8 research outputs found
Euclid preparation: XVII. Cosmic Dawn Survey: Spitzer Space Telescope observations of the Euclid deep fields and calibration fields
Get PDFWe present a new infrared survey covering the three Euclid deep fields and four other Euclid calibration fields using Spitzer Space Telescope's Infrared Array Camera (IRAC). We combined these new observations with all relevant IRAC archival data of these fields in order to produce the deepest possible mosaics of these regions. In total, these observations represent nearly 11 % of the total Spitzer Space Telescope mission time. The resulting mosaics cover a total of approximately 71.5 deg^{2} in the 3.6 and 4.5 μm bands, and approximately 21.8 deg^{2} in the 5.8 and 8 μm bands. They reach at least 24 AB magnitude (measured to 5σ, in a 2″.5 aperture) in the 3.6 μm band and up to ∼5 mag deeper in the deepest regions. The astrometry is tied to the Gaia astrometric reference system, and the typical astrometric uncertainty for sources with 16 "< "[3.6]< 19 is ≲ 0″.15. The photometric calibration is in excellent agreement with previous WISE measurements. We extracted source number counts from the 3.6 μm band mosaics, and they are in excellent agreement with previous measurements. Given that the Spitzer Space Telescope has now been decommissioned, these mosaics are likely to be the definitive reduction of these IRAC data. This survey therefore represents an essential first step in assembling multi-wavelength data on the Euclid deep fields, which are set to become some of the premier fields for extragalactic astronomy in the 2020s
Level 1 on-ground telemetry handling in Planck-LFI
Get PDFThe Planck Low Frequency Instrument (LFI) will observe the Cosmic Microwave Background (CMB) by covering the frequency range 30-70 GHz in three bands. The primary instrument data source are the temperature samples acquired by the 22 radiometers mounted on the Planck focal plane. Such samples represent the scientific data of LFI. In addition, the LFI instrument generates the so called housekeeping data by sampling regularly the on-board sensors and registers. The housekeeping data provides information on the overall health status of the instrument and on the scientific data quality. The scientific and housekeeping data are collected on-board into telemetry packets compliant with the ESA Packet Telemetry standards. They represent the primary input to the first processing level of the LFI Data Processing Centre. In this work we show the software systems which build the LFI Level 1. A real-time assessment system, based on the ESA SCOS 2000 generic mission control system, has the main purpose of monitoring the housekeeping parameters of LFI and detect possible anomalies. A telemetry handler system processes the housekeeping and scientific telemetry of LFI, generating timelines for each acquisition chain and each housekeeping parameter. Such timelines represent the main input to the subsequent processing levels of the LFI DPC. A telemetry quick-look system allows the real-time visualization of the LFI scientific and housekeeping data, by also calculating quick statistical functions and fast Fourier transforms. The LFI Level 1 has been designed to support all the mission phases, from the instrument ground tests and calibration to the flight operations, and developed according to the ESA engineering standards
Planck 2013 results.:XV. CMB power spectra and likelihood
Get PDFThis paper presents the Planck 2013 likelihood, a complete statistical description of the two-point correlation function of the CMB temperature fluctuations that accounts for all known relevant uncertainties, both instrumental and astrophysical in nature. We use this likelihood to derive our best estimate of the CMB angular power spectrum from Planck over three decades in multipole moment, covering 22500. The main source of uncertainty at 1500 is cosmic variance. Uncertainties in small-scale foreground modelling and instrumental noise dominate the error budget at higher s. For <50, our likelihood exploits all Planck frequency channels from 30 to 353 GHz, separating the cosmological CMB signal from diffuse Galactic foregrounds through a physically motivated Bayesian component separation technique. At 50, we employ a correlated Gaussian likelihood approximation based on a fine-grained set of angular cross-spectra derived from multiple detector combinations between the 100, 143, and 217 GHz frequency channels, marginalising over power spectrum foreground templates. We validate our likelihood through an extensive suite of consistency tests, and assess the impact of residual foreground and instrumental uncertainties on the final cosmological parameters. We find good internal agreement among the high-cross-spectra with residuals below a few K2 at 1000, in agreement with estimated calibration uncertainties. We compare our results with foreground-cleaned CMB maps derived from all Planck frequencies, as well as with cross-spectra derived from the 70 GHz Planck map, and find broad agreement in terms of spectrum residuals and cosmological parameters. We further show that the best-fit CDM cosmology is in excellent agreement with preliminary PlanckEE and TE polarisation spectra. We find that the standard CDM cosmology is well constrained by Planck from the measurements at 1500. One specific example is the spectral index of scalar perturbations, for which we report a 5.4 deviation from scale invariance, n= 1. Increasingthe multipole range beyond 1500 does not increase our accuracy for the CDM parameters, but instead allows us to study extensions beyond the standard model. We find no indication of significant departures from the CDM framework. Finally, we report a tension between the Planck best-fit CDM model and the low-spectrum in the form of a power deficit of 510% at 40, with a statistical significance of 2.53. Without a theoretically motivated model for this power deficit, we do not elaborate further on its cosmological implications, but note that this is our most puzzling finding in an otherwise remarkably consistent data set
