339 research outputs found
Sap Flow Responses to Warming and Fruit Load in Young Olive Trees
Global warming will likely lead to temperature increases in many regions of South America where temperatures are already considered to be high for olive production. Thus, experimental studies are needed to assess how water use in olive trees may be affected by global warming. The objectives of this study were to (i) evaluate the response of olive tree sap flow, stomatal conductance, and xylem anatomy to elevated temperature and (ii) determine whether fruit load may affect the temperature responses. A warming experiment using well-irrigated olive trees (cv. Arbequina) in open-top chambers (OTCs) with two temperature levels was performed from fruit set to the end of fruit growth in two seasons. Temperature levels were a near ambient control (T0) and a treatment 4°C above the control (T+). Trees were in the chambers for either one (2015–2016) or two seasons (2014–2015, 2015–2016) and were evaluated only in the second season when all trees were 3 years old. Whole-tree sap flow on leaf area basis, stomatal conductance, and aspects of xylem anatomy were measured. Sap flow was slightly higher in T+ than T0 trees heated for one season early in fruit development (summer) likely due to the elevated temperature and increase in vapor pressure deficit. Later in fruit development (fall), sap flow was substantially higher in the T+ trees heated for one season. Total vessel number per shoot was greater in the T+ than the T0 trees at this time due to more small-diameter vessels in the T+ trees, but this did not appear to explain the greater sap flow. The T+ trees that were heated for two seasons had less fruit load than the T0 trees due to little flowering. In contrast to trees heated for one season, sap flow was less in T+ than controls late in fruit development the second season, which was likely related to lower fruit load. An independent experiment using untreated trees confirmed that sap flow decreases when fruit load is below a threshold value. The results emphasize that multiple, interacting factors should be considered when predicting warming effects on water use in olive orchards.Fil: Miserere, Andrea. Universidad Nacional de La Rioja; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Searles, Peter Stoughton. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Manchó, Guadalupe. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Maseda, Pablo H.. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Rousseaux, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentin
Discovery of a Quadruple Lens in CANDELS with a Record Lens Redshift z=1.53
Using spectroscopy from the Large Binocular Telescope and imaging from the
Hubble Space Telescope we discovered the first strong galaxy lens at z(lens)>1.
The lens has a secure photometric redshift of z=1.53+/-0.09 and the source is
spectroscopically confirmed at z=3.417. The Einstein radius (0.35"; 3.0 kpc)
encloses 7.6 x 10^10 Msol, with an upper limit on the dark matter fraction of
60%. The highly magnified (40x) source galaxy has a very small stellar mass
(~10^8 Msol) and shows an extremely strong [OIII]_5007A emission line (EW_0 ~
1000A) bolstering the evidence that intense starbursts among very low-mass
galaxies are common at high redshift.Comment: accepted for publication in ApJ Letter
The MUSE-Wide Survey: Survey Description and First Data Release
We present the MUSE-Wide survey, a blind, 3D spectroscopic survey in the
CANDELS/GOODS-S and CANDELS/COSMOS regions. Each MUSE-Wide pointing has a depth
of 1 hour and hence targets more extreme and more luminous objects over 10
times the area of the MUSE-Deep fields (Bacon et al. 2017). The legacy value of
MUSE-Wide lies in providing "spectroscopy of everything" without photometric
pre-selection. We describe the data reduction, post-processing and PSF
characterization of the first 44 CANDELS/GOODS-S MUSE-Wide pointings released
with this publication. Using a 3D matched filtering approach we detected 1,602
emission line sources, including 479 Lyman- (Lya) emitting galaxies
with redshifts . We cross-match the emission line
sources to existing photometric catalogs, finding almost complete agreement in
redshifts and stellar masses for our low redshift (z < 1.5) emitters. At high
redshift, we only find ~55% matches to photometric catalogs. We encounter a
higher outlier rate and a systematic offset of z0.2 when
comparing our MUSE redshifts with photometric redshifts. Cross-matching the
emission line sources with X-ray catalogs from the Chandra Deep Field South, we
find 127 matches, including 10 objects with no prior spectroscopic
identification. Stacking X-ray images centered on our Lya emitters yielded no
signal; the Lya population is not dominated by even low luminosity AGN. A total
of 9,205 photometrically selected objects from the CANDELS survey lie in the
MUSE-Wide footprint, which we provide optimally extracted 1D spectra of. We are
able to determine the spectroscopic redshift of 98% of 772 photometrically
selected galaxies brighter than 24th F775W magnitude. All the data in the first
data release - datacubes, catalogs, extracted spectra, maps - are available on
the website https://musewide.aip.de. [abridged]Comment: 25 pages 15+1 figures. Accepted, A&A. Comments welcom
Risk assessment for the spread of Serratia marcescens within dental-unit waterline systems using Vermamoeba vermiformis
Vermamoeba vermiformis is associated with the biofilm ecology of dental-unit waterlines (DUWLs). This study investigated whether V. vermiformis is able to act as a vector for potentially pathogenic bacteria and so aid their dispersal within DUWL systems. Clinical dental water was initially examined for Legionella species by inoculating it onto Legionella selective-medium plates. The molecular identity/profile of the glassy colonies obtained indicated none of these isolates were Legionella species. During this work bacterial colonies were identified as a non-pigmented Serratia marcescens. As the water was from a clinical DUWL which had been treated with Alpron™ this prompted the question as to whether S. marcescens had developed resistance to the biocide. Exposure to Alpron™ indicated that this dental biocide was effective, under laboratory conditions, against S. marcescens at up to 1x108 colony forming units/millilitre (cfu/ml). V. vermiformis was cultured for eight weeks on cells of S. marcescens and Escherichia coli. Subsequent electron microscopy showed that V. vermiformis grew equally well on S. marcescens and E. coli (p = 0.0001). Failure to detect the presence of S. marcescens within the encysted amoebae suggests that V. vermiformis is unlikely to act as a vector supporting the growth of this newly isolated, nosocomial bacterium
3D-HST+CANDELS : the evolution of the galaxy size-mass distribution since z=3
Spectroscopic+photometric redshifts, stellar mass estimates, and rest-frame colors from the 3D-HST survey are combined with structural parameter measurements from CANDELS imaging to determine the galaxy size-mass distribution over the redshift range 0 < z < 3. Separating early- and late-type galaxies on the basis of star-formation activity, we confirm that early-type galaxies are on average smaller than late-type galaxies at all redshifts, and we find a significantly different rate of average size evolution at fixed galaxy mass, with fast evolution for the early-type population, R eff∝(1 + z)–1.48, and moderate evolution for the late-type population, R eff∝(1 + z)-0.75Peer reviewedFinal Accepted Versio
No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z~2 in CANDELS / 3D-HST
We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to
investigate if active galactic nuclei (AGNs) are preferentially fueled by
violent disk instabilities funneling gas into galaxy centers at 1.3<z<2.4. We
select galaxies undergoing gravitational instabilities using the number of
clumps and degree of patchiness as proxies. The CANDELS visual classification
system is used to identify 44 clumpy disk galaxies, along with mass-matched
comparison samples of smooth and intermediate morphology galaxies. We note
that, despite being being mass-matched and having similar star formation rates,
the smoother galaxies tend to be smaller disks with more prominent bulges
compared to the clumpy galaxies. The lack of smooth extended disks is probably
a general feature of the z~2 galaxy population, and means we cannot directly
compare with the clumpy and smooth extended disks observed at lower redshift.
We find that z~2 clumpy galaxies have slightly enhanced AGN fractions selected
by integrated line ratios (in the mass-excitation method), but the spatially
resolved line ratios indicate this is likely due to extended phenomena rather
than nuclear AGNs. Meanwhile the X-ray data show that clumpy, smooth, and
intermediate galaxies have nearly indistinguishable AGN fractions derived from
both individual detections and stacked non-detections. The data demonstrate
that AGN fueling modes at z~1.85 - whether violent disk instabilities or
secular processes - are as efficient in smooth galaxies as they are in clumpy
galaxies.Comment: ApJ accepted. 17 pages, 17 figure
Equivalent widths of Lyman emitters in MUSE-Wide and MUSE-Deep
The aim of this study is to better understand the connection between the
Lyman rest-frame equivalent width (EW) and spectral properties as
well as ultraviolet (UV) continuum morphology by obtaining reliable EW
histograms for a statistical sample of galaxies and by assessing the fraction
of objects with large equivalent widths. We used integral field spectroscopy
from MUSE combined with broad-band data from the Hubble Space Telescope (HST)
to measure EW. We analysed the emission lines of Lyman
emitters (LAEs) detected in the full MUSE-Wide (one hour exposure time) and
MUSE-Deep (ten hour exposure time) surveys and found UV continuum counterparts
in archival HST data. We fitted the UV continuum photometric images using the
Galfit software to gain morphological information on the rest-UV emission and
fitted the spectra obtained from MUSE to determine the double peak fraction,
asymmetry, full-width at half maximum, and flux of the Lyman line. The
two surveys show different histograms of Lyman EW. In MUSE-Wide,
of objects have EW \r{A}, while this fraction is only
in MUSE-Deep and for the full sample. This includes objects
without HST continuum counterparts (one-third of our sample), for which we give
lower limits for EW. The object with the highest securely measured EW
has EW \r{A} (the highest lower limit being EW \r{A}).
We investigate the connection between EW and Lyman spectral or UV
continuum morphological properties. The survey depth has to be taken into
account when studying EW distributions. We find that in general, high
EW objects can have a wide range of spectral and UV morphological
properties, which might reflect that the underlying causes for high EW
values are equally varied. (abridged)Comment: 28 pages, 21 + 1 figures, 7 + 1 tables, accepted for publication in
A&
The Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS)
Aims. We present the Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS) selected from MUSE and HST observations of 17 lensing clusters. The sample consists of 603 continuum-faint (−23 < MUV < −14) lensed Lyman-α emitters (producing 959 images) with secure spectroscopic redshifts between 2.9 and 6.7. Combining the power of cluster magnification with 3D spectroscopic observations, we were able to reveal the resolved morphological properties of 268 Lyman-α emitters. Methods. We used a forward-modeling approach to model both Lyman-α and rest-frame UV continuum emission profiles in the source plane and measure spatial extent, ellipticity, and spatial offsets between UV and Lyman-α emission. Results. We find a significant correlation between UV continuum and Lyman-α spatial extent. Our characterization of the Lyman-α halos indicates that the halo size is linked to the physical properties of the host galaxy (SFR, Lyman-α equivalent width, Lyman-α line FWHM). We find that 48% of Lyman-α halos are best fit by an elliptical emission distribution with a median axis ratio of q = 0.48. We observe that 60% of galaxies detected both in UV and Lyman-α emission show a significant spatial offset (ΔLyα − UV). We measure a median offset of ΔLyα − UV = 0.58 ± 0.14 kpc for the entire sample. By comparing the spatial offset values with the size of the UV component, we show that 40% of the offsets could be due to star-forming sub-structures in the UV component, while the larger offsets (60%) are more likely due to greater-distance processes such as scattering effects inside the circumgalactic medium or emission from faint satellites or merging galaxies. Comparisons with a zoom-in radiative hydrodynamics simulation of a typical Lyman-α emitting galaxy show a very good agreement with LLAMAS galaxies and indicate that bright star-formation clumps and satellite galaxies could produce a similar spatial offset distribution
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The Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS): I. Characterisation of extended Lyman-alpha halos and spatial offsets
Aims. We present the Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS) selected from MUSE and HST observations of 17 lensing clusters. The sample consists of 603 continuum-faint (23 < MUV<-14) lensed Lyman-α emitters (producing 959 images) with secure spectroscopic redshifts between 2.9 and 6.7. Combining the power of cluster magnification with 3D spectroscopic observations, we were able to reveal the resolved morphological properties of 268 Lyman-α emitters. Methods. We used a forward-modeling approach to model both Lyman-α and rest-frame UV continuum emission profiles in the source plane and measure spatial extent, ellipticity, and spatial offsets between UV and Lyman-α emission. Results. We find a significant correlation between UV continuum and Lyman-α spatial extent. Our characterization of the Lyman-α halos indicates that the halo size is linked to the physical properties of the host galaxy (SFR, Lyman-α equivalent width, Lyman-α line FWHM). We find that 48% of Lyman-α halos are best fit by an elliptical emission distribution with a median axis ratio of q =0.48. We observe that 60% of galaxies detected both in UV and Lyman-α emission show a significant spatial offset (ΔLyα-UV). We measure a median offset of ΔLyα-UV=0.58± 0.14 kpc for the entire sample. By comparing the spatial offset values with the size of the UV component, we show that 40% of the offsets could be due to star-forming sub-structures in the UV component, while the larger offsets (60%) are more likely due to greater-distance processes such as scattering effects inside the circumgalactic medium or emission from faint satellites or merging galaxies. Comparisons with a zoom-in radiative hydrodynamics simulation of a typical Lyman-α emitting galaxy show a very good agreement with LLAMAS galaxies and indicate that bright star-formation clumps and satellite galaxies could produce a similar spatial offset distribution
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