389 research outputs found
The Norma cluster (ACO3627): II. The near infrared K_s-band luminosity function
A deep K_s-band photometric catalogue of galaxies at the core of the rich,
nearby Norma cluster (ACO3627) is presented. The survey covers about 45 by 45
square arcmin (slightly less than 1/3 Abell radius), which corresponds to
approx. 0.8 Mpc^2 at the adopted distance (v_cmb/H0) of 70 Mpc of this cluster.
The survey is estimated to be complete to a magnitude of M_Ks <~ -19.5 mag.
This extends into the dwarf regime, 6 magnitudes below M_Ks*. The catalogue
contains 390 objects, 235 of which are classified as likely or definite
galaxies and 155 as candidate galaxies. The Ks-band luminosity function (LF) is
constructed from the photometric sample, using a spectroscopic subsample to
correct for fore- and background contamination. We fit a Schechter function
with a characteristic magnitude of M_Ks* = -25.39 \pm 0.80 mag and faint-end
slope of alpha = -1.26 \pm 0.10 to the data. The shape of the LF is similar to
those found in previous determinations of the cluster LF, in both optical and
near infrared. The Schechter parameters agree well with those of recent field
LFs, suggesting that both the shape of the bright end and the faint end slope
are relatively insensitive to environment.Comment: 18 pages, 6 figures, 8 tables (includes full photometric catalogue as
appendix), accepted for publication in MNRA
Applying Operations Research techniques to planning of train shunting
In this paper, we discuss a model-based algorithmic approach for supporting planners in the creation of shunt plans for passenger trains. The approach provides an example of a mathematical model and a corresponding solution approach for model based support. We introduce a four-step solution approach and we discuss how the planners are supported by this approach. Finally, we present computational results for these steps and give some suggestions for further research.A* search;railway optimization;real world application;routing
High Speed Photometry of SDSS J013701.06-091234.9
We present high speed photometry of the Sloan Digital Sky Survey cataclysmic
variable SDSS J013701.06-091234.9 in quiescence and during its 2003 December
superoutburst. The orbital modulation at 79.71\pm0.01 min is double humped; the
superhump period is 81.702\pm0.007 min. Towards the end of the outburst late
superhumps with a period of 81.29\pm0.01 min were observed. We argue that this
is a system of very low mass transfer rate, and that it probably has a long
outburst interval.Comment: 5 pages, 8 figures. Accepted for publication in MNRA
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/
SN 1998bw at late phases
We present observations of the peculiar supernova SN 1998bw, which was
probably associated with GRB 980425. The photometric and spectroscopic
evolution is monitored up to 500 days past explosion. We also present modeling
based on spherically symmetric, massive progenitor models and very energetic
explosions. The models allow line identification and clearly show the
importance of mixing. From the late light curves we estimate that about 0.3-0.9
solar masses of ejected Nickel-56 is required to power the supernova.Comment: With 3 figures Accepted for ApJ Letter
Extragalactic Large-Scale Structures behind the Southern Milky Way. -- II. Redshifts Obtained at the SAAO in the Crux Region
In our systematic optical galaxy search behind the southern Milky Way, 3760
(mostly unknown) galaxies with diameters D > 0.2 arcminutes were identified in
the Crux region (287 < l < 318 degrees, |b| < 10 degrees, Woudt &
Kraan-Korteweg 1997). Prior to this investigation, only 65 of these galaxies
had known redshifts. In order to map the galaxy distribution in redshift space
we obtained spectra for 226 bright (B_J < 18.0 mag) objects with the 1.9m
telescope of the South African Astronomical Observatory (SAAO). Two main
structures crossing the Galactic Plane in the Crux region have now become
clear. A narrow, nearby filament from (l,b) = (340 deg, -25 deg) to the
Centaurus cluster can be traced. This filament runs almost parallel to the
extension of the Hydra-Antlia clusters found earlier and is part of what we
have earlier termed the ``Centaurus Wall'' extending in redshift-space between
0 < v < 6000 km/s (Fairall & Paverd 1995). The main outcome of this survey
however, is the recognition of another massive extended structure between 4000
< v < 8000 km/s. This broad structure, dubbed the Norma Supercluster (Woudt et
al. 1997), runs nearly parallel to the Galactic Plane from Vela to ACO 3627
(its centre) from where it continues to the Pavo cluster. This massive
structure is believed to be associated with the Great Attractor. The survey has
furthermore revealed a set of cellular structures, similar to those seen in
redshift space at higher galactic latitudes, but never before seen so clearly
behind the Milky Way.Comment: Accepted for publication in Astronomy & Astrophysics. 13 pages,
LaTex, 6 encapsulated postscript figures, requires l-aa.sty and epsf.sty.
Original figures and tables are available upon request (E-mail:
[email protected]
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