688 research outputs found
Herschel-ATLAS: Blazars in the science demonstration phase field
To investigate the poorly constrained sub-mm counts and spectral properties of blazars we searched for these in the Herschel-ATLAS (H-ATLAS) science demonstration phase (SDP) survey catalog.
We cross-matched 500 μm sources brighter than 50 mJy with the FIRST radio catalogue. We found two blazars, both previously known. Our study is among the first blind blazar searches at sub-mm wavelengths, i.e., in the spectral regime where little is still known about the blazar SEDs, but where the synchrotron peak of the most luminous blazars is expected to occur. Our early results are consistent with educated extrapolations of lower frequency counts and question indications of substantial spectral curvature downwards and of spectral upturns at mm wavelengths. One of the two blazars is identified with a Fermi/LAT γ-ray source and a WMAP source. The physical parameters of the two blazars are briefly discussed. These observations demonstrate that the H-ATLAS survey will provide key information about the physics of blazars and their contribution to sub-mm counts
Mesozooplankton species distribution in the NW and N Iberian shelf during spring 2004: Relationship with frontal structures.
We have analysed the mesozooplankton community structure in the southern Bay of Biscay shelf and its relationship with the
hydrographic conditions during spring 2004. According to thermohaline characteristics, we observed two frontal zones of distinct
origin along the shelf (around 7° and 3°W), that allowed us to differentiate three different hydrographic domains. The westernmost
part of the shelf (WC), defined by the presence of relatively warm and salty water related to the presence of the Iberian Poleward
Current (IPC), the easternmost region (EC), characterized by colder and fresher water and subject to the influence of freshwater inputs
from the Adour river in the French coast, and a region in the Central Cantabrian Sea (CC), where thermohaline characteristics were
intermediate between these two extremes. The mixing layer depth (MLD) regime in these areas was also different: theWCregion was
characterized by a mixed water column, whereas in the EC region the river discharges produces stratification of the upper meters of the
water column (b10 m); in the CC region, we found a distinct vertical mixing regime that separated coastal (stratification) from shelf
(mixed water column) stations, giving rise to a notorious across-shelf front. We found a good match between the aforesaid
hydrographic regions and the distribution of mesozooplankton species composition and community assemblages: the Mantel
correlation between physical variables and mesozooplankton distribution was highly significant (n=63, r=0.70, αb0.001). In the
WC region, the community was dominated by Paracalanus parvus, Oithona helgolandica, Acartia clausi and Clausocalanus
pergens, while in the EC region the most dominant species were Noctiluca scintillans, Oncaea media and Temora longicornis. The
CC region showed similar composition of copepods than the WC region, but larvaceans (Oikopleura spp. and Fritillaria spp.) were
more abundant in the CC region than in the WC region. Within each zone, the relative abundances of the dominant species differed
between coastal and shelf locations.SARDYN EUproject (QLRT-2001-00818)
Consejería de Educación y Cultura del Principado de Asturias’ (FICYT)
Hydrographic conditions and mesozooplankton species distribution in the Bay of Biscay shelf during spring 2004
Mesozooplankton community structure on the southern Bay of Biscay shelf and its relationship with environmental conditions was analysed during spring 2004. According to thermohaline characteristics, we observed two frontal zones along the shelf (around 7° and 3°W) that gave rise to three distinct hydrographic regions. The westernmost part of the shelf (WC), defined by the presence of relatively warm and salty water related to the presence of the Iberian Poleward Current (IPC), the easternmost region (EC), characterised by colder and fresher water, and a region in the Central Cantabrian Sea (CC) with thermohaline characteristics in between these two extremes. Besides, a clear coastal-offshore pattern was found in relation to the mixed layer depth (MLD). We observed a good agreement between the aforesaid hydrographic regions and the distribution of zooplankton species. In the WC region, the community structure was dominated by Paracalanus parvus, Oithona helgolandica, Acartia clausii and Clausocalanus pergens, while in the EC region the most dominant species were Noctiluca scintillans and Oncaea media. The CC region showed similar composition of copepods than the WC region but larvaceans (Oikopleura and Fritilaria) were also abundant. Superimposed to this along-shelf pattern, relative abundances differed also between coastal and shelf stations.SARDYN EU –project (QLRT-2001-00818
A multifrequency method based on the Matched Multifilter for the detection of point sources in CMB maps
In this work we deal with the problem of simultaneous multifrequency
detection of extragalactic point sources in maps of the Cosmic Microwave
Background. We apply a linear filtering technique that uses spatial information
and the cross-power spectrum. To make this, we simulate realistic and
non-realistic flat patches of the sky at two frequencies of Planck: 44 and 100
GHz. We filter to detect and estimate the point sources and compare this
technique with the monofrequency matched filter in terms of completeness,
reliability, flux and spectral index accuracy. The multifrequency method
outperforms the matched filter at the two frequencies and in all the studied
cases in the work.Comment: 14 pages, 6 figures, 1 tabl
Methodological refinement of the submillimeter galaxy magnification bias. Paper I: cross-correlation function measurements
The measurement of the cross-correlation function is crucial to assess
magnification bias in galaxy surveys. Previous works used mini-tile
subsampling, but accurately determining the integral constraint (IC) correction
for unbiased estimation is challenging due to various factors. We present a new
methodology for estimating the cross-correlation function, utilizing full field
area and reducing statistical uncertainty. Covariance matrices were estimated
by dividing each field into at least five patches using a k-mean clustering
algorithm. Robustness was assessed by comparing spectroscopic and photometric
lens samples, yielding compatible results. Cross-correlation and
auto-correlation analyses in the GAMA fields revealed a stronger signal in
GAMA15, likely due to rare large-scale structure combinations. Our findings
highlight the robustness of the new methodology and suggest sample-specific
effects. Subsequent papers in this series will explore other aspects of
magnification bias and address potential biases from the GAMA15 signal on
cosmological parameter constraints.Comment: This work is the first one of a three-paper serie. 14 pages, 9
figures, submitted for publication by A&
- …