511 research outputs found
Noise reduction through joint processing of gravity and gravity gradient data
International audienceIn mineral and oil exploration, gravity gradient data can help to delineate small-scale features that cannot be retrieved from gravity measurements. Removing high-frequency noise while preserving the high-frequency real signal is one of the most challenging tasks associated with gravity gradi-ometry data processing. We present a method to reduce gravity and gravity gradient data noise when both are measured in the same area, based on a least-squares simultaneous inversion of observations and physical constraints, inferred from the gravity gradient tensor definition and its mathematical properties. Instead of handling profiles individually, our noise-reduction method uses simultaneously measured values of the tensor components and of gravity in the whole survey area, benefiting from all available information. Synthetic examples show that more than half of the random noise can be removed from all tensor components and nearly all the noise from the gravity anomaly without altering the high-frequency information. We apply our method to a set of marine gravity gradiometry data acquired by Bell Geospace in the Faroe-Shetland Basin to demonstrate its power to resolve small-scale features
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
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Impact of particles on the Planck HFI detectors: Ground-based measurements and physical interpretation
The Planck High Frequency Instrument (HFI) surveyed the sky continuously from
August 2009 to January 2012. Its noise and sensitivity performance were
excellent, but the rate of cosmic ray impacts on the HFI detectors was
unexpectedly high. Furthermore, collisions of cosmic rays with the focal plane
produced transient signals in the data (glitches) with a wide range of
characteristics. A study of cosmic ray impacts on the HFI detector modules has
been undertaken to categorize and characterize the glitches, to correct the HFI
time-ordered data, and understand the residual effects on Planck maps and data
products. This paper presents an evaluation of the physical origins of glitches
observed by the HFI detectors. In order to better understand the glitches
observed by HFI in flight, several ground-based experiments were conducted with
flight-spare HFI bolometer modules. The experiments were conducted between 2010
and 2013 with HFI test bolometers in different configurations using varying
particles and impact energies. The bolometer modules were exposed to 23 MeV
protons from the Orsay IPN TANDEM accelerator, and to Am and Cm
-particle and Fe radioactive X-ray sources. The calibration data
from the HFI ground-based preflight tests were used to further characterize the
glitches and compare glitch rates with statistical expectations under
laboratory conditions. Test results provide strong evidence that the dominant
family of glitches observed in flight are due to cosmic ray absorption by the
silicon die substrate on which the HFI detectors reside. Glitch energy is
propagated to the thermistor by ballistic phonons, while there is also a
thermal diffusion contribution. The implications of these results for future
satellite missions, especially those in the far-infrared to sub-millimetre and
millimetre regions of the electromagnetic spectrum, are discussed.Comment: 11 pages, 13 figure
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
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
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
NIKA 2: next-generation continuum/polarized camera at the IRAM 30 m telescope and its prototype
NIKA 2 (New Instrument of Kids Array) is a next generation continuum and
polarized instrument successfully installed in October 2015 at the IRAM 30 m
telescope on Pico-Veleta (Granada, Spain). NIKA 2 is a high resolution
dual-band camera, operating with frequency multiplexed LEKIDs (Lumped Element
Kinetic Inductance Detectors) cooled at 100 mK. Dual color images are obtained
thanks to the simultaneous readout of a 1020 pixels array at 2 mm and 1140 x 2
pixels arrays at 1.15 mm with a final resolution of 18 and 12 arcsec
respectively, and 6.5 arcmin of Field of View (FoV). The two arrays at 1.15 mm
allow us to measure the linear polarization of the incoming light. This will
place NIKA 2 as an instrument of choice to study the role of magnetic fields in
the star formation process. The NIKA experiment, a prototype for NIKA 2 with a
reduced number of detectors (about 400 LEKIDs) and FoV (1.8 arcmin), has been
successfully operated at the IRAM 30 telescope in several open observational
campaigns. The performance of the NIKA 2 polarization setup has been
successfully validated with the NIKA prototype.Comment: 5 pages, 4 figures, proceeding for the conference: Extragalactic
radio surveys 201
High angular resolution Sunyaev-Zel'dovich observations of MACS J1423.8+2404 with NIKA: Multiwavelength analysis
The prototype of the NIKA2 camera, NIKA, is an instrument operating at the
IRAM 30-m telescope, which can observe simultaneously at 150 and 260GHz. One of
the main goals of NIKA2 is to measure the pressure distribution in galaxy
clusters at high resolution using the thermal SZ (tSZ) effect. Such
observations have already proved to be an excellent probe of cluster pressure
distributions even at high redshifts. However, an important fraction of
clusters host submm and/or radio point sources, which can significantly affect
the reconstructed signal. Here we report on <20" resolution observations at 150
and 260GHz of the cluster MACSJ1424, which hosts both radio and submm point
sources. We examine the morphology of the tSZ signal and compare it to other
datasets. The NIKA data are combined with Herschel satellite data to study the
SED of the submm point source contaminants. We then perform a joint
reconstruction of the intracluster medium (ICM) electronic pressure and density
by combining NIKA, Planck, XMM-Newton, and Chandra data, focusing on the impact
of the radio and submm sources on the reconstructed pressure profile. We find
that large-scale pressure distribution is unaffected by the point sources
because of the resolved nature of the NIKA observations. The reconstructed
pressure in the inner region is slightly higher when the contribution of point
sources are removed. We show that it is not possible to set strong constraints
on the central pressure distribution without accurately removing these
contaminants. The comparison with X-ray only data shows good agreement for the
pressure, temperature, and entropy profiles, which all indicate that MACSJ1424
is a dynamically relaxed cool core system. The present observations illustrate
the possibility of measuring these quantities with a relatively small
integration time, even at high redshift and without X-ray spectroscopy.Comment: 15 pages, 17 figures, submitted to A&
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