PM_RA*cos(DEC),
PM_DEC)=(-2.23 +/- 0.14, -1.83 +/- 0.24) mas/yr.Comment: 12 figures and 4 tables, accepted for publication in MNRAS Main
Journal; full PM catalogue (Table 3) at http://case.camk.edu.p
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