1,325 research outputs found
The VIMOS Public Extragalactic Redshift Survey (VIPERS): PCA-based automatic cleaning and reconstruction of survey spectra
Identifying spurious reduction artefacts in galaxy spectra is a challenge for
large surveys. We present an algorithm for identifying and repairing residual
spurious features in sky-subtracted galaxy spectra with application to the
VIPERS survey. The algorithm uses principal component analysis (PCA) applied to
the galaxy spectra in the observed frame to identify sky line residuals
imprinted at characteristic wavelengths. We further model the galaxy spectra in
the rest-frame using PCA to estimate the most probable continuum in the
corrupted spectral regions, which are then repaired. We apply the method to
90,000 spectra from the VIPERS survey and compare the results with a subset
where careful editing was performed by hand. We find that the automatic
technique does an extremely good job in reproducing the time-consuming manual
cleaning and does it in a uniform and objective manner across a large data
sample. The mask data products produced in this work are released together with
the VIPERS second public data release (PDR-2).Comment: Find the VIPERS data release at http://vipers.inaf.i
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Exploring the dependence of the three-point correlation function on stellar mass and luminosity at 0.5<z<1.1
The three-point correlation function (3PCF) is a powerful probe to
investigate the clustering of matter in the Universe in a complementary way
with respect to lower-order statistics, providing additional information with
respect to the two-point correlation function and allowing us to shed light on
biasing, nonlinear processes, and deviations from Gaussian statistics. In this
paper, we analyse the first data release of the VIMOS Public Extragalactic
Redshift Survey (VIPERS), determining the dependence of the three-point
correlation function on luminosity and stellar mass at . We
exploit the VIPERS Public Data Release 1, consisting of more than 50,000
galaxies with B-band magnitudes in the range and stellar masses in the range
. We measure both the
connected 3PCF and the reduced 3PCF in redshift space, probing different
configurations and scales, in the range [Mpc/h]. We find a
significant dependence of the reduced 3PCF on scales and triangle shapes, with
stronger anisotropy at larger scales ( Mpc/h) and an almost flat trend
at smaller scales, Mpc/h. Massive and luminous galaxies present a
larger connected 3PCF, while the reduced 3PCF is remarkably insensitive to
magnitude and stellar masses in the range we explored. These trends, already
observed at low redshifts, are confirmed for the first time to be still valid
up to , providing support to the hierarchical scenario for which massive
and bright systems are expected to be more clustered. The possibility of using
the measured 3PCF to provide independent constraints on the linear galaxy bias
has also been explored, showing promising results in agreement with other
probes.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in A&
Projet de conservation de la biodiversité dans la moyenne vallée du Zambèze après éradication de la mouche tsé-tsé (Zimbabwé). Etude de faisabilité d'un microprojet : le ranch communal de gibier de Gonono (Gonono communal game ranch)
Le "ranch communal de gibier de Gonono" s'inscrit dans le cadre des micro-projets proposés de manière consensuelle au Comité exécutif du "Projet de Conservation de la Biodiversité dans la Moyenne Vallée du Zambèze après l'Eradication. de la Mouche Tsé-tsé". Dans le but global d'améliorer durablement les conditions de vie de la population du Ward de Gonono, l'objectif spécifique de ce micro-projet est de mettre au point un mode local de production alternative de viande à bas prix à partir de la faune sauvage. Décidé et conçu avec les autorités du Ward, le ranch doit être progressivement géré par et pour la population du Ward. Il doit d'abord produire sur place une viande de gibier recherchée par les communautés locales qui n'y avaient accès jusqu'à présent que de manière illégale. Cette viande doit être produite à un coût modéré accessible à la population. Le ranch doit aussi permettre de conserver un espace étendu encore faiblement anthropisé en le valorisant par des productions à faible impact écologique. En phase de croisière, l'exploitation sur 3.000 hectares du peuplement multispécifique de gibier devrait permettre la fourniture annuelle de 3 0 tonnes carcasse de viande d'impala et 10. tonnes carcasse de viande d'autres espèces, soit une productivité de 13 kg carcasse de venaison par hectare. Quelques productions annexes sont aussi prévues. L'objectif économique est la couverture du prix de revient de la viande et non pas la recherche d'un profit financier. La création de ce ranch communal de gibier est une entreprise à caractère hautement innovant aux plans institutionnel et technique. Il doit donc être considéré comme une opération pilote à part entière et, à ce titre, doit pouvoir bénéficier d'un encadrement serré et d'un appui scientifique conséquent, tout au moins les premières années. (Résumé d'auteur
The VIMOS Public Extragalactic Survey (VIPERS): First Data Release of 57 204 spectroscopic measurements
We present the first Public Data Release (PDR-1) of the VIMOS Public
Extragalactic Survey (VIPERS). It comprises 57 204 spectroscopic measurements
together with all additional information necessary for optimal scientific
exploitation of the data, in particular the associated photometric measurements
and quantification of the photometric and survey completeness. VIPERS is an ESO
Large Programme designed to build a spectroscopic sample of ' 100 000 galaxies
with iAB < 22.5 and 0.5 < z < 1.5 with high sampling rate (~45%). The survey
spectroscopic targets are selected from the CFHTLS-Wide five-band catalogues in
the W1 and W4 fields. The final survey will cover a total area of nearly 24
deg2, for a total comoving volume between z = 0.5 and 1.2 of ~4x10^7
h^(-3)Mpc^3 and a median galaxy redshift of z~0.8. The release presented in
this paper includes data from virtually the entire W4 field and nearly half of
the W1 area, thus representing 64% of the final dataset. We provide a detailed
description of sample selection, observations and data reduction procedures; we
summarise the global properties of the spectroscopic catalogue and explain the
associated data products and their use, and provide all the details for
accessing the data through the survey database (http://vipers.inaf.it) where
all information can be queried interactively.Comment: Accepted for publication in A&A Added and/or replaced some figure,
added section on DataBase interface, expaned Introductio
The VIMOS Public Extragalactic Redshift Survey (VIPERS): A quiescent formation of massive red-sequence galaxies over the past 9 Gyr
We explore the evolution of the Colour-Magnitude Relation (CMR) and
Luminosity Function (LF) at 0.4<z<1.3 from the VIMOS Public Extragalactic
Redshift Survey (VIPERS) using ~45,000 galaxies with precise spectroscopic
redshifts down to i'_AB<22.5 over ~10.32 deg^2 in two fields. From z=0.5 to
z=1.3 the LF and CMR are well defined for different galaxy populations and
M^*_B evolves by ~1.04(1.09)+/-0.06(0.10) mag for the total (red) galaxy
sample. We compare different criteria for selecting early-type galaxies (ETGs):
(1) fixed cut in rest-frame (U-V) colours, (2) evolving cut in (U-V) colours,
(3) rest-frame (NUV-r')-(r'-K) colour selection, and (4) SED classification.
Regardless of the method we measure a consistent evolution of the red-sequence
(RS). Between 0.4<z<1.3 we find a moderate evolution of the RS intercept of
Delta(U-V)=0.28+/-0.14 mag, favouring exponentially declining star formation
(SF) histories with SF truncation at 1.7<=z<=2.3. Together with the rise in the
ETG number density by 0.64 dex since z=1, this suggests a rapid build-up of
massive galaxies (M>10^11 M_sun) and expeditious RS formation over a short
period of ~1.5 Gyr starting before z=1. This is supported by the detection of
ongoing SF in ETGs at 0.9<z<1.0, in contrast with the quiescent red stellar
populations of ETGs at 0.5<z<0.6. There is an increase in the observed CMR
scatter with redshift, two times larger than in galaxy clusters and at variance
with theoretical models. We discuss possible physical mechanisms that support
the observed evolution of the red galaxy population. Our findings point out
that massive galaxies have experienced a sharp SF quenching at z~1 with only
limited additional merging. In contrast, less-massive galaxies experience a mix
of SF truncation and minor mergers which build-up the low- and
intermediate-mass end of the CMR.Comment: 27 pages, 21 figures, accepted for publication in A&
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Luminosity and stellar mass dependence of galaxy clustering at 0.5<z<1.1
We investigate the dependence of galaxy clustering on luminosity and stellar
mass in the redshift range 0.5<z<1.1, using the first ~55000 redshifts from the
VIMOS Public Extragalactic Redshift Survey (VIPERS). We measured the
redshift-space two-point correlation functions (2PCF), and the projected
correlation function, in samples covering different ranges of B-band absolute
magnitudes and stellar masses. We considered both threshold and binned galaxy
samples, with median B-band absolute magnitudes -21.6<MB-5log(h)<-19.5 and
median stellar masses 9.8<log(M*[Msun/h^2])<10.7. We assessed the real-space
clustering in the data from the projected correlation function, which we model
as a power law in the range 0.2<r_p[Mpc/h]<20. Finally, we estimated the galaxy
bias as a function of luminosity, stellar mass, and redshift, assuming a flat
LCDM model to derive the dark matter 2PCF. We provide the best-fit parameters
of the power-law model assumed for the real-space 2PCF -- the correlation
length and the slope -- as well as the linear bias parameter, as a function of
the B-band absolute magnitude, stellar mass, and redshift. We confirm and
provide the tightest constraints on the dependence of clustering on luminosity
at 0.5<z<1.1. We prove the complexity of comparing the clustering dependence on
stellar mass from samples that are originally flux-limited and discuss the
possible origin of the observed discrepancies. Overall, our measurements
provide stronger constraints on galaxy formation models, which are now required
to match, in addition to local observations, the clustering evolution measured
by VIPERS galaxies between z=0.5 and z=1.1 for a broad range of luminosities
and stellar masses.Comment: 17 pages, 10 figures, 4 tables. Accepted for publication in A&
The VIMOS Public Extragalactic Redshift Survey - Searching for Cosmic Voids
The characterisation of cosmic voids gives unique information about the
large-scale distribution of galaxies, their evolution and the cosmological
model. We identify and characterise cosmic voids in the VIMOS Public
Extragalactic Redshift Survey (VIPERS) at redshift 0.55 < z < 0.9. A new void
search method is developed based upon the identification of empty spheres that
fit between galaxies. The method can be used to characterise the cosmic voids
despite the presence of complex survey boundaries and internal gaps. We
investigate the impact of systematic observational effects and validate the
method against mock catalogues. We measure the void size distribution and the
void-galaxy correlation function. We construct a catalogue of voids in VIPERS.
The distribution of voids is found to agree well with the distribution of voids
found in mock catalogues. The void-galaxy correlation function shows
indications of outflow velocity from the voids
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Galaxy clustering and redshift-space distortions at z=0.8 in the first data release
We present in this paper the general real- and redshift-space clustering
properties of galaxies as measured in the first data release of the VIPERS
survey. VIPERS is a large redshift survey designed to probe the distant
Universe and its large-scale structure at 0.5 < z < 1.2. We describe in this
analysis the global properties of the sample and discuss the survey
completeness and associated corrections. This sample allows us to measure the
galaxy clustering with an unprecedented accuracy at these redshifts. From the
redshift-space distortions observed in the galaxy clustering pattern we provide
a first measurement of the growth rate of structure at z = 0.8: f\sigma_8 =
0.47 +/- 0.08. This is completely consistent with the predictions of standard
cosmological models based on Einstein gravity, although this measurement alone
does not discriminate between different gravity models.Comment: 19 pages, 19 figures, accepted for publication in A&
VIPERS: An Unprecedented View of Galaxies and Large-Scale Structure Halfway Back in the Life of the Universe
The VIMOS Public Extragalactic Redshift Survey (VIPERS) is an ongoing ESO
Large Programme to map in detail the large-scale distribution of galaxies at
0.5 < z <1.2. With a combination of volume and sampling density that is unique
for these redshifts, it focuses on measuring galaxy clustering and related
cosmological quantities as part of the grand challenge of understanding the
origin of cosmic acceleration. VIPERS has also been designed to guarantee a
broader legacy, allowing detailed investigations of the properties and
evolutionary trends of z~1 galaxies. The survey strategy exploits the specific
advantages of the VIMOS spectrograph at the VLT, aiming at a final sample of
nearly 100,000 galaxy redshifts to iAB = 22.5 mag, which represents the largest
redshift survey ever performed with ESO telescopes. In this introductory
article we describe the survey construction, together with early results based
on a first sample of ~55,000 galaxies.Comment: 6 pages, 8 figures; introductory pape
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