64 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
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/
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
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
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
Parkes HI observations of galaxies behind the southern Milky Way. - I. The Hydra/Antlia region (l : 266 to 296 deg)
As part of our program to map the large-scale distribution of galaxies behind
the Milky Way, we used the Parkes 210 ft (64 m) radio telescope for pointed HI
observations of a sample of low surface-brightness (due to heavy obscuration)
spiral galaxies selected from the deep optical Zone of Avoidance (ZOA) galaxy
catalog in the Hydra/Antlia region (Kraan-Korteweg 2000a). Searching a
simultaneous velocity range of either 300 to 5500 km/s or 300 to 10500 km/s to
an rms level of typically 2 - 4 mJy resulted in detections in 61 of the 139
pointings, leading to a total of 66 detections (an additional detection was
made in a reference position, and two other pointings revealed two and four
independent signals respectively). Except for 2 strong HI emitters identified
in the shallow Zone of Avoidance HI survey (Henning et al. 2000), all HI
detections are new. An analysis of the properties of the observed and detected
galaxies prove that pointed HI observations of highly obscured galaxies allow
the tracing of a population of nearby, intrinsically large and bright spiral
galaxies that otherwise would not be recovered. The new data identified a
previously unrecognized nearby group at l=287.5, b=-9.5, V=1700 km/s, the
continuation of the Hydra/Antlia filament on the opposite side of the Galactic
plane, and helped to delimit a distinct void in the ZOA centered at 2000 km/s.Comment: Accepted for publication in Astron. & Astrophys., 17 pages with 12
encapsulated ps-figure
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
The CRE1 carbon catabolite repressor of the fungus Trichoderma reesei: a master regulator of carbon assimilation
<p>Abstract</p> <p>Background</p> <p>The identification and characterization of the transcriptional regulatory networks governing the physiology and adaptation of microbial cells is a key step in understanding their behaviour. One such wide-domain regulatory circuit, essential to all cells, is carbon catabolite repression (CCR): it allows the cell to prefer some carbon sources, whose assimilation is of high nutritional value, over less profitable ones. In lower multicellular fungi, the C2H2 zinc finger CreA/CRE1 protein has been shown to act as the transcriptional repressor in this process. However, the complete list of its gene targets is not known.</p> <p>Results</p> <p>Here, we deciphered the CRE1 regulatory range in the model cellulose and hemicellulose-degrading fungus <it>Trichoderma reesei </it>(anamorph of <it>Hypocrea jecorina</it>) by profiling transcription in a wild-type and a delta-<it>cre1 </it>mutant strain on glucose at constant growth rates known to repress and de-repress CCR-affected genes. Analysis of genome-wide microarrays reveals 2.8% of transcripts whose expression was regulated in at least one of the four experimental conditions: 47.3% of which were repressed by CRE1, whereas 29.0% were actually induced by CRE1, and 17.2% only affected by the growth rate but CRE1 independent. Among CRE1 repressed transcripts, genes encoding unknown proteins and transport proteins were overrepresented. In addition, we found CRE1-repression of nitrogenous substances uptake, components of chromatin remodeling and the transcriptional mediator complex, as well as developmental processes.</p> <p>Conclusions</p> <p>Our study provides the first global insight into the molecular physiological response of a multicellular fungus to carbon catabolite regulation and identifies several not yet known targets in a growth-controlled environment.</p
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