Photometric Profiles Research Articles

Physical conditions in the plasma tail of comet C/1987 P1 bradfield

Photometric measurements of photographic images of comet C/1987 P1 Bradfield have been carried out with a flat-bed scanner equipped with a slide module. Lengthwise and transverse photometric profiles of the cometary plasma tail have been obtained. Magnetic field induction and some other physical characteristics of the cometary plasma tail observed in November 1987 have been estimated with the use of the diffusion model for a cometary tail by Shul’man and Nazarchuk (1968). It has been shown that the scanned images of comets can be used for estimating the physical characteristics of cometary tails.

The nature of late-type spiral galaxies: structural parameters, optical and near-infrared colour profiles and dust extinction

We analyse V- and H-band surface photometry of a sample of 18 Sb–Sd galaxies. Combining high-resolution Hubble Space Telescope (HST) images with ground-based near-infrared observations, we extract photometric profiles, which cover the whole disc and provide the highest possible resolution. This is the first photometric study of late-type spirals for which the stellar kinematics have been measured. For 10 out of the 18 galaxies, HST data in both F160W (H) and F606W (V) are available, and, for those, we present colour maps and radial colour profiles at the resolution of the HST. Colours vary significantly from galaxy to galaxy, but tend to be highly homogeneous within each galaxy, with smooth and flat colour profiles. Some of the colour maps show jumps in the inner regions, likely due to dust. We determine extinction maps in an almost model-independent way using the V−H colour map and the SAURON Mgb absorption line map of Ganda et al. The maps show that AV ranges from 0 to 2 mag, in the centre from 0 to 1.5 mag, in agreement with the models of Tuffs et al. We describe the surface brightness profiles as the superposition of an exponential disc and a Sérsic bulge. The bulges are small (0.1–2.5 kpc), and show a shape parameter n ranging from ≈0.7 to 3, with a mean value smaller than two: well below the value for the classical de Vaucouleurs bulges. Most galaxies (16 out of 18) show a central light excess above the Sérsic fit to the bulge, which can be interpreted as a nuclear cluster, as shown by previous studies. We provide zero-order estimates for the magnitude of these components. We discuss the correlations among the structural galaxy parameters and with other relevant quantities, such as Hubble type and stellar velocity dispersion. We compare these results with a recent paper by Graham & Worley, who present a summary of most of the NIR surface photometry of spirals in the literature. For both early- and late-type spirals, bulge luminosity strongly correlates with central velocity dispersion; at constant velocity dispersion, later type bulges are larger and less dense, and have lower Sérsic n-values.

Existe-t-il une « résistance » biologique au traitement antiplaquettaire associant aspirine et clopidogrel chez les patients ayant présenté une occlusion de stent ?

Interindividual variability of biological response to antiplatelet agents is an opened question, which constitute the purpose of recent publications. Indeed, a wide interindividual variability in the laboratory response to antiplatelet agents such as aspirin and/or clopidogrel has been shown. However, only few clinical data are available to demonstrate the relationship between a poor laboratory response to antiplatelet treatment and the occurrence of stent thrombosis. The aim of this study is to compare photometric platelet aggregation profiles of two groups of patients who had undergone percutaneous coronary intervention with stent implantation (one group with at least one subacute thrombotic event following stent implantation and one historical control group free of thrombotic events) to determine whether there is a parameter which could be useful in identifying patients with a risk of having a thrombotic event related to poor response to antiplatelet treatment. We found some differences between the two groups regarding the maximal light transmission after stimulation with arachidonic acid (1,39 mM) or collagen at low concentration (Horm, 2 microg/mL) but not after stimulation with ADP irrespective of the concentration studied (10, 5 and 2,5 microM). However, platelet inhibition response to ADP could be assessed with another parameter, the disaggregation percentage, which was significantly lower in patients with than without thrombosis, and may be used as marker to distinguish patients with a higher risk of thrombosis.

A Kinematically Selected, Metal‐poor Stellar Halo in the Outskirts of M31

We present evidence for a metal-poor, [Fe/H] ~- 1:4,σ = 0.2 dex, stellar halo component detectable at radii from 10 to 70 kpc, in our nearest giant spiral neighbor, the Andromeda galaxy. This metal-poor sample underlies the recently discovered extended rotating component and has no detected metallicity gradient. This discovery uses a large sample of 9861 radial velocities of red giant branch (RGB) stars obtained with the Keck II Telescope and DEIMOS spectrograph, with 827 stars with robust radial velocity measurements isolated kinematically to lie in the halo component primarily by windowing out the extended rotating component, which dominates the photometric profile of Andromeda out to<50 kpc (deprojected). The stars lie in 54 spectroscopic fields spread over an 8 deg^2 region, and are expected to fairly sample the halo to a radius of 70 kpc. The halo sample shows no significant evidence for rotation. Fitting a simple model in which the velocity dispersion of the component decreases with radius, we find a central velocity dispersion of 152 km s^(-1) decreasing by 0.90 km s^(-1) kpc^(-1). By fitting a cosmologically motivated NFW halo model to the halo stars we constrain the virial mass of M31 to be greater than 9.0 x 10^(11) M_☉ with 99% confidence. The properties of this halo component are very similar to that found in our Milky Way, revealing that these roughly equal mass galaxies may have led similar accretion and evolutionary paths in the early universe.

Photometric properties of Titan's surface from Cassini VIMS: Relevance to titan's hemispherical albedo dichotomy and surface stability

The Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini Saturn Orbiter returned spectral imaging data as the spacecraft undertook six close encounters with Titan beginning 7 July, 2004. Three of these flybys each produced overlapping coverage of two distinct regions of Titan's surface. Twenty-four points were selected on approximately opposite hemispheres to serve as photometric controls. Six points were selected in each of four reflectance classes. On one hemisphere each control point was observed at three distinct phase angles. From the derived phase coefficients, preliminary normal reflectances were derived for each reflectance class. The normal reflectance of Titan's surface units at 2.0178 μm ranged from 0.079 to 0.185 for the most absorbing to the most reflective units assuming no contribution from absorbing haze. When a modest haze contribution of τ =0.1 is considered these numbers increase to 0.089–0.215. We find that the lowest three reflectance classes have comparable normal reflectance on either hemisphere. However, for the highest brightness class the normal reflectance is higher on the hemisphere encompassing longitude 14–65° compared to the same high brightness class for the hemisphere encompassing 122–156° longitude. We conclude that an albedo dichotomy observed in continental sized units on Titan is due not only to one unit having more areal coverage of reflective material than the other but the material on the brighter unit is intrinsically more reflective than the most reflective material on the other unit. This suggests that surface renewal processes are more widespread on Titan's more reflective units than on its less reflective units. We note that one of our photometric control points has increased in reflectance by 12% relative to the surrounding terrain from July of 2004 to April and May of 2005. Possible causes of this effect include atmospheric processes such as ground fog or orographic clouds; the suggestion of active volcanism cannot be ruled out. Several interesting circular features which resembled impact craters were identified on Titan's surface at the time of the initial Titan flyby in July of 2004. We traced photometric profiles through two of these candidate craters and attempted to fit these profiles to the photometric properties expected from model depressions. We find that the best-fit attempt to model these features as craters requires that they be unrealistically deep, approximately 70 km deep. We conclude that despite their appearance, these circular features are not craters, however, the possibility that they are palimpsests cannot be ruled out. We used two methods to test for the presence of vast expanses of liquids on Titan's surface that had been suggested to resemble oceans. Specular reflection of sunlight would be indicative of widespread liquids on the surface; we found no evidence of this. A large liquid body should also show uniformity in photometric profile; we found the profiles to be highly variable. The lack of specular reflection and the high photometric variability in the profiles across candidate oceans is inconsistent with the presence of vast expanses of flat-lying liquids on Titan's surface. While liquid accumulation may be present as small, sub-pixel-sized bodies, or in areas of the surface which still remain to be observed by VIMS, the presence of large ocean-sized accumulations of liquids can be ruled out. The Cassini orbital tour offers the opportunity for VIMS to image the same parts of Titan's surface repeatedly at many different illumination and observation geometries. This creates the possibility of understanding the properties of Titan's atmosphere and haze by iteratively adapting models to create a best fit to the surface reflectance properties.

Multicolor CCD photometry of six lenticular and spiral galaxies. Structure of the galaxies

The results of multicolor surface photometry of the S0 galaxies NGC 524, NGC 1138, and NGC 7280 and the spiral galaxies NGC 532, NGC 783, and NGC 1589 are reported. U BV RI observations were acquired with the 1.5-m telescope of the Maidanak Observatory (Uzbekistan), while JHK data were taken from the 2MASS catalog. The overall structure of the galaxies is analyzed and the galaxy images decomposed into bulge and disk components. The parameters of the galaxy components—rings, bars, spiral arms, and dust lanes—are determined. The bulge/disk decompositions based on averaged one-dimensional photometric profiles yield incorrect parameters for the bulges of the S0-Sa galaxies with bars and/or rings, whose inner regions are dominated by the radiation of the bulge.

On the Correlations of Massive Black Holes with Their Host Galaxies

We address the correlations of black hole (BH) mass with four different host-galaxy properties from 11 existing data sets. For the purpose of guiding theoretical understanding, we first try to quantify the tightness of the intrinsic correlations. We assume that all of the relations are power laws and perform linear regressions that are symmetric in the two variables on the logarithms of the data points. Given the estimated measurement errors, we evaluate the probability distribution of the residual variance in excess of that expected from the measurement errors. Our central result is that the current data sets do not allow definite conclusions regarding the quality of the true correlations because the obtained probability distributions for the residual variance overlap for most quantities. Velocity dispersion as collected by Merritt & Ferrarese (σMF) and galaxy light concentration as measured by Graham and coworkers (CRe) are consistent with zero residual variance. Taken at face value, this means that these two correlations are better than the others, but this conclusion is highly sensitive to the assumed measurement errors and would be undone if the present estimated errors were too large. We then consider which of the relations offer the best inferences of BH mass when there is no direct measurement available. As with the residual variances, we find that the probability distribution of expected uncertainty in inferred BH masses overlaps significantly for most of the relations. Photometric methods would then be preferred because the data are easier to obtain, as long as bulge-disk decomposition or detailed modeling of the photometric profile (as studied by Graham and coworkers) do not present problems. Determining which correlation offers the best inferences requires reducing the uncertainty in the expected in the inferred BH masses (the error on the error). This uncertainty is currently limited by uncertainty in the residual variance for all of the relations. The only quantities for which BH mass inferences are limited by measurement are σMF and CRe. Therefore, if these relations are truly better than the others, then new, improved measurements should allow improved inferences of BH masses. If they do not, the conclusion must be that the present low residual variances for these two relations result from overestimated bars.

Differential Time‐Series CCD Photometry of BL Camelopardalis Revisited

ABSTRACTNew differential time‐series observations of BL Camelopardalis were secured using B and V filters. It was confirmed that BL Cam is an optical double star. Differential magnitudes were obtained through a photometric profile reduction procedure to eliminate the influence of a faint adjacent star. Variations in O - C values for light maxima were investigated. We found that the parabolic period variation was recently reversed. The periods of BL Cam were investigated, and five frequencies were determined using Fourier analysis. We also investigated the relationship between metallicities and period ratios, and we compared the theoretical and observational relationships. It was found that the theoretical relationship is better than the observational one for BL Cam.

Calibration of the photometric method of heavy ion charge measurements in emulsion using a CCD camera

Abstract A previously developed method of heavy ion charge measurements in emulsion has been significantly improved. The charge measurements are based on analysis of photometric profiles of the particle tracks in emulsion. These profiles are obtained using a CCD camera mounted on an optical microscope. So far, the manual charge determination by delta ray counting had to be used for calibration of the photometric method. In this paper a complete procedure for calibration of the photometric method is shown, without resorting to the manual method.

Relationship between the thickness of stellar disks and the relative mass of a dark galactic halo

We analyze the R-and K s-band photometric profiles for two independent samples of edge-on galaxies. The thickness of old stellar disks is shown to be related to the relative masses of the spherical and disk components of galaxies. The radial-to-vertical scale length ratio for galactic disks increases (the disks become thinner) with increasing total mass-to-light ratio of the galaxies, which reflects the relative contribution of the dark halo to the total mass, and with decreasing central deprojected disk brightness (density). Our results are in good agreement with numerical models of collisionless disks that evolved to a marginally stable equilibrium state. This suggests that, in most galaxies, the vertical stellar-velocity dispersion, on which the equilibrium-disk thickness depends, is close to a minimum value that ensures disk stability. The thinnest edge-on disks appear to be low-brightness galaxies in which the dark-halo mass far exceeds the stellar-disk mass.

Weak homology of elliptical galaxies

We start by studying a small set of objects characterized by photometric profiles that have been pointed out to deviate significantly from the standard R^{1/4} law. For these objects we confirm that a generic R^{1/n} law, with n a free parameter, can provide superior fits (the best-fit value of n can be lower than 2.5 or higher than 10), better than those that can be obtained by a pure R^{1/4} law, by an R^{1/4}+exponential model, and by other dynamically justified self--consistent models. Therefore, strictly speaking, elliptical galaxies should not be considered homologous dynamical systems. Still, a case for weak homology, useful for the interpretation of the Fundamental Plane of elliptical galaxies, could be made if the best-fit parameter n, as often reported, correlates with galaxy luminosity L, provided the underlying dynamical structure also follows a systematic trend with luminosity. We demonstrate that this statement may be true even in the presence of significant scatter in the correlation n(L). Preliminary indications provided by a set of data points associated with a sample of 14 galaxies suggest that neither the strict homology nor the constant stellar mass--to--light solution are a satisfactory explanation of the observed Fundamental Plane (abridged).

Evidence for a massive dark object in NGC 4350

ABSTRACT In this work we build a detailed dynamic model for a S0 galaxy possibly hostinga central massive dark object (MDO). We show that the photometric profiles and thekinematics along the major and minor axes, including the h 3 and h 4 profiles, imply thepresence of a central MDO of mass M MDO ∼ 1.5−9.7· 10 8 M ⊙ , i.e. 0.3−2.8% of themass derived for the stellar spheroidal component. Models without MDO are unableto reproduce the kinematic properties of the inner stars and of the rapidly rotatingnuclear gas.The stellar population comprise of an exponential disc (27% of the light) anda diffuse spheroidal component (73% of the light) that cannot be represented by asimple de Vaucouleurs profile at any radius. The M/L ratios we found for the stellarcomponents (respectively 3.3 and 6.6) are typical of those ofdisc and elliptical galaxies.Key words: galaxies: individual: NGC 4350 – galaxies: kinematics and dynamics –galaxies: structure – galaxies: nuclei – dark matter 1 INTRODUCTIONThere is increasing evidence that most galaxies with a largespheroidal component host a Massive Dark Object (MDO)at their centre, with masses ranging from ∼ 10

Optical surface photometry of radio galaxies

Optical imaging observations for 50 radio galaxies are presented. For each object isophotal contours, photometric profiles, structural parameters (position angle, ellipticity, Fourier coefficients), and total magnitudes are given. These observations, obtained in the Cousins R band, complement the data presented in a previous paper and are part of a larger project aimed at studying the optical properties of low redshift () radio galaxies (Govoni et al. 1999). Comments for each individual source are reported.

Colour distributions in E-S0 galaxies

The colours distributions (with R in Cousins's system) have been measured in 44 E classified galaxies in the Local Supercluster, from pairs of frames collected by Nieto and co-workers in 1989-91. These are nearly all from the CFHT, and of sub-arsec resolution. Great attention has been given to the effects of unequal PSF's in the B and R frames upon colour distributions near centre; such effects are illustrated from model calculations and from pseudo-colours obtained from pairs of frames taken in the same band but with different seeing conditions. Appropriate corrections were systematically applied in order to derive central colours and inner gradients, although still affected by the limited resolution of the frames. The radial colour distributions have been measured in more detail than usual, considering separately the near major axis and near minor axis regions of the isophotal contours. Azimuthal colour distributions, in rings limited by selected isophotes, were also obtained. Dust patterns, i.e. patches, lanes, arcs, ..., have been detected and mapped from the colour distributions. An ad hoc dust pattern importance index (or DPII ) in a scale of 0 to 3, has been introduced to qualify their size and contrast. We have tried to find evidence of a diffuse dust concentration towards the disk, if one is apparent. Positive results (noted by the dd symbol) have been obtained for disky E's, whenever the inclination of their disk to the line of sight is large enough, and eventually also in the small isolated disks sometimes present in both boxy and disky galaxies. The red central peak occurring in many E-galaxies might be the signature of a central concentration of dust, also in cases where this peak is isolated rather than embedded in some extensive colour pattern. The properties of the near centre colour profiles have been related to a classification of nuclear photometric profiles into flat topped and sharply peaked (equivalent to core-like and power-law in the terminology of Faber et al. 1997). The published here data include the following: . Short descriptions and codes for the characters of the distribution of each object, and comparison to the results of recent surveys. . A table of the mean at the centre and at two selected isophotes, a colour gradient and the usual logarithmic gradient. . Maps of near core isochromes and B isophotes for comparison. Images of the colour distribution are made available in electronic form.

The Universality of the Fundamental Plane of E and S0 Galaxies: Sample Definition and [ITAL]I[/ITAL]-Band Photometric Data

As part of a project to compare the fundamental plane and Tully-Fisher distance scales, we present here I-band CCD photometry for 636 early-type galaxies in eight clusters and groups of galaxies. These are the A262, A1367, Coma (A1656), A2634, Cancer and Pegasus Clusters, and the NGC 383 and NGC 507 Groups. Sample selection, cluster properties, and cluster membership assignment criteria are discussed. We present photometric parameters that are used in the fundamental plane relation, the effective radius re, and the effective surface brightness μe, as derived from a r1/4 fit to the observed radial photometric profile of each galaxy. A comparison with similar data found in the literature for the Coma Cluster shows that large systematic uncertainties can be introduced in the measurement of re and μe by the particular method used to derive those parameters. However, the particular combination of these two parameters that enters in the fundamental plane relation is a quantity that can be measured with high accuracy.

Near-Infrared and Optical Morphology of the Dusty Galaxy NGC 972

Near-infrared (NIR) and optical surface photometric analyses of the dusty galaxy NGC 972 are presented. The photometric profiles in the BVRJHK bands can be fitted with a combination of Gaussian and exponential profiles, corresponding to a starburst nucleus and a stellar disk, respectively. The exponential scale length in the B band is 2.8 times larger than in the K band, which implies a central B-band optical depth as high as 11. A bulge is absent even in the NIR bands, and hence the galaxy must be of a morphological type later than the usually adopted Sb type. Relatively low rotational velocity and high gas content also favor a later type, probably Sd, for the galaxy. Only one arm can be traced in the distribution of old stars; the second arm, however, can be traced in the distribution of dust and H II regions. Data suggest a short NIR bar, which ends inside the nuclear ring. The slowly rising nature of the rotation curve rules out a resonance origin of the nuclear ring. The ring is most likely not in the plane of the galaxy, given its circular appearance, in spite of the moderately high inclination of the galaxy. The off-planar nature of the star-forming ring, the unusually high fraction (30%) of the total mass in molecular form, the presence of a nuclear starburst, and the asymmetry of spiral arms are probably the result of a merger with a gas-rich companion galaxy.

Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies

We present a catalogue of aperture photometry of galaxies, in UBVRI , assembled from three different origins: (i) an update of the catalogue of Buta et al. (1995) (ii) published photometric profiles and (iii) aperture photometry performed on CCD images. We explored different sets of growth curves to fit these data: (i) The Sersic law, (ii) The net of growth curves used for the preparation of the RC3 and (iii) A linear interpolation between the de Vaucouleurs () and exponential laws. Finally we adopted the latter solution. Fitting these growth curves, we derive (1) the total magnitude, (2) the effective radius, (3) the colour indices and (4) gradients and (5) the photometric type of 5169 galaxies. The photometric type is defined to statistically match the revised morphologic type and parametrizes the shape of the growth curve. It is coded from -9, for very concentrated galaxies, to +10, for diffuse galaxies.

Ice hazes and clouds in the Martian atmosphere as derived from the Phobos/KRFM data

During the 1989 Phobos mission, the KRFM instrument observed the equatorial region of Mars in eight spectral bands from 315 to 550 nm. Previous analysis of the data mostly concentrated on extracting the optical properties of the dust particles in the atmosphere of Mars and the properties of the surface (Moroz et al., Planet. Space Sci. 41, 569, 1993). Some features of the KRFM photometric profiles, which appear to be of atmospheric origin, have however, remained unexplained. The present work considers three cases that exhibit such features and infers the effects to be caused by various types of water ice in the atmosphere. (1) For two sessions of observations, the intensity in UV near the limb was much higher than the mean of the morning limb profiles, but decreased later to the mean level as the line of sight moved further from the limb. Explaining these variations with a model of a homogeneous constant silicate haze does not seem possible. A model including a time evolving, near surface layer of silicate partieles covered with water ice provides a better fit to the data. The inferred column density of water vapour that condensed overnight on the dust particles is about 0.5 × 10 −5 gcm −2, and the sublimation rate of these ice mantles after sunrise is of the order of 10 −15 g μm −2 s −3. The ice haze contribution to the total optical depth decreases from about 0.05 at dawn to zero within about an hour. (2) A brightness increase of another type, observed in the afternoon UV profiles of the Valles Marineris is shown to be consistent with the presence of water ice clouds. The dependence on the properties of the clouds is discussed. The size distribution of the cloud particles seems of secondary importance. Their assumed shape, however, is critical. For spherical particles, the optical depth of the cloud is deduced to be 0.05 and the water content within the cloud to be 0.54 × 10 −5 g cm −2. For particles with slightly irregular shape and rough surface both of these estimates are three times higher. (3) The photometric profiles of the Tharsis Ridge where the KRFM traces passed over the Martian volcanoes exhibit an increase in brightness in all wavelengths, but stronger in shorter wavelengths. The spectral dependence of the measured brightening is analysed to extract the properties of the clouds around Arsia Mons and Pavonis Mons. The particles of these clouds are likely to be smaller than 1 μm, and the ice column density is estimated to be in the range of 2.5 × 10 −6–4.1 × 10 −6 g cm −2.

MIXED PAIRS OF GALAXIES

ABSTRACT According to many schemes for galaxy formation, galaxy morphology should depend strongly on the environment in which a galaxy resides and, especially, in which it was formed. Therefore, in pairs of galaxies one expects to find members of similar morphological type. However, morphological studies of paired galaxies show two different categories: pairs formed by galaxies with similar morphology (EE and SS) and pairs of mixed morphology (ES), where E represents early--type galaxies and S represents late--types. Actually a significant percentage of pairs in reasonably complete samples of binary galaxies (e.g. Catalog of Isolated Pairs of Galaxies by Karachentsev) are of mixed type. Moreover, the distribution of radial velocity differences between components of mixed pairs is similar to that for concordant type (especially SS) pairs. This is further support for the contention that most are physical binaries. We used imaging, spectroscopy and stellar population synthesis to study the interaction effects in 5 mixed pairs of galaxies (AM0327-285, AM1806-852, AM1907-504, AM2016-330, AM2055-492). The present pair sample originated from a sample of 126 candidate mixed pairs that were found during a visual search on the ESO sky surveys. An isolation criterion was employed that required the distance to the nearest neighbor (with major axis diameter ≥ the diameters of the pair components) to be at least five times the pair component separation. Many of these pairs are also found in the Catalogue of Southern Peculiar Galaxies and Associations by Arp & Madore. We find that one of them, AM1907--504, is unlikely to be a physical pair because of the large velocity difference. The other 4 pairs are most likely physically bound with Delta-V ≤ 600 km/s. They can also be classified as true ES pairs since the photometric profiles for the early-type components obey an r1/4 law. We find diverse signs of interaction in our pair sample ranging from direct collisions to small distortions. In principle, this evidence is less ambiguous in mixed pairs because we are dealing with a single gas rich component. A strong but indirect form of evidence for interaction between the galaxies involves the detection of a young stellar component in the early-type members. We used Bica's stellar synthesis approach in order to detect the young stellar population in these pairs. We find that 10% to 37% of their fluxes arises from a young age population (< 5 x 108 years). We suggest that a transfer of gas appears to be the most likely way for the E components to acquire fuel for star formation activity. The only other alternative would be to invoke an unusual star formation history in ellipticals that inhabit mixed pairs.

Spectrophotometry of Mars in the KRFM experiment of the Phobos mission : some properties of the particles of atmospheric aerosols and the surface

A new analysis of the data of the KRFM experiment ( Phobos mission) is presented. The five complete photometric profiles (eight wavelengths for each) obtained in this experiment have been processed, and the calibration and the method of modelling calculations have been specified. The optical depth of the constant haze has been estimated to be within the range 0.1 < τ < 0.2. This is essentially smaller than the value predicted for the same season on the basis of the Viking landers' measurements. The imaginary part of the refraction index of the particles in the constant haze changes smoothly from 0.015 at 315 nm to 0.005 at 550 nm. This behaviour corresponds to some basaltic material, containing several percent of iron oxides (limonite, geothite, hematite). Their presence in the Martian soil was recognized a long time ago, but our study gives some new quantitative estimations of Fe 2O 3 content. The clouds above the large volcanoes have an optical depth ∼0.1 and contain about 5 × 10 −6 g cm −2 of ice particles. All the evaluations of the constant haze particles' properties have been made assuming a gamma size distribution of particles with modal radius r m = 0.4 μm and α = γ = 1. For the description of the surface's photometric properties in the whole range 315–550 nm, the roughness factor q = 0.5 is acceptable as a first approximation, although one cannot exclude that q rises with increasing wavelength. The averaged radius of the optically active particles of the surface has been evaluated as 6–7 μm. The method for the calculation of photometric profiles of Mars used in the paper is more reliable than any published version we know, because it takes into account the main optical properties of the Martian atmosphere (the presence of absorption, strong forward scattering) and surface (including a non-Lambertian reflection law).