7,829 research outputs found
Comprehensive analysis of RGU photometry in the direction to M5
The RGU-photographic investigation of an intermediate latitude field in the
direction to the Galactic center is presented. 164 extra-galactic objects,
identified by comparison of Minnesota and Basel charts, are excluded from the
program. Also, a region with size 0.104 square-degrees, contaminated by cluster
(M5) stars and affected by background light of the bright star HD 136202 is
omitted. Contrary to previous investigations, a reddening of ,
corresponding to E(G-R)=0.07 mag is adopted. The separation of dwarfs and
evolved stars is carried out by an empirical method, already applied in some of
our works. A new calibration for the metallicity determination is used for
dwarfs, while the absolute magnitude determination for stars of all categories
is performed using the procedures given in the literature. There is good
agreement between the observed logarithmic space density histograms and the
galactic model gradients. Also, the local luminosity function agrees with
Gliese's (1969) and Hipparcos' (Jahreiss & Wielen 1997) luminosity functions,
for stars with mag. For giants, we obtained two different local
space densities from comparison with two Galactic models, i.e. ,
close to that of Gliese (1969), and . A metallicity gradient,
dex/kpc, is detected for dwarfs (only) with absolute
magnitudes , corresponding to a spectral type interval F5-K0.Comment: 17 pages, including 13 figures and 3 tables, accepted for publication
in PAS
Empirical Color Transformations Between SDSS Photometry and Other Photometric Systems
We present empirical color transformations between the Sloan Digital Sky
Survey (SDSS) ugriz photometry and Johnson-Cousins UBVRI system and Becker's
RGU system, respectively. Owing to the magnitude of data that is becoming
available in the SDSS photometric system it is particularly important to be
able to convert between this new system and traditional photometric systems.
Unlike earlier published transformations we based our calculations on stars
actually measured by the SDSS with the SDSS 2.5-m telescope. The photometric
database of the SDSS provides in a sense a single-epoch set of 'tertiary
standards' covering more than one quarter of the sky. Our transformations
should facilitate their use to easily and reliably derive the corresponding
approximate Johnson-Cousins or RGU magnitudes. The SDSS survey covers a number
of areas that were previously established as standard fields in the
Johnson-Cousins system, in particular, fields established by Landolt and by
Stetson. We used these overlapping fields to create well-photometered star
samples on which our calculated transformations are based. For the RGU
photometry we used fields observed in the framework of the new Basel
high-latitude field star survey. We calculated empirical color transformations
between SDSS photometry and Johnson-Cousins UBVRI and Becker's RGU system. For
all transformations we found linear relations to be sufficient. Furthermore we
showed that the transformations between the Johnson-Cousins and the SDSS system
have a slight dependence on metallicity.Comment: 11 pages, 7 figures, Accepted for publication in A&
Foodscapes: bake, grow, share, eat
Foodscapes Exhibition Project Information & Background Idea
Volume limited dependent Galactic model parameters
We estimated 34 sets of Galactic model parameters for three intermediate
latitude fields with Galactic longitudes l=60, l=90, and l=180, and we
discussed their dependence on the volume. Also, we confirmed the variation of
these parameters with absolute magnitude and Galactic longitude. The star
samples in two fields are restricted with bright and unit absolute magnitude
intervals, (4,5], and (5,6], whereas for the third field a larger absolute
magnitude interval is adopted, (4,10]. The limiting apparent magnitudes of star
samples are g=15 and g=22.5 mag which provide space densities within distances
in the line of sight 0.9 and 25 kpc. The Galactic model parameters for the thin
disc are not volume dependent. However, the ones for thick disc and halo do
show spectacular trends in their variations with volume, except for the
scalelength of the thick disc. The local space density of the thick disc
increases, whereas the scaleheight of the same Galactic component decreases
monotonically. However, both model parameters approach asymptotic values at
large distances. The axial ratio of the halo increases abruptly for the volumes
where thick disc is dominant, whereas it approaches an asymptotic value
gradually for larger volumes, indicating a continuous transition from disclike
structure to a spherical one at the outermost region of the Galaxy. The
variation of the Galactic model parameters with absolute magnitude can be
explained by their dependence on the stellar luminosity, whereas the variation
with volume and Galactic longitude at short distances is a bias in analysis.Comment: 12 pages, including 8 figures and 5 tables, accepted for publication
in PAS
New colour-transformations for the Sloan photometry and revised metallicity calibration and equations for photometric parallax estimation
We evaluated new colour-transformations for the Sloan photometry by 224
standards and used them to revise both the equations for photometric parallax
estimation and metallicity calibration cited by Karaali et al. (2003). This
process improves the metallicity and absolute magnitude estimations by
[Fe/H]<=0.3 dex and M^{H}_{g} <= 0.1 mag respectively. There is a high
correlation for metallicities and absolute magnitudes derived for two systems,
UBV and Sloan, by means of the revised calibrations.Comment: 11 pages, including 7 figures and 2 tables, accepted for publication
in PAS
A methodology to allow avalanche forecasting on an information retrieval system
This paper presents adaptations and tests undertaken to allow an information retrieval (IR) system to forecast the likelihood of avalanches on a particular day. The forecasting process uses historical data of the weather and avalanche conditions for a large number of days. A method for adapting these data into a form usable by a text-based IR system is first described, followed by tests showing the resulting system’s accuracy to be equal to existing ‘custom built’ forecasting systems. From this, it is concluded that the adaptation methodology is effective at allowing such data to be used in a text-based IR system. A number of advantages in using an IR system for avalanche forecasting are also presented
- …