304 research outputs found
Easylife: the data reduction and survey handling system for VIPERS
We present Easylife, the software environment developed within the framework
of the VIPERS project for automatic data reduction and survey handling.
Easylife is a comprehensive system to automatically reduce spectroscopic data,
to monitor the survey advancement at all stages, to distribute data within the
collaboration and to release data to the whole community. It is based on the
OPTICON founded project FASE, and inherits the FASE capabilities of modularity
and scalability. After describing the software architecture, the main reduction
and quality control features and the main services made available, we show its
performance in terms of reliability of results. We also show how it can be
ported to other projects having different characteristics.Comment: pre-print, 17 pages, 4 figures, accepted for publication in
Publications of the Astronomical Society of the Pacifi
The blue sky of GJ3470b: the atmosphere of a low-mass planet unveiled by ground-based photometry
GJ3470b is a rare example of a "hot Uranus" transiting exoplanet orbiting a
nearby M1.5 dwarf. It is of crucial interest for atmospheric studies because it
is one of the most inflated low-mass planets known, bridging the boundary
between "super-Earths" and Neptunian planets. We present two new ground-based
light curves of GJ3470b gathered by the LBC camera at the Large Binocular
Telescope. Simultaneous photometry in the ultraviolet (lambda_c = 357.5 nm) and
optical infrared (lambda_c = 963.5 nm) allowed us to detect a significant
change of the effective radius of GJ3470b as a function of wavelength. This can
be interpreted as a signature of scattering processes occurring in the
planetary atmosphere, which should be cloud-free and with a low mean molecular
weight. The unprecedented accuracy of our measurements demonstrates that the
photometric detection of Earth-sized planets around M dwarfs is achievable
using 8-10m size ground-based telescopes. We provide updated planetary
parameters, and a greatly improved orbital ephemeris for any forthcoming study
of this planet.Comment: 8 pages, 6 figures, 1 table; accepted for publication in A&
EZ: A Tool for Automatic Redshift Measurement
We present EZ (Easy redshift), a tool we have developed within the VVDS
project to help in redshift measurement from otpical spectra. EZ has been
designed with large spectroscopic surveys in mind, and in its development
particular care has been given to the reliability of the results obtained in an
automatic and unsupervised mode. Nevertheless, the possibility of running it
interactively has been preserved, and a graphical user interface for results
inspection has been designed. EZ has been successfully used within the VVDS
project, as well as the zCosmos one. In this paper we describe its architecture
and the algorithms used, and evaluate its performances both on simulated and
real data. EZ is an open source program, freely downloadable from
http://cosmos.iasf-milano.inaf.it/pandora.Comment: accepted for publication in Publications of the Astronomical Society
of the Pacifi
PNe and H II regions in the starburst irregular galaxy NGC 4449 from LBT MODS data
We present deep 350010000 spectra of H II regions and planetary
nebulae (PNe) in the starburst irregular galaxy NGC 4449, acquired with the
Multi Object Double Spectrograph at the Large Binocular Telescope. Using the
"direct" method, we derived the abundance of He, N, O, Ne, Ar, and S in six H
II regions and in four PNe in NGC 4449. This is the first case of PNe studied
in a starburst irregular outside the Local Group. Our H II region and PN sample
extends over a galacto-centric distance range of 2 kpc and spans
0.2 dex in oxygen abundance, with average values of and for H II regions and PNe, respectively. PNe and H
II regions exhibit similar oxygen abundances in the galacto-centric distance
range of overlap, while PNe appear more than 1 dex enhanced in nitrogen
with respect to H II regions. The latter result is the natural consequence of N
being mostly synthesized in intermediate-mass stars and brought to the stellar
surface during dredge-up episodes. On the other hand, the similarity in O
abundance between H II regions and PNe suggests that NGC 4449' s interstellar
medium has been poorly enriched in elements since the progenitors of
the PNe were formed. Finally, our data reveal the presence of a negative oxygen
gradient for both H II regions and PNe, whilst nitrogen does not exhibit any
significant radial trend. We ascribe the (unexpected) nitrogen behaviour as due
to local N enrichment by the conspicuous Wolf-Rayet population in NGC 4449.Comment: Accepted for publication on Ap
HII regions within a compact high velocity cloud. A nearly star-less dwarf galaxy?
Within the SECCO survey we identified a candidate stellar counterpart to the
Ultra Compact High Velocity Cloud (UCHVC) HVC274.68+74.70-123, that was
suggested by Adams et al. (2013) as a possible mini-halo within the Local Group
of galaxies. The spectroscopic follow-up of the brightest sources within the
candidate reveals the presence of two HII regions whose radial velocity is
compatible with physical association with the UVHVC. The available data does
not allow us to give a definite answer on the nature of the newly identified
system. A few alternative hypotheses are discussed. However, the most likely
possibility is that we have found a new faint dwarf galaxy residing in the
Virgo cluster of galaxies, which we name SECCO-1. Independently of its actual
distance, SECCO-1 displays a ratio of neutral hydrogen mass to V luminosity of
M_{HI}/L_V>= 20, by far the largest among local dwarfs. Hence, it appears as a
nearly star-less galaxy and it may be an example of the missing links between
normal dwarfs and the dark mini halos that are predicted to exist in large
numbers according to the currently accepted cosmological model.Comment: Accepted for publication in ApJ Letters. Pdflatex, emulateapj.cls. 6
pages, 3 figures, 2 table
Scaling relations of cluster elliptical galaxies at z~1.3. Distinguishing luminosity and structural evolution
[Abridged] We studied the size-surface brightness and the size-mass relations
of a sample of 16 cluster elliptical galaxies in the mass range
10^{10}-2x10^{11} M_sun which were morphologically selected in the cluster RDCS
J0848+4453 at z=1.27. Our aim is to assess whether they have completed their
mass growth at their redshift or significant mass and/or size growth can or
must take place until z=0 in order to understand whether elliptical galaxies of
clusters follow the observed size evolution of passive galaxies. To compare our
data with the local universe we considered the Kormendy relation derived from
the early-type galaxies of a local Coma Cluster reference sample and the WINGS
survey sample. The comparison with the local Kormendy relation shows that the
luminosity evolution due to the aging of the stellar content already assembled
at z=1.27 brings them on the local relation. Moreover, this stellar content
places them on the size-mass relation of the local cluster ellipticals. These
results imply that for a given mass, the stellar mass at z~1.3 is distributed
within these ellipticals according to the same stellar mass profile of local
ellipticals. We find that a pure size evolution, even mild, is ruled out for
our galaxies since it would lead them away from both the Kormendy and the
size-mass relation. If an evolution of the effective radius takes place, this
must be compensated by an increase in the luminosity, hence of the stellar mass
of the galaxies, to keep them on the local relations. We show that to follow
the Kormendy relation, the stellar mass must increase as the effective radius.
However, this mass growth is not sufficient to keep the galaxies on the
size-mass relation for the same variation in effective radius. Thus, if we want
to preserve the Kormendy relation, we fail to satisfy the size-mass relation
and vice versa.Comment: Accepted for publication in A&A, updated to match final journal
versio
LBT/MODS spectroscopy of globular clusters in the irregular galaxy NGC 4449
We present intermediate-resolution (R1000) spectra in the
3500-10,000 A range of 14 globular clusters in the magellanic irregular
galaxy NGC 4449 acquired with the Multi Object Double Spectrograph on the Large
Binocular Telescope. We derived Lick indices in the optical and the
CaII-triplet index in the near-infrared in order to infer the clusters' stellar
population properties. The inferred cluster ages are typically older than
9 Gyr, although ages are derived with large uncertainties. The clusters
exhibit intermediate metallicities, in the range
[Fe/H], and typically sub-solar []
ratios, with a peak at . These properties suggest that i) during the
first few Gyrs NGC 4449 formed stars slowly and inefficiently, with galactic
winds having possibly contributed to the expulsion of the -elements,
and ii) globular clusters in NGC 4449 formed relatively "late", from a medium
already enriched in the products of type Ia supernovae. The majority of
clusters appear also under-abundant in CN compared to Milky Way halo globular
clusters, perhaps because of the lack of a conspicuous N-enriched,
second-generation of stars like that observed in Galactic globular clusters.
Using the cluster velocities, we infer the dynamical mass of NGC 4449 inside
2.88 kpc to be M(2.88 kpc)=. We
also report the serendipitous discovery of a planetary nebula within one of the
targeted clusters, a rather rare event.Comment: Accepted for publication in MNRAS; corrected typo in author lis
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Never mind the gaps: comparing techniques to restore homogeneous sky coverage
[Abridged] Non-uniform sampling and gaps in sky coverage are common in galaxy
redshift surveys, but these effects can degrade galaxy counts-in-cells and
density estimates. We carry out a comparison of methods that aim to fill the
gaps to correct for the systematic effects. Our study is motivated by the
analysis of the VIMOS Extragalactic Redshift Survey (VIPERS), a flux-limited
survey (i<22.5) based on one-pass observations with VIMOS, with gaps covering
25% of the surveyed area and a mean sampling rate of 35%. Our findings are
applicable to other surveys with similar observing strategies. We compare 1)
two algorithms based on photometric redshift, that assign redshifts to galaxies
based on the spectroscopic redshifts of the nearest neighbours, 2) two Bayesian
methods, the Wiener filter and the Poisson-Lognormal filter. Using galaxy mock
catalogues we quantify the accuracy of the counts-in-cells measurements on
scales of R=5 and 8 Mpc/h after applying each of these methods. We also study
how they perform to account for spectroscopic redshift error and inhomogeneous
and sparse sampling rate. We find that in VIPERS the errors in counts-in-cells
measurements on R<10 Mpc/h scales are dominated by the sparseness of the
sample. All methods underpredict by 20-35% the counts at high densities. This
systematic bias is of the same order as random errors. No method outperforms
the others. Random and systematic errors decrease for larger cells. We show
that it is possible to separate the lowest and highest densities on scales of 5
Mpc/h at redshifts 0.5<z<1.1, over a large volume such as in VIPERS survey.
This is vital for the characterisation of cosmic variance and rare populations
(e.g, brightest galaxies) in environmental studies at these redshifts.Comment: 17 pages, 13 figures, accepted for publication in A&A (revised
version after minor revision and language editing
The absolute age of the globular cluster M15 using near-infrared adaptive optics images from PISCES/LBT
We present deep near-infrared (NIR) J, Ks photometry of the old, metal-poor
Galactic globular cluster M\,15 obtained with images collected with the LUCI1
and PISCES cameras available at the Large Binocular Telescope (LBT). We show
how the use of First Light Adaptive Optics system coupled with the (FLAO)
PISCES camera allows us to improve the limiting magnitude by ~2 mag in Ks. By
analyzing archival HST data, we demonstrate that the quality of the LBT/PISCES
color magnitude diagram is fully comparable with analogous space-based data.
The smaller field of view is balanced by the shorter exposure time required to
reach a similar photometric limit. We investigated the absolute age of M\,15 by
means of two methods: i) by determining the age from the position of the main
sequence turn-off; and ii) by the magnitude difference between the MSTO and the
well-defined knee detected along the faint portion of the MS. We derive
consistent values of the absolute age of M15, that is 12.9+-2.6 Gyr and
13.3+-1.1 Gyr, respectively.Comment: 13 pages, 8 figures, ApJ accepte
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&
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