1,957 research outputs found
The Canada-France High-z Quasar Survey: 1.2mm Observations
We report 250 GHz (1.2 mm) observations of a sample of 20 QSOs at redshifts
5.8<z<6.5 from the the Canada-France High-z Quasar Survey (CFHQS), using the
Max-Planck Millimeter Bolometer (MAMBO) array at the IRAM 30-metre telescope. A
rms sensitivity <~ 0.6 mJy was achieved for 65% of the sample, and <~ 1.0 mJy
for 90%. Only one QSO, CFHQS J142952+544717, was robustly detected with
S_250GHz = 3.46 +/-0.52 mJy. This indicates that one of the most powerful known
starbursts at z~6 is associated with this radio loud QSO. On average, the other
CFHQS QSOs, which have a mean optical magnitude fainter than previously studied
SDSS samples of z~6 QSOs, have a mean 1.2 mm flux density = 0.41
+/-0.14 mJy; such a 2.9-sigma average detection is hardly meaningful. It would
correspond to ~ 0.94+/-0.32 10^12 Lo, and an average star formation
rate of a few 100's Mo/yr, depending on the IMF and a possible AGN contribution
to . This is consistent with previous findings of Wang et al. (2011) on
the far-infrared emission of z~6 QSOs and extends them toward optically fainter
sources.Comment: 6 pages, 1 figure, A&A in pres
The dust emission of high-redshift quasars
The detection of powerful near-infrared emission in high redshift (z>5)
quasars demonstrates that very hot dust is present close to the active nucleus
also in the very early universe. A number of high-redshift objects even show
significant excess emission in the rest frame NIR over more local AGN spectral
energy distribution (SED) templates. In order to test if this is a result of
the very high luminosities and redshifts, we construct mean SEDs from the
latest SDSS quasar catalogue in combination with MIR data from the WISE
preliminary data release for several redshift and luminosity bins. Comparing
these mean SEDs with a large sample of z>5 quasars we could not identify any
significant trends of the NIR spectral slope with luminosity or redshift in the
regime 2.5 < z < 6 and 10^45 < nuL_nu(1350AA) < 10^47 erg/s. In addition to the
NIR regime, our combined Herschel and Spitzer photometry provides full infrared
SED coverage of the same sample of z>5 quasars. These observations reveal
strong FIR emission (L_FIR > 10^13 L_sun) in seven objects, possibly indicating
star-formation rates of several thousand solar masses per year. The FIR excess
emission has unusally high temperatures (T ~ 65 K) which is in contrast to the
temperature typically expected from studies at lower redshift (T ~ 45 K). These
objects are currently being investigated in more detail.Comment: 6 pages, 3 figures, to appear in the proceedings to "The Central
Kiloparsec in Galactic Nuclei (AHAR2011)", Journal of Physics: Conference
Series (JPCS), IOP Publishin
Resolving the molecular gas around the lensed quasar RXJ0911.4+0551
We report on high angular resolution observations of the CO(7-6) line and
millimeter continuum in the host galaxy of the gravitationally lensed (z~2.8)
quasar RXJ0911.4+0551 using the Plateau de Bure Interferometer. Our CO
observations resolve the molecular disk of the source. Using a lens model based
on HST observations we fit source models to the observed visibilities. We
estimate a molecular disk radius of 10.2 kpc and an inclination of
696\deg, the continuum is more compact and is only marginally resolved by
our observations. The relatively low molecular gas mass, Msolar, and far infrared luminosity, Lsolar, of this quasar could be explained by its relatively low
dynamical mass, Msolar. It would be a
scaled-down version the QSOs usually found at high-z. The FIR and CO
luminosities lie on the correlation found for QSOs from low to high redshifts
and the gas-to-dust ratio () is similar to the one measured in the
z=6.4 QSO, SDSS J1148+5251. Differential magnification affects the
continuum-to-line luminosity ratio, the line profile and possibly the spectral
energy distribution.Comment: Accepted for publication in A&A, revised after language editin
Compact polymer components for an integrated add-drop multiplexer
A phasar and a digital thermo optic switch have been designed and processed in a high index contrast polymer technology. Both devices are small enough to fabricate two integrated add-drop multiplexers on one 4 inch wafe
Tanino condensando das espécies jurema preta (Mimosa hostilis), sabiá (Mimosa caesalpinifolia) e mororó (Bauhinia cheilantha), em três fases do ciclo fenológico.
Resumo: O objetivo do presente trabalho foi caracterizar os taninos condensados das espécies Jurema Preta (Mimosa hostilis), Sabiá (Mimosa caesalpinifolia) e Mororó (Bauhinia cheilantha) nas fases de vegetação(Mimosa hostilis), Sabiá (Mimosa caesalpinifolia) e Mororó (Bauhinia cheilantha) nas fases de vegetação plena, floração plena e frutificação. A concentração em tanino solúvel, tanino ligado ao resíduo e tanino total (TT) foi determinada pelo método butanol-HCL e a adstringência pelo método de difusão radial. Foram observadas diferenças entre as espécies quanto a concentração (P<0,05) e adstringência (P<0,05) dos taninos. A Jurema Preta apresentou os maiores valores (30,98% TT e 22% de adstringência na vegetação plena) e Mororó as menores (10,38% TT e 14% de adstringência na frutificação). A concentração e adstringência dos taninos condensados, assim como a adstringência variaram entre as espécies e, em alguns casos, entre as fases do ciclo fenológico. Os valores observados foram sempre superiores aos considerados benéficos (5%) para a digestão ruminal e aproveitamento geral da dieta. Abstract: This study was conducted aiming at characterizing the condensed tannins present in the legumes species Jurema Preta (Mimosa hostilis), Sabiá (Mimosa caesalpinifolia) and Mororó (Bauhinia cheilantha) at three stages of their phenological cycle. The concentration of soluble tannin, bound tannin and total tannin (TT) was determined using the butanol-HCL method and astringency was determined using the radial diffusion method. Jurema Preta presented the highest values (30.98% TT and 22 % astringency at full growth stage), and Mororó the lowest (10.38% TT and 14 % astringency during fructification). Concentration and astringency of condensed tannins, as well as their monomeric composition varied between species, and in some cases among phenological cycles. The values observed were always above the limits considered beneficial for ruminal digestion (i.e. 5%)
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