4,928 research outputs found
The Different Environmental Dependencies of Star-formation for Giant and Dwarf Galaxies
We examine the origins of the bimodality observed in the global properties of
galaxies around a stellar mass of 3x10^10 M_sun by comparing the environmental
dependencies of star-formation for the giant and dwarf galaxy populations. The
Sloan Digital Sky Survey DR4 spectroscopic dataset is used to produce a sample
of galaxies in the vicinity of the supercluster centered on the cluster A2199
at z=0.03 that is ~90% complete to a magnitude limit of M*+3.3. From these we
measure global trends with environment for both giant (M_r<-20 mag) and dwarf
(-19<M_r<-17.8 mag) subsamples using the luminosity-weighted mean stellar age
and H_alpha emission as independent measures of star-formation history. The
fraction of giant galaxies classed as old (t>7 Gyr) or passive (EW[H_alpha]<4
A) falls gradually from ~80% in the cluster cores to ~40% in field regions
beyond 3-4 R_virial, as found in previous studies. In contrast, we find that
the dwarf galaxy population shows a sharp transition at ~1 R_virial, from being
predominantly old/passive within the cluster, to outside where virtually all
galaxies are forming stars and old/passive galaxies are only found as
satellites to more massive galaxies. These results imply fundamental
differences in the evolution of giant and dwarf galaxies: whereas the
star-formation histories of giant galaxies are determined primarily by their
merger history, star-formation in dwarf galaxies is much more resilient to the
effects of major mergers. Instead dwarf galaxies become passive only once they
become satellites within a more massive halo, by losing their halo gas
reservoir to the host halo, or through other environment-related processes such
as galaxy harassment and/or ram-pressure stripping.Comment: 4 pages, 4 figures, accepted for publication in ApJ
Effects of mycorrhizal inoculation and digestate fertilisation on triticale biomass production using fungicide-coated seeds
peer-reviewedCrop fertilisation management using organic wastes and arbuscular mycorrhizal fungi (AMF) inoculation can play a crucial role in the sustainability of agroecosystems. However, in conventional agricultural systems, agrochemicals like fungicides could reduce the positive effect of AMF. The aim of this study was to evaluate the agronomic (biomass production) and environmental (soil CO2 emission) effects of AMF inoculation and digestate spreading on triticale cultivation using commercial seeds coated with fungicide. The field experiment was conducted in 2014–2015 at the University of Padua’s experimental farm (Italy), adopting a split-plot design, where the main plot factor was AMF inoculation (inoculated vs. uninoculated) and the subplot factor was fertilisation treatment (no fertilisation (NF), digestate liquid fraction (DL), digestate solid fraction (DS), mineral fertilisation (MF)). Low AMF root colonization was observed, likely due to the effect of fungicide; the only significant effect of AMF inoculation was a lower shoot density. Dry biomass production was significantly higher in the MF treatment (21.8 ± 1.04 Mg/ha) and lower in the NF treatment (14.5 ± 0.73 Mg/ha) compared to DS and DL treatments, which were not significantly different with an average yield of 17.2 ± 2.10 Mg/ha. During the cropping season, soil CO2 emissions were not significantly affected by either AMF inoculation or fertilisation treatment. The median value of soil CO2 emissions was 447.3 mg/m2 per hour
IMF and [Na/Fe] abundance ratios from optical and NIR Spectral Features in Early-type Galaxies
We present a joint analysis of the four most prominent sodium-sensitive
features (NaD, NaI8190, NaI1.14, and NaI2.21), in the optical and Near-Infrared
spectral range, of two nearby, massive (sigma~300km/s), early-type galaxies
(named XSG1 and XSG2). Our analysis relies on deep VLT/X-Shooter long-slit
spectra, along with newly developed stellar population models, allowing for
[Na/Fe] variations, up to 1.2dex, over a wide range of age, total metallicity,
and IMF slope. The new models show that the response of the Na-dependent
spectral indices to [Na/Fe] is stronger when the IMF is bottom heavier. For the
first time, we are able to match all four Na features in the central regions of
massive early-type galaxies, finding an overabundance of [Na/Fe], in the range
0.5-0.7dex, and a bottom-heavy IMF. Therefore, individual abundance variations
cannot be fully responsible for the trends of gravity-sensitive indices,
strengthening the case towards a non-universal IMF. Given current limitations
of theoretical atmosphere models, our [Na/Fe] estimates should be taken as
upper limits. For XSG1, where line strengths are measured out to 0.8Re, the
radial trend of [Na/Fe] is similar to [Mg/Fe] and [C/Fe], being constant out to
0.5Re, and decreasing by 0.2-0.3dex at 0.8Re, without any clear correlation
with local metallicity. Such a result seems to be in contrast with the
predicted increase of Na nucleosynthetic yields from AGB stars and TypeII SNe.
For XSG1, the Na-inferred IMF radial profile is consistent, within the errors,
with that derived from TiO features and the Wing-Ford band, presented in a
recent paper.Comment: 22 pages, 8 figure, accepted for publication in MNRAS. The new
Na-enhanced models will be available soon at http://miles.iac.es
Global Properties of the Rich Cluster ABCG 209 at z~0.2. Spectroscopic and Photometric Catalogue
This paper is aimed at giving an overview of the global properties of the
rich cluster of galaxies ABCG 209. This is achieved by complementing the
already available data with new medium resolution spectroscopy and NIR
photometry which allow us to i) analyse in detail the cluster dynamics,
distinguishing among galaxies belonging to different substructures and deriving
their individual velocity distributions, using a total sample of 148 galaxies
in the cluster region, of which 134 belonging to the cluster; ii) derive the
cluster NIR luminosity function; iii) study the Kormendy relation and the
photometric plane of cluster early-type galaxies (ETGs). Finally we provide an
extensive photometric (optical and NIR) and spectroscopic dataset for such a
complex system to be used in further analyses investigating the nature,
formation and evolution of rich clusters of galaxies. The observational
scenario confirms that ABCG 209 is presently undergoing strong dynamical
evolution with the merging of two or more subclumps. This interpretation is
also supported by the detection of a radio halo (Giovannini et al. 2006)
suggesting that there is a recent or ongoing merging. Cluster ETGs follow a
Kormendy relation whose slope is consistent with previous studies both at
optical and NIR wavelengths. We investigate the origin of the intrinsic scatter
of the photometric plane due to trends of stellar populations, using line
indices as indicators of age, metallicity and alpha/Fe enhancement. We find
that the chemical evolution of galaxies could be responsible for the intrinsic
dispersion of the Photometric Plane.Comment: 39 pages, 17 figures, MNRAS in pres
The puzzling interpretation of NIR indices: The case of NaI2.21
We present a detailed study of the Na I line strength index centered in the
-band at , {\AA} (NaI2.21 hereafter) relying on different samples of
early-type galaxies. Consistent with previous studies, we find that the
observed line strength indices cannot be fit by state-of-art scaled-solar
stellar population models, even using our newly developed models in the NIR.
The models clearly underestimate the large NaI2.21 values measured for most
early-type galaxies. However, we develop a Na-enhanced version of our newly
developed models in the NIR, which - together with the effect of a bottom-heavy
initial mass function - yield NaI2.21 indices in the range of the observations.
Therefore, we suggest a scenario in which the combined effect of [Na/Fe]
enhancement and a bottom-heavy initial mass function are mainly responsible for
the large NaI2.21 indices observed for most early-type galaxies. To a smaller
extent, also [C/Fe] enhancement might contribute to the large observed NaI2.21
values.Comment: 13 pages, 4 figures, accepted for publication in MNRA
New insights into the structure of early-type galaxies: the Photometric Plane at z~0.3
We study the Photometric Plane (PHP), namely the relation between the
effective radius re, the mean surface brightness within that radius e, and
the Sersic index n, in optical (R and I) and near-infrared (K) bands for a
large sample of early-type galaxies (ETGs) in the rich cluster MS1008-1224 at
z=0.306. The PHP relation has an intrinsic dispersion of ~32% in re, and turns
out to be independent of waveband. This result is consistent with the fact that
internal colour gradients of ETGs can have only a mild dependence on galaxy
luminosity (mass). There is no evidence for a significant curvature in the PHP.
We show that this can be explained if this relation origins from a systematic
variation of the specific entropy of ETGs along the galaxy sequence, as was
suggested from previous works. The intrinsic scatter of the PHP is
significantly smaller than for other purely photometric relations, such as the
Kormendy relation and the photometric Fundamental Plane, which is constructed
by using colours in place of velocity dispersions. The scatter does not depend
on the waveband and the residuals about the plane do not correlate with
residuals of the colour-magnitude relation. Finally, we compare the
coefficients of the PHP at z~0.3 with those of ETGs at z~0, showing that the
PHP is a valuable tool to constrain the luminosity evolution of ETGs with
redshift. The slopes of the PHP do not change significantly with redshift,
while the zero-point is consistent with cosmological dimming of the surface
brightness in an expanding universe plus the passive fading of galaxy stellar
populations with a high formation redshift (z_f >1-2).Comment: 21 pages, 10 figures, MNRAS in pres
Modeling storm water control operated by green roofs at the urban catchment scale
The urban catchment of Colle Ometti, in the town of Genoa, Italy, where storm water runoff is monitored for both quantity and quality, was selected as a test site for the hydrologic modelling of greening scenarios. Although no green roof installations are now present in the area, this study modelled \u2013 using extensive green roof details \u2013 the hydrologic effects of three hypothetical roof greenin scenarios at the catchment scale (conversion of 10%, 20%, and 100% impervious to green roofs). The modelling of green roof performances was undertaken using the EPA SWMM and was calibrated and validated on a small size green roof system completed in September 2007 in the laboratory of the Department of Civil, Environmental and Architectural Engineering (DICAT \u2013 University of Genoa). Precipitation scenarios were developed based on eighteen years of high resolution (one minute) rain gauge data in Genoa (1990-2007).Hydrologic modelling demonstrated that widespread green roof implementation can significantly reduce peak runoff rates and the lag time (7min and 15 min) runoff volume (detention effect) while after introducing the drying process operated by evapo-traspiration during the inter-event period the runoff volume reduction at the event scale (retention effect) can also be appreciated
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