903 research outputs found
Geometrical tests of cosmological models. II. Calibration of rotational widths and disc scaling relations
This series of papers is dedicated to a new technique to select galaxies that
can act as standard rods and standard candles in order to perform geometrical
tests on large samples of high redshift galaxies to constrain different
cosmological parameters. The goals of this paper are (1) to compare different
rotation indicators in order to understand the relation between rotation
velocities extracted from observations of the Halpha line and the [OII]3727
line, and (2) determine the scaling relations between physical size, surface
brightness and magnitude of galaxies and their rotation velocity using the
SFI++, a large catalog of nearby galaxies observed at I-band. A good
correlation is observed between the rotation curve-derived velocities of the
Halpha and [OII] observations, as well as between those calculated from
velocity histograms, justifying the direct comparison of velocities measured
from Halpha rotation curves in nearby galaxies and from [OII] line widths at
higher redshifts. To provide calibration for the geometrical tests, we give
expressions for the different scaling relations between properties of galaxies
(size, surface brightness, magnitude) and their rotation speeds. Apart from the
Tully-Fisher relation, we derive the size-rotation velocity and surface
brightness-rotation velocity relations with unprecedentedly small scatters. We
show how the best size-rotation velocity relation is derived when size is
estimated not from disc scale lengths but from the isophotal diameter r23.5,
once these have been corrected for inclination and extinction effects.Comment: 14 pages and 10 figures. A&A submitte
Selection and micropropagation of valuable caper genotypes
The high quality of the various biotypes present in the natural or cultivated state is one of the main features for caper production. Up to now, however, no selection activity has been carried out in order to identify the most suitable accessions for providing better quality products. In this paper, we report the first results of a selection of caper genotypes characterised by significant qualitative traits. A micropropagation protocol was evaluated in order to improve and allow the multiplication of the most promising Capparis spinosa L. subsp. spinosa genotypes, selected in Salina (Aeolian Islands), Sicily (Italy), in collaboration with the most important local growers
Geometrical tests of cosmological models. III. The cosmology-evolution diagram at z=1
The rotational velocity of distant galaxies, when interpreted as a size
(luminosity) indicator, may be used as a tool to select high redshift standard
rods (candles) and probe world models and galaxy evolution via the classical
angular diameter-redshift or Hubble diagram tests. We implement the proposed
testing strategy using a sample of 30 rotators spanning the redshift range
0.2<z<1 with high resolution spectra and images obtained by the VIMOS/VLT Deep
Redshift Survey (VVDS) and the Great Observatories Origins Deep Survey (GOODs).
We show that by applying at the same time the angular diameter-redshift and
Hubble diagrams to the same sample of objects (i.e. velocity selected galactic
discs) one can derive a characteristic chart, the cosmology-evolution diagram,
mapping the relation between global cosmological parameters and local
structural parameters of discs such as size and luminosity. This chart allows
to put constraints on cosmological parameters when general prior information
about discs evolution is available. In particular, by assuming that equally
rotating large discs cannot be less luminous at z=1 than at present (M(z=1) <
M(0)), we find that a flat matter dominated cosmology (Omega_m=1) is excluded
at a confidence level of 2sigma and an open cosmology with low mass density
(Omega_m = 0.3) and no dark energy contribution is excluded at a confidence
level greater than 1 sigma. Inversely, by assuming prior knowledge about the
cosmological model, the cosmology-evolution diagram can be used to gain useful
insights about the redshift evolution of the structural parameters of baryonic
discs hosted in dark matter halos of nearly equal masses.Comment: 14 pages and 11 figures. A&A in pres
Geometrical tests of cosmological models. I. Probing dark energy using the kinematics of high redshift galaxies
We suggest to use the observationally measured and theoretically justified correlation between size and rotational velocity of galactic discs as a viable method to select a set of high redshift standard rods which may be used to explore the dark energy content of the universe via the classical angular-diameter test. Here we explore a new strategy for an optimal implementation of this test.We propose to use the rotation speed of high redshift galaxies as a standard size indicator and show how high resolution multi-object spectroscopy and ACS/HST high quality spatial images, may be combined to measure the amplitude of the dark energy density parameter ΩQ, or to constrain the cosmic equation of state parameter for a smooth dark energy component (w = p/Ï, â1 †w < â1/3). Nearly 1300 standard rods with high velocity rotation in the bin V = 200 ± 20 km sâ1 are expected in a field of 1 sq. degree and over the
redshift baseline 0 < z < 1.4. This sample is sufficient to constrain the cosmic equation of state parameter w at a level of 20% (without priors in the [Ωm,ΩQ] plane) even when the [OII]λ3727 Ă
linewidth-diameter relationship is calibrated with a scatter of âŒ40%. We evaluate how systematics may affect the proposed tests, and find that a linear standard rod evolution, causing galaxy dimensions
to be up to 30% smaller at z = 1.5, can be uniquely diagnosed, and will minimally bias the confidence level contours in the [ΩQ, w] plane. Finally, we show how to derive, without a priori knowing the specific functional form of disc evolution, a cosmologyevolution diagram with which it is possible to establish a mapping between different cosmological models and the amount of galaxy
disc/luminosity evolution expected at a given redshift
Studying the evolution of large-scale structure with the VIMOS-VLT Deep Survey
The VIMOS-VLT Deep Survey (VVDS) currently offers a unique combination of
depth, angular size and number of measured galaxies among surveys of the
distant Universe: ~ 11,000 spectra over 0.5 deg2 to I_{AB}=24 (VVDS-Deep),
35,000 spectra over ~ 7 deg2 to I_{AB}=22.5 (VVDS-Wide). The current ``First
Epoch'' data from VVDS-Deep already allow investigations of galaxy clustering
and its dependence on galaxy properties to be extended to redshifts ~1.2-1.5,
in addition to measuring accurately evolution in the properties of galaxies up
to z~4. This paper concentrates on the main results obtained so far on galaxy
clustering. Overall, L* galaxies at z~ 1.5 show a correlation length r_0=3.6\pm
0.7. As a consequence, the linear galaxy bias at fixed luminosity rises over
the same range from the value b~1 measured locally, to b=1.5 +/- 0.1. The
interplay of galaxy and structure evolution in producing this observation is
discussed in some detail. Galaxy clustering is found to depend on galaxy
luminosity also at z~ 1, but luminous galaxies at this redshift show a
significantly steeper small-scale correlation function than their z=0
counterparts. Finally, red galaxies remain more clustered than blue galaxies
out to similar redshifts, with a nearly constant relative bias among the two
classes, b_{rel}~1.4, despite the rather dramatic evolution of the
color-density relation over the same redshift range.Comment: 14 pages. Extended, combined version of two invited review papers
presented at: 1) XXVIth Astrophysics Moriond Meeting: "From Dark Halos to
Light", March 2006, proc. edited by L.Tresse, S. Maurogordato and J. Tran
Thanh Van (Editions Frontieres); 2) Vulcano Workshop 2006 "Frontier Objects
in Astrophysics and Particle Physics", May 2006, proc. edited by F.
Giovannelli & G. Mannocchi, Italian Physical Society (Editrice Compositori,
Bologna
The VIMOS VLT Deep Survey: The build-up of the colour-density relation
We investigate the redshift and luminosity evolution of the galaxy
colour-density relation using the data from the First Epoch VIMOS-VLT Deep
Survey (VVDS). The size (6582 galaxies), depth (I_AB<=24) and redshift sampling
rate of the survey enable us to reconstruct the 3D galaxy environment on
relatively local scales (R=5 Mpc) up to z~1.5. Particular attention has been
devoted to calibrate a density reconstruction scheme, which factors out survey
selection effects and reproduces in an unbiased way the underlying `real'
galaxy environment. While at lower redshift we confirm the existence of a steep
colour-density relation, with the fraction of the reddest(/bluest) galaxies of
the same luminosity increasing(/decreasing) as a function of density, this
trend progressively disappears in the highest redshift bins investigated. The
rest frame u*-g' colour-magnitude diagram shows a bimodal pattern in both low
and high density environments up to z~1.5. We find that the bimodal
distribution is not universal but strongly depends upon environment: at lower
redshifts the colour-magnitude diagrams in low and high density regions are
significantly different while the progressive weakening of the colour-density
relation causes the two bimodal distributions to nearly mirror each other in
the highest redshift bin investigated. Both the colour-density and the
colour-magnitude-density relations appear to be a transient, cumulative product
of genetic and environmental factors operating over at least a period of 9 Gyr.
These findings support an evolutionary scenario in which star formation/gas
depletion processes are accelerated in more luminous objects and in high
density environments: star formation activity is shifting with cosmic time
towards lower luminosity (downsizing), and out of high density environments.Comment: 17 pages, 10 figures, figures added, accepted by A&
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