Video surveillance systems are commonly used as important sources of quantitative information but from the acquired images it is possible to obtain a large amount of metric information. Yet, ...different methodological issues must be considered in order to perform accurate measurements using images. The most important one is the camera calibration, which is the estimation of the parameters defining the camera model. One of the most used camera calibration method is the Zhang's method, that allows the estimation of the linear parameters of the camera model. This method is very diffused as it requires a simple setup and it allows to calibrate cameras using a simple and fast procedure, but it does not consider lenses distortions, that must be taken into account with short focal lenses, commonly used in video surveillance systems. In order to perform accurate measurements, the linear camera model and the Zhang's method are improved in order to take nonlinear parameters into account and compensate the distortion contribute. In this paper we first describe the pinhole camera model that considers cameras as central projection systems. After a brief introduction to the camera calibration process and in particular the Zhang's method, we give a description of the different types of lens distortions and the techniques used for the distortion compensation. At the end some numerical example are shown in order to demonstrate the importance of the distortion compensation to obtain accurate measurements.
Context. Studies of the generation and assembly of stellar populations in galaxies largely benefit from far-IR observations, considering that the IR flux is a close prior to the rate of star ...formation (the bulk of which happens in dust-obscured environments). At the same time, major episodes of nuclear AGN accretion are also dust-obscured and visible in the IR. Aims. At the end of the Spitzer cryogenic mission and the onset of the Herschel era, we review our current knowledge of galaxy evolution at IR wavelengths, and model it to achieve as far as a complete view of the evolution of cosmic sources. We also develop new tools for the analysis of background fluctuations to constrain source counts in regimes of high confusion, as it happens for the Herschel sub-mm surveys. Methods. We analysed a wide variety of new data on galaxy evolution and high-redshift source populations from Spitzer cosmological surveys, and confront them with complementary data from mm ground-based observations and constraints from the far-IR diffuse radiation, as well as preliminary results from Herschel surveys. Results. These data confirm earlier indications about a very rapid increase in galaxy volume emissivity with redshift up to z $\simeq$ 1 ρ(z) $\propto$ (1+z)4 , the fastest evolution rate observed for galaxies at any wavelengths. The observed Spitzer counts require a combination of fast evolution for the dominant population and a bumpy spectrum with substantial PAH emission at z ~ 1 to 2. Number counts at long wavelengths (70 through 1100 μm) confirm these results. All the present data require that the fast observed evolution from z = 0 to 1 flattens around redshift 1 and then keeps approximately constant up to z $\simeq$ 2.5 at least. Our estimated redshift-dependent bolometric comoving energy density keeps lower at z $\ga$ 1.5 than some previously published results based on either large extinction corrections, or large spectral extrapolations. Conclusions. The present-day IR/sub-mm data provide evidence of a distinct population of very luminous galaxies becoming dominant at z > 1. Their cosmological evolution, peaking around z $\simeq$ 2, shows a faster decay with cosmic time than lower luminosity systems, whose maximal activity is set around z $\simeq$ 1, then supporting an earlier phase of formation for the most luminous and massive galaxies. From a comparison of our results on the comoving IR emissivity with recent estimates of the redshift-dependent stellar mass functions of galaxies, we find that the two agree well with each other if we assume standard recipes for star formation (a universal Salpeter IMF) and standard fractions (~ 20–30%) for the contribution of obscured AGN accretion. Systematic exploitation of the forthcoming Herschel survey data will be important for confirming all this.
We present the data processing pipeline to generate calibrated data products from the Spectral and Photometric Imaging Receiver (SPIRE) imaging Fourier Transform Spectrometer on the Herschel Space ...Observatory. The pipeline processes telemetry from SPIRE observations and produces calibrated spectra for all resolution modes. The spectrometer pipeline shares some elements with the SPIRE photometer pipeline, including the conversion of telemetry packets into data timelines and calculation of bolometer voltages. We present the following fundamental processing steps unique to the spectrometer: temporal and spatial interpolation of the scan mechanism and detector data to create interferograms; Fourier transformation; apodization; and creation of a data cube. We also describe the corrections for various instrumental effects including first- and second-level glitch identification and removal, correction of the effects due to emission from the Herschel telescope and from within the spectrometer instrument, interferogram baseline correction, temporal and spatial phase correction, non-linear response of the bolometers, and variation of instrument performance across the focal plane arrays. Astronomical calibration is based on combinations of observations of standard astronomical sources and regions of space known to contain minimal emission.
This paper presents an overview of the Lecco Innovation Hub project and in particular to the Sailing Yacht Lab project a 10m length sailing yacht which aims to be a full scale measurement device in ...the sailing yacht research field. A description of scientific framework, measurement capabilities as well as of the principal design, building process, project management and commissioning is provided with some examples of preliminary collected data obtained during the first sea trials. Finally an overview of the ongoing project tasks and future project developments is provided including potential research and knowledge achievements for sailing yacht research field.
•Overview of the Lecco Innovation Hub – Sailing Yacht Lab project.•Description of scientific frame, measurement capabilities.•Examples of preliminary data collected.•Overview of the ongoing project tasks and future project developments.•Discussion on the potential research and knowledge achievements.
HerMES: The SPIRE confusion limit Nguyen, H. T.; Schulz, B.; Levenson, L. ...
Astronomy & astrophysics,
07/2010, Letnik:
518, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We report on the sensitivity of SPIRE photometers on the Herschel Space Observatory. Specifically, we measure the confusion noise from observations taken during the science demonstration phase of the ...Herschel Multi-tiered Extragalactic Survey. Confusion noise is defined to be the spatial variation of the sky intensity in the limit of infinite integration time, and is found to be consistent among the different fields in our survey at the level of 5.8, 6.3 and 6.8 mJy/beam at 250, 350 and 500 μm, respectively. These results, together with the measured instrument noise, may be used to estimate the integration time required for confusion limited maps, and provide a noise estimate for maps obtained by SPIRE.
Emission at far-infrared wavelengths makes up a significant fraction of the total light detected from galaxies over the age of Universe. Herschel provides an opportunity for studying galaxies at the ...peak wavelength of their emission. Our aim is to provide a benchmark for models of galaxy population evolution and to test pre-existing models of galaxies. With the Herschel Multi-tiered Extra-galactic survey, HerMES, we have observed a number of fields of different areas and sensitivity using the SPIRE instrument on Herschel. We have determined the number counts of galaxies down to similar to 20 mJy. Our constraints from directly counting galaxies are consistent with, though more precise than, estimates from the BLAST fluctuation analysis. We have found a steep rise in the Euclidean normalised counts \textless 100 mJy. We have directly resolved similar to 15% of the infrared extra-galactic background at the wavelength near where it peaks.
We present the cross-identification and source photometry techniques used to process Herschel SPIRE imaging taken as part of the Herschel Multi-Tiered Extragalactic Survey (HerMES). ...Cross-identifications are performed in map-space so as to minimize source-blending effects. We make use of a combination of linear inversion and model selection techniques to produce reliable cross-identification catalogues based on Spitzer MIPS 24-μm source positions. Testing on simulations and real Herschel observations shows that this approach gives robust results for even the faintest sources (S250∼ 10 mJy). We apply our new technique to HerMES SPIRE observations taken as part of the science demonstration phase of Herschel. For our real SPIRE observations, we show that, for bright unconfused sources, our flux density estimates are in good agreement with those produced via more traditional point source detection methods (SUSSEXtractor) by Smith et al. When compared to the measured number density of sources in the SPIRE bands, we show that our method allows the recovery of a larger fraction of faint sources than these traditional methods. However, this completeness is heavily dependent on the relative depth of the existing 24-μm catalogues and SPIRE imaging. Using our deepest multiwavelength data set in the GOODS-N, we estimate that the use of shallow 24-μm catalogues in our other fields introduces an incompleteness at faint levels of between 20–40 per cent at 250 μm.
The Herschel Space Observatory enables us to accurately measure the bolometric output of starburst galaxies and active galactic nuclei (AGN) by directly sampling the peak of their far-infrared (IR) ...emission. Here we examine whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved over the last 80% of the age of the Universe. We discuss possible consequences for the determination of star-formation rates (SFR) and any evidence for a major change in their star-formation properties. We use Herschel deep extragalactic surveys from 100 to 500 μm to compute total IR luminosities in galaxies down to the faintest levels, using PACS and SPIRE in the GOODS-North field (PEP and HerMES key programs). An extension to fainter luminosities is done by stacking images on 24 μm prior positions. We show that measurements in the SPIRE bands can be used below the statistical confusion limit if information at higher spatial resolution is used, e.g. at 24 μm, to identify “isolated” galaxies whose flux is not boosted by bright neighbors. Below z ~ 1.5, mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15 dex), therefore similar to z ~ 0 galaxies, over three decades in luminosity below the regime of ultra-luminous IR galaxies (ULIRGs, LIR ≥ 1012 $L_{\sun}$). This narrow distribution is puzzling when considering the range of physical processes that could have affected the SED of these galaxies. Extrapolations from only one of the 160 μm, 250 μm or 350 μm bands alone tend to overestimate the total IR luminosity. This may be explained by the lack of far-IR constraints around and above ~150 μm (rest-frame) before Herschel on those templates. We also note that the dust temperature of luminous IR galaxies (LIRGs, LIR ≥ 1011 $L_{\sun}$) around z ~ 1 is mildly colder by 10–15% than their local analogs and up to 20% for ULIRGs at z ~ 1.6 (using a single modified blackbody-fit to the peak far-IR emission with an emissivity index of β = 1.5). Above z = 1.5, distant galaxies are found to exhibit a substantially larger mid- over far-IR ratio, which could either result from stronger broad emission lines or warm dust continuum heated by a hidden AGN. Two thirds of the AGNs identified in the field with a measured redshift exhibit the same behavior as purely star-forming galaxies. Hence a large fraction of AGNs harbor coeval star formation at very high SFR and in conditions similar to purely star-forming galaxies.
We investigate the potential of submm-mm and submm-mm-radio photometric redshifts using a sample of mm-selected sources as seen at 250, 350 and 500μm by the SPIRE instrument on Herschel. From a ...sample of 63 previously identified mm sources with reliable radio identifications in the Great Observatories Origins Deep Survey North and Lockman Hole North fields, 46 (73 per cent) are found to have detections in at least one SPIRE band. We explore the observed submm/mm colour evolution with redshift, finding that the colours of mm sources are adequately described by a modified blackbody with constant optical depth τ= (ν/nu
0)β, where β=+1.8 and ν0=c/100 μm. We find a tight correlation between dust temperature and IR luminosity. Using a single model of the dust temperature and IR luminosity relation, we derive photometric redshift estimates for the 46 SPIRE-detected mm sources. Testing against the 22 sources with known spectroscopic or good quality optical/near-IR photometric redshifts, we find submm/mm photometric redshifts offer a redshift accuracy of |Δz|/(1 +z) = 0.16 (〈|Δz|〉= 0.51). Including constraints from the radio-far-IR correlation, the accuracy is improved to |Δz|/(1 +z) = 0.15 (〈|Δz|〉= 0.45). We estimate the redshift distribution of mm-selected sources finding a significant excess at z > 3 when compared to ∼ 850 μm selected samples.
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