772 research outputs found
A multi-wavelength study of the evolution of Early-Type Galaxies in Groups: the ultraviolet view
ABRIDGED- The UV-optical color magnitude diagram (CMD) of rich galaxy groups
is characterised by a well developed Red Sequence (RS), a Blue Cloud (BC) and
the so-called Green Valley (GV). Loose, less evolved groups of galaxies likely
not virialized yet may lack a well defined RS. This is actually explained in
the framework of galaxy evolution. We are focussing on understanding galaxy
migration towards the RS, checking for signatures of such a transition in their
photometric and morphological properties. We report on the UV properties of a
sample of ETGs galaxies inhabiting the RS. The analysis of their structures, as
derived by fitting a Sersic law to their UV luminosity profiles, suggests the
presence of an underlying disk. This is the hallmark of dissipation processes
that still must have a role in the evolution of this class of galaxies. SPH
simulations with chemo-photometric implementations able to match the global
properties of our targets are used to derive their evolutionary paths through
UV-optical CDM, providing some fundamental information such as the crossing
time through the GV, which depends on their luminosity. The transition from the
BC to the RS takes several Gyrs, being about 3-5 Gyr for the the brightest
galaxies and more long for fainter ones, if it occurs. The photometric study of
nearby galaxy structures in UV is seriously hampered by either the limited FoV
of the cameras (e.g in HST) or by the low spatial resolution of the images (e.g
in the GALEX). Current missions equipped with telescopes and cameras sensitive
to UV wavelengths, such as Swift-UVOT and Astrosat-UVIT, provide a relatively
large FoV and better resolution than the GALEX. More powerful UV instruments
(size, resolution and FoV) are obviously bound to yield fundamental advances in
the accuracy and depth of the surface photometry and in the characterisation of
the galaxy environment.Comment: 12 pages, 6 figures: accepted for publication in Astrophysics & Space
Science as contributions to the workshop: "UV astronomy, the needs and the
means
On the Orbital Period of the Intermediate Polar 1WGA J1958.2+3232
Recently, Norton et al. 2002, on the basis of multiwavelength photometry of
1WGA J1958.2+3232, argued that the -1 day alias of the strongest peak in the
power spectrum is the true orbital period of the system, casting doubts on the
period estimated by Zharikov et al. 2001. We re-analyzed this system using our
photometric and spectroscopic data along with the data kindly provided by Andy
Norton and confirm our previous finding. After refining our analysis we find
that the true orbital period of this binary system is 4.35h.Comment: 4 pages, 5 figures, Accepted for publication in A&A Letter
Near-infrared adaptive optics imaging of high redshift quasars
The properties of high redshift quasar host galaxies are studied, in order to
investigate the connection between galaxy evolution, nuclear activity, and the
formation of supermassive black holes. We combine new near-infrared
observations of three high redshift quasars (2 < z < 3), obtained at the ESO
Very Large Telescope equipped with adaptive optics, with selected data from the
literature. For the three new objects we were able to detect and characterize
the properties of the host galaxy, found to be consistent with those of massive
elliptical galaxies of M(R) ~ -24.7 for the one radio loud quasar, and M(R) ~
-23.8 for the two radio quiet quasars. When combined with existing data at
lower redshift, these new observations depict a scenario where the host
galaxies of radio loud quasars are seen to follow the expected trend of
luminous (~5L*) elliptical galaxies undergoing passive evolution. This trend is
remarkably similar to that followed by radio galaxies at z > 1.5. Radio quiet
quasars hosts also follow a similar trend but at a lower average luminosity
(~0.5 mag dimmer). The data indicate that quasar host galaxies are already
fully formed at epochs as early as ~2 Gyr after the Big Bang and then passively
fade in luminosity to the present epoch.Comment: Accepted for publication in ApJ, 24 pages, 10 figure
Size-independent cylindrical resonator half-filled with DNG metamaterial
A circular cylindrical metallic resonator half filled with DPS material and half with DNG metamaterial is analyzed, in the frequency domain. The two materials are linear, lossless, homogeneous, and anti-isorefractive to each other. The electric field is assumed to be parallel to the cylinder axis. It is shown that the resonator performs independently of diameter size. Numerical results are presented and discussed for a resonator excited by a line source parallel to the axis
The nuclear to host galaxy relation of high redshift quasars
We present near-infrared imaging with ESO VLT+ISAAC of the host galaxies of
low luminosity quasars in the redshift range 1 < z < 2, aimed at investigating
the relationship between the nuclear and host galaxy luminosities at high
redshift. This work complements our previous study to trace the cosmological
evolution of the host galaxies of high luminosity quasars (Falomo et al. 2004).
The new sample includes 15 low luminosity quasars, nine radio-loud (RLQ) and
six radio-quiet (RQQ). They have similar distribution of redshift and optical
luminosity, and together with the high luminosity quasars they cover a large
range (~4 mag) of the quasar luminosity function. The host galaxies of both
types of quasars are in the range of massive inactive ellipticals between L*
and 10 L*. RLQ hosts are systematically more luminous than RQQ hosts by a
factor of ~2. This difference is similar to that found for the high luminosity
quasars. This luminosity gap appears to be independent of the rest-frame U-band
luminosity but clearly correlated with the rest-frame R-band luminosity. The
color difference between the RQQs and the RLQs is likely a combination of an
intrinsic difference in the strength of the thermal and nonthermal components
in the SEDs of RLQs and RQQs, and a selection effect due to internal dust
extinction. For the combined set of quasars, we find a reasonable correlation
between the nuclear and the host luminosities. This correlation is less
apparent for RQQs than for RLQs. If the R-band luminosity is representative of
the bolometric luminosity, and assuming that the host luminosity is
proportional to the black hole mass, as observed in nearby massive spheroids,
quasars emit with a relatively narrow range of power with respect to their
Eddington luminosity and with the same distribution for RLQs and RQQs.Comment: Accepted for publication in ApJ, 24 pages, 4 figure
Cylindrical resonators partially filled with a DNG metamaterial sector
A metallic cylindrical resonator partially filled with double-negative (DNG) metamaterial with sector shape is analyzed in the frequency domain. The remaining part of the resonator is filled by a double-positive (DPS) medium. The structure results in a cylindrical resonator of finite length with a metamaterial wedge whose edge is on the cylinder axis. A line source excitation located in the DPS region is applied to investigate the properties of the structure by exciting the compatible modes of the structure. An exact analytical solution is obtained
Efectividad del cipionato de estradiol inyectado al final de un tratamiento con progesterona sobre la eficiencia reproductiva
El cipionato de estradiol (CPE) ha sido utilizado para reemplazar al benzoato de estradiol (BE) administrado vía IM 24 h después de retirado el dispositivo intravaginal con progesterona (DISP), sin afectar los porcentajes de preñez. El objetivo del trabajo fue evaluar el efecto de dos dosis de CPE inyectado al retirar un DISP, sobre el porcentaje de preñez post inseminación artificial a tiempo fijo (IATF). Como objetivo secundario, se planteó comparar la eficiencia reproductiva de los tratamientos utilizados. Se emplearon 79 vaquillonas de 15 meses de edad. El día 0, se les colocó un DISP más BE. El día 7 se retiró el DISP, se administró D(+) cloprostenol y en forma aleatoria se inyectó 0,5 mg de CPE, 1 mg de CPE o BE 24 h después. Para la IATF (52–56 h) se utilizó semen proveniente de un toro de probada fertilidad. El día 22 se colocó a todas las vaquillonas un DISP de segundo uso, retirándolo 7 días después. Se continuó con detección de celo e IA. El diagnóstico de gestación se realizó por ultrasonografía en dos oportunidades para evaluar preñez de IATF y retorno, así como para verificar mortalidad embrionaria. Se evaluó el efecto de los tratamientos sobre la preñez a la IATF, del retorno y final. No se observaron efectos del tratamiento (p>0,05) sobre los porcentajes de preñez a la IATF (51,9%), del retorno (61,1%) y final (65,8%). Se observó un 7,3% de pérdidas embrionarias (p>0,05). Se concluye que la administración de 0,5 o 1 mg de CPE al retirar un DISP con progesterona en lugar de BE a las 24 h posteriores es igualmente efectiva para implementar una IATF. Además, no resulta afectada la eficiencia reproductiva del rodeo.
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