35 research outputs found
Optical counterparts of undetermined type -ray Active Galactic Nuclei with blazar-like Spectral Energy Distributions
During its first four years of scientific observations, the Fermi Large Area
Telescope (Fermi-LAT) detected 3033 -ray sources above a 4
significance level. Although most of the extra-Galactic sources are active
galactic nuclei (AGN) of the blazar class, other families of AGNs are observed
too, while a still high fraction of detections () remains with
uncertain association or classification. According to the currently accepted
interpretation, the AGN -ray emission arises from inverse Compton (IC)
scattering of low energy photons by relativistic particles confined in a jet
that, in the case of blazars, is oriented very close to our line of sight.
Taking advantage of data from radio and X-ray wavelengths, which we expect to
be produced together with -rays, providing a much better source
localization potential, we focused our attention on a sample of -ray
Blazar Candidates of Undetermined Type (BCUs), starting a campaign of optical
spectroscopic observations. The main aims of our investigation include a census
of the AGN families that contribute to -ray emission and a study of
their redshift distribution, with the subsequent implications on the intrinsic
source power. We furthermore analyze which -ray properties can better
constrain the nature of the source, thus helping in the study of objects not
yet associated with a reliable low frequency counterpart. In this communication
we report on the instruments and techniques used to identify the optical
counterparts of -ray sources, we give an overview on the status of our
work, and we discuss the implications of a large scale study of -ray
emitting AGNs.Comment: 9 pages, 2 figures, proceedings of the 10th Serbian Conference on
Spectral Line Shapes in Astrophysics. JOAA, accepte
Caracterização físico-química da própolis georreferenciada de 14 localidades do Uruguai
Honey bee propolis is studied around the world. Its plant origin, associated with different soils and climates, determines different physicochemical properties. These different properties determine diverse medicinal potentials. Uruguay has few scientific papers that characterize the propolis it produces. This study analyzes propolis from 14 locations of Uruguay, obtained over a year. The vegetation environment of these localities was characterized in a radius of 2 km by satellite images. Color (CIELAB) was measured in ethanolic solution, as well as pH and conductivity in aqueous solution, ashes, total polyphenols (Folin-Ciocalteau) and total flavonoids. The similarities of the localities in terms of their vegetation do not correspond to the similarities between propolis; another method of plant characterization must be used. Differences were found between locations, but not between stations within the same location. The parameters L* and a* are correlated with the polyphenolic content of propolis (R²=0.61 and R²=0.81, respectively). Conductivity is correlated (R²=0.66) with ash content, but it would be necessary to determine what minerals are present to use this tool. The polyphenolic and flavonoid content allows regionalizing the country in southwest and northeast. Southwest with high contents (177 to 262 gGAE/kg and 66 to 131 gQE/kg) and northeast zones with lower contents (27 to 88 gGAE/kg and 10 to 27 gQE/kg). It is necessary to continue studying propolis from Uruguay, its mineral and polyphenol content and its profile in other locations for a longer time.Los propóleos de abejas melíferas se estudian en todo el mundo. Su origen vegetal, asociado a diferentes suelos y climas, determina diferentes propiedades fisicoquímicas. Estas distintas propiedades determinan diferentes potenciales medicinales. Uruguay cuenta con pocos trabajos científicos que caractericen los propóleos que produce. Este trabajo analiza propóleos de 14 localidades de Uruguay, obtenidos a lo largo de un año. El entorno de vegetación de estas localidades se caracterizó en un radio de 2 km por imágenes satelitales. Se midió color (CIELAB) en solución etanólica, y pH y conductividad en solución acuosa, cenizas, polifenoles totales (Folin-Ciocalteau) y flavonoides totales. Las similitudes de las localidades en cuanto a su vegetación no se corresponden con las similitudes entre propóleos, otro método de caracterización vegetal deberá ser empleado. Se encontraron diferencias entre localidades, no entre estaciones dentro de la misma localidad. Los parámetros L* y a* se correlacionan con el contenido polifenólico de propóleos (R²=0,61 y R²=0,81, respectivamente). La conductividad se correlaciona (R²=0,66) con el contenido de cenizas, pero se debería determinar qué minerales se encuentran presentes para poder utilizar esta herramienta. El contenido polifenólico y de flavonoides permite regionalizar el país en las zonas sur, suroeste y oeste, de contenidos altos (177 a 262 g EAG/kg y 66 a 131 g EQ/kg), y las zonas norte y este de contenido menor (27 a 88 g EAG/kg y 10 a 27 gEQ/kg). Se debe continuar estudiando propóleos de Uruguay, en su contenido mineral, contenido de polifenoles y perfil de estos en otras localidades durante más tiempo.A própolis de abelha é estudada em todo o mundo. Sua origem vegetal, associada a diferentes solos e climas, determina diferentes propriedades físico-químicas. Essas diferentes propriedades determinam diferentes potenciais medicinais. O Uruguai tem poucos trabalhos científicos que caracterizam a própolis que produz. Este trabalho analisa a própolis de 14 localidades do Uruguai, obtida ao longo de um ano. O ambiente vegetacional dessas localidades foi caracterizado em um raio de 2 km por imagens de satélite. Cor (CIELAB) em solução etanólica e pH e condutividade em solução aquosa, cinzas, polifenóis totais (Folin-Ciocalteau) e flavonoides totais foram medidos. As semelhanças das localidades quanto à sua vegetação não correspondem às semelhanças entre as própolis, devendo ser utilizado outro método de caracterização vegetal. As diferenças foram encontradas entre locais, não entre estações dentro do mesmo local. Os parâmetros L* e a* estão correlacionados com o teor de polifenóis da própolis (R²=0,61 e R²=0,81 respectivamente). A condutividade se correlaciona (R²=0,66) com o teor de cinzas, más seria necessário determinar quais minerais estão presentes para usar esta ferramenta. O teor de polifenólicos e flavonóides permite regionalizar o país nas zonas sul, sudoeste e oeste, com teores elevados (177 a 262 gEAG/kg e 66 a 131 gEQ/kg) e nas zonas norte e leste com teores mais baixos (27 a 88 gEAG/kg), gEAG/kg e 10 a 27 gEQ/kg). É necessário continuar estudando a própolis do Uruguai, em seu conteúdo mineral, teor de polifenóis e seu perfil em outras localidades por mais tempo
Relativistic plasmas in AGN jets - From synchrotron radiation to -ray emission
Relativistic jets of plasma are a key ingredient of many types of Active
Galactic Nuclei (AGN). Today we know that AGNs are powered by the accretion of
inter stellar material into the gravitational field of a Super Massive Black
Hole and that this process can release as much power as a whole galaxy, like
the Milky Way, from a region that is comparable to the Solar System in size.
Depending on the properties of the central energy source, a large fraction of
this power can be involved in the acceleration of magnetized plasmas at
relativistic speeds, to form large scale jets. The presence of jets affects the
spectrum of AGNs through the emission of synchrotron radiation and Inverse
Compton scattering of low energy photons, thus leading to a prominent
non-thermal spectrum, some times extending from radio frequencies all the way
up to -ray energies. Here we review some characteristic processes of
radiation emission in AGN jets, which lead to the emission of photons in the
radio, optical, X-ray and -ray bands, and we present the results of a
spectroscopic campaign of optical counterparts. We discuss our observations and
their connection with -ray properties in a scenario that traces the
role of relativistic jets in different classes of AGNs, detected both in the
local as well as in the remote Universe.Comment: 11 pages, 5 figures (3 in color), proceedings of the XXVIII School on
Physics of Ionized Gases (SPIG), accepted for publication on the European
Journal of Physics
X-Ray Grating Observations of Recurrent Nova T Pyxidis During The 2011 Outburst
The recurrent nova T Pyx was observed with the X-ray gratings of Chandra and
XMM-Newton, 210 and 235 days, respectively, after the discovery of the 2011
April 14 outburst. The X-ray spectra show prominent emission lines of C, N, and
O, with broadening corresponding to a full width at half maximum of ~2000-3000
km/s, and line ratios consistent with high-density plasma in collisional
ionization equilibrium. On day 210 we also measured soft X-ray continuum
emission that appears to be consistent with a white dwarf (WD) atmosphere at a
temperature ~420,000 K, partially obscured by anisotropic, optically thick
ejecta. The X-ray continuum emission is modulated with the photometric and
spectroscopic period observed in quiescence. The continuum at day 235 indicated
a WD atmosphere at a consistent effective temperature of 25 days earlier, but
with a lower flux. The effective temperature indicates a mass of ~1 solar mass.
The conclusion of partial WD obscuration is supported by the complex geometry
of non-spherically-symmetric ejecta confirmed in recent optical spectra
obtained with the Southern African Large Telescope (SALT) in November and
December of 2012. These spectra exhibited prominent [O III] nebular lines with
velocity structures typical of bipolar ejecta.Comment: Accepted to ApJ 2013 October 23, 14 pages, 9 figures, 3 table
Models of emission line profiles and spectral energy distributions to characterize the multi-frequency properties of active galactic nuclei
The spectra of Active Galactic Nuclei (AGNs) are often characterized by a
wealth of emission lines with different profiles and intensity ratios that led
to a complicated classification. Their electro-magnetic radiation spans more
than 10 orders of magnitude in frequency. In spite of the differences between
various classes, the origin of their activity is attributed to a combination of
emitting components, surrounding an accreting Super Massive Black Hole, in the
so called Unified Model. Currently, the execution of sky surveys, with
instruments operating at various frequencies, provides the possibility to
detect and to investigate the properties of AGNs on very large statistical
samples. Thanks to the spectroscopic surveys that allow investigation of many
objects, we have the opportunity to place new constraints on the nature and
evolution of AGNs. In this contribution we present the results obtained by
working on multi-frequency data and we discuss their relations with the
available optical spectra. We compare our findings with the AGN Unified Model
predictions, and we present a revised technique to select AGNs of different
types from other line emitting objects. We discuss the multi-frequency
properties in terms of the innermost structures of the sources.Comment: 11 pages, 4 figures. Proceedings of the XI Serbian Conference on
Spectral Line Shapes in Astrophysics. Accepted for publication on Atom
An orientation-based unification of young jetted AGN: the case of 3C 286
In recent years, the old paradigm according to which only high-mass black
holes can launch powerful relativistic jets in active galactic nuclei (AGN) has
begun to crumble. The discovery of -rays coming from narrow-line
Seyfert 1 galaxies (NLS1s), usually considered young and growing AGN harboring
a central black hole with mass typically lower than 10 M, indicated
that also these low-mass AGN can produce powerful relativistic jets. The search
for parent population of -ray emitting NLS1s revealed their connection
with compact steep-spectrum sources (CSS). In this proceeding we present a
review of the current knowledge of these sources, we present the new important
case of 3C 286, classified here for the fist time as NLS1, and we finally
provide a tentative orientation based unification of NLS1s and CSS sources.Comment: 12 pages, 3 figures. Proceeding of the conference "Quasars at all
cosmic epochs", held in Padova, April 2-7, 2017, published on Frontiers in
Astronomy and Space Science
Extended narrow-line region in Seyfert galaxies
We present our recent results about the extended narrow-line region (ENLR) of
two nearby Seyfert 2 galaxies (IC 5063 and NGC 7212) obtained by modelling the
observed line profiles and spectra with composite models
(photoionization+shocks) in the different regions surrounding the AGN. Then, we
compare the Seyfert 2 ENLRs with the very extended one recently discovered in
the narrow-line Seyfert 1 (NLS1) galaxy Mrk 783. We have found several
evidences of interaction between the ISM of the galaxies and their radio jets,
such as a) the contribution of shocks in ionizing the high velocity gas, b) the
complex kinematics showed by the profile of the emission lines, c) the high
fragmentation of matter, etc. The results suggest that the ENLR of IC 5063 have
a hollow bi-conical shape, with one edge aligned to the galaxy disk, which may
cause some kind of dependence on velocity of the ionization parameter.
Regarding the Mrk 783 properties, it is found that the extension of the optical
emission is almost twice the size of the radio one and it seems due to the AGN
activity, although there is contamination by star formation around 12 arcsec
from the nucleus. Diagnostic diagrams excluded the contribution of star
formation in IC 5063 and NGC 7212, while the shock contribution was used to
explain the spectra emitted by their high velocity gas.Comment: 9 pages, 2 figures, proceeding of the conference "Quasars at all
cosmic epochs", accepted for publication in Front. Astron. Space Sci. - Milky
Way and Galaxie
Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies
Flat-spectrum radio-loud Narrow-Line Seyfert 1 galaxies (NLS1s) are a
recently discovered class of -ray emitting Active Galactic Nuclei
(AGN), that exhibit some blazar-like properties which are explained with the
presence of a relativistic jet viewed at small angles. When blazars are
observed at larger angles they appear as radio-galaxies, and we expect to
observe an analogue parent population for beamed NLS1s. However, the number of
known NLS1s with the jet viewed at large angles is not enough. Therefore, we
tried to understand the origin of this deficit. Current hypotheses about the
nature of parent sources are steep-spectrum radio-loud NLS1s, radio-quiet NLS1s
and disk-hosted radio-galaxies. To test these hypotheses we built three samples
of candidate sources plus a control sample, and calculated their black hole
mass and Eddington ratio using their optical spectra. We then performed a
Kolmogorov-Smirnov statistical test to investigate the compatibility of our
different samples with a beamed population. Our results indicate that, when the
inclination angle increases, a beamed source appears as a steep-spectrum
radio-loud NLS1, or possibly even as a disk-hosted radio-galaxy with low black
hole mass and high Eddington ratio. Further investigations, involving larger
complete samples and observations at radio frequency, are needed to understand
the incidence of disk-hosted radio-galaxies in the parent population, and to
assess whether radio-quiet NLS1s can play a role, as well.Comment: 12 pages, 6 figures, accepted for publication by Astronomy and
Astrophysic
Compact steep-spectrum sources as the parent population of flat-spectrum radio-loud NLS1s
Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active
galactic nuclei (AGN), which tipically does not exhibit any strong radio
emission. Seven percent of them, though, are radio-loud and often show a flat
radio-spectrum (F-NLS1s). This, along to the detection of -ray emission
coming from them, is usually interpreted as a sign of a relativistic beamed jet
oriented along the line of sight. An important aspect of these AGN that must be
understood is the nature of their parent population, in other words how do they
appear when observed under different angles. In the recent literature it has
been proposed that a specific class of radio-galaxies, compact-steep sources
(CSS) classified as high excitation radio galaxies (HERG), can represent the
parent population of F-NLS1s. To test this hypothesis in a quantitative way,in
this paper we analyzed the only two statistically complete samples of CSS/HERGs
and F-NLS1s available in the literature. We derived the black hole mass and
Eddington ratio distributions, and we built for the first time the radio
luminosity function of F-NLS1s. Finally, we applied a relativistic beaming
model to the luminosity function of CSS/HERGs, and compared the result with the
observed function of F-NLS1s. We found that compact steep-spectrum sources are
valid parent candidates and that F-NLS1s, when observed with a different
inclination, might actually appear as CSS/HERGs.Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in Astronomy &
Astrophysic
Caracterização de méis de diferentes regiões do Uruguai, marcadores de origem
Uruguay produces and exports honey. Honey is appreciated worldwide and has been well studied in terms of its chemical composition. These studies help determine botanical origin and prevent fraud. However, Uruguay exports honey without differentiating; the diversity of soils and vegetation in the country allows different types of honey production. Therefore, the aim of this work was to characterize honey from four regions of the country including three protected areas. The samples were collected during one year in two stations and electrical conductivity, humidity, sugar profile, macrominerals (K, Ca, Na and Mg) and pollen content were analyzed. The quality of the studied environments was evaluated by determining the presence of glyphosate. Results from this study confirm significant differences among the analyzed honeys from the different regions (Tukey-Kramer, p 0.8 mS / cm) associated with high mineral content were found. 37 different pollen taxa (family, genus or species) were detected. Some samples are monofloral (main pollen> 45%) of cultivated species (Lotus sp and Trifolium repens) or native species (Parkinsonia aculeata, Lithraea brasiliensis, Myrcianthes sp and Tripodanthus acutifolius). Calcium and sodium are suggested as markers of geographic origin. Mannose is suggested as a marker of botanical origin. The detection of glyphosate appears associated with agricultural activities even in protected areas. Uruguay produces different honeys that can be marketed indicating origin. More regions should be studied and for longer periods.Uruguay produce y exporta miel, alimento mundialmente apreciado y estudiado en términos de su composición química. Estos estudios ayudan a determinar el origen geográfico y botánico y a prevenir fraudes. Sin embargo, Uruguay exporta miel sin diferenciar. La diversidad de suelos y vegetación del país permite diferentes tipos de producción de miel. El objetivo de este trabajo fue caracterizar la miel de cuatro regiones del país, de las que tres son áreas protegidas. Las muestras se recolectaron durante un año en dos estaciones. Se analizó conductividad eléctrica, humedad, perfil de azúcar, macrominerales (K, Ca, Na y Mg) y contenido de polen. Se evaluó la calidad de los ambientes estudiados determinando la presencia de glifosato. Se encontraron diferencias entre las mieles analizadas (Tukey-Kramer, p 0.8 mS / cm) asociadas a altos contenidos minerales. Se detectaron 37 taxas de pólenes diferentes (familia, género o especie). Algunas muestras son monoflorales (polen principal> 45%) de especies cultivadas (Lotus sp y Trifolium repens) o especies nativas (Parkinsonia aculeata, Lithraea brasiliensis, Myrcianthes sp y Tripodanthus acutifolius). Se sugieren calcio y sodio como marcadores de origen geográfico. Se sugiere la manosa como marcador de origen botánico. La detección de glifosato aparece asociada con las actividades agrícolas incluso en áreas protegidas. Uruguay produce diferentes mieles que se pueden comercializar indicando origen, se deberían estudiar más regiones y durante más tiempo.O Uruguai produz e exporta mel. Um alimento apreciado em todo o mundo e estudado quanto à sua composição química. Esses estudos ajudam a determinar a origem geográfica e botânica e a prevenir fraudes. No entanto, o Uruguai exporta mel sem se diferenciar. A diversidade de solos e vegetação do país permite diferentes tipos de produção de mel. O objetivo deste trabalho foi caracterizar mel de quatro regiões do país. Três são áreas protegidas. As amostras foram coletadas durante um ano em duas estações. Condutividade elétrica, umidade, perfil de açúcar, macrominerais (K, Ca, Na e Mg) e conteúdo de pólen foram analisados. A qualidade dos ambientes estudados foi avaliada pela determinação da presença de glifosato. Foram encontradas diferenças entre os méis analisados (Tukey-Kramer, p 0,8 mS / cm) associadas a alto teor de minerais foram encontradas. 37 taxa de pólen diferentes (família, gênero ou espécie) foram detectados. Algumas amostras são monoflorais (pólen principal> 45%) de espécies cultivadas (Lotus sp e Trifolium repens) ou espécies nativas, Parkinsonia aculeata, Lithraea brasiliensis, Myrcianthes sp e Tripodanthus acutifolius). O cálcio e o sódio são sugeridos como marcadores de origem geográfica. A manose é sugerida como um marcador de origem botânica. A detecção do glifosato aparece associada às atividades agrícolas mesmo em áreas protegidas. O Uruguai produz diferentes méis que podem ser comercializados com indicação de origem. Mais regiões devem ser estudadas e por mais tempo