Using photometric and redshift data for the Virgo and Coma clusters, we
present evidence for a correlation between the light concentration of
elliptical galaxies (including dwarf ellipticals) and the ...local 3-D (i.e.
non-projected) density of the clusters: more concentrated ellipticals are
located in denser regions. The null hypothesis (i.e. the absence of any
relation) is rejected at a significance level better than 99.9%. In order to
explain the observed relation, a power law relating the galaxy light
concentration and the cluster 3-D density is proposed. We study how the
projection effects affect the form and dispersion of the data-points in the
light concentration-projected density diagram. The agreement between our model
and the observed data suggests that there is a paucity of dwarf elliptical
galaxies in the cluster central regions.
Astrophys.J.656:66-72,2007 We present deep, high angular-resolution HST/NICMOS imaging in the Hubble
Deep Field South (HDF-S), focusing on a subset of 14 Distant Red Galaxies
(DRGs) at z ~ 2.5 ...galaxies that have been pre-selected to have J-K > 2.3. We
find a clear trend between the rest-frame optical sizes of these sources and
their luminosity-weighted stellar ages as inferred from their broad-band
spectral energy distributions (SEDs). Galaxies whose SEDs are consistent with
being dusty and actively star forming generally show extended morphologies in
the NICMOS images (r_e >~ 2 kpc), while the 5 sources which are not vigorously
forming stars are extremely compact (r_e <~ 1 kpc). This trend suggests a
direct link between the mean ages of the stars and the size and density of the
galaxies and supports the conjecture that early events quench star-formation
and leave compact remnants. Furthermore, the compact galaxies have stellar
surface mass densities which exceed those of local galaxies by more than an
order of magnitude. The existence of such massive dense galaxies presents a
problem for models of early-type galaxy formation and evolution. Larger samples
of DRGs and higher spatial resolution imaging will allow us to determine the
universality of the results presented here for a small sample.
We report the discovery of a strong correlation between the shape of a bulge's light-profile and the mass of its central supermassive black hole (M_{bh}). We find that log(M_{bh}/M_{sun}) = ...2.91(+/-0.38)log(n) + 6.37(+/-0.21), where `n' is the Sersic r^{1/n} shape index of the bulge. This correlation is marginally stronger than the relationship between the logarithm of the stellar velocity dispersion and log(M_{bh}) and has comparable scatter. It therefore offers a cheap (in terms of telescope time) alternative to estimating the masses of supermassive black holes.
Las bacterias promotoras del crecimiento vegetal (PGPB) influyen de forma directa o indirecta en el desarrollo de los cultivos. Este trabajo tiene como objetivos determinar la actividad antagónica y ...el efecto inhibitorio de los metabolitos activos producidos por rizobacterias ante fitopatógenos que afectan a los cultivos del maíz y el arroz. Para ello se desarrollaron bioensayos in vitro en el medio King B. Se utilizaron cepas de referencia y autóctonas de Pseudomonas fluorescens y Burkholderia cepacia, previamente aisladas de la rizosfera del maíz variedad Francisco mejorado, para determinar sus potencialidades como antagonistas de los patógenos fúngicos Fusarium oxysporum, Alternaria alternata, Curvularia sp. y Fusarium sp. Los resultados mostraron que la rizobacterias estudiadas tienen actividad antagónica y sus metabolitos efecto inhibitorio ante los hongos fitopatógenos enfrentados, destacándose con el mejor comportamiento las cepas de P. fluorescens MPf2, MPf3, J-143 y B. cepacia MPp8. Se observó un mayor efecto de las rizobacterias frente Curvularia sp. y A. alternata. Estos resultados poseen valor práctico, pues se selecciona un conjunto de cepas potencialmente eficientes en el control biológico de patógenos que podrían ser utilizadas en la agricultura en beneficio de los cultivos del arroz y el maíz.
Plant Growth Promoting Bacteria (PGPB) has been proved to exert a beneficial effect on crop yield, directly or indirectly. This work was aimed to determine the antagonistic activity and inhibitory effect exerted on different plant pathogens by rhizobacteria. A number of bioassays was carried in vitro in King B medium. Previously isolated bacterial strains of Pseudomonas fluorescens and Burkholderia cepacia, from corn plants var. Francisco mejorado, were assayed to determine their potential as antagonists of the phytopathogenic fungi Fusarium oxysporum, Alternaria alternata, Curvularia sp. and Fusarium sp. The results showed the capability of inhibiting the pathogen growth by the rhizobacterial strains, proving the best behaviour the strains P. fluorescens MPf2, MPf3, J-143 and B. cepacia MPp8. It was shown that there was a greater inhibitory effect on the fungi strains Curvularia sp. A1 and A. alternata M2. Considering these results, the bacterial strains were competent for pathogen biocontrol, and could be used in agriculture as valuable growth promoting agents in maize and rice crops.
The effects of seeing on Sersic r^{1/n} profile parameters are extensively studied using a Moffat function. This analytical approximation to the point spread function (PSF) is shown to provide the ...best fit to the PSF predicted from atmospheric turbulence theory when beta=4.765. The Moffat PSF is additionally shown to contain the Gaussian PSF as a limiting case beta->infinity. The Moffat function is also shown to be numerically well behaved when modelling narrow PSFs in HST images. Seeing effects are computed for elliptically symmetric surface brightness distributions. The widely used assumption of circular symmetry when studying the effects of seeing on intrinsically elliptical sources is shown to produce significant discrepancies with respect to the true effects of seeing on these sources. A prescription to correct raw (observed) central intensities, effective radii, index n and mean effective surface brightness is given.
We present broad-band photometry and provide a quantitative analysis of the
structure of galaxies in the inner region of the Abell Cluster 2443 (z~0.1).
The galaxy parameters have been derived by ...fitting a two-component model
(Sersic r^{1/n} bulge and exponential disk) to a magnitude-limited sample.
Using a new method of analysis which takes into account the effects of seeing
on the structural parameters and considers the ellipticity as an active
parameter, we avoid systematic errors arising from assumptions of circular
symmetry. 76% of the sample galaxies were classified with these models, the
rest were morphologically peculiar. For the spiral galaxies, the relation
between n and B/D is consistent with the trend observed in nearby field galaxy
samples. The Sersic index n (which can be considered as a concentration index)
of the elliptical galaxies is correlated with the local surface density of the
cluster. Monte Carlo simulations were used to check the reliability of the
method and determine the magnitude selection criteria.
Mon.Not.Roy.Astron.Soc. 321 (2001) 269 The effects of seeing on the parameters of the S\`ersic profile are studied
in an analytical form using a Gaussian point spread function. The surface
brightness ...of S\`ersic profiles is proportional (in magnitudes) to $r^{1/n}$.
The parameter $n$ serves to classify the type of profile and is related to the
central luminosity concentration. It is the parameter most affected by seeing;
furthermore, the value of $n$ that can be measured is always smaller than the
real one. It is shown that the luminosity density of the S\`ersic profile with
$n$ less than 0.5 has a central depression, which is physically unlikely. Also,
the intrinsic ellipticity of the sources has been taken into account and we
show that the parameters are dependent when the effects of seeing are
non-negligible. Finally, a prescription for correcting raw effective radii,
central intensities and $n$ parameters is given.
Through participatory research two methods for sampling the abundance of coffee berry borer (CBB) populations were compared in the field with the objective of contributing to the integrated ...management of this insect. This experiment was carried out on 11 farms: four in Quimbaya, two in Belalcazar, one in Viterbo, three in Balboa and one in Risaralda. One commercial coffee plot was selected from each farm and CBB infestation was evaluated using two methods: 30-Branch Method (the number of green fruits per branch and the number of fruits infested by CBB are quantified, followed by determination of percent infestation). Measure Method (initially, the distance that contains 50 green fruits is assessed through direct measurement in 100 branches; this distance is then used to make the monthly samplings counting the fruits infested in only 30 branches; finally the percent infestation is determined). The 30-branch sampling plan obtained similar results to the measure method, but the latter requires less time. The different levels of CBB infestation were similar between the two sampling methods. The coffee growers show interest in continuing to evaluate this new sampling method (measure method). They indicated that with this new sampling method they can save more time.
Astrophys.J.624:L81-L84,2005 We present deep 3.6 - 8 micron imaging of the Hubble Deep Field South with
IRAC on the Spitzer Space Telescope. We study Distant Red Galaxies (DRGs) at
z>2 selected by Js ...- Ks > 2.3 and compare them to a sample of Lyman Break
Galaxies (LBGs) at z=2-3. The observed UV-to-8 micron spectral energy
distributions are fit with stellar population models to constrain star
formation histories and derive stellar masses. We find that 70% of the DRGs are
best described by dust-reddened star forming models and 30% are very well fit
with old and ``dead'' models. Using only the I - Ks and Ks - 4.5 micron colors
we can effectively separate the two groups. The dead systems are among the most
massive at z~2.5 (mean stellar mass <M*> = 0.8 x 10^11 Msun) and likely formed
most of their stellar mass at z>5. To a limit of 0.5 x 10^11 Msun their number
density is ~10 x lower than that of local early-type galaxies. Furthermore, we
use the IRAC photometry to derive rest-frame near-infrared J, H, and K fluxes.
The DRGs and LBGs together show a large variation (a factor of 6) in the
rest-frame K-band mass-to-light ratios (M/L_K), implying that even a Spitzer 8
micron-selected sample would be very different from a mass-selected sample. The
average M/L_K of the DRGs is about three times higher than that of the LBGs,
and DRGs dominate the high-mass end. The M/L_K ratios and ages of the two
samples appear to correlate with derived stellar mass, with the most massive
galaxies being the oldest and having the highest mass-to-light ratios, similar
as found in the low-redshift universe.
We summarize the main properties of the extended UV (XUV) emission found in roughly 30% of the nearby spiral galaxies observed by the GALEX satellite. Two different classes of XUV disks are ...identified, the Type 1 XUV disks where significant, structured UV-bright features are found beyond the "classical" azimuthally-averaged star-formation threshold, and the Type 2 XUV disks, which are characterized by very extended (seven times the area where most of the stellar mass is found), blue (FUV-K)<5mag outer disks. These latter disks are extreme examples of galaxies growing inside-out. The few XUV disks studied in detail to date are rich in HI but relatively poor in molecular gas, have stellar populations with luminosity-weighted ages of ~1 Gyr, and ionized-gas metal abundances of ~Zsun/10. As part of the CAHA-XUV project we are in the process of obtaining deep multi-wavelength imaging and spectroscopy of 65 XUV-disk galaxies so to determine whether or not these properties are common among XUV disks.
