5,449 research outputs found
Integral field observations of the blue compact galaxy Haro14. Star formation and feedback in dwarf galaxies
(Abridged) Low-luminosity, gas-rich blue compact galaxies (BCG) are ideal
laboratories to investigate many aspects of the star formation in galaxies. We
study the morphology, stellar content, kinematics, and the nebular excitation
and ionization mechanism in the BCG Haro 14 by means of integral field
observations with VIMOS in the VLT. From these data we build maps in continuum
and in the brighter emission lines, produce line-ratio maps, and obtain the
velocity and velocity dispersion fields. We also generate the integrated
spectrum of the major HII regions and young stellar clusters identified in the
maps to determine reliable physical parameters and oxygen abundances. We find
as follows: i) the current star formation in Haro 14 is spatially extended with
the major HII regions placed along a linear structure, elongated in the
north-south direction, and in a horseshoe-like curvilinear feature that extends
about 760 pc eastward; the continuum emission is more concentrated and peaks
close to the galaxy center; ii) two different episodes of star formation are
present: the recent starburst, with ages 6 Myrs and the intermediate-age
clusters, with ages between 10 and 30 Myrs; these stellar components rest on a
several Gyr old underlying host galaxy; iii) the H/H pattern is
inhomogeneous, with excess color values varying from E(B-V)=0.04 up to
E(B-V)=1.09; iv) shocks play a significant role in the galaxy; and v) the
velocity field displays a complicated pattern with regions of material moving
toward us in the east and north galaxy areas. The morphology of Haro 14, its
irregular velocity field, and the presence of shocks speak in favor of a
scenario of triggered star formation. Ages of the knots are consistent with the
ongoing burst being triggered by the collective action of stellar winds and
supernovae originated in the central clusters.Comment: 18 pages, 17 figures. Accepted for publication in A&
Probing star formation and feedback in dwarf galaxies. Integral field view of the blue compact galaxy Tololo 1937-423
(Abridged) Blue compact galaxies (BCG) are gas-rich, low-mass, small systems
that form stars at unusually high rates. This makes them excellent laboratories
for investigating the process of star-formation (SF) at galactic scales and the
effects of massive stellar feedback on the interstellar (and intergalactic)
medium.
We analyzed the BCG Tololo 1937-423 using optical integral field spectroscopy
with VIMOS at the Very Large Telescope to probe its morphology, stellar
content, nebular excitation and ionization properties, and the kinematics of
its warm ionized gas.
We found that Tololo 1937-423 is currently undergoing an extended starburst,
with nine major clumps. The galaxy presents a single continuum peak
that is not cospatial with any knot in emission lines, indicating at least two
relatively recent episodes of SF. The inhomogeneous dust distribution reaches
its maximum roughly at the position of the continuum peak. We found shocked
regions in the galaxy outer regions and at the edges of the SF knots. The
oxygen abundance is similar in all the SF regions, suggesting a chemically
homogeneous ionized interstellar medium over spatial scales of several kpc. The
ionized gas kinematics displays an overall regular rotation around a
northwest-southeast axis.
The morphology of the galaxy and the two different episodes of SF suggest a
scenario of triggered (induced by supernova shock waves) SF acting in Tololo
1937-423. The inferred ages for the different SF episodes (~13-80 Myr for the
central post-starburst and 5-7 Myr for the ongoing SF) are consistent with
triggered SF, with the most recent SF episode caused by the collective effect
of stellar winds and supernova explosions from the central post-starburst. The
velocity dispersion pattern, with higher velocity dispersions found at the
edges of the SF regions, and shocked regions in the galaxy, also favor this
scenario.Comment: 16 pages, 18 figures. Accepted for publication in A&
Understanding star formation and feedback in small galaxies. The case of the blue compact dwarf Mrk 900
(Abridged) Low-luminosity, active star-forming blue compact galaxies (BCGs)
are excellent laboratories for investigating the process of star formation on
galactic scales and probing the interplay between massive stars and the
surrounding interstellar (or intergalactic) medium. We investigated the
morphology, structure, and stellar content of the Blue Compact Galaxy Mrk 900,
combining optical integral field observations obtained with VIMOS at the VLT
and deep broad-band photometry taken at the 2.5 m NOT telescope. From the
integral field data, we built continuum, emission, and diagnostic line ratio
maps and produced velocity and velocity dispersion maps. We also generated the
integrated spectrum of the major HII regions and the nuclear area to determine
reliable physical parameters and oxygen abundances. The broad-band data,
tracing the galaxy up to radius 4 kpc, allowed us to investigate the properties
of the low surface brightness underlying stellar host. We disentangle two
different stellar components in Mrk 900: a young population, which resolves
into individual stellar clusters with ages ~5.5-6.6 Myr and extends about 1 kpc
along the galaxy minor axis, is placed on top of a rather red and regular
shaped underlying stellar host, several Gyr old. We find evidence of a
substantial amount of dust and an inhomogeneous extinction pattern, with a dust
lane crossing the central starburst. Mrk 900 displays overall rotation,
although distorted in the central, starburst regions; the dispersion velocity
map is highly inhomogeneous, with values increasing up to 60 kms at the
periphery of the SF regions, where we also find hints of the presence of
shocks. Our observational results point to an interaction or merger with a
low-mass object or infalling gas as plausible trigger mechanisms for the
present starburst event.Comment: 17 pages, 19 figures. Accepted for publication in A&
The Ca II infrared triplet's performance as an activity indicator compared to Ca II H and K
Aims. A large number of Calcium Infrared Triplet (IRT) spectra are expected
from the GAIA- and CARMENES missions. Conversion of these spectra into known
activity indicators will allow analysis of their temporal evolution to a better
degree. We set out to find such a conversion formula and to determine its
robustness.
Methods. We have compared 2274 Ca II IRT spectra of active main-sequence F to
K stars taken by the TIGRE telescope with those of inactive stars of the same
spectral type. After normalizing and applying rotational broadening, we
subtracted the comparison spectra to find the chromospheric excess flux caused
by activity. We obtained the total excess flux, and compared it to established
activity indices derived from the Ca II H & K lines, the spectra of which were
obtained simultaneously to the infrared spectra.
Results. The excess flux in the Ca II IRT is found to correlate well with
and , as well as , if the
-dependency is taken into account. We find an empirical conversion formula
to calculate the corresponding value of one activity indicator from the
measurement of another, by comparing groups of datapoints of stars with similar
B-V.Comment: 16 pages, 15 figures. Accepted for publication in Astronomy &
Astrophysic
Uv-to-fir analysis of spitzer/irac sources in the extended groth strip i: Multi-wavelength photometry and spectral energy distributions
We present an IRAC 3.6+4.5 microns selected catalog in the Extended Groth
Strip (EGS) containing photometry from the ultraviolet to the far-infrared and
stellar parameters derived from the analysis of the multi-wavelength data. In
this paper, we describe the method used to build coherent spectral energy
distributions (SEDs) for all the sources. In a companion paper, we analyze
those SEDs to obtain robust estimations of stellar parameters such as
photometric redshifts, stellar masses, and star formation rates. The catalog
comprises 76,936 sources with [3.6]<23.75 mag (85% completeness level of the
IRAC survey in the EGS) over 0.48 square degrees. For approximately 16% of this
sample, we are able to deconvolve the IRAC data to obtain robust fluxes for the
multiple counterparts found in ground-based optical images. Typically, the SEDs
of the IRAC sources in our catalog count with more than 15 photometric data
points, spanning from the UV to the FIR. Approximately 95% and 90% of all IRAC
sources are detected in the deepest optical and near-infrared bands. Only 10%
of the sources have optical spectroscopy and redshift estimations. Almost 20%
and 2% of the sources are detected by MIPS at 24 and 70 microns, respectively.
We also cross-correlate our catalog with public X-ray and radio catalogs.
Finally, we present the Rainbow Navigator public web-interface utility designed
to browse all the data products resulting from this work, including images,
spectra, photometry, and stellar parameters.Comment: 28 pages, 12 figures, Accepted for publication in ApJ. Access the
Rainbow Database at: http://rainbowx.fis.ucm.e
Ovine HSP90AA1 Expression Rate Is Affected by Several SNPs at the Promoter under Both Basal and Heat Stress Conditions
The aim of this work was to investigate the association between polymorphisms located at the HSP90AA1 ovine gene promoter and gene expression rate under different environmental conditions, using a mixed model approach. Blood samples from 120 unrelated rams of the Manchega sheep breed were collected at three time points differing in environmental conditions. Rams were selected on the basis of their genotype for the transversion G/C located 660 base pairs upstream the gene transcription initiation site. Animals were also genotyped for another set of 6 SNPs located at the gene promoter. Two SNPs, G/C-660 and A/G-444, were associated with gene overexpression resulting from heat stress. The composed genotype CC-660-AG-444 was the genotype having the highest expression rates with fold changes ranging from 2.2 to 3.0. The genotype AG-522 showed the highest expression levels under control conditions with a fold change of 1.4. Under these conditions, the composed genotype CC-601-TT-524-AG-522-TT-468 is expected to be correlated with higher basal expression of the gene according to genotype frequencies and linkage disequilibrium values. Some putative transcription factors were predicted for binding sites where the SNPs considered are located. Since the expression rate of the gene under alternative environmental conditions seems to depend on the composed genotype of several SNPs located at its promoter, a cooperative regulation of the transcription of the HSP90AA1 gene could be hypothesized. Nevertheless epigenetic regulation mechanisms cannot be discarded. © 2013 Salces-Ortiz et al
USCID fourth international conference
Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.This study, carried out between October 2004 and November 2005 on the island of Tenerife, covers: (1) characterization of the irrigated crops and quantification of the gross irrigation requirements (GIRs) of each crop using surveys; (2) field evaluation of drip/micro, spray and sprinkle irrigation systems to obtain global distribution uniformity (DU) as indicated by the Cal Poly ITRC (Irrigation Training and Research Centre, California Polytechnic State University, San Luis Obispo, California, USA); (3) analysis of on farm irrigation efficiency using local climatic data; and (4) inclusion of this data into a Geographic Information System (GIS). Crop GIRs show high deviations mainly because of the multiple microclimate conditions on the island, the irrigation methods used, the crop systems (greenhouses, etc) and the irrigation management. Field evaluation provided an average DU of 0.83 in drip/micro and spray irrigated banana crops, 0.69 in sprinkle irrigated ones, 0.58 in sprinkle irrigated horticulture and 0.81 for tomato crops (100% drip). Data showed that approximately 30% of the non-uniformity was due to pressure differences in the irrigation system, 3% due to unequal drainage, 7% due to unequal application rates, and 60% was due to other causes (which include manufacturing variation, plugging, and wear). Irrigation efficiency is around 80% in drip irrigated tomato and banana crops and 75% in sprinkle systems. Data showed that efficiency is slightly lower in greenhouses and mesh greenhouse crops than in non-protected crops basically due to the fact that although protected crops require less water, they receive an equal quantity of water. Inclusion of the data into a GIS makes possible a high level of agronomic water consumption control on the island
Investigating evidence for different black hole accretion modes since redshift z~1
Chandra data in the COSMOS, AEGIS-XD and 4Ms CDFS are combined with
optical/near-IR photometry to determine the rest-frame U-V vs V-J colours of
X-ray AGN hosts at mean redshifts 0.40 and 0.85. This combination of colours
(UVJ) provides an efficient means of separating quiescent from star-forming,
including dust reddened, galaxies. Morphological information emphasises
differences between AGN split by their UVJ colours. AGN in quiescent galaxies
are dominated by spheroids, while star-forming hosts are split between bulges
and disks. The UVJ diagram of AGN hosts is then used to set limits on the
accretion density associated with evolved and star-forming systems. Most of the
black hole growth since z~1 is associated with star-forming hosts.
Nevertheless, ~15-20% of the X-ray luminosity density since z~1, is taking
place in the quiescent region of the UVJ diagram. For the z~0.40 subsample,
there is tentative evidence (2sigma significance), that AGN split by their UVJ
colours differ in Eddington ratio. AGN in star-forming hosts dominate at high
Eddington ratios, while AGN in quiescent hosts become increasingly important as
a fraction of the total population toward low Eddington ratios. At higher
redshift, z~0.8, such differences are significant at the 2sigma level only at
Eddington ratios >1e-3. These findings are consistent with scenarios in which
diverse accretion modes are responsible for the build-up of SMBHs at the
centres of galaxies. We compare our results with the GALFORM semi-analytic
model, which postulates two black hole fuelling modes, the first linked to
star-formation and the second occuring in passive galaxies. GALFORM predicts a
larger fraction of black hole growth in quiescent galaxies at z<1, compared to
the data. Relaxing the strong assumption of the model that passive AGN hosts
have zero star-formation rate could reconcile this disagreement.Comment: MNRAS accepte
Role of lysosomal enzymes released by alveolar macrophages in the pathogenesis of the acute phase of hypersensitivity pneumonitis
Hydrolytic enzymes are the major constituents of alveolar macrophages (AM) and have been shown to be involved in many aspects of the inflammatory pulmonary response. The aim of this study was to evaluate the role of lysosomal enzymes in the acute phase of hypersensitivity pneumonitis (HPs). An experimental study on AM lysosomal enzymes of an HP-guinea-pig model was performed. The results obtained both in vivo and in vitro suggest that intracellular enzymatic activity decrease is, at least partly, due to release of lysosomal enzymes into the medium. A positive but slight correlation was found between extracellular lysosomal activity and four parameters of lung lesion (lung index, bronchoalveolar fluid total (BALF) protein concentration, BALF LDH and BALF alkaline phosphatase activities). All the above findings suggest that the AM release of lysosomal enzymes during HP is a factor involved, although possibly not the only one, in the pulmonary lesions appearing in this disease
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