The global star formation rate in high redshift galaxies, based on optical surveys, shows a strong peak at a redshift of z ∼ 1.5, which implies that we have already seen most of the formation. High redshift galaxies may, however, emit most of their energy at submillimeter wavelengths if they contain substantial amounts of dust. The dust would absorb the starlight and reradiate it as far-infrared light, which would be redshifted to the submillimeter range. Here we report a deep survey of two blank regions of sky performed at submillimeter wavelengths (450 and 850µm). If the sources we detect in the 850µm band are powered by star formation, then each must be converting more than 100 solar masses of gas per year into stars, which is larger than the maximum star formation rates inferred for most optically-selected galaxies. The total amount of high redshift star formation is essentially fixed by the level of background light, but where the peak occurs in redshift for the submillimeter is not yet established. However, the background light contribution from only the sources detected at 850µm is already comparable to that from the optically-selected sources. Establishing the main epoch of star formation will therefore require a combination of optical and submillimeter studies.In recent years high redshift optical galaxy searches have become increasingly successful at uncovering significant populations of galaxies that are likely to be in early phases of evolution. However, the global star formation rate (SFR) inferred 1, 3, 4 omits the many fainter sources that are now being detected. 5,6 Furthermore, the effects of dust can cause the SFRs in the detected UV-bright objects to be grossly underestimated (see, e.g., ref. 7), and many rapid star forming galaxies may even be omitted from the optical samples.Nearby star forming galaxies emit a large fraction of their bolometric luminosity in the far infrared waveband, which for distant sources is redshifted into the submillimeter waveband. Because the spectra of these star forming galaxies are very steep, if they are at large redshifts their flux density decreases much less rapidly with increasing redshift

We present the spectra of 14 quasars with a wide coverage of rest wavelengths from 1000 to 7300 8. The redshift ranges from z ¼ 0:061 to 0.555 and the luminosity from M B ¼ À22:69 to À26.32. These spectra of high quality result from combining Hubble Space Telescope spectra with those taken from ground-based telescopes. We describe the procedure of generating the template spectrum of Fe ii line emission from the spectrum of a narrow-line Seyfert 1 galaxy, I Zw 1, that covers two wavelength regions of 2200-3500 and 4200-5600 8. Our template Fe ii spectrum is semiempirical in the sense that the synthetic spectrum calculated with the CLOUDY photoionization code is used to separate the Fe ii emission from the Mg ii k2798 line. The procedure of measuring the strengths of Fe ii emission lines is twofold: (1) subtracting the continuum components by fitting models of the power-law and Balmer continua in the continuum windows, which are relatively free from line emissions, and (2) fitting models of the Fe ii emission based on the Fe ii template to the continuum-subtracted spectra. From 14 quasars including I Zw 1, we obtained the Fe ii fluxes in five wavelength bands (U 1 [2200-2660 8], U 2 [2660-3000 8], U 3 [3000-3500 8], O1 [4400-4700 8], and O2 [5100-5600 8]), the total flux of Balmer continuum, and the fluxes of Mg ii k2798, H, and other emission lines, together with the full widths at half-maximum (FWHMs) of these lines. Regression analysis was performed by assuming a linear relation between any two of these quantities. Eight correlations were found with a confidence level higher than 99%: (1) larger Mg ii FWHM for larger H FWHM, (2) larger À for fainter M B , (3) smaller Mg ii FWHM for larger À, (4) larger Mg ii FWHM for smaller Fe ii(O1)/ Mg ii, (5) larger M BH for smaller À, (6) larger M BH for smaller Fe ii(O1)/ Mg ii, (7) larger [O iii]/H for larger Mg ii FWHM, and (8) larger Fe ii(O1)/ Mg ii for larger Fe ii(O1)/ Fe ii(U 1).The fact that six of these eight are related to FWHM or M BH (/ FWHM 2 ) may imply that M BH is a fundamental quantity that controls À or the spectral energy distribution (SED) of the incident continuum, which in turn controls the Fe ii emission. Furthermore, it is worthy of noting that Fe ii(O1)/ Fe ii(U 1) is found to tightly correlate with Fe ii(O1)/ Mg ii, but not with Fe ii(U 1)/ Mg ii.

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The observed Fe II(UV+optical)/Mg II λλ2796,2804 flux ratio from a gravitationally lensed quasar B1422+231 at z=3.62 is interpreted in terms of detailed modeling of photoionization and chemical enrichment in the broad-line region (BLR) of the host galaxy. The delayed iron enrichment by Type Ia supernovae is used as a cosmic clock. Our standard model, which matches the Fe II/Mg II ratio, requires the age of 1.5 Gyr for B1422+231 with a lower bound of 1.3 Gyr, which exceeds the expansion age of the Einstein-de Sitter Ω 0 = 1 universe at a redshift of 3.62 for any value of the Hubble constant in the currently accepted range, H 0 =60-80 km s −1 Mpc −1 . This problem of an age discrepancy at z = 3.62 can be unraveled in a low-density Ω 0 < ∼ 0.2 universe, either with or without a cosmological constant, depending on the allowable redshift range of galaxy formation. However, whether the cosmological constant is a required option in modern cosmology awaits a thorough understanding of line transfer processes in the BLRs.

We have conducted B-, g-, V-, and R-band imaging in a 45 × 40 field containing part of the high Galactic latitude translucent cloud MBM32, and correlated the intensity of diffuse optical light S ν (λ) with that of 100 μm emission S ν (100 μm). A χ 2 minimum analysis is applied to fit a linear function to the measured correlation and derive the slope parameter b(λ) = ΔS ν (λ)/ΔS ν (100 μm) of the best-fit linear function. Compiling a sample by combining our b(λ) and published ones, we show that the b(λ) strength varies from cloud to cloud by a factor of four. Finding that b(λ) decreases as S ν (100 μm) increases in the sample, we suggest that a nonlinear correlation including a quadratic term of S ν (100 μm) 2 should be fitted to the measured correlation. The variation of optical depth, which is A V = 0.16-2.0 in the sample, can change b(λ) by a factor of 2-3. There would be some contribution to the large b(λ) variation from the forward-scattering characteristic of dust grains which is coupled to the non-isotropic interstellar radiation field (ISRF). Models of the scattering of diffuse Galactic light (DGL) underestimate the b(λ) values by a factor of two. This could be reconciled by deficiency in UV photons in the ISRF or by a moderate increase in dust albedo. Our b(λ) spectrum favors a contribution from extended red emission (ERE) to the diffuse optical light; b(λ) rises from B to V faster than the models, seems to peak around 6000 Å and decreases toward long wavelengths. Such a characteristic is expected from the models in which the DGL is combined with ERE.

We present results of the near-infrared (IR) spectroscopy of six quasars whose redshifts range from 0.158 to 1.084. Combined with the satellite ultraviolet data, the relative line strengths of O I λ1304, O I λ8446, O I λ11287, and the near-IR Ca II triplet are given. In addition, the corresponding O I line strengths measured in normal Seyfert 1s and narrow-line Seyfert 1s are collected from the literature. These lines are thought to emerge from the same gas as do the Fe II lines, so they are good tracers of the Fe II emission region within a broad emission line region (BELR) in active galactic nuclei (AGNs). In order to reveal the physical condition within the relevant emission region, we performed photoionized model calculations and compared them to the observations. It suggests that a rather dense gas with density n H ∼ 10 11.5 cm −3 is present at an outer portion of the BELR, illuminated by the ionizing radiation corresponding to an ionization parameter U ∼ 10 −2.5 and is primarily responsible for the observed O I, Ca II, and Fe II lines, based on the resemblance of their profiles. The three O I lines

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