Beamswitching has been used at 10, 15 and 33 GHz to map the microwave background over the Declination range 30° to 45°, covering more than one steradian of the sky. The beamwidth is 5° and the beam-throw is ±8° at each frequency. The three data sets are used to separate Galactic emission from intrinsic CMB emission. For the scan at Dec = 40° the intrinsic fluctuation level is ΔTrms = 48+21−15 μK on a coherence scale of 4°; the equivalent analysis for a Harrison-Zeldovich model gives a power spectrum normalisation of Qrms = 22+10−6 μK. The value of the fluctuation amplitude calculated from the likelihood analysis of the two-dimensional data set is ΔTrms = 54 ± 13 μK at 10 GHz and 39+8−7 μK at 15 GHz.

While the temperature anisotropy of the cosmic microwave background is proved to be a promising tool for probing the early Universe, the CMB polarization is another important clue for extracting more cosmic information. We give a full analysis of the auto- and cross-correlations between the CMB Stokes parameters. In particular, we derive the windowing function for an antenna with Gaussian response in polarization experiment, and construct correlation function estimators corrected for instrumental noise. They are applied to calculate the signal to noise ratios for future MAP and Planck anisotropy and polarization measurements.

The anisotropy of cosmic microwave background radiation (CMBR) was measured by COBE satellite (Smoot et al. 1992). Their remarkable results show a rms-normalized amplitude of (1.3 ± 0.4) ×10−5 on the scale of 10° with a thermal spectrum for CMBR quadrupole anisotropy. In near future a new generation of COBE, e.g. COBERAS or Planck (Lubin, 1997) would be lunched, the precision of which is 3–4 magnitude higher than nowaday COBE's. But the anisotropy can be explained in a different way, since a 10−5 anisotropy on scale of 10° might be caused by voids and supercluster (Blumenthal et al., 1992). The additional redshift from voids or supercluster is called Rees-Sciama effects.

Although the CMB anisotropy is an important probe of primordial fluctuations at recombination, which carries information on the cosmological parameters as well as the nature of dark matter, CMB photons are also affected gravitationally by nonlinear structures between recombination and the present epoch. In this paper, using Thompson & Vishniac's model [1], we investigate the effect of a void network on the CMB anisotropy in the Einstein-de Sitter background. In particular, we estimate both the Rees-Sciama effect [2] and the gravitational lensing effect (see, e.g., [3]).

I review recent observational progress concerning the evolution of the morphological distribution of galaxies in the rich cluster environment and in the faint field population. By coupling HST imagery with ground-based spectroscopic diagnostics, evidence accumulates that galaxy morphology can be a transient phenomenon reflecting various changes in the star formation rate. Possible physical processes responsible for these changes are discussed. Future progress in understanding them will depend on securing 2-D spectroscopic data for representative systems.

We discuss the formation and evolution of galaxies in view of recent mid-infrared deep surveys made using Infrared Space Observatory. A special interest is addressed to finding reddened massive populations at high redshifts.

A recognized problem when searching for primeval galaxies at cosmological distances is a definition of a firm selection criterion (alternative to a direct but extremely time-demanding measure of z) to single out high-redshift candidates from the plethora of other more or less peculiar objects (i.e. AGN, starburst galaxies etc.) at lower distances.

The case of the HST “Deep Field” (HDF) observations (Williams et al. 1996) is especially relevant in this regard as galaxies up to z = 3.2 have been detected in the field (Steidel et al. 1996).

There is a compelling evidence for old ages of giant elliptical galaxies, about 3 Gyrs older than our Galaxy, from space ultraviolet observations and new population synthesis models. Alternative interpretation requires ad-hoc assumptions yet it produces poor fitting to observational data. If confirmed by future space UV mission, this would provide evidence for non-zero cosmological constant from time scale test.

Star formation history in galaxies is strongly correlated to their present-day colors and the Hubble sequence can be considered as a sequence of different star formation history. Therefore we can model the cosmic star formation history based on the colors of local galaxies, and comparison to direct observations of luminosity density evolution at high redshift gives a new test for the cosmological parameters which is insensitive to merger history of galaxies. The luminosity density evolution in 0 < z < 1 observed by the Canada-France Redshift Survey in three wavebands of 2800Å, 4400Å, and 1μm indicates that the Λ-dominated flat universe with λ0 ∼ 0.8 (> 0.53 at 95%CL) is strongly favored.

The cosmic star formation rate (SFR) at z > 2 is also compared to the latest data of the Hubble Deep Field including new data which were not incorporated in the previous work of Totani, Yoshii, & Sato (1997), and our model of the luminosity density of spiral galaxies taking account of gas infall is consistent with the observations. Starbursts in elliptical galaxies, which are expected from the galactic wind model, however overproduce SFRs and hence they should be formed at z ≳ 5 or their UV emission has to be hidden by dust extinction. The amount of metals in galactic winds and escaping ionizing photons are enough to contaminate the Lyα forests or to reionize the universe.

Some aspect of a semi-empirical model of galaxy formation is presented. In this model, galaxy formation proceeds through a series of rapid non-merging collisions with surrounding objects. For a given galaxy, a collision at an epoch z is characterized in terms of the fractional rate of change of binding energy induced by the tidal field [1]. The total rate of change of binding energy during the lifetime of the galaxy is computed in an Einstein-de Sitter universe, assuming that collisions continuously occur from birth up to the present day against a set of background galaxies with various masses. Rules for the formation of morphological types are then derived along the following (phenomenological) line: substantial or efficient collisions – characterized by a high rate of energy exchange – drive the formation of elliptical galaxies, whereas little or inefficient collisions lead to the formation of disks. These rules are coupled to the Press & Schechter mass function for a Cold Dark Matter spectrum normalized to the present distribution of X-ray clusters, allowing one to predict the evolution, for each morphological type, of number densities as a function of redshift. The model reproduces the observed present-day morphology-density relation [2] and predicts the formation redshift of field ellipticals to be z ≥ 2, while spirals form at z ≤ 1.5. Predictions are made for the redshift evolution of morphological populations in the field as well as in clusters (see [3] for more details).

Empirical evidence suggests that the stellar population in LBDS 53W091 is significantly younger than the dominant population in M32. We have used evolutionary population synthesis models to estimate the age of the dominant population in these stellar systems. The age of LBDS 53W091 is in the range from 1 to 2 Gyr and depends on the specific model. Older ages require sub-solar metallicity models. The estimates of the age of the dominant population in M32 range from 3 to 5 Gyr and depend not only on the model but also on the SED of this galaxy used in the fits. The same models predict an age of 11 to 13 Gyr for the stars in a typical old E/S0 galaxy. This age is consistent with the age of the metal-rich galactic bulge globular clusters NGC 6553, NGC 6528, and Terzan 5. Passive evolution seems an adequate scenario for the evolution of the stellar population in E galaxies from z = 1.6 to z = 0. The dominant population in M32 is genuinely young (3 to 5 Gyr), independently than an older stellar population may be present in this galaxy. Thus, M32 may not be representative of galaxies that evolve passively. The length of time for which these galaxies have existed as individual dynamical entities is not determined by our models. The age of the Λ = 0, Ω = 1 universe at z = 1.552 is 1.6h–1 Gyr. Hence, a 1 to 2 Gyr old galaxy at z = 1.552 poses no problem for this universe as long as h ≤ 0.8. In this universe, the 13 Gyr limit for the E/S0 galaxy at z = 0 requires h ≤ 0.5. The most likely reason for the difference between our age estimate of 1 to 2 Gyr for LBDS 53W091 and the value of 3.5 Gyr derived by Dunlop et al. (1996) and Spinrad et al. (1997), is the fact that these authors did not require that the population synthesis models that they used fitted simultaneously the UV break amplitudes and the observed R – J, R – H, and R – K colors of this galaxy. This will be discussed in detail elsewhere. We thank H. Spinrad, A. Dey, and D. Stern for kindly sending to us their remarkable spectrum of LBDS 53W091.

We have developed a semianalitical approach to study galaxy formation and evolution in the cosmological context. Disk galaxies (dark matter halo+luminous disk) are considered to be formed through an extended process of gravitational collapse, whose character is determined by the statistical properties of the density fluctuation field assumed here to be Gaussian. Gas disks in centrifugal equilibrium within the collapsing dark halos are built up (detailed angular momentum conservation is assumed), and their galactic evolution is calculated with a model which consider all the gravitational interactions, the hydrodynamics of the ISM, and the SF process. A bulge as product of stellar disk gravitational instabilities is constructed. To study general behaviors a Gaussian σ8 = 1 SCDM model is used. For a given mass one obtains a range of dark matter configurations. The average case is in excellent agreement with results of cosmological N-body simulations. The slope of the mass-velocity relation agrees with the slope of the H- and I-band Tully-Fisher relations, but the velocities are too high. This problem dissapears if the power spectrum is renormalized to σ8 = 0.57, suggesting that the TF relation is result of the natural extension to galactic scales of the galaxy distribution power spectrum, and that on the basis of its origin are the cosmological initial conditions. The scatter on the mass-velocity relation is realistic. The models predict disk exponential surface brightness (SB) profiles, nearly flat rotation curves, and negative radial gradients in the B-V color. The obtained, gas fractions, B-V colors, central SBs μB0, bulge-to-disk (b/d) ratios, and rotation velocities (for σ8 = 0.57) are in agreement with observations, and their correlations are similar to those which define the Hubble sequence, including the LSB galaxies. These properties and correlations are the product of the combination of three fundamental physical factors: the mass, the mass aggregation history (MAH), and the initial angular momentum. The intensive properties are almost invariant to the mass, the MAH determines the B-V color, and the spin parameter λ mainly influences on μB0, and b/d ratio.

We present a method for automated classification of galaxies with low signal-to-noise (S/N) spectra typical of redshift surveys. We develop spectral simulations based on the parameters for the 2dF Galaxy Redshift Survey and investigate the technique of Principal Component Analysis when applied to spectra of low S/N. It is found that the projection onto the first 8 Principal Components hold most of the real spectral information, with later projections only adding noise. Using these components as input, we train an Artificial Neural Network (ANN) to classify the noisy simulated spectra into morphological classes. We find that more than 90% of our sample of normal galaxies are correctly classified into one of five morphological classes for simulations at bJ=19.7.

We performed N-body simulation on special-purpose computer, GRAPE-4, to investigate the structure of dark matter halos (Fukushige, T. and Makino, J. 1997, ApJL, 477, L9). Universal profile proposed by Navarro, Frenk, and White (1996, ApJ, 462, 563), which has cusp with density profiles ρ ∝ r−1 in density profile, cannot be reproduced in the standard Cold Dark Matter (CDM) picture of hierarchical clustering. Previous claims to the contrary were based on simulations with relatively few particles, and substantial softening. We performed simulations with particle numbers an order of magnitude higher, and essentially no softening, and found that typical central density profiles are clearly steeper than ρ ∝ r−1, as shown in Figure 1. In addition, we confirm the presence of a temperature inversion in the inner 5 kpc of massive galactic halos, and give a natural explanation for formation of the temperature structure.

The aim of this programme is to determine the luminosity function of field galaxies in different bands for a unique sample. From the ESP [1] redshift survey of 3344 bj ≤ 19.4 galaxies, we have extracted a fair subsample and obtained multicolor photometry for 354 (11%) galaxies in the V, R (Johnson) and i (Gunn) filters and for 148 (4%) in the K′ band. Errors on the total magnitudes are smaller than 0.1 in all bands. In order to obtain absolute magnitudes, we applied k-corrections [2] after deriving a rough morphological classification based on color information. Here we present a by product of this programme: the determination of the color-luminosity relationship. The figure shows how the rest-frame Bj-K' color is strongly related to the absolute i magnitude while such correlation is not present using optical colors. If we assume Mi is a good mass tracer, the figure indicates that bluer galaxies are the less massive ones.

We have investigated the masses and extents of dark halos of spiral galaxies by two methods. First, we have reanalyzed HI outer rotation curves so far obtained considering the velocity uncertainties. We confirmed that many HI rotation curves indicate the existence of dark matter to some extent. However, we also found that only few rotation curves provide direct evidences for halos extended beyond 10 disk scale length. On the other hand, recent HI observations revealed that several galaxies have declining rotation curves that are approximated by Keplerian in the outermost regions. Considering the velocity uncertainties in the outer rotation curves, we found that these declining rotation curves are not rare compared to flat rotation curves. If these declining rotation curves indeed trace the mass truncation, these results indicate that some dark halos have moderate masses that are comparable or slightly larger than disk masses.

We calculate the evolution of high redshift galaxies by spectral type with our unified chemically consistent spectrophotometric evolution code. This model takes into account the increasing initial metallicity of successive stellar generations using recently published metallicity dependent stellar evolutionary tracks, color calibrations and spectra (Möller et al. 1997).

We analyse how the consideration of a realistic metallicity distribution affects the evolutionary and cosmological corrections in various bands as a function of redshift. For various spectral types of galaxies and various cosmological parameters we present the color and magnitude evolution as a function of redshift and compare them with observations.

We have made a CO (J=2−1) observation using the Nobeyama 45m telescope aimed at examining physical properties of the molecular gas in the object. Upper limit obtained is 1.8 mK (3σ) at a velocity resolution of 100 km s−1, which leads to an upper limit on the molecular gas mass of 5.3 × 1011M⊙, if we assume a line width of 250 km s−1 obtained in J = 5–4 line and the Galactic CO-to-H2 conversion factor of 4.5 M⊙ K km s−1 pc2. The line ratio between 2–1 line and 5–4 line as well as those from 7–6 and 4–3 lines (Omont et al. 1996) imply that the mean gas density is as high as 103–5 cm−3, which is comparable to that in nearby star burst galaxies (e.g., Solomon et al. 1992).

We observed three 0.44 square degree fields centered on the Coma cluster center (Coma-1), about 1 degree SW of the Coma center (Coma-3), and on a control field in SA57 with the mosaic CCD camera at the prime focus of the 4.2-m William Herschel Telescope. We detected 5628, 5020, and 4323 galaxies down to R = 22 mag in Coma-1, Coma-3, and SA57 fields, respectively. We measure the magnitude and color within the variable aperture r90 in which about 90% of the total flux is included. The histograms of (B–R) colors of galaxies are made for four magnitude bins of width ΔR = 2 mag covering 13 < R < 21 mag for each of the three fields. The mean colors and the 1σ scatters of the Coma galaxies are obtained by a histogram subtraction technique (Coma-1/3 minus SA57). We find a very shallow slope of the color-magnitude relation (CMR), Δ(B–R)/ΔR=−0.0037, which indicates nearly a constant (B–R) color over 6 magnitude in 15 < R < 21 mag (−19.5 < MR < −13.5 at Coma cluster). Dwarf galaxies are dominant in this magnitude range, and we conclude that the mean color of dwarf galaxies in the Coma clusters is nearly constant at (B–R) ∼ 1.6–1.7, which is similar to the color of the faint end of giant elliptical galaxies.

The formation of stars in proto-galactic clouds can be viewed as two step processes i.e. the fragmentation of proto-galactic clouds and evolution of these fragments into stars. We consider here the latter process, the contraction of protosteller clouds (∼ 1M⊙) which consist of primordial gas. We investigate cooling processes by calculating the radiative transfer of H2 rotational/vibrational lines. We consider clouds in hydrostatic equilibrium as initial conditions. Comparing two timescales, the freefall time and the timescale of quasi-static contraction (∼ tcool, the cooling time) of these clouds, we find that as the clouds contract, the ratio of two timescales tff/tqsc, i.e. the efficiency of cooling, becomes larger even under the existence of cold and opaque envelope. Especially for the fragments of primordial filamentary clouds (tff ∼ tqsc initially), they collapse dynamically in the freefall timescale. This efficiency of cooling is utterly peculiar to the line cooling.