127 research outputs found
Influence of latitude and climate on spread, radiation and rise to dominance of early angiosperms during the Cretaceous in the Northern Hemisphere
Our aim is to evaluate the influence of climate and latitude on the rise to dominance of angiosperms in space and time during the Cretaceous. The main objectives of the study are: 1) to determine whether a relationship existed between plant biogeographical distribution and Cretaceous climate changes; 2) to explore latitude-dependent forcing on early angiosperm ecology; 3) to propose a mechanism explaining the observed stages of radiation in early angiosperms. The study focuses on 18 Cretaceous megafossil localities and reviews on microfossils in the Northern Hemisphere. A database has been compiled using literature and personal unpublished data. The data document occurrences of micro- and megafossil plant remains including spores, pollen grains, leaves and whole plants. They are placed in context through the use of Cretaceous geographical maps and temperature curves or values. There is a clear correlation between latitude and the composition of Cretaceous floras. Latitudinal vegetation belts fluctuated in concert with climate changes during the Cretaceous. Differences in original plant associations may have driven the gradual plant turnover that resulted in the rise to dominance of early angiosperms during the Cretaceous. Cretaceous climate changes created dispersal bottlenecks. Bottlenecks induced the extinction of some plant groups and the radiation of others. Those that successfully radiated continued to spread
Uniform non-stoichiometric titanium nitride thin films for improved kinetic inductance detector array
We describe the fabrication of homogeneous sub-stoichiometric titanium
nitride films for microwave kinetic inductance detector (mKID) arrays. Using a
6 inch sputtering target and a homogeneous nitrogen inlet, the variation of the
critical temperature over a 2 inch wafer was reduced to <25 %. Measurements of
a 132-pixel mKID array from these films reveal a sensitivity of 16 kHz/pW in
the 100 GHz band, comparable to the best aluminium mKIDs. We measured a noise
equivalent power of NEP = 3.6e-15 W/Hz^(1/2). Finally, we describe possible
routes to further improve the performance of these TiN mKID arrays.Comment: 7 pages, 4 figures, submitted to Journal of low temperature physics,
Proceedings of LTD-1
The NIKA instrument: results and perspectives towards a permanent KID based camera for the Pico Veleta observatory
The New IRAM KIDs Array (NIKA) is a pathfinder instrument devoted to
millimetric astronomy. In 2009 it was the first multiplexed KID camera on the
sky; currently it is installed at the focal plane of the IRAM 30-meters
telescope at Pico Veleta (Spain). We present preliminary data from the last
observational run and the ongoing developments devoted to the next NIKA-2
kilopixels camera, to be commissioned in 2015. We also report on the latest
laboratory measurements, and recent improvements in detector cosmetics and
read-out electronics. Furthermore, we describe a new acquisition strategy
allowing us to improve the photometric accuracy, and the related automatic
tuning procedure.Comment: 24th International Symposium on Space Terahertz Technology, ISSTT
2013, April 8 to 10, 2013, Groningen, the Netherland
Latest NIKA results and the NIKA-2 project
NIKA (New IRAM KID Arrays) is a dual-band imaging instrument installed at the
IRAM (Institut de RadioAstronomie Millimetrique) 30-meter telescope at Pico
Veleta (Spain). Two distinct Kinetic Inductance Detectors (KID) focal planes
allow the camera to simultaneously image a field-of-view of about 2 arc-min in
the bands 125 to 175 GHz (150 GHz) and 200 to 280 GHz (240 GHz). The
sensitivity and stability achieved during the last commissioning Run in June
2013 allows opening the instrument to general observers. We report here the
latest results, in particular in terms of sensitivity, now comparable to the
state-of-the-art Transition Edge Sensors (TES) bolometers, relative and
absolute photometry. We describe briefly the next generation NIKA-2 instrument,
selected by IRAM to occupy, from 2015, the continuum imager/polarimeter slot at
the 30-m telescope.Comment: Proceedings of Low Temperature Detectors 15 (LTD-15), Pasadena, June
201
Non-parametric deprojection of NIKA SZ observations: Pressure distribution in the Planck-discovered cluster PSZ1 G045.85+57.71
The determination of the thermodynamic properties of clusters of galaxies at
intermediate and high redshift can bring new insights into the formation of
large-scale structures. It is essential for a robust calibration of the
mass-observable scaling relations and their scatter, which are key ingredients
for precise cosmology using cluster statistics. Here we illustrate an
application of high resolution arcsec) thermal Sunyaev-Zel'dovich (tSZ)
observations by probing the intracluster medium (ICM) of the \planck-discovered
galaxy cluster \psz\ at redshift , using tSZ data obtained with the
NIKA camera, which is a dual-band (150 and 260~GHz) instrument operated at the
IRAM 30-meter telescope. We deproject jointly NIKA and \planck\ data to extract
the electronic pressure distribution from the cluster core () to its outskirts () non-parametrically for the
first time at intermediate redshift. The constraints on the resulting pressure
profile allow us to reduce the relative uncertainty on the integrated Compton
parameter by a factor of two compared to the \planck\ value. Combining the tSZ
data and the deprojected electronic density profile from \xmm\ allows us to
undertake a hydrostatic mass analysis, for which we study the impact of a
spherical model assumption on the total mass estimate. We also investigate the
radial temperature and entropy distributions. These data indicate that \psz\ is
a massive ( M) cool-core cluster.
This work is part of a pilot study aiming at optimizing the treatment of the
NIKA2 tSZ large program dedicated to the follow-up of SZ-discovered clusters at
intermediate and high redshifts. (abridged)Comment: 16 pages, 10 figure
Microfabrication technology for large LEKID arrays : from NIKA2 to future applications
The Lumped Element Kinetic Inductance Detectors (LEKID)demonstrated full
maturity in the NIKA (New IRAM KID Arrays)instrument. These results allow
directly comparing LEKID performance with other competing technologies (TES,
doped silicon) in the mm and sub-mm range. A continuing effort is ongoing to
improve the microfabrication technologies and concepts in order to satisfy the
requirements of new instruments. More precisely, future satellites dedicated to
CMB (Cosmic Microwave Background) studies will require the same focal plane
technology to cover, at least, the frequency range of 60 to 600 GHz. Aluminium
LEKID developed for NIKA have so far demonstrated, under real telescope
conditions, performance approaching photon-noise limitation in the band 120-300
GHz. By implementing superconducting bi-layers we recently demonstrated LEKID
arrays working in the range 80-120 GHz and with sensitivities approaching the
goals for CMB missions. NIKA itself (350 pixels) is followed by a more
ambitious project requiring several thousands (3000-5000) pixels. NIKA2 has
been installed in October 2015 at the IRAM 30-m telescope. We will describe in
detail the technological improvements that allowed a relatively harmless
10-fold up-scaling in pixels count without degrading the initial sensitivity.
In particular we will briefly describe a solution to simplify the difficult
fabrication step linked to the slot-line propagation mode in coplanar
waveguide
Detection of the tSZ effect with the NIKA camera
We present the first detection of the thermal Sunyaev-Zel'dovich (tSZ) effect
from a cluster of galaxies performed with a KIDs (Kinetic Inductance Detectors)
based instrument. The tSZ effect is a distortion of the black body CMB (Cosmic
Microwave Background) spectrum produced by the inverse Compton interaction of
CMB photons with the hot electrons of the ionized intra-cluster medium. The
massive, intermediate redshift cluster RX J1347.5-1145 has been observed using
NIKA (New IRAM KIDs arrays), a dual-band (140 and 240 GHz) mm-wave imaging
camera, which exploits two arrays of hundreds of KIDs: the resonant frequencies
of the superconducting resonators are shifted by mm-wave photons absorption.
This tSZ cluster observation demonstrates the potential of the next generation
NIKA2 instrument, being developed for the 30m telescope of IRAM, at Pico Veleta
(Spain). NIKA2 will have 1000 detectors at 140GHz and 2x2000 detectors at
240GHz, providing in that band also a measurement of the linear polarization.
NIKA2 will be commissioned in 2015.Comment: SF2A Proceedings 201
High resolution SZ observations at the IRAM 30-m telescope with NIKA
High resolution observations of the thermal Sunyaev-Zel'dovich (tSZ) effect
are necessary to allow the use of clusters of galaxies as a probe for large
scale structures at high redshifts. With its high resolution and dual-band
capability at millimeter wavelengths, the NIKA camera can play a significant
role in this context. NIKA is based on newly developed Kinetic Inductance
Detectors (KIDs) and operates at the IRAM 30m telescope, Pico Veleta, Spain. In
this paper, we give the status of the NIKA camera, focussing on the KID
technology. We then present observations of three galaxy clusters: RX
J1347.5-1145 as a demonstrator of the NIKA capabilities and the recent
observations of CL J1226.9+3332 (z = 0.89) and MACS J0717.5+3745 (z = 0.55). We
also discuss prospects for the final NIKA2 camera, which will have a 6.5
arcminute field of view with about 5000 detectors in two bands at 150 and 260
GHz
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