arXiv subjects

V. Cayatte

Publications and source records attributed to V. Cayatte.

43 records · Page 3Linked to original sources

arXiv1998

Multiwavelength Observations of a Seyfert 1 Galaxy Detected in ACO 3627

ACO 3627 is a rich, nearby cluster of galaxies at the core of the Great Attractor. At the low galactic latitude of b = -7.2 the galactic extinction is significant. Nevertheless, its proximity makes it a prime target for studies of environmental effects on its cluster members. Here, we report on a multi-wavelength study of a Seyfert 1 galaxy at 30 arcminutes from the centre of ACO 3627. Its Seyfert nature was discovered spectroscopically and confirmed in X-rays. We have obtained B_J and R_C CCD photometry as well as J, H, K and L aperture photometry at the SAAO, low and high resolution spectroscopy (ESO and SAAO), 21 cm line observations (Parkes Observatory) and X-ray ROSAT PSPC data. The Seyfert 1 galaxy is of morphology SBa(r). It has a nearby companion (dS0) but shows no signs of interaction. A consistent value for the galactic extinction of A_B = 1.6 mag could be determined. The nucleus of the Seyfert is very blue with a strong (B_J - R_C) colour gradient in the inner 2.5 arcsec. The extinction-corrected near-infrared colours of WKK 6092 are typical of a Seyfert 1 and the X-ray spectrum conforms to the expectation of a Seyfert as well. The galaxy has a very low HI flux. This could be explained by its morphology, but also -- due to its very central position within the rich Norma cluster -- to ram pressure stripping.

astro-ph↗

arXiv1998

The ESO Slice Project [ESP] galaxy redshift survey: V. Evidence for a D=3 sample dimensionality

The issue of the approximate isotropy and homogeneity of the observable universe is one of the major topics in modern Cosmology: the common use of the Friedmann-Robertson-Walker [FWR] metric relies on these assumptions. Therefore, results conflicting with the ``canonical'' picture would be of the utmost importance. In a number of recent papers it has been suggested that strong evidence of a fractal distribution with dimension D~2 exists in several samples, including Abell clusters [ACO] and galaxies from the ESO Slice Project redshift survey [ESP].Here we report the results of an independent analysis of the radial density run,N(<R)~R^D, of the ESP and ACO data. For the ESP data the situation is such that the explored volume, albeit reasonably deep, is still influenced by the presence of large structures. Moreover, the depth of the ESP survey (z<0.2) is such to cause noticeable effects according to different choices of k-corrections, and this adds some additional uncertainty in the results. However, we find that for a variety of volume limited samples the dimensionality of the ESP sample is D~3, and the value $D = 2$ is always excluded at the level of at least five (bootstrap) standard deviations. The only way in which we reproduce D~2 is by both unphysically ignoring the galaxy k-correction and using Euclidean rather than FRW cosmological distances. In the cluster case the problems related to the choice of metrics and k-correction are much lessened, and we find that ACO clusters have D_{ACO} = 3.07 +- 0.18 and D_{ACO} = 2.93 +- 0.15 for richness class R \geq 1 and R \geq 0, respectively. Therefore D=2 is excluded with high significance also for the cluster data.

astro-ph↗

arXiv1997

The ESO Slice Project (ESP) galaxy redshift survey: II. The luminosity function and mean galaxy density

(Abridged) The ESO Slice Project (ESP) is a galaxy redshift survey we have completed as an ESO Key-Project over ~23 square degrees, in a region near the South Galactic Pole. The survey is nearly complete to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with reliable redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams: spanning a volume of ~ 5 x 10^4 Mpc^3 at the sensitivity peak (z ~ 0.1), it provides an accurate determination of the "local" luminosity function and the mean galaxy density. We find that, although a Schechter function is an acceptable representation of the luminosity function over the entire range of magnitudes (M < -12.4), our data suggest the presence of a steepening of the luminosity function for M > -17. The amplitude and the alpha and M^* parameters of our luminosity function are in good agreement with those of the AUTOFIB redshift survey (Ellis et al. 1996). Viceversa, our amplitude is significantly higher, by a factor ~ 1.6 at M ~ M^*, than that found for both the Stromlo-APM (Loveday et al. 1992) and the Las Campanas (Lin et al. 1996) redshift surveys. Also the faint end slope of our luminosity function is significantly steeper than that found in these two surveys. Large over- and under- densities are clearly seen in our data. In particular, we find evidence for a "local" underdensity (for D < 140 Mpc) and a significant overdensity at z ~ 0.1. When these radial density variations are taken into account, our derived luminosity function reproduces very well the observed counts for b_J < 19.4, including the steeper than Euclidean slope for b_J < 17.

astro-ph↗

arXiv1997

The ESO Slice Project (ESP) galaxy redshift survey: I. Description and First Results

The ESO Slice Project (ESP) is a galaxy redshift survey we have recently completed as an ESO Key-Project. The ESP covers 23.3 square degrees in a region close to the South Galactic Pole. The survey is nearly complete (85%) to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with reliable redshift determination. In this paper, the first in a series that will present the results of the ESP survey, we describe the main characteristics of the survey and briefly discuss the properties of the galaxy sample. From a preliminary spectral analysis of a large sub-sample of 2550 galaxies we find that the fraction of actively star-forming galaxies increases from a few percent for the brightest galaxies up to about 40% for the galaxies fainter than M= -16.5. The most outstanding feature in the ESP redshift distribution is a very significant peak at z ~ 0.1. The detection of similar peaks, at the same distance, in other surveys in the same region of the sky, suggests the presence of a large bidimensional structure perpendicular to the line of sight. The minimum size of this structure would be of the order of 100 x 50 Mpc, comparable with the size of the Great Wall.

astro-ph↗

arXiv1996

The Performance of MEFOS, the ESO Multi-Object Fibre Spectrograph

We are describing a new multi-fibre positioner, MEFOS, that was in general use at the La Silla Observatory, and implemented at the prime focus of the ESO 3.6 m telescope. It is an arm positioner using 29 arms in a one degree field. Each arm is equipped with an individual viewing system for accurate setting and carries two spectroscopic fibres, one for the astronomical object and the other one for the sky recording needed for sky subtraction. The spectral fibres intercept 2.5 arcsec on the sky and run from the prime focus to the Cassegrain, where the B&C spectrograph is located. After describing the observational procedure, we present the first scientific results.

astro-ph↗

arXiv1994

Preliminary Results from the ESO Slice Project (ESP)

We present the first results of a galaxy redshift survey, ESO Slice Project (ESP), we are accomplishing as an ESO Key-Project over about 30 square degrees in a region near the South Galactic Pole. The limiting magnitude is b_J = 19.4. Observations have been almost completed and about 90% of the data obtained so far has been reduced providing about 3000 galaxy redshifts. We present some preliminary results concerning the large scale galaxy distribution and their luminosity function.

astro-ph↗

arXiv1993

Preliminary Results from the ESO Slice Project (ESP)

We present the first results of a galaxy redshift survey, ESO Slice Project (ESP), we are accomplishing as an ESO Key--Project over about 40 square degrees in a region near the South Galactic Pole. The limiting magnitude is $b_J = 19.4$. Up to now $\sim 85\%$ of the observations has been completed and $\sim 65\%$ of the data has been reduced providing $\sim 2000$ galaxy redshifts. We present some preliminary results concerning the large scale galaxy distribution, the luminosity function and the properties of galaxies with spectra showing prominent emission lines.

astro-ph↗