69 research outputs found
The GALANTE Photometric System
This paper describes the characterization of the GALANTE photometric system,
a seven intermediate- and narrow-band filter system with a wavelength coverage
from 3000 to 9000 . We describe the photometric system
presenting the full sensitivity curve as a product of the filter sensitivity,
CCD, telescope mirror, and atmospheric transmission curves, as well as some
first- and second-order moments of this sensitivity function. The GALANTE
photometric system is composed of four filters from the J-PLUS photometric
system, a twelve broad-to-narrow filter system, and three exclusive filters,
specifically designed to measure the physical parameters of stars such as
effective temperature , , metallicity, colour excess
, and extinction type . Two libraries, the Next
Generation Spectral Library (NGSL) and the one presented in Ma\'iz Apell\'aniz
& Weiler (2018), have been used to determine the transformation equations
between the Sloan Digital Sky Survey ()
photometry and the GALANTE photometric system. We will use this transformation
to calibrate the zero points of GALANTE images. To this end, a preliminary
photometric calibration of GALANTE has been made based on two different
libraries ( DR12 and ATLAS All-Sky Stellar
Reference Catalog, hereinafter ). A comparison between both
zero points is performed leading us to the choice of as the
base catalogue for this calibration, and applied to a field in the Cyg OB2
association.Comment: Accepted in MNRA
An eclipsing post-common-envelope binary in the field of the Kepler mission
We present a new eclipsing post-common-envelope binary, identified inside the Kepler field prior to the launch of the spacecraft. Multifilter photometry and radial velocity data are analysed with an eclipsing-binary modelling code to determine the physical parameters of the binary. Spectra of the system within the primary eclipse and uneclipsed allow us to identify the spectral characteristics of the primary and secondary components. The primary component of the binary is a DA white dwarf, with M≃ 0.61 M⊙, log g≃ 7.95 and Teff≃ 20 500 K. The detection of two flares and the emission signatures displayed in the spectra show that the secondary component of the system is chromospherically active and is classified as an active M4 main-sequence star. Its mass, radius and temperature are estimated as M≃ 0.39 M⊙, R≃ 0.37 R⊙ and Teff≃ 3200 K. The ephemeris of the system is HJD = 245 3590.436 126(10) + 0.350 468 722(6) ×E. This binary is a new post-common-envelope binary (PCEB), with physical parameters within the range found in other systems of this small group of evolved binarie
Re-calibrated Generalized-Scidar measurements at Cerro Paranal (VLT's site)
Generalized Scidar (GS) measurements taken at the Paranal Observatory in
November/December 2007 in the context of a site qualification for the future
European Extremely Large Telescope E-ELT are re-calibrated to overcome the bias
induced on the CN2 profiles by a not correct normalization of the
autocorrelation of the scintillation maps that has been recently identified in
the GS technique. A complete analysis of the GS corrected measurements as well
as of the corrected errors is performed statistically as well as on individual
nights and for each time during all nights. The relative errors of the CN2
profiles can reach up to 60% in some narrow temporal windows and some vertical
slabs, the total seeing up to 12% and the total integrated turbulence J up to
21%. However, the statistic analysis tells us that the absolute errors of the
median values of the total seeing is 0.06 arcsec (relative error 5.6%), for the
boundary seeing 0.05 arcsec (relative error 5.6%) and for the seeing in the
free atmosphere 0.04 arcsec (relative error 9%). We find that, in spite of the
fact that the relative error increases with the height, the boundary and the
free atmosphere seeing contribute in an equivalent way to the error on the
total seeing in absolute terms. Besides, we find that there are no correlations
between the relative errors and the value of the correspondent seeing. The
absolute error of the median value of the isoplanatic angle is 0.13 arcsec
(relative error 6.9%).Comment: 22 figures, MNRAS accepte
Galaxy properties from J-PAS narrow-band photometry
We study the consistency of the physical properties of galaxies retrieved
from SED-fitting as a function of spectral resolution and signal-to-noise ratio
(SNR). Using a selection of physically motivated star formation histories, we
set up a control sample of mock galaxy spectra representing observations of the
local universe in high-resolution spectroscopy, and in 56 narrow-band and 5
broad-band photometry. We fit the SEDs at these spectral resolutions and
compute their corresponding the stellar mass, the mass- and luminosity-weighted
age and metallicity, and the dust extinction. We study the biases,
correlations, and degeneracies affecting the retrieved parameters and explore
the r\^ole of the spectral resolution and the SNR in regulating these
degeneracies. We find that narrow-band photometry and spectroscopy yield
similar trends in the physical properties derived, the former being
considerably more precise. Using a galaxy sample from the SDSS, we compare more
realistically the results obtained from high-resolution and narrow-band SEDs
(synthesized from the same SDSS spectra) following the same spectral fitting
procedures. We use results from the literature as a benchmark to our
spectroscopic estimates and show that the prior PDFs, commonly adopted in
parametric methods, may introduce biases not accounted for in a Bayesian
framework. We conclude that narrow-band photometry yields the same trend in the
age-metallicity relation in the literature, provided it is affected by the same
biases as spectroscopy; albeit the precision achieved with the latter is
generally twice as large as with the narrow-band, at SNR values typical of the
different kinds of data.Comment: 26 pages, 15 figures. Accepted for publication in MNRA
The GALANTE photometric survey of the northern Galactic plane: Project description and pipeline
The GALANTE optical photometric survey is observing the northern Galactic
plane and some adjacent regions using seven narrow- and intermediate-filters,
covering a total of 1618 square degrees. The survey has been designed with
multiple exposure times and at least two different air masses per field to
maximize its photometric dynamic range, comparable to that of Gaia, and ensure
the accuracy of its photometric calibration. The goal is to reach at least 1%
accuracy and precision in the seven bands for all stars brighter than AB
magnitude 17 while detecting fainter stars with lower values of the
signal-to-noise ratio.The main purposes of GALANTE are the identification and
study of extinguished O+B+WR stars, the derivation of their extinction
characteristics, and the cataloguing of F and G stars in the solar
neighbourhood. Its data will be also used for a variety of other stellar
studies and to generate a high-resolution continuum-free map of the H{\alpha}
emission in the Galactic plane. We describe the techniques and the pipeline
that are being used to process the data, including the basis of an innovative
calibration system based on Gaia DR2 and 2MASS photometry.Comment: 18 pages, accepted for publication in MNRA
J-PLUS: analysis of the intracluster light in the Coma cluster
The intracluster light (ICL) is a luminous component of galaxy clusters
composed of stars that are gravitationally bound to the cluster potential but
do not belong to the individual galaxies. Previous studies of the ICL have
shown that its formation and evolution are intimately linked to the
evolutionary stage of the cluster. Thus, the analysis of the ICL in the Coma
cluster will give insights into the main processes driving the dynamics in this
highly complex system. Using a recently developed technique, we measure the ICL
fraction in Coma at several wavelengths, using the J-PLUS unique filter system.
The combination of narrow- and broadband filters provides valuable information
on the dynamical state of the cluster, the ICL stellar types, and the
morphology of the diffuse light. We use the Chebyshev-Fourier Intracluster
Light Estimator (CICLE) to disentangle the ICL from the light of the galaxies,
and to robustly measure the ICL fraction in seven J-PLUS filters. We obtain the
ICL fraction distribution of the Coma cluster at different optical wavelengths,
which varies from , showing the highest values in the narrowband
filters J0395, J0410, and J0430. This ICL fraction excess is distinctive
pattern recently observed in dynamically active clusters (mergers), indicating
a higher amount of bluer stars in the ICL compared to the cluster galaxies.
Both the high ICL fractions and the excess in the bluer filters are indicative
of a merging state. The presence of younger/lower-metallicity stars the ICL
suggests that the main mechanism of ICL formation for the Coma cluster is the
stripping of the stars in the outskirts of infalling galaxies and, possibly,
the disruption of dwarf galaxies during past/ongoing mergers.Comment: 10 pages, 3 figures, 1 table. Accepted for publication in A&
Testing the models of CV evolution
The study of Cataclysmic Variables (CVs) is crucial to test our understanding of binary evolution and its application to many astrophysical phenomena, such as short gamma-ray bursts, X-ray transients and, more important, Supernovae Ia, our yardsticks for measuring distances. Yet, the predicted major component of the present-day CV population, the so-called "period bouncers" (CVs containing a white dwarf and a degenerate donor), has not been detected, highlighting a major discrepancy between theory and observations.
We present here CHiCaS, the Compact binary HIgh CAdence Survey, which will perform three hours of uninterrupted time series photometry over 136 square degrees of the sky with JAST/T80Cam. By the end of next year, this program will deliver one minute cadence lightcurves for ¿2.5 million objects as faint as g¿21.5, along with full colour information. Via detection of their eclipses, CHiCaS will finally, and unambiguously identify the predicted large population of period bouncers. The identification of the missing population will provide an observational support for the current models for the mechanisms of angular momentum loss in compact binaries, which also describe the evolution of all kind of binaries.
CHiCaS will also offer a complete and unbiased view into the short term variability of thousands of binaries, eclipsing systems, pulsating stars and CVs in the period gap, which will allow to improve our knowledge of these objects and to carry out additional tests on CV evolution.Peer ReviewedPostprint (published version
J-PLUS: Identification of low-metallicity stars with artificial neural networks using SPHINX
We present a new methodology for the estimation of stellar atmospheric
parameters from narrow- and intermediate-band photometry of the Javalambre
Photometric Local Universe Survey (J-PLUS), and propose a method for target
pre-selection of low-metallicity stars for follow-up spectroscopic studies.
Photometric metallicity estimates for stars in the globular cluster M15 are
determined using this method. By development of a neural-network-based
photometry pipeline, we aim to produce estimates of effective temperature,
, and metallicity, [Fe/H], for a large subset of stars in the
J-PLUS footprint. The Stellar Photometric Index Network Explorer, SPHINX, is
developed to produce estimates of and [Fe/H], after training on a
combination of J-PLUS photometric inputs and synthetic magnitudes computed for
medium-resolution (R ~ 2000) spectra of the Sloan Digital Sky Survey. This
methodology is applied to J-PLUS photometry of the globular cluster M15.
Effective temperature estimates made with J-PLUS Early Data Release photometry
exhibit low scatter, \sigma() = 91 K, over the temperature range
4500 < (K) < 8500. For stars from the J-PLUS First Data Release
with 4500 < (K) < 6200, 85 3% of stars known to have [Fe/H]
<-2.0 are recovered by SPHINX. A mean metallicity of [Fe/H]=-2.32 0.01,
with a residual spread of 0.3 dex, is determined for M15 using J-PLUS
photometry of 664 likely cluster members. We confirm the performance of SPHINX
within the ranges specified, and verify its utility as a stand-alone tool for
photometric estimation of effective temperature and metallicity, and for
pre-selection of metal-poor spectroscopic targets.Comment: 18 pages, 12 figure
J-PAS: forecasts on interacting vacuum energy models
The next generation of galaxy surveys will allow us to test some fundamental
aspects of the standard cosmological model, including the assumption of a
minimal coupling between the components of the dark sector. In this paper, we
present the Javalambre Physics of the Accelerated Universe Astrophysical Survey
(J-PAS) forecasts on a class of unified models where cold dark matter interacts
with a vacuum energy, considering future observations of baryon acoustic
oscillations, redshift-space distortions, and the matter power spectrum. After
providing a general framework to study the background and linear perturbations,
we focus on a concrete interacting model without momentum exchange by taking
into account the contribution of baryons. We compare the J-PAS results with
those expected for DESI and Euclid surveys and show that J-PAS is competitive
to them, especially at low redshifts. Indeed, the predicted errors for the
interaction parameter, which measures the departure from a CDM model,
can be comparable to the actual errors derived from the current data of cosmic
microwave background temperature anisotropies.Comment: 34 pages, 9 figures, 14 table
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