Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds

TL;DR

The paper constructs a full-sky, temperature-corrected dust emission map by coherently merging DIRBE and ISSA data while rigorously removing zodiacal light, point sources, and extragalactic contaminants. It derives dust temperature from 100 and 240 μm emissions to translate 100 μm flux into dust column density, calibrated to Galactic reddening with elliptical galaxies, achieving ~16% reddening accuracy—twice the reliability of Burstein & Heiles estimates. A careful analysis separates the cosmic infrared background, detecting isotropic flux at 140 μm and 240 μm, and provides insights into dust structure, gas–dust variations, and high-latitude extinction. The resulting maps serve as improved reddening estimators and foreground models for CMBR experiments, soft X-ray absorption studies, and large-scale structure analyses, and are made publicly available for broad use.

Abstract

We present a full sky 100 micron map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 micron and 240 micron data, we have constructed a map of the dust temperature, so that the 100 micron map can be converted to a map proportional to dust column density. The result of these manipulations is a map with DIRBE-quality calibration and IRAS resolution. To generate the full sky dust maps, we must first remove zodiacal light contamination as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 micron DIRBE map against the Leiden- Dwingeloo map of H_I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 micron flux. For the 100 micron map, no significant CIB is detected. In the 140 micron and 240 micron maps, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 \pm 13 nW/m^2/sr at 140 micron, and 17 \pm 4 nW/m^2/sr at 240 micron (95% confidence). This integrated flux is ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles estimates in regions of low and moderate reddening. These dust maps will also be useful for estimating millimeter emission that contaminates CMBR experiments and for estimating soft X-ray absorption.

Figures (14)

• Figure 1: The $100\micron$-H I correlation with (a) no correction, (b) linear correction, and (c) quadratic correction for zodiacal contamination. The fits in the range $[0,200] {\rm ~K~km/s}$ are shown as solid lines.
• Figure 2: Ratio of recovered versus true column density of dust using a single-temperature fit to two components. A fraction of dust, $f_B$, at temperature $T_B$ is added to $18{\rm ~K}$ dust. The recovered column density is always lower than the true column density, with contours spaced in units of $0.1$.
• Figure 3: Temperature map as determined with an $\alpha=2$ emissivity model. These Lambert projections are centered on the NGP (top), and SGP (bottom), with Galactic latitude labelled in degrees. Lines of constant latitude and longitude are spaced every 30 degrees. Note the cool molecular cloud regions and the hot star-forming regions.
• Figure 4: Fourier destriping of plate 379: (a) raw ISSA HCON-0 image, (b) FFT with wavenumber 0 in center, (c) destriped image, (d) FFT of destriped image. Note that one of the $k_\theta$ bins contains less power than the rest. These are modes in which power from HCON-3 has replaced power in the other HCONs; however HCON-3 covers only half the plate, resulting in less power.
• Figure 5: Ratio of power in destriped ISSA image versus power in raw image. Ratios for four arbitrary plates are shown (plate numbers 199, 216, 217 and 379).