5,822 research outputs found
Color bimodality: Implications for galaxy evolution
We use a sample of 69726 galaxies from the SDSS to study the variation of the
bimodal color-magnitude (CM) distribution with environment. Dividing the galaxy
population by environment (Sigma_5) and luminosity (-23<M_r<-17), the u-r color
functions are modeled using double-Gaussian functions. This enables a
deconvolution of the CM distributions into two populations: red and blue
sequences. The changes with increasing environmental density can be separated
into two effects: a large increase in the fraction of galaxies in the red
distribution, and a small color shift in the CM relations of each distribution.
The average color shifts are 0.05+-0.01 and 0.11+-0.02 for the red and blue
distributions, respectively, over a factor of 100 in projected neighbor
density. The red fraction varies between about 0% and 70% for low-luminosity
galaxies and between about 50% and 90% for high-luminosity galaxies. This
difference is also shown by the variation of the luminosity functions with
environment. We demonstrate that the effects of environment and luminosity can
be unified. A combined quantity, Sigma_mod = Sigma_5/Mpc^{-2} + L_r/L_{-20.2},
predicts the fraction of red galaxies, which may be related to the probability
of transformation events. Our results are consistent with major interactions
(mergers and/or harassment) causing galaxies to transform from the blue to the
red distribution. We discuss this and other implications for galaxy evolution
from earlier results and model the effect of slow transformations on the color
functions.Comment: 14 pages, 8 figures, in AIP Conf. Proc., The New Cosmology, eds. R.
E. Allen et al. (aka. The Mitchell Symposium), see
http://proceedings.aip.org/proceedings/confproceed/743.jsp ; v2: replaced
Figure 5 which was incomplete in original submissio
Study of thin film large area photovoltaic solar energy converter Final report
Thin film large area cadmium sulfide solar cell
Study of thin film large area photovoltaic solar energy converter Third quarterly report, 25 Apr. - 24 Jul. 1966
Cadmium sulfide-thin film large area photovoltaic solar energy converter - plastic substrate cell fabrication and stability testing under various conditions of temperature and humidit
CdS solar cell development Interim technical report
Cadmium sulfide solar cell design criteri
Investigation of tidal displacements of the Earth's surface by laser ranging to GEOS-3
An analysis of laser ranging data from three stations was carried out in an attempt to measure the geometric Earth tide. Two different approaches to the problem were investigated. The dynamic method computes pass to pass apparent movements in stations height relative to short arcs fitted to several passes of data from the same station by the program GEODYNE. The quasi-geometric method reduces the dependence on unmodelled satellite dynamics to a knowledge of only the radial position of the satellite by considering two station simultaneous ranging at the precise time that the satellite passes through the plane defined by two stations and the center of mass of the Earth
Study of thin film large area photovoltaic solar energy converter First quarterly report, 25 Oct. 1965 - 24 Jan. 1966
Cadmium sulfide thin film photovoltaic cell for large area solar energy converte
Study of thin film large area photovoltaic solar energy converter Second quarterly report, 25 Feb. - 24 May 1966
Cadmium sulfide thin film solar cell developmen
Development of cadmium sulfide thin film photovoltaic cells third quarterly report, apr. 15 - jul. 14, 1965
Cadmium sulfide thin film photovoltaic cells - cadmium sulfide film evaporation, cell testing, improvement, and stability, and plastic and metal substrate cell
Galaxy bimodality versus stellar mass and environment
We analyse a z<0.1 galaxy sample from the Sloan Digital Sky Survey focusing
on the variation of the galaxy colour bimodality with stellar mass and
projected neighbour density Sigma, and on measurements of the galaxy stellar
mass functions. The characteristic mass increases with environmental density
from about 10^10.6 Msun to 10^10.9 Msun (Kroupa IMF, H_0=70) for Sigma in the
range 0.1--10 per Mpc^2. The galaxy population naturally divides into a red and
blue sequence with the locus of the sequences in colour-mass and
colour-concentration index not varying strongly with environment. The fraction
of galaxies on the red sequence is determined in bins of 0.2 in log Sigma and
log mass (12 x 13 bins). The red fraction f_r generally increases continuously
in both Sigma and mass such that there is a unified relation: f_r =
F(Sigma,mass). Two simple functions are proposed which provide good fits to the
data. These data are compared with analogous quantities in semi-analytical
models based on the Millennium N-body simulation: the Bower et al. (2006) and
Croton et al. (2006) models that incorporate AGN feedback. Both models predict
a strong dependence of the red fraction on stellar mass and environment that is
qualitatively similar to the observations. However, a quantitative comparison
shows that the Bower et al. model is a significantly better match; this appears
to be due to the different treatment of feedback in central galaxies.Comment: 19 pages, 17 figures; accepted by MNRAS, minor change
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