148 research outputs found
A catalogue of velocities in the cluster of galaxies Abell 85
We present a catalogue of velocities for 551 galaxies (and give the
coordinates of 39 stars misclassified as galaxies in our photometric plate
catalogue) in a region covering about 100'100' (0.940.94 Mpc
for an average redshift of 0.0555, assuming H=50 km s
Mpc) in the direction of the rich cluster Abell 85. This catalogue
includes previously published redshifts by Beers et al. (1991) and Malumuth et
al. (1992), together with our 367 new measurements. A total of 305 galaxies
have velocities in the interval 13350-20000 km s, and will be considered
as members of the cluster. Abell 85 therefore becomes one of the clusters with
the highest number of measured redshifts; its optical properties are being
investigated in a companion paper.Comment: Accepted for publication in A&AS, Table 4 available in electronic
form onl
A catalogue of velocities in the direction of the cluster of galaxies Abell 496
We present a catalogue of velocities for 466 galaxies in the direction of the
cluster Abell 496, in a region covering about 160' x 160' (9.2 x 9.2 Mpc for an
average redshift for Abell 496 of 0.0331, assuming H=50 km s
Mpc). This catalogue includes previously published redshifts by Proust
et al. (1987), Quintana and Ramirez (1990) and Malumuth et al. (1992),
redshifts from the CfA redshift survey, together with our new measurements. A
total of 274 galaxies have velocities in the 7800-11800 km/s interval, and will
be considered as members of the cluster. Abell 496 therefore becomes one of the
few clusters with a high number of measured redshifts; its physical properties
are investigated in a companion paper.Comment: Accepted for publication in Astronomy & Astrophysics, Supplement
Serie
Extragalactic Large-Scale Structures behind the Southern Milky Way. IV. Redshifts Obtained with MEFOS
Abbreviated: As part of our efforts to unveil extragalactic large-scale
structures behind the southern Milky Way, we here present redshifts for 764
galaxies in the Hydra/Antlia, Crux and Great Attractor region (266deg < l <
338deg, |b| < 10deg), obtained with the Meudon-ESO Fibre Object Spectrograph
(MEFOS) at the 3.6-m telescope of ESO. The observations are part of a redshift
survey of partially obscured galaxies recorded in the course of a deep optical
galaxy search behind the southern Milky Way. A total of 947 galaxies have been
observed, a small percentage of the spectra (N=109, 11.5%) were contaminated by
foreground stars, and 74 galaxies (7.8%) were too faint to allow a reliable
redshift determination. With MEFOS we obtained spectra down to the faintest
galaxies of our optical galaxy survey, and hence probe large-scale structures
out to larger distances (v <~ 30000 km/s) than our other redshift follow-ups.
The most distinct large-scale structures revealed in the southern Zone of
Avoidance are discussed in context to known structures adjacent to the Milky
Way.Comment: 11 pages, 7 figures; accepted for publication in A&A. Tables 1 and 2
will be available in electronic format at the CDS. Figure 1 at full
resolution, and both tables are available at
http://mensa.ast.uct.ac.za/~pwoudt/data/H4462/
A far UV study of interstellar gas towards HD34078: high excitation H2 and small scale structure - Based on observations performed by the FUSE mission and at the CFHT telescope
To investigate the presence of small scale structure in the spatial
distribution of H2 molecules we have undertaken repeated FUSE UV observations
of the runaway O9.5V star, HD34078. In this paper we present five spectra
obtained between January 2000 and October 2002. These observations reveal an
unexpectedly large amount of highly excited H2. Column densities for H2 levels
from (v = 0, J = 0) up to (v = 0, J = 11) and for several v = 1 and v = 2
levels are determined. These results are interpreted in the frame of a model
involving essentially two components: i) a foreground cloud (unaffected by
HD34078) responsible for the H2 (J = 0, 1), CI, CH, CH+ and CO absorptions; ii)
a dense layer of gas (n = 10E4 cm-3) close to the O star and strongly
illuminated by its UV flux which accounts for the presence of highly excited
H2. Our model successfully reproduces the H2 excitation, the CI fine-structure
level populations as well as the CH, CH+ and CO column densities. We also
examine the time variability of H2 absorption lines tracing each of these two
components. From the stability of the J = 0, 1 and 2 damped H2 profiles we
infer a 3 sigma upper limit on column density variations Delta(N(H2))/N(H2) of
5% over scales ranging from 5 to 50 AU. This result clearly rules out any
pronounced ubiquitous small scale "density" structure of the kind apparently
seen in HI. The lines from highly excited gas are also quite stable (equivalent
to Delta(N)/N <= 30%) indicating i) that the ambient gas through which HD34078
is moving is relatively uniform and ii) that the gas flow along the shocked
layer is not subject to marked instabilitie
Mm-wave HCO+, HCN and CO absorption toward NGC1052
We used the Plateau de Bure Interferometer to observe 3mm J=1-0
absorption lines of \hcop, HCN and CO toward the core of the nearby elliptical,
megamaser-host galaxy NGC1052. The lines are relatively weak, with peak optical
depths 0.03 for \hcop and HCN and 0.1 for CO. Nonetheless the inferred column
density of molecular gas 2N(\HH) \simeq 5\times10^{21}~\pcc is consistent
with the degree of reddening inferred toward the nucleus from observations of
the Balmer series of hydrogen. Mm-wave absorption line profiles are somewhat
broader than those of H I and OH, perhaps because lower free-free opacity at
mm-wavelengths exposes higher-velocity material nearer the nucleus. Overall,
the OH/\hcop ratio in NGC1052 is as expected from the strong relationship
established in local diffuse clouds but the optical depth ratio varies strongly
over the line profiles. Similar variations are also seen toward Cen A, which
has very different line ratios among H I, OH and \hcop for very nearly the same
amount of OH absorption.Comment: Accepted, A&A August 26, 200
The relation between column densities of interstellar OH and CH molecules
We present a new, close relation between column densities of OH and CH
molecules based on 16 translucent sightlines (six of them new) and confirm the
theoretical oscillator strengths of the OH A--X transitions at 3078 and 3082
\AA (0.00105, 0.000648) and CH B--X transitions at 3886 and 3890 \AA, (0.00320,
0.00210), respectively. We also report no difference between observed and
previously modelled abundances of the OH molecule.Comment: 4 pages, 0 figures, accepted for publication in MNRA
Discovery of Extreme Examples of Superclustering in Aquarius
We report the discovery of two highly extended filaments and one extremely
high density knot within the region of Aquarius. The supercluster candidates
were chosen via percolation analysis of the Abell and ACO catalogs and include
only the richest clusters (R >= 1). The region examined is a 10x45 degree strip
and is now 87% complete in cluster redshift measurements to mag_10 = 18.3. In
all, we report 737 galaxy redshifts in 46 cluster fields. One of the
superclusters, dubbed Aquarius, is comprised of 14 Abell/ACO clusters and
extends 110h^-1Mpc in length only 7 degrees off the line-of-sight. On the
near-end of the Aquarius filament, another supercluster, dubbed Aquarius-Cetus,
extends for 75h^-1Mpc perpendicular to the line-of-sight. After fitting
ellipsoids to both Aquarius and Aquarius-Cetus, we find axis ratios (long-to-
midlength axis) of 4.3 for Aquarius and 3.0 for Aquarius-Cetus. We fit
ellipsoids to all N>=5 clumps of clusters in the Abell/ACO measured-z cluster
sample. The frequency of filaments with axis ratios >=3.0 (~20%) is nearly
identical with that found among `superclusters' in Monte Carlo simulations of
random and random- clumped clusters, however, so the rich Abell/ACO clusters
have no particular tendency toward filamentation. The Aquarius filament also
contains a `knot' of 6 clusters at Z ~0.11, with five of the clusters near
enough togeteher to represent an apparent overdensity of 150. There are
three other R >= 1 cluster density enhancements similar to this knot at lower
redshifts: Corona Borealis, the Shapely Concentration, and another grouping of
seven clusters in Microscopium. All four of these dense superclusters appear
near the point of breaking away from the Hubble Flow, and some may now be in
collapse, but there is little evidence of any being virialized.Comment: 45 pages (+ e-tables), 7 figures, AASTeX Accepted for Publication in
Ap
The ESO Slice Project (ESP) galaxy redshift survey: III. The Sample
The ESO Slice Project (ESP) is a galaxy redshift survey extending over about
23 square degrees, in a region near the South Galactic Pole. The survey is ~85%
complete to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with
redshift determination.
The ESP survey is intermediate between shallow, wide angle samples and very
deep, one-dimensional pencil beams; the spanned volume is ~ 5 x 10^4 Mpc^3 at
the sensitivity peak (z ~ 0.1).
In this paper we present the description of the observations and of the data
reduction, the ESP redshift catalogue and the analysis of the quality of the
velocity determinations.Comment: 10 pages, 4 encapsulated figures, uses A&A LATEX; A&A Supplements in
press (June 1998 issue
The Stellar Composition of the Star Formation Region CMa R1 -- III. A new outburst of the Be star component in Z CMa
We report on a recent event in which, after more than a decade of slowly
fading, the visual brightness of the massive young binary Z CMa suddenly
started to rise by about 1 magnitude in December 1999, followed by a rapid
decline to its previous brightness over the next six months. This behaviour is
similar to that exhibited by this system around its eruption in February 1987.
A comparison of the intrinsic luminosities of the system with recent
evolutionary calculations shows that Z CMa may consist of a 16 M_sun B0 IIIe
primary star and a ~ 3 M_sun FUOr secondary with a common age of ~ 3 x 10^5 yr.
We also compare new high-resolution spectra obtained in Jan. and Feb. 2000,
during the recent rise in brightness, with archive data from 1991 and 1996. The
spectra are rich in emission lines, which originate from the envelope of the
early B-type primary star. The strength of these emission lines increased
strongly with the brightness of Z CMa. We interpret the collected spectral data
in terms of an accretion disc with atmosphere around the Herbig B0e component
of Z CMa, which has expanded during the outbursts of 1987 and 2000. A high
resolution profile of the 6300 A [O I] emission line, obtained by us in March
2002 shows an increase in flux and a prominent blue shoulder to the feature
extending to ~ -700 km/s, which was much fainter in the pre-outburst spectra.
We propose that this change in profile is a result of a strong change in the
collimation of a jet, as a result of the outburst at the start of this century.Comment: 22 pages, 12 figures, accepted for publication in MNRA
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