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In this work we show how well can the cosmological parameters be constrained using galaxy cluster data. We also show how in the process of fitting the model which attempts to describe the data it is possible to get some information about the cluster scaling relations T-M and L_x-T. Among other conclusions we found that only low density universes (Omega approx. 0.3 with or without cosmological constant) are compatible with recent data sets. These constraints will be improved with future SZ data., Comment: Proceedings of 'Galaxy Clusters and the High Redshift Universe Observed in X-rays' at XXIth Moriond Astrophysics Meeting (March 2001). 8 pages, 6 figures. Uses moriond.sty

An estimation of the number and amplitude (in flux) of the extragalactic point sources that will be observed by the Planck Mission is presented in this paper. The study is based on the Mexican Hat wavelet formalism introduced by Cayon et al. 2000. Simulations at Planck observing frequencies are analysed, taking into account all the possible cosmological, Galactic and Extragalactic emissions together with noise. With the technique used in this work the Planck Mission will produce a catalogue of extragalactic point sources above fluxes: 1.03 Jy (857 GHz), 0.53 Jy (545 GHz), 0.28 Jy (353 GHz), 0.24 Jy (217 GHz), 0.32 Jy (143 GHz), 0.41 Jy (100 GHz HFI), 0.34 Jy (100 GHz LFI), 0.57 Jy (70 GHz), 0.54 Jy (44 GHz) and 0.54 Jy (30 GHz), which are only slightly model dependent (see text). Amplitudes of these sources are estimated with errors below 15%. Moreover, we also provide a complete catalogue (for the point sources simulation analysed) with errors in the estimation of the amplitude below 10%. In addition we discuss the possibility of identifying different point source populations in the Planck catalogue by estimating their spectral indices., Comment: 13 pages, 2 figures, submitted to MNRAS

We show how future measurements of the SZ effect (SZE) can be used to constrain the cosmological parameters. We combine the SZ information expected from the Planck full-sky survey, N(S), where no redshift information is included, with the N(z) obtained from an optically-identified SZ-selected survey covering less than 1% of the sky. We demonstrate how with a small subsample (approx. 300 clusters) of the whole SZ catalogue observed optically it is possible to drastically reduce the degeneracy among the cosmological parameters. We have studied the requirements for performing the optical follow-up and we show the feasibility of such a project. Finally we have compared the cluster expectations for Planck with those expected for Newton-XMM during their lifetimes. It is shown that, due to its larger sky coverage, Planck will detect a factor approx. 5 times more clusters than Newton-XMM and also with a larger redshift coverage., Comment: 14 pages, 10 figures. Submitted to MNRAS. Figs. 4 and 5 are bitmapped versions of the full resolution figures which can be found in http://www.ifca.unican.es/~diego/

We present a combined maximum-entropy method (MEM) and Mexican Hat wavelet (MHW) analysis in order to recover the different components of the microwave sky. We apply this technique to simulated observations by the ESA Planck satellite in small patches of the sky. In particular, the introduction of the MHW allows one to detect and subtract the brightest point sources present in the input data and therefore to improve the reconstructions of the CMB and foreground components achieved by MEM on its own. In addition, a point source catalogue at each Planck frequency is produced, which is more complete and accurate than those obtained by each technique independently., Comment: 7 pages, 2 figures. To appear in the proceedings of The MPA/ESO/MPE Joint Astronomy Conference "Mining the Sky" held in Garching, Germany, July 31 - August 4 2000

We study two different methods to test Gaussianity in CMB maps. One of them is based on the partition function and the other on the morphology of hot and cold spots. The partition function contains information on all the moments and scales, being a useful quantity to compress the large data sets expected from future space missions like Planck. In particular, it contains much richer information than the one available through the radiation power spectrum. The second method utilizes morphological properties of hot and cold spots such as the eccentricity and number of spots in CMB maps. We study the performance of both methods in detecting non-Gaussian features in small scale CMB simulated maps as those which will be provided by the Planck mission., Comment: 6 pages, 2 figures

In this work we show how galaxy clusters can be used to discriminate among different cosmological models. We have used available X-ray & optical cluster data to constrain the cosmological parameters as well as the cluster scaling relations, T-M and L-T. We also show the power of future SZE data to constrain even more these parameters., Comment: 3 pages, 1 figure. To appear in the proceedings of The MPA/ESO/MPE Joint Astronomy Conference "Mining the Sky" held in Garching, Germany, July 31 - August 4 2000. To be publisehd in the Springer-Verlag series "ESO Astrophysics Symposia"

We investigate the power of geometrical estimators on detecting non-Gaussianity in the cosmic microwave background. In particular the number, eccentricity and Gaussian curvature of excursion sets above (and below) a threshold are studied. We compare their different performance when applied to non-Gaussian simulated maps of small patches of the sky, which take into account the angular resolution and instrumental noise of the Planck satellite. These non-Gaussian simulations are obtained as perturbations of a Gaussian field in two different ways which introduce a small level of skewness or kurtosis in the distribution. A comparison with a classical estimator, the genus, is also shown. We find that the Gaussian curvature is the best of our estimators in all the considered cases. Therefore we propose the use of this quantity as a particularly useful test to look for non-Gaussianity in the CMB., Comment: 9 pages, 6 postscript figures, submitted to MNRAS

We have used recent X-ray and optical data in order to impose some constraints on the cosmology and cluster scaling relations. Generically two kind of hypotheses define our model. First we consider that the cluster population is well described by the standard Press-Schechter (PS) formalism, and second, these clusters are supposed to follow scaling relations with mass: Temperature-Mass (T-M) and X-ray Luminosity-Mass (L_x - M). As a difference with many other authors we do not assume specific scaling relations to model cluster properties such as the usual $T-M$ virial relation or one observational determination of the $L_x-T$ relation. Instead we consider general free parameter scaling relations. With the previous model (PS plus scalings) we fit our free parameters to several X-ray and optical data with the advantage over many other works that we consider all the data sets at the same time. This prevents us from being inconsistent with some of the available observations. Among other interesting conclusions, we find that only low-density universes are compatible with all the data considered and that the degeneracy between $\Omega_m$ and $\sigma_8$ is broken. Also we obtain interesting limits on the parameters characterizing the scaling relations., Comment: 11 pages, 7 figures. MNRAS accepted version

Gravitational lensing predicts an enhancement of the density of bright, distant QSOs around foreground galaxies. We measure this QSO-galaxy correlation w_qg for two complete samples of radio-loud quasars, the southern 1Jy and Half-Jansky samples. The existence of a positive correlation between z~1 quasars and z~0.15 galaxies is confirmed at a p=99.0% significance level (>99.9%) if previous measurements on the northern hemisphere are included). A comparison with the results obtained for incomplete quasar catalogs (e.g. the Veron-Cetty and Veron compilation) suggests the existence of an `identification bias', which spuriously increases the estimated amplitude of the quasar-galaxy correlation for incomplete samples. This effect may explain many of the surprisingly strong quasar-galaxy associations found in the literature. Nevertheless, the value of w_qg that we measure in our complete catalogs is still considerably higher than the predictions from weak lensing. We consider two effects which could help to explain this discrepancy: galactic dust extinction and strong lensing., Comment: 9 pages, 6 figures, MNRAS accepted

In this work we show that combining different cluster data sets is a powerful tool to constrain both, the cosmology and cluster properties. We assume a model with 9 parameters and fit them to 5 cluster data sets. From that fit, we conclude that only low density universes are compatible with the previous data and we also get some interesting conclusions on the rest of parameters., Comment: 6 pages, 2 figures. Contribution to the Proceedings of Moriond 2000 "Energy Densities in the Universe", Les Arcs, France, January 22-29 2000

We consider the 2D wavelet transform with two scales to study sky maps of temperature anisotropies in the cosmic microwave background radiation (CMB). We apply this technique to simulated maps of small sky patches of size 12.8 \times 12.8 square degrees and 1.5' \times 1.5' pixels. The relation to the standard approach, based on the cl's is established through the introduction of the scalogram. We consider temperature fluctuations derived from standard, open and flat-Lambda CDM models. We analyze CMB anisotropies maps plus uncorrelated Gaussian noise (uniform and non-uniform) at idfferent S/N levels. We explore in detail the denoising of such maps and compare the results with other techniques already proposed in the literature. Wavelet methods provide a good reconstruction of the image and power spectrum. Moreover, they are faster than previously proposed methods., Comment: latex file 7 pages + 5 postscript files + 1 gif file; accepted for publication in A&AS

Analysis and denoising of Cosmic Microwave Background (CMB) maps are performed using wavelet multiresolution techniques. The method is tested on $12^{\circ}.8\times 12^{\circ}.8$ maps with resolution resembling the experimental one expected for future high resolution space observations. Semianalytic formulae of the variance of wavelet coefficients are given for the Haar and Mexican Hat wavelet bases. Results are presented for the standard Cold Dark Matter (CDM) model. Denoising of simulated maps is carried out by removal of wavelet coefficients dominated by instrumental noise. CMB maps with a signal-to-noise, $S/N \sim 1$, are denoised with an error improvement factor between 3 and 5. Moreover we have also tested how well the CMB temperature power spectrum is recovered after denoising. We are able to reconstruct the $C_{\ell}$'s up to $l\sim 1500$ with errors always below $20% $ in cases with $S/N \ge 1$., Comment: latex file 9 pages + 5 postscript figures + 1 gif figure (figure 6), to be published in MNRAS

We propose an alternative analysis of the microwave background temperature anisotropy maps that is based on the study of the roughness of natural surfaces. We apply it to large angle anisotropies, such as those measured by COBE-DMR. We show that for a large signal to noise experiment, the spectral index can be determined independently of the normalization. We then analyze the 4 yr COBE map and find for a flat $\Omega=1$ universe, that the best-fitting value for the spectral index is $n = 1.15^{+0.39}_{-0.34}$ and for the amplitude $Q_{rms-PS}= 14.1^{+3.9}_{-3.5}\mu K$. For $n=1$, the best-fitting normalization is $Q_{rms-PS}|_{n=1}= 16.2^{+1.4}_{-1.3}\mu K$., Comment: 17 pages, 4 figures (1 in colour), LaTeX, uses aaspp4.sty, ApJ, in press, November 1, 1999 issue, Vol. 525 #1

We present an alternative method to analyse cosmic microwave background (CMB) maps. We base our analysis on the study of the partition function. This function is used to examine the CMB maps making use of the different information embedded at different scales and moments. Using the partition function in a likelihood analysis in two dimensions (Q_rms,n), we find the best-fitting model to the best data available at present the COBE--DMR 4 years data set. By means of this analysis we find a maximum in the likelihood function for n=1.8 (-0.65 +0.35) and Q_rms-PS = 10 (-2.5 +3) muK (95 % confidence level) in agreement with the results of other similar analyses (Smoot et al. 1994 (1 yr), Bennet et al. 1996 (4 yr)). Also making use of the partition function we perform a multifractal analysis and study the possible fractal nature of the CMB sky. We find that the measure used in the analysis is not a fractal. Finally, we use the partition function for testing the statistical distribution of the COBE--DMR data set. We conclude that no evidence of non-Gaussianity can be found by means of this method., Comment: 9 pages, 7 figures. To be published in MNRAS

We imaged the X-ray error box of GRB 980703, beginning 22.5 hours after the gamma--ray event, in both the optical R and near-infrared H bands. A fading optical/IR object was detected within the X-ray error box, coincident with the variable radio source reported by Frail et al. (1998a), who also detected the optical transient independently of us. Further imagery revealed the GRB host galaxy, with R = 22.49 +/- 0.04 and H = 20.5 +/- 0.25, the brightest so far detected. When excluding its contribution to the total flux, both the R and H-band light curves are well-fit by a power-law decay with index alpha~1.4. Our data suggest an intrinsic column density in the host galaxy of ~ 3.5 x 10^21 cm^-2 which indicates the existence of a dense and rich-gas medium in which the GRB occurred, thus supporting the hypernova model scenarios., Comment: Accepted for publication in Astrophysical Journal Letters

We present a K survey of 29 fields covering approximately 90 arcmin^2 from the Medium Deep Survey (MDS) catalogue down to a completeness magnitude of K=18.0 (limiting magnitude K=19.0). The morphology obtained by the MDS team using high resolution images from HST/WFPC2 along with our NIR observations allow a Colour-Magnitude and Colour-Colour analysis that agrees in general with spectral evolution models (Bruzual & Charlot 1998) especially if a reasonable range of metallicities for the Simple Stellar Populations used (0.2 < Z/Zsolar < 2.5) is considered. However, a significant population of spheroids was found, which appear bluer than expected, confirming previous observations (Forbes et al. 1996, Koo et al. 1996, Glazebrook et al. 1998). This blueness might possibly signal the existence of non-negligible star formation in ellipticals and bulges at medium redshift. A number counts calculation for different morphological types show disks become the dominant population at faint magnitudes. The median redshift of the sample is z~0.2, from a photometric redshift estimation using V-K and I-K. A search for EROs in the survey field was also performed, with no detection of objects having I-K > 4.5, setting an upper limit to the number density of EROs at dn_{EROs}/d\Omega < 0.011 arcmin^{-2} (K < 18.0)., Comment: LaTeX file, uses mn.sty. Submitted to MNRAS, revised version after referee's report. 7 pages with 8 EPS figures

We present a list of candidates for high redshift late-type galaxies in the field around the z=3.79 quasar PC1643+4631A. Deep U,V and R imaging has been used to search for objects with a strong Lyman break between U and V, characteristic of galaxies with high hydrogen column densities at $z\sim 3$. A further study of the red objects detected by Hu & Ridgway (1994) has been done, allowing the temptative identification of many of them as low redshift ($z\sim 0.4$) elliptical galaxies., Comment: 5 pages LaTeX (aa.cls), plus 4 EPS figures. Accepted in Astronomy & Astrophysics

We present a method, based on the correlation function of excursion sets above a given threshold, to test the Gaussianity of the CMB temperature fluctuations in the sky. In particular, this method can be applied to discriminate between standard inflationary scenarios and those producing non-Gaussianity such as topological defects. We have obtained the normalized correlation of excursion sets, including different levels of noise, for 2-point probability density functions constructed from the Gaussian, \chi_n^2 and Laplace 1-point probability density functions in two different ways. Considering subdegree angular scales, we find that this method can distinguish between different distributions even if the corresponding marginal probability density functions and/or the radiation power spectra are the same., Comment: 7 pages latex file using mn.sty + 4 postscript figures, to appear in MNRAS

A thorough study of QSO-galaxy correlations has been done on a region close to the North Galactic Pole using a complete subsample of the optically selected CFHT/MMT QSO survey and the galaxy catalog of Odewahn and Aldering (1995). Although a positive correlation between bright QSOs and galaxies is expected because of the magnification bias effect, none is detected. On the contrary, there is a significant (>99.6%) anticorrelation between z<1.6 QSOs and red galaxies on rather large angular distances. This anticorrelation is much less pronounced for high redshift z>1.6 QSOs, which seems to exclude dust as a cause of the QSO underdensity. This result suggests that the selection process employed in the CFHT/MMT QSO survey is losing up to 50% of low redshift z<1.6 QSOs in regions of high galaxy density. The incompleteness in the whole z<1.6 QSO sample may reach 10% and have important consequences in the estimation of QSO evolution and the QSO autocorrelation function., Comment: 17 pages LaTeX (aasms4), plus 6 EPS figures. To be published in the Astronomical Journal

Correlations between the magnification or polarization of background sources, induced by gravitational lensing due to the large-scale structure, and the positions of foreground galaxies are investigated. We found that their amplitude is enhanced with respect to correlations for a single population. We analize the dependence of the correlations with the density parameter \Omega considering a nonlinear evolution of the matter power spectrum. The contribution of the linear evolution is negligible at scales below several arcminutes. Detailed results on the dependence of the correlations on the redshift of the foreground and background populations for different cosmological models are presented. The effect reaches its maximum amplitude for foreground populations with relatively small redshifts due to the fast increase of the nonlinear matter power spectrum at recent times., Comment: 7 pages, 7 figures, mn.sty, accepted in MNRAS

K-band imaging of a sample of 21 radiogalaxies with z \sim 1.5 reveals the existence of a statistical association of foreground galaxies with the positions of the radiosources. The excess is detected within a 1' radius at a high significance level (>99.8%). K-band light is a good tracer of stellar mass, so this result indicates the existence of an association between foreground mass perturbations and background radiosources, as expected from the magnification bias effect, and confirms previous results obtained for other high-z radio-loud AGN., Comment: 4 pages, 1 figure, A&A Latex, accepted for publication as a letter to A&A

We present properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We obtain analytical expressions of several topological descriptors: mean number of maxima and the probability distribution of the gaussian curvature and the eccentricity of the peaks. These quantities are calculated as functions of the radiation power spectrum, assuming a gaussian distribution of temperature anisotropies. We present results for angular resolutions ranging from 5' to 20' (antenna FWHM), scales that are relevant for the MAP and COBRAS/SAMBA space missions and the ground-based interferometer experiments. Our analysis also includes the effects of noise. We find that the number of peaks can discriminate between standard CDM models, and that the gaussian curvature distribution provides a useful test for these various models, whereas the eccentricity distribution can not distinguish between them., Comment: 13 pages latex file using aasms4.sty + 3 tables + 2 postscript figures, to appear in ApJ (March 1997)

We have performed RIJHK_S imaging of the field around the z=2.67 quasar Q0836+113, which presents several metal line and a damped Ly\alpha absorption systems in its spectrum. The images reveal the existence of a red K_S=18.9 object \approx 11 arcsec from the quasar. On the basis of the empirical relationships between absorption radius and luminosity we conclude that this object may be the CIV absorber at z=1.82. This could be the first detection of a high redshift galaxy causing high-ionisation absorption. After carefully subtracting the QSO, we do not detect, up to a 3\sigma limiting magnitude for extended objects of K_S=20.8, the damped Ly\alpha absorber apparently detected as a Ly\alpha emitter at z=2.47. It is also suggested, that object ``SW'' from Wolfe et al. (1992) could be the galaxy responsible for the claimed MgII absorption at z=0.37., Comment: 6 pages, 6 figures, aatex. Accepted for publication in Astronomy & Astrophysics

We have studied the distribution of $B_J<20.5$ galaxies from the ROE/NRL COSMOS/UKST catalogue around two samples of $z>0.3$ QSOs with similar redshift distributions. The first sample is formed by 144 radio-loud QSOs from the Parkes Catalogue, and the other contains 167 optically selected QSOs extracted from the Large Bright Quasar Survey. It is found that there is a $\approx 99.0%$ significance level excess of COSMOS/UKST galaxies around the PKS QSOs, whereas there is a marginal defect of galaxies around the LBQS QSOs. When the distribution of galaxies around both samples is compared, we found that there is an overdensity of galaxies around the PKS sample with respect to the LBQS sample anticorrelated with the distance from the QSOs at a $99.7%$ significance level. Although this result apparently agrees with the predictions of the double magnification bias, it is difficult to explain by gravitational lensing effects alone; dust in the foreground galaxies and selection effects in the detection of LBQS QSOs should be taken into account. It has been established that the lines of sight to PKS flat-spectrum QSOs go through significatively higher foreground galaxy densities than the directions to LBQS quasars, what may be partially related with the reported reddening of PKS QSOs., Comment: 18 pages, 8 figures, AASTeX, accepted for publication in ApJ

We have made a likelihood statistical analysis of the angular correlations in the {\it COBE}-DMR two-year sky maps by Monte Carlo simulation of the temperature fluctuations. We assume an open universe and consider as primordial power spectrum the Harrison-Zeldovich one, $P(k)=Ak$. We find that the flatness of the universe is not implied by the data. The quadrupole normalization amplitude, $Q_{rms-PS}$, is related to the density parameter, $\Omega$, by $Q_{rms-PS} = 10.67 + 55.81 \Omega - 128.59 \Omega^2 + 81.26 \Omega^3\ \mu$K. We have determined the p.d.f. of $\Omega$ due to cosmic plus sampling (i.e. $20^\circ$ galactic cut) variance which generically shows a bimodal shape. The uncertainty as given by the r.m.s. is $\approx 0.35$, therefore to better constrain $\Omega$ experiments sensitive to higher multipoles ($l>20$) should be considered., Comment: 4 pages, 2 figures, 1 table, uuencoded encapsulated postscript file. Figure 2 available upon request

We have found a statistically significant (99.1 \%) excess of red ($O-E>2$) galaxies with photographic magnitudes $E<19.5$, $O< 21$ taken from the APM Sky Catalogue around $z \sim 1$ radiosources from the 1Jy catalogue. The amplitude, scale and dependence on galaxy colours of the observed overdensity are consistent with its being a result of the magnification bias caused by the weak gravitational lensing of large scale structures at redshift $z \approx 0.2-0.4$ and are hardly explained by other causes, as obscuration by dust., Comment: uuencoded file containing 3 ps files: the main text, a table and a figure. To appear in ApJ Letters

We have carried out spectroscopic observations of the high redshift ($z\approx 3.4$) radio galaxy 0902+34 at intermediate resolution with the William Herschel Telescope. The dynamical spectral ranges covered are 4600-5480 \AA and 5920-7680 \AA with resolutions of 5.4 \AA and 9.5 \AA, respectively. We detect a continuum that is almost flat and resolve three emission lines: Ly$\alpha$, C IV $\lambda$1549 and He II $\lambda$1640, the last one previously undetected. The line ratios are similar to the typical values found for narrow-line high redshift radio galaxies. Line ratios observed in different regions of the galaxy seem to indicate the presence of strong ionization and/or dust density gradients. We have not detected any Ly$\alpha$ absorption at z=3.3968 (red wing of the Ly$\alpha$ emission line) as might be expected from the absorption found at 21 cm by other authors using the VLA and Arecibo antennas. We discuss possible models for the H I absorbing cloud., Comment: 14 pages; uuencode file containing 2 .ps files; figures upon request

A statistical analysis of texture on the {\it COBE}-DMR first year sky maps based on the genus and spot number is presented. A generalized $\chi^2$ statistic is defined in terms of ``observable'' quantities: the genus and spot density that would be measured by different cosmic observers. This strategy together with the use of Monte Carlo simulations of the temperature fluctuations, including all the relevant experimental parameters, represent the main difference with previous analyses. Based on the genus analysis we find a strong anticorrelation between the quadrupole amplitude $Q_{rms-PS}$ and the spectral index $n$ of the density fluctuation power spectrum at recombination of the form $Q_{rms-PS}= 22.2 \pm 1.7 - (4.7 \pm 1.3) \times n\ \mu$K for fixed $n$, consistent with previous works. The result obtained based on the spot density is consistent with this $Q_{rms-PS} (n)$ relation. In addition to the previous results we have determined, using Monte Carlo simulations, the minimum uncertainty due to cosmic variance for the determination of the spectral index with the genus analysis. This uncertainty is $\delta n\approx 0.2$., Comment: 5 pages, uuencode file containing text and 1 figure. MNRAS in press.

We have taken deep $R$-band images of fields around five radiogalaxies: 0956+47, 1217+36, 3C256, 3C324 and 3C294 with $1

The LiteBIRD mission will map polarized fluctuations in the cosmic microwave background (CMB) to search for the signature of gravitational waves from inflation, potentially opening a window on the Universe a fraction of a second after the Big Bang. CMB measurements from space give access to the largest angular scales and the full frequency range to constrain Galactic foregrounds, and LiteBIRD has been designed to take best advantage of the unique window of space. LiteBIRD will have a powerful ability to separate Galactic foreground emission from the CMB due to its 15 frequency bands spaced between 40 and 402 GHz and sensitive 100-mK bolometers. LiteBIRD will provide stringent control of systematic errors due to the benign thermal environment at the second Lagrange point, L2, 20-K rapidly rotating half-wave plates on each telescope, and the ability to crosscheck its results by measuring both the reionization and recombination peaks in the B-mode power spectrum. LiteBIRD would be the next step in the series of CMB space missions, COBE, WMAP, and Planck, each of which has given landmark scientific discoveries.