We present a full-sky 100 km map that is a reprocessed composite of the COBE/DIRBE and IRAS/ ISSA maps, with the zodiacal foreground and conÐrmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 and 240 km data, we have constructed a map of the dust temperature so that the 100 km map may be converted to a map proportional to dust column density. The dust temperature varies from 17 to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5. The result of these manipulations is a map with DIRBE quality calibration and IRAS resolution. A wealth of Ðlamentary detail is apparent on many di †erent scales at all Galactic latitudes. In high-latitude regions, the dust map correlates well with maps of H I emission, but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and of formation of in molecular clouds. In contrast, H 2 high-velocity H I clouds are deÐcient in dust emission, as expected.To generate the full-sky dust maps, we must Ðrst remove zodiacal light contamination, as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 km 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 km Ñux. This procedure removes virtually all traces of the zodiacal foreground. For the 100 km map no signiÐcant CIB is detected. At longer wavelengths, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high Ñux levels of 32^13 nW m~2 sr~1 at 140 km and of 17^4 nW m~2 sr~1 at 240 km (95% conÐdence). This integrated Ñux D2 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. To calibrate our maps, we assume a standard reddening law and use the colors of elliptical galaxies to measure the reddening per unit Ñux density of 100 km emission. We Ðnd consistent calibration using the B[R color distribution of a sample of the 106 brightest cluster ellipticals, as well as a sample of 384 ellipticals with B[V and Mg line strength measurements. For the latter sample, we use the correlation of intrinsic B[V versus index to tighten the power of the test greatly. We demonstrate that the new maps are Mg 2 twice as accurate as the older Burstein-Heiles reddening estimates in regions of low and moderate reddening. The maps are expected to be signiÐcantly more accurate in regions of high reddening. These dust maps will also be useful for estimating millimeter emission that contaminates cosmic microwave background radiation experiments and for estimating soft X-ray absorption. We describe how to access our maps readily for general use.

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We use the first systematic data sets of CO molecular line emission in z ∼ 1-3 normal star-forming galaxies (SFGs) for a comparison of the dependence of galaxy-averaged star formation rates on molecular gas masses at low and high redshifts, and in different galactic environments. Although the current high-z samples are still small and biased towards the luminous and massive tail of the actively star-forming 'main-sequence', a fairly clear picture is emerging. Independent of whether galaxy-integrated quantities or surface densities are considered, low-and high-z SFG populations appear to follow similar molecular gas-star formation relations with slopes 1.1 to 1.2, over three orders of magnitude in gas mass or surface density. The gas-depletion time-scale in these SFGs grows from 0.5 Gyr at z ∼ 2 to 1.5 Gyr at z ∼ 0. The average corresponds to a fairly low star formation efficiency of 2 per cent per dynamical time. Because star formation depletion times are significantly smaller than the Hubble time at all redshifts sampled, star formation rates and gas fractions are set by the balance between gas accretion from the halo and stellar feedback.In contrast, very luminous and ultraluminous, gas-rich major mergers at both low and high z produce on average four to 10 times more far-infrared luminosity per unit gas mass. We show that only some fraction of this difference can be explained by uncertainties in gas mass or luminosity estimators; much of it must be intrinsic. A possible explanation is a top-heavy stellar mass function in the merging systems but the most likely interpretation is that the star formation relation is driven by global dynamical effects. For a given mass, the more compact merger systems produce stars more rapidly because their gas clouds are more compressed with shorter dynamical times, so that they churn more quickly through the available gas reservoir than the typical normal disc galaxies. When the dependence on galactic dynamical Based on observations with the Plateau de Bure millimetre interferometre, operated by the Institute for Radio Astronomy in the Millimetre Range (IRAM), which is funded by a partnership of INSU/CNRS (France), MPG (Germany) and IGN (Spain).

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The global properties of elliptical galaxies, such as luminosity, radius, projected velocity dispersion, projected luminosity, etc., form a two-dimensional family. This " fundamental plane " of elliptical galaxies can be defined in observable terms by the velocity dispersion and mean surface brightness. Its thickness is given at present by the present measurement error bars, and there are no significant indications of nonlinearity (deviation from power laws which define the surface), or higher dimensionality. This is indicative of a strong regularity in the process of galaxy formation. The equations of the plane can be used as new, substantially improved distance indicators for elliptical galaxies. However, all morphological parameters which describe the shape of the light distribution (ellipticity, ellipticity gradient, isophotal twist rate, slope of the surface brightness profile), and reflect dynamical anisotropies of stars, are completely independent of this fundamental plane, and thus, the elliptical galaxies are actually a "2 +AT" parameter family. The M/L ratios correlate only with the velocity dispersions and show a small intrinsic scatter, perhaps only ~30%, in a luminosity range spanning some four orders of magnitude; this suggests a constant fraction of the dark matter contribution in elliptical galaxies.