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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 an analysis of the blank sky spectra observed with the Faint Object Spectrograph on board the Hubble Space Telescope. We study the diffuse sky emission from ultraviolet to optical wavelengths, which is composed of the zodiacal light (ZL), diffuse Galactic light (DGL), and residual emission. The observations were performed toward 54 fields distributed widely over the sky, with the spectral coverage from 0.2 to 0.7µm. In order to avoid contaminating light from the earthshine, we use the data collected only in orbital nighttime. The observed intensity is decomposed into the ZL, DGL, and residual emission, in eight photometric bands spanning our spectral coverage. We found that the derived ZL reflectance spectrum is flat in the optical, which indicates major contribution of C-type asteroids to the interplanetary dust (IPD). In addition, the ZL reflectance spectrum has an absorption feature at ∼ 0.3µm. The shape of the DGL spectrum is consistent with those found in earlier measurements and model predictions. While the residual emission contains a contribution from the extragalactic background light, we found that the spectral shape of the residual looks similar to the ZL spectrum. Moreover, its optical intensity is much higher than that measured from beyond the IPD cloud by Pioneer10/11, and also than that of the integrated galaxy light. These findings may indicate the presence of an isotropic ZL component, which is missed in the conventional ZL models.

We investigate Fe II emission in the broad-line region (BLR) of active galactic nuclei by analysing the Fe II(UV), Fe II(λ4570) and Mg II emission lines in 884 quasars in the Sloan Digital Sky Survey Quasar catalogue in a redshift range of 0.727 < z < 0.804. Fe II(λ4570)/Fe II(UV) is used to infer the column density of Fe II-emitting clouds and explore the excitation mechanism of Fe II emission lines. As suggested before in various works, the classical photoionization models fail to account for Fe II(λ4570)/Fe II(UV) by a factor of 10, which may suggest anisotropy of UV Fe II emission, or an alternative mechanism like shocks. The column density distribution derived from Fe II(λ4570)/Fe II(UV) indicates that radiation pressure plays an important role in BLR gas dynamics. We find a positive correlation between Fe II(λ4570)/Fe II(UV) and the Eddington ratio. We also find that the ionizing photon fraction must be much smaller than that previously suggested unless Fe II-emitting clouds are super-Eddington. Finally, we propose a physical interpretation of a striking set of correlations between various emission-line properties, known as 'Eigenvector 1'.

We present the detailed optical to far-infrared observations of SST J1604+4304, an ULIRG at z = 1.135. Analyzing the stellar absorption lines, namely, the CaII H & K and Balmer H lines in the optical spectrum, we derive the upper limits of an age for the stellar population. Given this constraint, the minimum χ 2 method is used to fit the stellar population models to the observed SED from 0.44 to 5.8µm. We find the following properties. The stellar population has an age 40 -200 Myr with a metallicity 2.5 Z ⊙ . The starlight is reddened by E(B − V ) = 0.8. The reddening is caused by the foreground dust screen, indicating that dust is depleted in the starburst site and the starburst site is surrounded by a dust shell. The infrared (8-1000µm) luminosity is L ir = 1.78 ± 0.63 × 10 12 L ⊙ . This is two times greater than that expected from the observed starlight, suggesting either that 1/2 of the starburst site is completely obscured at UV-optical wavelengths, or that 1/2 of L ir comes from AGN emission. The inferred dust mass is 2.0±1.0×10 8 M ⊙ . This is sufficient to form a shell surrounding the galaxy with an optical depth E(B −V ) = 0.8. From our best stellar population modelan instantaneous starburst with an age 40 Myr, we infer the rate of 19 supernovae(SNe) per year. Simply analytical models imply that 2.5 Z ⊙ in stars was reached when the gas mass reduced to 30% of the galaxy mass. The gas metallcity is 4.8Z ⊙ at this point. The gas-to-dust mass ratio is then 120 ± 73. The inferred dust production rate is 0.24 ± 0.12M ⊙ per SN. If 1/2 of L ir comes from AGN emission, the rate is 0.48 ± 0.24M ⊙ per SN. We discuss the evolutionary link of SST J1604+4304 to other galaxy populations in terms of the stellar masses and the galactic winds, including optically selected low-luminosity Lyman α-emitters and submillimeter selected highluminosity galaxies.

We apply the supernova (SN) extinction curves to reproduce the observed properties of SST J1604+4304 which is a young infrared (IR) galaxy at z∼ 1. The SN extinction curves used in this work were obtained from models of unmixed ejecta of Type II supernovae for the Salpeter initial mass function with a mass range from 8 to 30 M⊙ or 8 to 40 M⊙. The effect of dust distributions on the attenuation of starlight is investigated by performing the χ2 fitting method against various dust distributions. These are the commonly used uniform dust screen, the clumpy dust screen and the internal dust geometry. We add to these geometries three scattering properties, namely, no scattering, isotropic scattering and forward‐only scattering. Judging from the χ2 values, we find that the uniform screen models with any scattering property provide good approximations to the real dust geometry. Internal dust is inefficient to attenuate starlight and thus cannot be the dominant source of the extinction. We show that the SN extinction curves reproduce the data of SST J1604+4304 comparable to or better than the Calzetti extinction curve. The Milky Way extinction curve is not in satisfactory agreement with the data unless several dusty clumps are in the line of sight. This trend may be explained by the abundance of SN‐origin dust in these galaxies; SN dust is the most abundant in the young IR galaxy at z∼ 1, abundant in local starbursts and less abundant in the Galaxy. If dust in SST J1604+4304 is dominated by SN dust, the dust production rate is ∼0.1 M⊙ per SN.

Abstract. We present the new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue (∼0.44 µm) and red (∼0.64 µm) bands. Accurate starlight subtraction is achieved by referring to all-sky star catalogs and a Galactic stellar population synthesis model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with thermal 100 µm brightness, while another betrays a constant level in the lowest 100 µm brightness region. Presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, thus it most likely has the extragalactic origin (i.e., the COB). The derived COB brightness is (1.8 ± 0.9) × 10 −9 and (1.2 ± 0.9) × 10 −9 erg s −1 cm −2 sr −1Å−1 at the blue and red band, respectively, or 7.9 ± 4.0 and 7.7 ± 5.8 nW m −2 sr −1 . Based on a comparison with the integrated brightness of galaxies, we conclude that the bulk of the COB is comprised of normal galaxies which have already been resolved by the current deepest observations. There seems to be little room for contributions of other populations including "first stars" at these wavelengths. On the other hand, the first component of the IPP residual light represents the diffuse Galactic light (DGL)-scattered starlight by the interstellar dust. We derive the mean DGL-to-100 µm brightness ratios of 2.1 × 10 −3 and 4.6 × 10 −3 at the two bands, which are roughly consistent with the previous observations toward denser dust regions. Extended red emission in the diffuse interstellar medium is also confirmed.

H I 1225+01 is an intergalactic gas cloud located on the outskirts of Virgo cluster. Its main components are two large clumps of comparable H I masses (M HI ∼ 10 9 M ⊙ ) separated by about 100 kpc. One of the clumps hosts a blue low-surface-brightness galaxy J1227+0136, while the other has no identified stellar emission and is sometimes referred to as a promising candidate of a "dark galaxy", an optically invisible massive intergalactic system. We present a deep optical image covering the whole H I 1225+01 structure for the first time, as well as a collection of archival data from ultraviolet to farinfrared (IR) spectral region of the brightest knot "R1" in J1227+0136. We find that R1 has a young stellar population of age 10-100 Myr and mass ∼ 10 6 M ⊙ , near-IR excess brightness which may point to the presence of hot dust with color temperature ∼ 600 K, and relatively faint mid-to far-IR fluxes corresponding to the dust mass of up to ∼ 100M ⊙ . Overall, it seems to share the general properties with low-metallicity blue compact dwarf galaxies. On the other hand, no optical counterpart to the other clump is found in our deepest-ever image. Now the limiting surface brightness reaches down to R AB > 28 mag arcsec −2 for any emission extended over 10 ′′ (comparable to R1), which is more than one hundred times fainter than the brightest part of the companion galaxy J1227+0136.