Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Charting the New Frontier of the Cosmic Microwave Background Polarization

4 pages, to appear in SF2A 2005 proceedingsInternational audienceThe anisotropies of the cosmic microwave background are a gold mine for cosmology and fundamental physics. ESA's Planck satellite should soon extract all information from the temperature vein but will be limited concerning the measurement of the degree of polarization of the anisotropies. This polarization information allows new independent tests of the standard cosmological paradigm, improves knowledge of cosmological parameters and last but not least is the best window available for constraining the physics of the very early universe, particularly the expected background of primordial gravitational waves. But exploiting this vein will be a challenge, since the sensitivity required is {\em at least} 10 times better than what Planck might achieve at best, with the necessary matching level of control of all systematics effects, both instrumental and astrophysical (foregrounds). We here recall the cosmological context and the case for CMB polarization studies. We also briefly introduce the SAMPAN project, a design study at CNES that aims at detecting the primoridal gravitational wave background for a tensor to scalar ratio T/S as small as 0.001

Improved mm-wave photometry for kinetic inductance detectors

Context. We have developed a dual-band (140 and 220 GHz) mm-wave imaging camera based on superconducting kinetic inductance detector (KID) arrays. Each array contains 132 superconducting resonators whose resonant frequencies are shifted by mm-wave photons absorption. The read out is achieved with a single electronics chain per band, taking advantage of the intrinsic KID frequency-domain multiplexability. The arrays are easily scalable and well adapted for future large format focal plane instruments. NIKA (formerly Neel IRAM KID Array, now New IRAM KID Array) has been specifically designed for the IRAM 30 m telescope at Pico Veleta, and is one of the first instruments using KIDs to have made measurements of astronomical sources. Aims. In this Letter we describe the solutions adopted to improve the calibration accuracy and the sensitivity of the instrument, and we report on the outcome of the 3rd NIKA observing run of October, 2011. Methods. We use a fast electronic modulation of the readout tone for each KID pixel in order to linearize the instrument calibration, which we track with measurements of planets. We also adopt a new design of the KIDs, sensitive to both polarizations, to increase the amount of radiation absorbed and thus the optical efficiency of the system. Results. We measured an average sensitivity on the sky of 21 mJys(0.5) per beam at 140 GHz and 140 mJys(0.5) at 220 GHz in the best observing conditions (tau(220) similar or equal to 0.2) after atmospheric noise decorrelation. The sensitivity at 220 GHz was limited by the atmospheric attenuation and loading as well as a reduction in the spectral bandwidth due to a misplaced filter. We found the repeatability in the photometry over the entire observing run to be better than 10% in both bands, thus demonstrating a significant improvement over the previous runs. We also find good agreement between NIKA measurements of faint astronomical sources and previous measurements of the same sources

The NIKA 2011 run: results and perspectives towards a permanent camera for the Pico Veleta observatory

The Neel Iram Kids Array (NIKA) is a prototype instrument devoted to millimetric astronomy that has been designed to be mounted at the focal plane of the IRAM 30m telescope at Pico Veleta (Spain). After the runs of 2009 and 2010, we carried a third technical run in October 2011. In its latest configuration, the instrument consists of a dual-band camera, with bands centered at 150 GHz and 220 GHz, each of them equipped with 116 pixels based on Lumped Element Kinetic Inductance Detectors. During the third run we tested many improvements that will play a crucial role in the development of the final, kilopixel sized camera. In particular, a new geometry based on a Hilbert curve has been adopted for the absorbing area of the LEKIDs, that makes the detectors dual-polarization sensitive. Furthermore, a different acquisition strategy has been adopted, which has allowed us to increase the photometric accuracy of the measurements, a fundamental step in order to get scientifically significant data. In this paper we describe the main characteristics of the 2011 NIKA instrument and outline some of its key features, discusse the results we obtained and give a brief outlook on the future NIKA camera which will be installed permanently on site

Archeops: A High Resolution, Large Sky Coverage Balloon Experiment for Mapping CMB Anisotropies

44 pages, 24 figures Full resolution postscript at http://publi.archeops.orgArcheops is a balloon-borne instrument dedicated to measuring cosmic microwave background (CMB) temperature anisotropies at high angular resolution (8 arcminutes) over a large fraction (25%) of the sky in the millimetre domain. Based on Planck High Frequency Instrument (HFI) technology, cooled bolometers (0.1 K) scan the sky in total power mode with large circles at constant elevation. During the course of a 24-hour Arctic-night balloon flight, Archeops will observe a complete annulus on the sky in four frequency bands centered at 143, 217, 353 and 545 GHz with an expected sensitivity to CMB fluctuations of \\~100muK for each of the 90 thousand 20 arcminute average pixels. We describe the instrument and its performance obtained during a test flight from Trapani (Sicily) to Spain in July 1999