1,721,259 research outputs found
The European Large Area ISO Survey
No full textThe European Large Area ISO Survey (ELAIS) was the largest Open Time survey on the Infrared Space Observatory (ISO). It was designed to explore obscured galaxies and hence quantify the recent star-formation history of the Universe. The final reanalysis of the data has been completed and a band-merged catalogue with associations across many wavelengths compiled and released the data to the global astronomical community (http://astro.imperial.ac.uk/Elais/). This paper summarises some of the key results
Rise of the titans: a dusty, hyper-luminous “870 µm riser” galaxy at z~6
No full textWe report the detection of ADFS-27, a dusty, starbursting major merger at a redshift of z=5.655, using the Atacama Large Millimeter/submillimeter Array (ALMA). ADFS-27 was selected from Herschel/SPIRE and APEX/LABOCA data as an extremely red “870 m riser” (i.e., S250
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FIRST extra-galactic surveys: practical considerations
No full textWe discuss some of the practical considerations that need to be made in the design of extra-galactic field surveys using FIRST. We investigate the various limitations that confusion noise imposes on possible FIRST surveys and the benefits of super resolution or decconvolution techniques. We consider the possible sizes and depths of survey fields in order to meet many of the scientific objectives of the FIRST mission. In particular we discuss the factors that need to be taken into account in selecting the survey fields. The final choice of fields will be influenced by the location of other surveys that are currently being planned; so it is vital that the FIRST community begin debating this issue now. We conclude that a substantial survey of order of 100 square degrees is likely to be sited in the region of the SIRTF Legacy survey, SWIRE
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Galaxy populations from deep ISO surveys
No full textI discuss some of the main extra-galactic field surveys which have been undertaken by the Infrared Space Observatory (ISO). I review the findings from the source counts analysies and then examine some of the more recent detailed investigations into the explicit nature of the populations that make up these source counts
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Large scale structure from SWIRE
No full textWe show that the Spitzer Wide-area InfraRed Extragalactic Legacy Survey (SWIRE) will provide the galaxy catalogues that can be used to measure the clustering of galaxies and its evolution for star-forming galaxies and galaxies selected on the basis of their stellar mass. High signal-to-noise measurements will be possible on co-moving scales around 10h(-1)Mpc; out to z similar to 2 - 2.5; after subdividing galaxy samples by factors of 10; or in redshift intervals of Delta z approximate to 0.2
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The European Large Area ISO Survey: a pathfinder for SIRTF.
No full textThe European Large Area ISO Survey, ELAIS, was the largest Open Time survey on the Infrared Space Observatory, ISO. It was designed to explore obscured galaxies and hence quantify the recent star-formation history of the Universe. We have recently completed our final reanalysis of the data, compiled band-merged catalogue products with associations across many wavelengths and released the data to the global astronomical community (http://astro.imperial.ac.uk/elais/). This paper summarizes some of the key results
Bayesian methods of astronomical source extraction
No full textWe present two new source extraction methods, based on Bayesian model selection and using the Bayesian information criterion. The first is a source detection filter, which is able to simultaneously detect point sources and estimate the image background. The second is an advanced photometry technique that measures the flux, position (to subpixel accuracy), local background, and point-spread function. We apply the source detection filter to simulated Herschel SPIRE data and demonstrate the filter's ability to both detect point sources and simultaneously estimate the image background. We use the photometry method to analyze a simple simulated image containing a source of unknown flux, position, and point-spread function; we not only accurately measure these parameters but also determine their uncertainties (using Markov chain Monte Carlo sampling). The method also characterizes the nature of the source (distinguishing between a point source and an extended source). We demonstrate the effect of including additional prior knowledge. Prior knowledge of the point-spread function increases the precision of the flux measurement, while prior knowledge of the background has only a small impact. In the presence of higher noise levels, we show that prior positional knowledge (such as might arise from a strong detection in another wave band) allows us to accurately measure the source flux even when the source is too faint to be detected directly. These methods are incorporated in SUSSEXtractor, the source extraction pipeline for the forthcoming Akari Far-Infrared Surveyor all-sky survey. They are also implemented in a stand-alone, beta-version tool that is freely available
Statistical constraints on the IR galaxy number counts and cosmic IR background from the Spitzer GOODS survey
No full textWe perform fluctuation analyses on the data from the Spitzer GOODS survey (epoch one) in the Hubble Deep Field North (HDF-N). We fit a parameterised power-law number count model of the form dN/dS = N_o S^{-\delta} to data from each of the four Spitzer IRAC bands, using Markov Chain Monte Carlo (MCMC) sampling to explore the posterior probability distribution in each case. We obtain best-fit reduced chi-squared values of (3.43 0.86 1.14 1.13) in the four IRAC bands. From this analysis we determine the likely differential faint source counts down to , over two orders of magnitude in flux fainter than has been previously determined. From these constrained number count models, we estimate a lower bound on the contribution to the Infra-Red (IR) background light arising from faint galaxies. We estimate the total integrated background IR light in the Spitzer GOODS HDF-N field due to faint sources. By adding the estimates of integrated light given by Fazio et al (2004), we calculate the total integrated background light in the four IRAC bands. We compare our 3.6 micron results with previous background estimates in similar bands and conclude that, subject to our assumptions about the noise characteristics, our analyses are able to account for the vast majority of the 3.6 micron background. Our analyses are sensitive to a number of potential systematic effects; we discuss our assumptions with regards to noise characteristics, flux calibration and flat-fielding artifacts
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Statistical constraints on the IR galaxy number counts and cosmic IR background from the Spitzer GOODS survey
No full textWe perform fluctuation analyses on the data from the Spitzer GOODS survey (epoch one) in the Hubble Deep Field North (HDF-N). We fit a parameterised power-law number count model of the form dN/dS = N_o S^{-\delta} to data from each of the four Spitzer IRAC bands, using Markov Chain Monte Carlo (MCMC) sampling to explore the posterior probability distribution in each case. We obtain best-fit reduced chi-squared values of (3.43 0.86 1.14 1.13) in the four IRAC bands. From this analysis we determine the likely differential faint source counts down to , over two orders of magnitude in flux fainter than has been previously determined. From these constrained number count models, we estimate a lower bound on the contribution to the Infra-Red (IR) background light arising from faint galaxies. We estimate the total integrated background IR light in the Spitzer GOODS HDF-N field due to faint sources. By adding the estimates of integrated light given by Fazio et al (2004), we calculate the total integrated background light in the four IRAC bands. We compare our 3.6 micron results with previous background estimates in similar bands and conclude that, subject to our assumptions about the noise characteristics, our analyses are able to account for the vast majority of the 3.6 micron background. Our analyses are sensitive to a number of potential systematic effects; we discuss our assumptions with regards to noise characteristics, flux calibration and flat-fielding artifacts
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HerMES: a search for high-redshift dusty galaxies in the HerMES Large Mode Survey - catalogue, number counts and early results
No full textSelecting sources with rising flux densities towards longer wavelengths from Herschel/SPIRE maps is an efficient way to produce a catalogue rich in high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this approach has already been confirmed by spectroscopic follow-up observations, but the previously available catalogues made this way are limited by small survey areas. Here we apply a map-based search method to 274 deg 2 of the HerMES Large Mode Survey (HeLMS) and create a catalogue of 477 objects with SPIRE flux densities S 500 >S 350 >S 250 and a 5s cut-off S 500 > 52 mJy. From this catalogue we determine that the total number of these "red" sources is at least an order of magnitude higher than predicted by galaxy evolution models. These results are in agreement with previous findings in smaller HerMES fields; however, due to our significantly larger sample size we are also able to investigate the shape of the red source counts for the first time. We have obtained spectroscopic redshift measurements for two of our sources using the Atacama Large Millimeter/submillimeter Array (ALMA). The redshifts z = 5.1 and z = 3.8 confirm that with our selection method we can indeed find high-redshift dusty star-forming galaxies
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