31 research outputs found
Integral field spectroscopy of M1-67. A Wolf-Rayet nebula with LBVN appearance
This work aims to disentangle the morphological, kinematic, and chemical
components of the nebula M1-67 to shed light on its process of formation around
the central Wolf-Rayet (WR) star WR124. We have carried out integral field
spectroscopy observations over two regions of M1-67, covering most of the
nebula in the optical range. Maps of electron density, line ratios, and radial
velocity were created to perform a detailed analysis of the two-dimensional
structure. We studied the physical and chemical properties by means of
integrated spectra selected over the whole nebula. Photoionization models were
performed to confirm the empirical chemical results theoretically. In addition,
we analysed infrared spectroscopic data and the MIPS 24micron image of M1-67
from Spitzer. We find that the ionized gas of M1-67 is condensed in knots
aligned in a preferred axis along the NE-SW direction, like a bipolar
structure. Both electron density and radial velocity decrease in this direction
when moving away from the central star. From the derived electron temperature,
Te~8200 K, we have estimated chemical abundances, obtaining that nitrogen
appears strongly enriched and oxygen depleted. From the last two results, we
infer that this bipolarity is the consequence of an ejection of an evolved
stage of WR124 with material processed in the CNO cycle. The infrared study has
revealed that the bipolar axis is composed of ionized gas with a low ionization
degree that is well mixed with warm dust and of a spherical bubble surrounding
the ejection at 24micron. Taking the evolution of a 60 Mo star and the temporal
scale of the bipolar ejection into account, we propose that the observed gas
was ejected during an eruption in the luminous blue variable. The star has
entered the WR phase recently without apparent signs of interaction between
WR-winds and interstellar material.Comment: Accepted for publication in section 6 of Astronomy and Astrophysics.
The official date of acceptance is 15/03/2013. 17 pages, 14 figures and 8
table
The interplay between ionized gas and massive stars in the HII galaxy IIZw70: integral field spectroscopy with PMAS
We performed an integral field spectroscopic study for the HII galaxy IIZw70
in order to investigate the interplay between its ionized interstellar medium
(ISM) and the massive star formation (SF). Observations were taken in the
optical spectral range (3700-6800 A) with the Potsdam Multi-Aperture
Spectrophotometer (PMAS) attached to the 3.5 m telescope at CAHA. We created
and analysed maps of spatially distributed emission-lines, continuum emission
and properties of the ionized ISM (e.g. physical-chemical conditions, dust
extinction, kinematics). We investigated the relation of these properties to
the spatial distribution and evolutionary stage of the massive stars. For the
first time we have detected the presence of Wolf-Rayet (WR) stars in this
galaxy. The peak of the ionized gas emission coincides with the location of the
WR bump. The region of the galaxy with lower dust extinction corresponds to the
region that shows the lowest values of velocity dispersion and radial velocity.
The overall picture suggests that the ISM of this region is being disrupted via
photoionization and stellar winds, leading to a spatial decoupling between
gas+stars and dust clouds. The bulk of dust appears to be located at the
boundaries of the region occupied by the probable ionizing cluster. We also
found that this region is associated to the nebular emission in HeII4686 and to
the intensity maximum of most emission lines. This indicates that the hard
ionizing radiation responsible for the HeII4686 nebular emission can be related
to the youngest stars. Within 0.4 x 0.3 kpc^2 in the central burst, we
derived O/H using direct determinations of Te[OIII]. We found abundances in the
range 12+log(O/H)=7.65-8.05, yielding an error-weighted mean of
12+log(O/H)=7.86 0.05.Comment: 10 pages, 10 figures, accepted for publication in A&A, minor changes
adde
Microalgae biorefinery alternatives and hazard evaluation
Biodiesel production based on microalgae and using carbon dioxide as feedstock constitutes an attractive biofuel alternative. Technology development and process optimization are necessary to minimize the overall production cost. Moreover, in the framework of process sustainability, social and environmental impacts should include process safety aspects. In this context, the objective of this work is to develop a biodiesel production process based on microalgae and the subsequent estimation of the associated risks, thus contributing to more sustainable and safe processes. The biodiesel biorefinery is optimized, taking into account alternative configurations for algae cultivation and lipid extraction. Algae cultivation options are open ponds and tubular photobioreactors. Regarding lipid extraction, dewatering and subsequent n-hexane extraction, and combined ethanol/n-hexane extraction are the studied alternatives. Numerical results showed that open ponds and n-hexane extraction provide maximum net present value. However, n-hexane consumption dramatically rises, and industrial hazards have not been considered in the optimization process. To overcome this issue, a preliminary hazard analysis is carried out to identify hazardous materials and operations. Event trees are formulated to derive the frequencies of different accident scenarios, further determining the consequences. The major consequences of accidents involve toxic releases of high quantities of n-hexane. By comparing the proposed alternatives, this work aims to highlight the need to consider not only economic but also safety and environmental objectives in the development of a biodiesel production project.The authors are grateful for the financial support provided by CONICET and the Spanish MICINN under projects CTQ2013-48280-C3-1-R and CTM2014-57833-R. J. Pinedo would also like to thank the financial support provided by “Becas Iberoamérica JPI España 2014”
The miniJPAS survey. Evolution of the luminosity and stellar mass functions of galaxies up to
We aim at developing a robust methodology for constraining the luminosity and
stellar mass functions (LMFs) of galaxies by solely using data from
multi-filter surveys and testing the potential of these techniques for
determining the evolution of the miniJPAS LMFs up to . Stellar mass
and -band luminosity for each of the miniJPAS galaxies are constrained using
an updated version of the SED-fitting code MUFFIT, whose values are based on
composite stellar population models and the probability distribution functions
of the miniJPAS photometric redshifts. Galaxies are classified through the
stellar mass versus rest-frame colour diagram corrected for extinction.
Different stellar mass and luminosity completeness limits are set and
parametrised as a function of redshift, for setting limits in our flux-limited
sample (). The miniJPAS LMFs are parametrised according to
Schechter-like functions via a novel maximum likelihood method accounting for
uncertainties, degeneracies, probabilities, completeness, and priors. Overall,
our results point to a smooth evolution with redshift () of the
miniJPAS LMFs in agreement with previous work. The LMF evolution of
star-forming galaxies mainly involve the bright and massive ends of these
functions, whereas the LMFs of quiescent galaxies also exhibit a non-negligible
evolution on their faint and less massive ends. The cosmic evolution of the
global -band luminosity density decreases ~0.1 dex from to 0,
whereas for quiescent galaxies this quantity roughly remains constant. In
contrast, the stellar mass density increases ~0.3 dex at the same redshift
range, where such evolution is mainly driven by quiescent galaxies owing to an
overall increasing number of this kind of galaxies, which in turn includes the
majority and most massive galaxies (60-100% fraction of galaxies at
).Comment: 31 pages, 15 figures. Submitted to A&
The miniJPAS survey: clusters and galaxy groups detection with AMICO
Samples of galaxy clusters allow us to better understand the physics at play
in galaxy formation and to constrain cosmological models once their mass,
position (for clustering studies) and redshift are known. In this context,
large optical data sets play a crucial role. We investigate the capabilities of
the Javalambre-Physics of the Accelerating Universe Astrophysical Survey
(J-PAS) in detecting and characterizing galaxy groups and clusters. We analyze
the data of the miniJPAS survey, obtained with the JPAS-Pathfinder camera and
covering deg centered on the AEGIS field to the same depths and with
the same 54 narrow band plus 2 broader band near-UV and near-IR filters
anticipated for the full J-PAS survey. We use the Adaptive Matched Identifier
of Clustered Objects (AMICO) to detect and characterize groups and clusters of
galaxies down to in the redshift range . We detect 80, 30
and 11 systems with signal-to-noise ratio larger than 2.5, 3.0 and 3.5,
respectively, down to . We derive mass-proxy scaling
relations based on Chandra and XMM-Newton X-ray data for the signal amplitude
returned by AMICO, the intrinsic richness and a new proxy that incorporates the
galaxies' stellar masses. The latter proxy is made possible thanks to the J-PAS
filters and shows a smaller scatter with respect to the richness. We fully
characterize the sample and use AMICO to derive a probabilistic membership
association of galaxies to the detected groups that we test against
spectroscopy. We further show how the narrow band filters of J-PAS provide a
gain of up to 100% in signal-to-noise ratio in detection and an uncertainty on
the redshift of clusters of only placing J-PAS in
between broadband photometric and spectroscopic surveys. The performances of
AMICO and J-PAS with respect to mass sensitivity, mass-proxies qualityComment: 15 pages, 12 figures, 3 tables, submitted to A&
The miniJPAS survey: Identification and characterization of the emission line galaxies down to in the AEGIS field
The Javalambre-Physics of the Accelerating Universe Astrophysical Survey
(J-PAS) is expected to map thousands of square degrees of the northern sky with
56 narrowband filters in the upcoming years. This will make J-PAS a very
competitive and unbiased emission line survey compared to spectroscopic or
narrowband surveys with fewer filters. The miniJPAS survey covered 1 deg,
and it used the same photometric system as J-PAS, but the observations were
carried out with the pathfinder J-PAS camera. In this work, we identify and
characterize the sample of emission line galaxies (ELGs) from miniJPAS with a
redshift lower than . Using a method based on artificial neural networks,
we detect the ELG population and measure the equivalent width and flux of the
, , [OIII], and [NII] emission lines. We explore the
ionization mechanism using the diagrams [OIII]/H versus [NII]/H
(BPT) and EW(H) versus [NII]/H (WHAN). We identify 1787 ELGs
(%) from the parent sample (2154 galaxies) in the AEGIS field. For the
galaxies with reliable EW values that can be placed in the WHAN diagram (2000
galaxies in total), we obtained that %, % , and
% are star-forming (SF), active galactic nucleus (Seyfert), and
quiescent galaxies, respectively. Based on the flux of we find that
the star formation main sequence is described as SFR and has an intrinsic scatter of . The cosmic evolution of the SFR density ()
is derived at three redshift bins: , , and
, which agrees with previous results that were based on
measurements of the emission line.Comment: 22 pages, 19 figure
Plasma Levels of Transforming Growth Factor-β1 Reflect Left Ventricular Remodeling in Aortic Stenosis
Background: TGF-b1 is involved in cardiac remodeling through an auto/paracrine mechanism. The contribution of TGF-b1
from plasmatic source to pressure overload myocardial remodeling has not been analyzed. We investigated, in patients with
valvular aortic stenosis (AS), and in mice subjected to transverse aortic arch constriction (TAC), whether plasma TGF-b1
relates with myocardial remodeling, reflected by LV transcriptional adaptations of genes linked to myocardial hypertrophy
and fibrosis, and by heart morphology and function.
Methodology/Principal Findings: The subjects of the study were: 39 patients operated of AS; 27 healthy volunteers; 12
mice subjected to TAC; and 6 mice sham-operated. Myocardial samples were subjected to quantitative PCR. Plasma TGF-b1
was determined by ELISA. Under pressure overload, TGF-b1 plasma levels were significantly increased both in AS patients
and TAC mice. In AS patients, plasma TGF-b1 correlated directly with aortic transvalvular gradients and LV mass surrogate
variables, both preoperatively and 1 year after surgery. Plasma TGF-b1 correlated positively with the myocardial expression
of genes encoding extracellular matrix (collagens I and III, fibronectin) and sarcomeric (myosin light chain-2, b-myosin heavy
chain) remodelling targets of TGF-b1, in TAC mice and in AS patients.
Conclusions/Significance: A circulating TGF-b1-mediated mechanism is involved, in both mice and humans, in the
excessive deposition of ECM elements and hypertrophic growth of cardiomyocytes under pressure overload. The possible
value of plasma TGF-b1 as a marker reflecting preoperative myocardial remodeling status in AS patients deserves further
analysis in larger patient cohorts