Jean-Loup Puget

Modelling infrared galaxy evolution using a phenomenological approach

To characterize the cosmological evolution of the sources contributing to the infrared extragalactic background, we have developed a phenomenological model that constrains in a simple way the evolution of the galaxy luminosity function with redshift, and fits all the existing source counts and redshift distributions, cosmic infrared background intensity and fluctuation observations, from the mid-infrared to the submillimetre range. The model is based on template spectra of starburst and normal galaxies, and on the local infrared luminosity function. Although the cosmic infrared background can be modelled with very different luminosity functions as long as the radiation production with redshift is the right one, the number counts and the anisotropies of the unresolved background imply that the luminosity function must change dramatically with redshift, with a rapid evolution of the high-luminosity sources (L > 3 × 10 11 L� ) from z = 0t oz = 1, which then stay rather constant up to redshift z = 5. The derived evolution of the infrared luminosity function may be linked to a bimodal star formation process: one associated with the quiescent and passive phase of the galaxy evolution, and one associated with the starburst phase, triggered by merging and interactions. The latter dominates the infrared and submillimetre output energy of the Universe. The model is intended as a convenient tool to plan further observations, as illustrated through predictions for Herschel, Planck and ALMA observations. Our model predictions for given wavelengths, together with some useful routines, are available for general use.

Dusty Infrared Galaxies: Sources of the Cosmic Infrared Background

▪ AbstractThe discovery of the Cosmic Infrared Background (CIB) in 1996, together with recent cosmological surveys from the mid-infrared to the millimeter, have revolutionized our view of star formation at high redshifts. It has become clear, in the last decade, that a population of galaxies that radiate most of their power in the far-infrared (the so-called infrared galaxies) contributes an important part of the whole galaxy build-up in the Universe. Since 1996, detailed (and often painful) investigations of the high-redshift infrared galaxies have resulted in the spectacular progress covered in this review. We outline the nature of the sources of the CIB, including their star-formation rate, stellar and total mass, morphology, metallicity, and clustering properties. We discuss their contribution to the stellar content of the Universe and their origin in the framework of the hierarchical growth of structures. We finally discuss open questions for a scenario of their evolution up to the present-day galaxies.

ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster

We present the results of the first extensive mid-infrared (IR) imaging survey of the rho Ophiuchi embedded cluster, performed with the ISOCAM camera on board the ISO satellite. The main molecular cloud L1688, as well as L1689N and L1689S, have been completely surveyed for point sources at 6.7 and 14.3 micron. A total of 425 sources are detected including 16 Class I, 123 Class II, and 77 Class III young stellar objects (YSOs). Essentially all of the mid-IR sources coincide with near-IR sources, but a large proportion of them are recognized for the first time as YSOs. Our dual-wavelength survey allows us to identify essentially all the YSOs with IR excess in the embedded cluster down to Fnu ~ 10 - 15 mJy. It more than doubles the known population of Class II YSOs and represents the most complete census to date of newly formed stars in the rho Ophiuchi central region. The stellar luminosity function of the complete sample of Class II YSOs is derived with a good accuracy down to L= 0.03 Lsun. A modeling of this lumino- sity function, using available pre-main sequence tracks and plausible star for- mation histories, allows us to derive the mass distribution of the Class II YSOs which arguably reflects the IMF of the embedded cluster. We estimate that the IMF in rho Ophiuchi is well described by a two-component power law with a low- mass index of -0.35+/-0.25, a high-mass index of -1.7 (to be compared with the Salpeter value of -1.35), and a break occurring at M = 0.55+/-0.25 Msun. This IMF is flat with no evidence for a low-mass cutoff down to at least 0.06 Msun.

Planck pre-launch status: The HFI instrument, from specification to actual performance

Context. The High Frequency Instrument (HFI) is one of the two focal instruments of the Planck mission. It will observe the whole sky in six bands in the 100 GHz-1 THz range. Aims: The HFI instrument is designed to measure the cosmic microwave background (CMB) with a sensitivity limited only by fundamental sources: the photon noise of the CMB itself and the residuals left after the removal of foregrounds. The two high frequency bands will provide full maps of the submillimetre sky, featuring mainly extended and point source foregrounds. Systematic effects must be kept at negligible levels or accurately monitored so that the signal can be corrected. This paper describes the HFI design and its characteristics deduced from ground tests and calibration. Methods: The HFI instrumental concept and architecture are feasible only by pushing new techniques to their extreme capabilities, mainly: (i) bolometers working at 100 mK and absorbing the radiation in grids; (ii) a dilution cooler providing 100 mK in microgravity conditions; (iii) a new type of AC biased readout electronics and (iv) optical channels using devices inspired from radio and infrared techniques. Results: The Planck-HFI instrument performance exceeds requirements for sensitivity and control of systematic effects. During ground-based calibration and tests, it was measured at instrument and system levels to be close to or better than the goal specification.

Polycyclic Aromatic Hydrocarbon Contribution to the Infrared Output Energy of the Universe at z 2

We present an updated phenomenological galaxy evolution model to fit the Spitzer 24, 70, and 160 μm number counts, as well as all the previous mid- and far-infrared observations. Only a minor change of the comoving luminosity density distribution in the previous model (Lagache, Dole, & Puget), combined with a slight modification of the starburst template spectra mainly between 12 and 30 μm, are required to fit all the data available. We show that the peak in the Spitzer Multiband Imaging Photometer 24 μm counts is dominated by galaxies with redshift between 1 and 2, with a nonnegligible contribution from the z ≥ 2 galaxies (~30% at S = 0.2 mJy). The very close agreement between the model and number counts at 15 and 24 μm strikingly implies that (1) the polycyclic aromatic hydrocarbon features remain prominent in the redshift band 0.5-2.5 and (2) the IR energy output has to be dominated by ~3 × 1011 L⊙ to ~3 × 1012 L⊙ galaxies from redshift 0.5 to 2.5. Combining Spitzer with Infrared Space Observatory deep cosmological surveys gives for the first time an unbiased view of the infrared universe from z = 0 to 2.5.

A calculation of confusion noise due to infrared cirrus

General expressions are developed for the statistical errors to be expected in photometric measurements due to confusion in a background of fluctuating surface brightness. Backgrounds actually observed in the far infrared by the IRAS satellite are used to calculate tables of these error expressions for two simple measurement techniques. The confusion noise limited sensitivities for NASAs planned Space Infrared Telescope Facility and the European Space Agencys Infrared Space Observatory are estimated at a wavelength of 100 μm from these tables

The European Large Area ISO Survey – II. Mid‐infrared extragalactic source counts

We present preliminary source counts at 6.7um and 15um from the Preliminary Analysis of the European Large Area ISO survey, with limiting flux densities of \~2mJy at 15um&~1mJy at 6.7um. We separate the stellar contribution from the extragalactic using identifications with APM sources made with the likelihood ratio technique. We quantify the completeness&reliability of our source extraction using (a) repeated observations over small areas, (b) cross-IDs with stars of known spectral type, (c) detections of the PSF wings around bright sources, (d) comparison with independent algorithms. Flux calibration at 15um was performed using stellar IDs; the calibration does not agree with the pre-flight estimates, probably due to effects of detector hysteresis and photometric aperture correction. The 6.7um extragalactic counts are broadly reproduced in the Pearson&Rowan-Robinson model, but the Franceschini et al. (1997) model underpredicts the observed source density by ~0.5-1 dex, though the photometry at 6.7um is still preliminary. At 15um the extragalactic counts are in excellent agreement with the predictions of the Pearson&Rowan-Robinson (1996), Franceschini et al. (1994), Guiderdoni et al. (1997) and the evolving models of Xu et al. (1998), over 7 orders of magnitude in 15um flux density. The counts agree with other estimates from the ISOCAM instrument at overlapping flux densities (Elbaz et al. 1999), provided a consistent flux calibration is used. Luminosity evolution at a rate of (1+z)^3, incorporating mid-IR spectral features, provides a better fit to the 15um differential counts than (1+z)^4 density evolution. No-evolution models are excluded, and implying that below around 10mJy at 15um the source counts become dominated by an evolving cosmological population of dust-shrouded starbursts and/or active galaxies.

A deep VLA survey at 20 cm of the ISO ELAIS survey regions

We have used the Very Large Array (VLA) in C configuration to carry out a sensitive 20-cm radio survey of regions of sky that have been surveyed in the far-infrared (FIR) over the wavelength range 5--200 μm with ISO (Infrared Space Observatory) as part of the European Large-Area ISO Survey (ELAIS). As usual in surveys based on a relatively small number of overlapping VLA pointings, the flux limit varies over the area surveyed: from a 5σ limit of 0.135 mJy over an area of 0.12 deg2 to 1.15 mJy or better over the whole region covered of 4.22 deg2. In this paper we present the complete radio catalogue of 867 sources, 428 of which form a complete sample in the flux range 0.2--1.0 mJy. These regions of sky have previously been surveyed to shallower flux limits at 20 cm with the VLA as part of the VLA D configuration NVSS (full width at half-maximum, FWHM=45 arcsec) and VLA B configuration FIRST (FWHM=5 arcsec) surveys. Our whole survey has a nominal 5σ flux limit a factor of 2 below that of the NVSS; 3.4 deg2 of the survey reaches the nominal flux limit of the FIRST survey and 1.5 deg2 reaches 0.25 mJy, a factor of 4 below the nominal FIRST survey limit. In addition, our survey is at a resolution intermediate between the two surveys and thus is well suited for a comparison of the reliability and resolution-dependent surface brightness effects that affect interferometric radio surveys. We have carried out a detailed comparison of our own survey and these two independent surveys in order to assess the reliability and completeness of each. Considering the whole sample, we found that to the 5σ nominal limits of 2.3 and 1.0 mJy, respectively, the NVSS and FIRST surveys have a completeness of 96+2-3 and 89+2-3 per cent and a reliability of 99+1-2 and 94+2-2 per cent.

Linking stellar mass and star formation in Spitzer MIPS 24 μm galaxies

We present deep K-s 83 mu Jy ( the similar to 80% completeness limit of the Spitzer/GTO 24 mu m catalog); 36% of our galaxies have spectroscopic redshifts ( mostly at z 10(12) L-circle dot) at redshifts z less than or similar to 2-3. Massive star-forming galaxies at redshifts 2 less than or similar to z less than or similar to 3 are characterized by very high star formation rates (SFR > 500 M-circle dot yr(-1)), and some of them are able to construct a mass of approximate to 10(10) - 10(11) M-circle dot in a single burst lifetime ( similar to 0.01 - 0.1 Gyr). At lower redshifts z less than or similar to 2, massive star-forming galaxies are also present but appear to be building their stars on long timescales, either quiescently or in multiple modest burstlike episodes. At redshifts z similar to 1 2, the ability of the burstlike mode to produce entire galaxies in a single event is limited to some lower ( M less than or similar to 7; 10(10) M-circle dot) mass systems, and it is basically negligible at z less than or similar to 1. Our results support a scenario in which star formation activity is differential with assembled stellar mass and redshift, and where the relative importance of the burstlike mode proceeds in a downsizing way from high to low redshifts.

Planck pre-launch status: High Frequency Instrument polarization calibration

The High Frequency Instrument of Planck will map the entire sky in the millimeter and sub-millimeter domain from 100 to 857 GHz with unprecedented sensitivity to polarization (ΔP/Tcmb ∼ 4 × 10 −6 for P either Q or U and Tcmb � 2.7 K) at 100, 143, 217 and 353 GHz. It will lead to major improvements in our understanding of the cosmic microwave background anisotropies and polarized foreground signals. Planck will make high resolution measurements of the E-mode spectrum (up to � ∼ 1500) and will also play a prominent role in the search for the faint imprint of primordial gravitational waves on the CMB polarization. This paper addresses the effects of calibration of both temperature (gain) and polarization (polarization efficiency and detector orientation) on polarization measurements. The specific requirements on the polarization parameters of the instrument are set and we report on their pre-flight measurement on HFI bolometers. We present a semi-analytical method that exactly accounts for the scanning strategy of the instrument as well as the combination of different detectors. We use this method to propagate errors through to the CMB angular power spectra in the particular case of Planck-HFI, and to derive constraints on polarization parameters. We show that in order to limit the systematic error to 10% of the cosmic variance of the E-mode power spectrum, uncertainties in gain, polarization efficiency and detector orientation must be below 0.15%, 0.3% and 1 ◦ respectively. Pre-launch ground measurements reported in this paper already fulfill these requirements.