FIRBACK: II. Data Reduction and Calibration of the 170 micron ISO Deep Cosmological Survey

We present the final reduction and calibration of the FIRBACK ISOPHOT data. FIRBACK is a deep cosmological survey performed at 170 microns. This paper deals with the ISOPHOT C200 camera with the C160 filter. We review the whole data reduction process and compare our final calibration with DIRBE (for the extended emission) and IRAS (for point sources). The FIRBACK source extraction and galaxy counts is discussed in a companion paper (Dole et al., 2001).Comment: Accepted for publication in A&A. 9 pages, includes new aa.cls. Also available (with better quality figures) at http://wwwfirback.ias.u-psud.fr and http://mips.as.arizona.edu/~hdole/firback (new aa.cls is here

Power Spectrum Analysis of Far-IR Background Fluctuations in 160 Micron Maps From the Multiband Imaging Photometer for Spitzer

We describe data reduction and analysis of fluctuations in the cosmic far-IR background (CFIB) in observations with the Multiband Imaging Photometer for Spitzer (MIPS) instrument 160 micron detectors. We analyzed observations of an 8.5 square degree region in the Lockman Hole, part of the largest low-cirrus mapping observation with this instrument. We measured the power spectrum of the CFIB in these observations by fitting a power law to the IR cirrus component, the dominant foreground contaminant, and subtracting this cirrus signal. The CFIB power spectrum in the range 0.2 arc min^{-1} <k< 0.5 arc min^{-1} is consistent with previous measurements of a relatively flat component. However, we find a large power excess at low k, which falls steeply to the flat component in the range 0.03 arc min^{-1} <k< 0.1 arc min^{-1}. This low-k power spectrum excess is consistent with predictions of a source clustering "signature". This is the first report of such a detection in the far-IR.Comment: This is the version of the paper accepted by A&A, which includes various changes and new material. The superior-quality PDF with integrated figures may be downloaded at http://www-astro.lbl.gov/~bruce/spitzerpaper1/cfibaa_pub.pdf 15 pages, figures integrated with text. This paper supersedes astro-ph/050416

Microwave and radio emission of dusty star-forming galaxies: Implication for the cosmic radio background

We use the most up-to-date cosmological evolution models of star-forming (SF) galaxies and radio sources to compute the extragalactic number counts and the cosmic background from 408MHz to 12THz. The model of SF galaxies reproduces the constraints obtained by Spitzer, Herschel, and ground-based submm/mm experiments: number counts, redshift distribution of galaxies, cosmic background intensity and anisotropies. The template SEDs of this model are extrapolated to the radio adding synchrotron, free-free, and spinning dust emissions. To fix the synchrotron intensity, we use the IR/radio flux ratio, q70, and a spectral index beta=-3. For a constant q70, our model added to the AGN contribution provides a good fit to the number counts from 12THz to 408MHz and to the CIB. Spinning dust accounts for up to 20% of the cosmic microwave background produced by SF galaxies, but for less than 10% of the total background when AGN are included. The SF galaxies account for 77.5% of the number counts at 1.4GHz for a flux of 1e-4Jy. However, the model does not explain the CRB measured with the ARCADE2 experiment. Considering the case when q70 decreases strongly with redshift, this still does not explain the ARCADE2 results. It also yields to an overestimate of the low-flux number counts in the radio. Thus, we rule out a steep variation of q70 with redshift at least for z<3.5. Adding a population of faint SF galaxies at high redshift (Lir<1e11Lsun and 4<z<6), which would reproduce the ARCADE2 results, leads to predictions of the CIB much higher than what is observed, ruling out this as the explanation for the ARCADE2 results. Considering our findings and previous studies, we conclude that if the radio emission measured by ARCADE2 is astrophysical in origin, it has to originate in the Galaxy or in a new kind of radio sources (with no mid- to far-IR counterparts) or emission mechanism still to be discovered.Comment: accepted for publication by A&A, modification of one citatio

Comments on the paper "The initial conditions of isolated star formation - VI. SCUBA mapping of prestellar cores" (Kirk et al. 2005)

In their survey paper of prestellar cores with SCUBA, Kirk et al. (2005) have discarded two of our papers on L183 (Pagani et al. 2003, 2004). However these papers bring two important pieces of information that they cannot ignore. Namely, the real structure of L183 and the very poor correlation between submillimeter and far infrared (FIR) dust emission beyond \Avb $\approx$ 15 mag. Making the erroneous assumption that it is the same dust that we are seeing in emission at both 200 and 850 $\mu$m, they derive constant temperatures which are only approximate, and column densities which are too low. In fact dust temperatures do decrease inside dark clouds and the FIR emission is only tracing the outer parts of the dark clouds (Pagani et al. 2004

Determination of the cosmic far-infrared background level with the ISOPHOT instrument

The cosmic infrared background (CIRB) consists mainly of the integrated light of distant galaxies. In the far-infrared the current estimates of its surface brightness are based on the measurements of the COBE satellite. Independent confirmation of these results is still needed from other instruments. In this paper we derive estimates of the far-infrared CIRB using measurements made with the ISOPHOT instrument aboard the ISO satellite. The results are used to seek further confirmation of the CIRB levels that have been derived by various groups using the COBE data. We study three regions of very low cirrus emission. The surface brightness observed with the ISOPHOT instrument at 90, 150, and 180 um is correlated with hydrogen 21 cm line data from the Effelsberg radio telescope. Extrapolation to zero hydrogen column density gives an estimate for the sum of extragalactic signal plus zodiacal light. The zodiacal light is subtracted using ISOPHOT data at shorter wavelengths. Thus, the resulting estimate of the far-infrared CIRB is based on ISO measurements alone. In the range 150 to 180 um, we obtain a CIRB value of 1.08+-0.32+-0.30 MJy/sr quoting statistical and systematic errors separately. In the 90 um band, we obtain a 2-sigma upper limit of 2.3 MJy/sr. The estimates derived from ISOPHOT far-infrared maps are consistent with the earlier COBE results.Comment: Accepted for publication in A&A, 17 page

Dissecting the high-z interstellar medium through intensity mapping cross-correlations

We explore the detection, with upcoming spectroscopic surveys, of three-dimensional power spectra of emission line fluctuations produced in different phases of the Interstellar Medium (ISM) by ionized carbon, ionized nitrogen and neutral oxygen at redshift z>4. The emission line [CII] from ionized carbon at 157.7 micron, and multiple emission lines from carbon monoxide, are the main targets of planned ground-based surveys, and an important foreground for future space-based surveys like the Primordial Inflation Explorer (PIXIE). However, the oxygen [OI] (145.5 micron) line, and the nitrogen [NII] (121.9 micron and 205.2 micron) lines, might be detected in correlation with [CII] with reasonable signal-to-noise ratio (SNR). These lines are important coolants of both the neutral and the ionized medium, and probe multiple phases of the ISM. We compute predictions of the three-dimensional power spectra for two surveys designed to target the [CII] line, showing that they have the required sensitivity to detect cross-power spectra with the [OI] line, and the [NII] lines with sufficient SNR. The importance of cross-correlating multiple lines is twofold. On the one hand, we will have multiple probes of the different phases of the ISM, which is key to understand the interplay between energetic sources, the gas and dust at high redshift. This kind of studies will be useful for a next-generation space observatory such as the NASA Far-IR Surveyor. On the other end, emission lines from external galaxies are an important foreground when measuring spectral distortions of the Cosmic Microwave Background spectrum with future space-based experiments like PIXIE; measuring fluctuations in the intensity mapping regime will help constraining the mean amplitude of these lines, and will allow us to better handle this important foreground.Comment: 13 pages, 2 table, 7 figures, Accepted for publication in Ap