753 research outputs found
Large-scale analysis of the SDSS-III DR8 photometric luminous galaxies angular correlation function
We analyse the large-scale angular correlation function (ACF) of the CMASS
luminous galaxies (LGs), a photometric-redshift catalogue based on the Data
Release 8 (DR8) of the Sloan Digital Sky Survey-III. This catalogue contains
over LGs in the range , which was split
into four redshift shells of constant width. First, we estimate the constraints
on the redshift-space distortion (RSD) parameters and ,
where is the galaxy bias, the growth rate and is the
normalization of the perturbations, finding that they vary appreciably among
different redshift shells, in agreement with previous results using DR7 data.
When assuming constant RSD parameters over the survey redshift range, we obtain
, which agrees at the level with Baryon
Oscillation Spectroscopic Survey DR9 spectroscopic results. Next, we performed
two cosmological analyses, where relevant parameters not fitted were kept fixed
at their fiducial values. In the first analysis, we extracted the baryon
acoustic oscillation peak position for the four redshift shells, and combined
with the sound horizon scale from 7-year \textit{Wilkinson Microwave Anisotropy
Probe} to produce the constraints and
. In the second analysis, we used the ACF full shape
information to constrain cosmology using real data for the first time, finding
and .
These results are in good agreement with findings, showing that the ACF
can be efficiently applied to constrain cosmology in future photometric galaxy
surveys.Comment: MNRAS accepted. Minor corrections to match publish versio
Line strengths of early-type galaxies
In this paper we present measurements of velocity dispersions and Lick
indices for 509 galaxies in the local Universe, based on high signal-to-noise,
long slit spectra obtained with the 1.52 m ESO telescope at La Silla. The
conversion of our measurements into the Lick/IDS system was carried out
following the general prescription of Worthey and Ottaviani 1997. Comparisons
of our measurements with those of other authors show, in general, good
agreement. We also examine the dependence between these indices (e.g., Hbeta,
Mg_2, Fe5270 and NaD) and the central velocity dispersion (sigma), and we find
that they are consistent with those previously reported in the literature.
Benefiting from the relatively large size of the sample, we are able to
investigate the dependence of these relations on morphology and environment,
here represented by the local galaxy density. We find that for metallic lines
these relations show no significant dependence on environment or morphology,
except in the case of NaD, which shows distinct behavior for E and S0. On the
other hand, the Hbeta-logsigma shows a significant difference as a function of
the local density of galaxies, which we interpret as being caused by the
truncation of star formation in high density environments. Comparing our
results with those obtained by other authors we find a few discrepancies,
adding to the ongoing debate about the nature of these relations. Finally, we
report that the scatter of the Mg indices versus sigma relations correlate with
Hbeta, suggesting that age may contribute to the scatter. Furthermore, this
scatter shows no significant dependence on morphology or environment. Our
results are consistent with the current downsizing model, where low mass
galaxies have an extended star formation history (abridged).Comment: 88 pages, 24 figures, to be published in AJ, for further information
see http://staff.on.br/ogand
Comparison of the ENEAR Peculiar Velocities with the PSCz Gravity Field
We present a comparison between the peculiar velocity field measured from the
ENEAR all-sky catalog and that derived from the galaxy
distribution of the IRAS PSCz redshift survey. The analysis is based on a modal
expansion of these data in redshift space by means of spherical harmonics and
Bessel functions. The effective smoothing scale of the expansion is almost
linear with redshift reaching 1500km/s at 3000km/s. The general flow patterns
in the filtered ENEAR and PSCz velocity fields agree well within 6000km/s,
assuming a linear biasing relation between the mass and the PSCz galaxies. The
comparison allows us to determine the parameter , where
is the cosmological density parameter and is the linear biasing
factor. A likelihood analysis of the ENEAR and PSCz modes yields , in good agreement with values obtained from Tully-Fisher surveys.Comment: Submitted to MNRA
An estimate of \Omega_m without priors
Using mean relative peculiar velocity measurements for pairs of galaxies, we
estimate the cosmological density parameter and the amplitude of
density fluctuations . Our results suggest that our statistic is a
robust and reproducible measure of the mean pairwise velocity and thereby the
parameter. We get and . These estimates do not depend on prior assumptions on
the adiabaticity of the initial density fluctuations, the ionization history,
or the values of other cosmological parameters.Comment: 12 pages, 4 figures, slight changes to reflect published versio
The Motions of Clusters of Galaxies and the Dipoles of the Peculiar Velocity Field
In preceding papers of this series, TF relations for galaxies in 24 clusters
with radial velocities between 1000 and 9200 km/s (SCI sample) were obtained, a
Tully-Fisher (TF) template relation was constructed and mean offsets of each
cluster with respect to the template obtained. Here, an estimate of the
line-of-sight peculiar velocities of the clusters and their associated errors
are given. It is found that cluster peculiar velocities in the Cosmic Microwave
Background reference frame do not exceed 600 k/ms and that their distribution
has a line-of-sight dispersion of 300 k/ms, suggesting a more quiescent cluster
peculiar velocity field than previously reported. When measured in a reference
frame in which the Local Group is at rest, the set of clusters at cz > 3000
km/s exhibits a dipole moment in agreement with that of the CMB, both in
amplitude and apex direction. It is estimated that the bulk flow of a sphere of
6000 km/s radius in the CMB reference frame is between 140 and 320 km/s. These
results are in agreement with those obtained from an independent sample of
field galaxies (Giovanelli et al. 1998; see astro-ph/9807274)Comment: 9 pages, 2 tables, 7 figures, uses AAS LaTex; to appear in A
Cluster vs. Field Elliptical Galaxies and Clues on their Formation
Using new observations for a sample of 931 early-type galaxies we investigate
whether the \mg2--\so relation shows any dependence on the local environment.
The galaxies have been assigned to three different environments depending on
the local overdensity: clusters, groups, and field, having used our
completeredshift database to guide the assignment of galaxies. It is found that
cluster, group and field early-type galaxies follow almost identical \mg2--\so\
relations, with the largest \mg2 zero-point difference (clusters minus field)
being only mag. No correlation of the residuals is found with
the morphological type or the bulge to disk ratio. Using stellar population
models in a differential fashion, this small zero-point difference implies a
luminosity-weighted age difference of only Gyr between the
corresponding stellar populations, with field galaxies being younger. The
mass-weighted age difference could be significantly smaller, if minor events of
late star formation took place preferentially in field galaxies. We combine
these results with the existing evidence for the bulk of stars in cluster
early-type galaxies having formed at very high redshift, and conclude that the
bulk of stars in galactic spheroids had to form at high redshifts (z\gsim 3),
no matter whether such spheroids now reside in low or high density regions. The
cosmological implications of these findings are briefly discussed.Comment: 16 pages, 2 figures, accepted for publication in the ApJ.
Espécies de Cigarrinhas (Hemiptera, Membracoidea, Cicadellidae) Registradas no Estado do Rio De Janeiro, Brasil
A preliminary list of the species of Cicadellidae from Rio de Janeiro State, southeastern Brazil, is presented. The list, which was prepared based on a careful survey of the literature and examination of insect collections, includes 340 leafhopper species. This number represents an increase of over 150 species in comparison to a list published in 1982. The numbers of species recorded for each subfamily are as follows: Agalliinae: 31, Cicadellinae: 162, Coelidiinae: 13, Deltocephalinae: 35, Gyponinae: 63, Iassinae: 8, Idiocerinae: 1, Ledrinae: 2, Neobalinae: 3, Neocoelidiinae: 3, Nioniinae: 1, Nirvaninae: 3, Phereurhininae: 2, Typhlocybinae: 9, and Xestocephalinae: 4. The available data on the distribution of each species within the State (municipalities) are given. Most of the recorded species are from the now heavily fragmented Brazilian Atlantic Forest.Uma lista preliminar das espécies de Cicadellidae do Estado do Rio de Janeiro, sudeste do Brasil, é apresentada. A lista, preparada a partir de cuidadoso estudo da literatura e exame de coleções de insetos, inclui 340 espécies de cigarrinhas. Esse número representa o aumento de mais de 150 espécies em comparação com uma lista publicada em 1982. Os números de espécies registradas de cada subfamília são os seguintes: Agalliinae: 31, Cicadellinae: 162, Coelidiinae: 13, Deltocephalinae: 35, Gyponinae: 63, Iassinae: 8, Idiocerinae: 1, Ledrinae: 2, Neobalinae: 3, Neocoelidiinae: 3, Nioniinae: 1, Nirvaninae: 3, Phereurhininae: 2, Typhlocybinae: 9, e Xestocephalinae: 4. As informações disponíveis sobre a distribuição de cada espécie no Estado (municípios) são fornecidas. A maior parte das espécies registradas é proveniente da Mata Atlântica brasileira, que hoje se encontra intensamente fragmentada
The Tully-Fisher Relation and H_not
The use of the Tully-Fisher (TF) relation for the determination of the Hubble
Constant relies on the availability of an adequate template TF relation and of
reliable primary distances. Here we use a TF template relation with the best
available kinematical zero-point, obtained from a sample of 24 clusters of
galaxies extending to cz ~ 9,000 km/s, and the most recent set of Cepheid
distances for galaxies fit for TF use. The combination of these two ingredients
yields H_not = 69+/-5 km/(s Mpc). The approach is significantly more accurate
than the more common application with single cluster (e.g. Virgo, Coma)
samples.Comment: 10 pages, including 2 figures and 1 table; uses AAS LaTex. Submitted
to ApJ Letter
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