Monochromatic intensity measurements of selected areas of lunar surface for possible investigations

Absolute photoelectric intensity measurements of 104 selected lunar regions are given in five interference filters 4035 Å, 4765 Å, 5538 Å, 6692 Å and 7922 Å. Among these regions, eighteen lunar regions have been measured repeatedly for several phase angles between +86° and ?43°. They include observations made very close to the full Moon. A catalogue has been compiled to serve as a basin for possible investigations of colour contrasts of lunar grounds, variation of the ratio of reflectivity with wavelengths and phase angles for morphological studies. The study can be extended for the brightness phase variation, opposition effect and radiance factors at zero phase in five colours.     

Spectral photometry of selected areas of the lunar surface during maximum solar activity

Photoelectric observations have been carried out during maximum solar activity in order to investigate the variation of the brightness of the lunar surface with the solar cycle and to detect the possiblity of existing colour anomaly. The brightness data, using a wide-passband filter, do not show any evidence of variation with the solar cycle. No colour anomaly is found for the investigated lunar regions, and the doubt that has been felt by some investigators about the nonexistence of certain colour indices' variation with phase is not confirmed.     

Properties and emergence patterns of bipolar active regions

Patterns in the properties of bipolar active regions are determined throughout Cycle 21. Active regions that emerged on the visible hemisphere were identified on NSO/KP full-disk magnetograms during 29 solar rotations selected from 1975 through 1986. The bipolar active regions are included only once in this sampling; their properties are derived at the time of maximum development. In order to study an unbiased sample over the entire range of areas larger than 2.5 square degrees (or 373 Mm²), their counts are corrected for size-dependent effects that reduce the chance of their identifications.The size distribution of bipolar active regions is a well-defined function that decreases with increasing size. Except for the smallest regions, the shape of the size distribution is independent of the phase of a cycle, only the scaling factor varies. The shape of the size distribution function for bipoles emerging within existing sunspot regions is virtually the same as that for bipoles emerging outside existing regions. Over the cycle, at least 44% of the regions larger than 3.5 square degrees emerge within existing sunspot regions. Hence, the rate at which new regions emerge is much higher within the boundaries of existing sunspot regions than it is in the activity belts outside existing regions. For regions emerging outside of existing sunspot regions, this rate increases by a factor of 3.5 from cycle minimum to maximum, while for new bipoles within existing active regions, the emergence rate varies with a significantly lower magnitude.Through the cycle, for regions in all size bins, the emergence frequencies appear to vary in phase. The frequencies increase by a factor of more than 8 from minimum to maximum for regions larger than 3.5 square degrees, but no more than 4.7 for the smaller regions. Short-term variations in the emergence frequency of regions do not necessarily occur simultaneously for regions of all sizes, implying that the size distribution is variable on time scales of less than six rotations.     

The DEEP2 galaxy redshift survey: evolution of the colour–density relation at 0.4 < z < 1.35

Using a sample of 19 464 galaxies drawn from the DEEP2 Galaxy Redshift Survey, we study the relationship between galaxy colour and environment at  0.4 < z < 1.35  . We find that the fraction of galaxies on the red sequence depends strongly on local environment out to   z > 1  , being larger in regions of greater galaxy density. At all epochs probed, we also find a small population of red, morphologically early-type galaxies residing in regions of low measured overdensity. The observed correlations between the red fraction and local overdensity are highly significant, with the trend at   z > 1  detected at a greater than 5σ level. Over the entire redshift regime studied, we find that the colour–density relation evolves continuously, with red galaxies more strongly favouring overdense regions at low z relative to their red-sequence counterparts at high redshift. At   z ≳ 1.3  , the red fraction only weakly correlates with overdensity, implying that any colour dependence to the clustering of  ∼ L *  galaxies at that epoch must be small. Our findings add weight to existing evidence that the build-up of galaxies on the red sequence has occurred preferentially in overdense environments (i.e. galaxy groups) at   z ≲ 1.5  . Furthermore, we identify the epoch  ( z ∼ 2)  at which typical  ∼ L *  galaxies began quenching and moved on to the red sequence in significant number. The strength of the observed evolutionary trends at  0 < z < 1.35  suggests that the correlations observed locally, such as the morphology–density and colour–density relations, are the result of environment-driven mechanisms (i.e. 'nurture') and do not appear to have been imprinted (by 'nature') upon the galaxy population during their epoch of formation.     

The phase ratios of the color index: Mapping of two regions of the near side of the Moon

From the ground-based colorimetry performed for two surface regions of the near side of the Moon, images of the phase ratio of the color index C(600 nm/470 nm) have been built for the phase angles between 2° and 95°. It has been found that for phase angles smaller than α ∼ 40°–50°, the color index of the highlands grows with the phase quicker than that of the mare regions. For larger phase angles, α > 50°, a reverse situation is observed. The laboratory data on the spectrophotometry of the lunar samples confirm the peculiarities found in the phase dependence of color. The influence of multiple scattering on the phase dependence of the color of the mare and highland regions of the Moon are discussed.     

The far-infrared signature of dust in high-latitude regions

We present ISOPHOT observations of eight interstellar regions in the 60–200 μm wavelength range. The regions belong to mostly quiescent high-latitude clouds and have optical extinction peaks from   A_V ∼1–6 mag  . From the 150- and 200-μm emission, we derived colour temperatures for the classical big grain component which show a clear trend of decreasing temperature with increasing 200-μm emission. The 200-μm emission per unit   A_V   , however, does not drop at lower temperatures. This fact can be interpreted in terms of an increased far-infrared (FIR) emissivity of the big grains. We developed a two-component model including warm dust with the temperature of the diffuse interstellar medium (ISM) of   T = 17.5 K  , and cold dust with   T = 13.5 K  and FIR emissivity increased by a factor of >4. A mixture of the two components can reproduce the observed colour variations and the ratios   I ₂₀₀/ A_V   and  τ₂₀₀/ A_V   . The relative abundance of small grains with respect to the big grains shows significant variations from region to region at low column densities. However, in lines of sight of higher column density, our data indicate the disappearance of small grains, perhaps a signature of adsorption/coagulation of dust. The larger size and porous structure could also explain the increased FIR emissivity. Our results from eight independent regions suggest that these grains might be ubiquitous in the galactic ISM.     

Colour contrasts of lunar grounds

Four colour contrasts have been studied for 104 lunar regions between wavelengths 4000 Å and 8000 Å. Distinct colour differences are found. The greatest contrast between topographs occurs at longer wavelengths. The regional colour differences between the two short wavelengths 4035 Å and 5538 Å show a general trend of increasing reddening with age. For the other three colour differences \(\Delta (\tfrac{{{\text{4 7 6 5}}}}{{{\text{7 9 2 2}}}}), \Delta (\tfrac{{{\text{4 7 6 5}}}}{{{\text{6 6 9 2}}}}) and \Delta (\tfrac{{{\text{6 6 9 2}}}}{{{\text{7 9 2 2}}}})\) , a trend of variation with albedo is detected, and the less scatter on points for the colour differences above the wavelength 6000 Å.     

Near-infrared surface photometry of bulges and disks of spiral galaxies. The data

We present optical and near-infrared (NIR) surface brightness and colour profiles, in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 °. We describe in detail the observations and the determination of colour parameters. Calibrated monochromatic and real-colour images are presented, as well as colour index maps. This data set, tailored for the study of the population characteristics of galaxy bulges, provides useful information on the colours of inner disks as well. In related papers, we have used them to quantify colour gradients in bulges, and age differentials between bulge and inner disk.     

The Mars opposition effect at 20°N. latitude and 20°W. longitude

Low phase angle observations in the Chryse-Acidalia region have been obtained the Viking Orbiter 1 spacecraft under clearer atmospheric conditions than reported earlier. A variety of surface features were recorded, e.g., crater streaks, dark and bright patches. Several findings for this scene include: an abrupt brightness increase (10%) was found at phase angles less than 3°, an effect dependent on surface albedo and possibly particle distribution; a slight weakening of reflectance surge with decreasing wavelengths; a larger opposition effect for features of high albedo was recorded; and a greater reddening with increase phase angle took place for low albedo regions. Both reflectance and contrast values are provided at three wavelengths as a function of phase angle from 0.15 to 20°.     

Extinction of H ii regions in the Large Magellanic Cloud

The extinction properties of H  ii regions in the Large Magellanic Cloud are investigated using radio continuum data obtained from the Molonglo Observatory Synthesis Telescope, digitized and calibrated Hα data and published Balmer decrement measurements. The resulting extinction–colour excess diagram suggests that (1) most H  ii regions in the Magellanic Clouds have similar extinction properties to the Galactic ones, (2) all imaginable gas/dust configurations are possible, (3) the extinction of some highly reddened H  ii region cores originates externally in cocoon shells.   The puzzle of different extinction–colour excess ratios of Galactic and extragalactic H  ii regions is explained as being due to the different populations of observed samples rather than any intrinsic differences. The extinction of the observed Galactic H  ii regions produced by foreground dust overwhelms the internal extinction, while the situation in the observed extragalactic H  ii regions is just the opposite.     

Multicolour observations of V404 Cyg with ULTRACAM

We present high-time-resolution multicolour observations of the quiescent soft X-ray transient V404 Cyg obtained with ULTRACAM. Superimposed on the ellipsoidal modulation of the secondary star are large flares on time-scales of a few hours, as well as several distinct rapid flares on time-scales of tens of minutes. The rapid flares, most of which show further variability and unresolved peaks, cover shorter time-scales than those reported in previous observations. The power density spectrum of the 5-s time-resolution data shows a quasi-periodic oscillation (QPO) feature at 0.78 mHz (=21.5 min). Assuming this periodicity represents the Keplerian period at the transition between the thin and advective disc regions, we determine the transition radius. We discuss the possible origins for the QPO feature in the context of the advection-dominated accretion flow model.
We determine the colour of the large flares and find that the i '-band flux per unit frequency interval is larger than that in the g ' band. The colour is consistent with optically thin gas with a temperature of ∼8000 K arising from a region with an equivalent blackbody radius of at least  2 R_⊙  , which covers 3 per cent of the surface of the accretion disc. Our timing and spectral analysis results support the idea that the rapid flares (i.e. the QPO feature) most likely arise from regions near the transition radius.     

Optical multiband observations of BL Lacertae during the outburst of 2005

The aim of our observations is to investigate the intranight variability properties and the spectral variability of BL Lacertae. 799 optical multiband observations were intensively made with the Beijing–Arizona–Taiwan–Connecticut (BATC) 60/90 cm Schmidt telescope during the outburst composed of two subsequent flares in 2005. The second flare, whose rising phase lasted at least 44 d, was observed with amplitudes of more than 1.1 mag in three BATC optical bands. In general, on intranight time-scale the amplitude of variability and the variation rate are larger at the shorter wavelength, and the variation rate is comparable in the rising and decaying phases within each band. A possible time-lag between the light curves in bands e and m , around 11.6 min, was obtained. Based on the analysis of the colour index variation with the source brightness, the variability of BL Lacertae can be interpreted as having two components: a 'strongly chromatic' intranight component and a 'mildly chromatic' internight component, which may be the results of both intrinsic physical mechanism and geometric effects.     

Observations Of Scattered Light From Cometary Dust And Their Interpretation

This review begins with a discussion of the techniques needed for observations of scattered light from cometary dust. After an introduction into the basic concepts of the scattering process, observations of the phase curves of brightness, colour and polarization are covered. Images of colour and polarization are presented and the observed relation of colour and polarization in jets and shells is discussed. The interpretation of the measurements is based on the power law size distributions of dust grains observed from space. The power index must lie between 2 and 4 to provide the mass budget and visibility of the dust coma in accordance with the basic facts of cometary physics. Application of mechanical (radiation pressure) theory to cometary images allows us to derive related power law distributions for comets not explored by spacecraft. Grain scattering models are presented and compared with observations. A prediction is made of the spatial distribution of Stokes parameters U and V in the presence of aligned particles. Up to now such patterns have not been observed. Future work should include the exploration of comets at small and possibly very small phase angles and a detailed comparison of polarization and colour images of comets with thermal images and with models based on mechanical theory. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation of colour gradients in non-active and active spiral galaxies

Near-infrared and optical colour gradients of the discs of non-active and active spiral galaxies are investigated by using disc scalelengths. The measurements indicate that the colour gradients for JHK′ are small and no significant differences exist between the non-active and the active galaxies. This result is different from what is found for the optical wavelength regions, where significant colour gradients are observed in the discs of the non-active galaxies, but not in the discs of the active ones. This indicates that the differences between non-active and active galaxies found in the optical do not exist in the near-infrared. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cooling of quark stars in the colour superconductive phase: effect of photons from glueball decay

The cooling history of a quark star in the colour superconductive phase is investigated. Here we specifically focus on the two-flavour colour (2SC) phase where the novel process of photon generation via glueball (GLB) decay has already been investigated. The picture we present here can, in principle, be generalized to quark stars entering a superconductive phase where similar photon generation mechanisms are at play. As much as 10⁴⁵–10⁴⁷ erg of energy is provided by the GLB decay in the 2SC phase. The generated photons slowly diffuse out of the quark star, keeping it hot and radiating as a blackbody (with possibly a Wien spectrum in gamma-rays) for millions of years. We discuss hot radio-quiet isolated neutron stars in our picture (such as RX J185635–3754 and RX J0720.4–3125) and argue that their nearly blackbody spectra (with a few broad features) and their remarkably tiny hydrogen atmosphere are indications that these might be quark stars in the colour superconductive phase where some sort of photon generation mechanism (reminiscent of the GLB decay) has taken place. Fits to observed data of cooling compact stars favour models with superconductive gaps of  Δ_2SC∼ 15–35 MeV  and densities  ρ_2SC= (2.5–3.0) ×ρ_N  (ρ_N being the nuclear matter saturation density) for quark matter in the 2SC phase. If correct, our model combined with more observations of isolated compact stars could provide vital information to studies of quark matter and its exotic phases.     

Long-Term Photometry of RT Lacertae: 1. Light and Colour Variation

The peculiar chromospherically active binary system RT Lac was observed in B and V bands between 1989 and 1992. The four-year photoelectric B and V light curves are presented. The light and colour variations in the four special regions of the light curve between 1978 and 1992 are discussed. The available photometry obtained by the present authors defines at least three consecutive maxima in the variation of the brightness of the system at second maximum and in mid-primary eclipse. The behaviour of the light and colour changes in mid-primary and at second maximum harmonizes with the common property of the RS CVn-type binaries. However, the light changes at first maximum do not resemble either at second maximum or in mid-primary minimum. Therefore, we conclude that the observed features cannot be attributed to the spottedness of the more massive component alone. The signs of the starspots are masked by the matter in front of the more massive component at the first maximum. The present data indicate that the magnetic cycle in RT Lac is about 12 years, which is analogous to the Sun's 11-year sunspot cycle.     

Colour dependence of zodiacal light models

Colour models of the zodiacal light in the ecliptic have been calculated for both dielectric and metallic particles in the sub-micron and micron size range. Two colour ratios were computed, a blue ratio C_b (0.40 μm, 0.53 μm) and a red ratio, either C_r (0.82 μm, 0.53 μm) or C_r' (0.71 μm, 0.53 μm). The models with a size distribution ∝s^−2.5ds generally show a colour close to the solar colour and almost independent of elongation. Especially in the blue colour ratio there is generally no significant dependence on the lower cutoff size (0.1–1 μm). The main feature of absorbing particles is a reddening at small elongations. The models for size distributions ∝s⁻⁴ds show larger departures from solar colour and more variation with model parameters. Colour measurements, including red and near infra-red, therefore are useful to distinguish between flat and steep size spectra and to verify the presence of slightly absorbing particles.     

Circumnuclear regions in barred spiral galaxies – I. Near-infrared imaging

We present subarcsecond-resolution, ground-based, near-infrared images of the central regions of a sample of 12 barred galaxies with circumnuclear star formation activity, which is organized in ring-like regions typically 1 kpc in diameter. We also present Hubble Space Telescope near-infrared images of 10 of our sample galaxies, and compare them with our ground-based data. Although our sample galaxies were selected for the presence of circumnuclear star formation activity, our broad-band near-infrared images are heterogeneous, showing a substantial amount of small-scale structure in some galaxies, and practically none in others. We argue that, where it exists, this structure is caused by young stars, which also cause the characteristic bumps or changes in slope in the radial profiles of ellipticity, major axis position angle, surface brightness and colour at the radius of the circumnuclear ring in most of our sample galaxies. In seven out of 10 HST images, star formation in the nuclear ring is clearly visible as a large number of small emitting regions, organized into spiral arm fragments, which are accompanied by dust lanes. Near-infrared colour index maps show much more clearly the location of dust lanes and, in certain cases, regions of star formation than single broad-band images. Circumnuclear spiral structure thus outlined appears to be common in barred spiral galaxies with circumnuclear star formation.     

A GLIMPSE-based search for 6.7-GHz methanol masers and the lifetime of their spectral features

The University of Tasmania Mt Pleasant 26-m and Ceduna 30-m radio telescopes have been used to search for 6.7-GHz class II methanol masers towards 200 GLIMPSE ( The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire ) sources. The target regions were selected on the basis of their mid-infrared colours as being likely to be young high-mass star formation regions and are either bright at 8.0 μm, or have extreme [3.6]–[4.5] colour. Methanol masers were detected towards 38 sites, nine of these being new detections. The prediction was that approximately 20 new 6.7-GHz methanol masers would be detected within 3.5 arcmin of the target GLIMPSE sources, but this is the case for only six of the new detections. A number of possible reasons for the discrepancy between the predicted and actual number of new detections have been investigated. It was not possible to draw any firm conclusions as to the cause, but it may be because many of the target sources are at an evolutionary phase prior to that associated with 6.7-GHz methanol masers. Through comparison of the spectra collected as part of this search with those in the literature, the average lifetime of individual 6.7-GHz methanol maser spectral features is estimated to be around 150 yr, much longer than is observed for 22-GHz water masers.     

The magnetic fields of active regions

The Mount Wilson coarse array data set is used to define active regions in the interval 1967 to August, 1988. From the positions of these active regions on consecutive days, rotation rates are derived. The differential rotation of the active regions is calculated and compared with previous magnetic field and plage rates. The agreement is good except for the variation with time. The active region rates are slower by a few percent than the magnetic field or facular rates. The differential rotation rate of active regions with reversed magnetic polarity orientations is calculated. These regions show little or no evidence for differential rotation, although uncertainties in this determination are large. A correlation is found between rotation rate and region size in the sense that larger regions rotate more slowly. A correlation between rotation rate and cycle phase is suggested which is in agreement with earlier sunspot results. Leading and following portions of active regions, unlike leading and following spots, show little or no difference in their rotation rates. The regions with polarity orientations nearest the normal configuration tend to show rotation rates that are nearest the average values. Most of these results generally support the conclusion that old, weaker magnetic fields have evolved different subsurface connections from the time they were a part of sunspots or plages. It seems possible that they are connected at a shallower layer than are sunspot or plage fields.Operated by the Association of Universities for Research in Astronomy, Inc., under Contract with the National Science Foundation.