My recent publications in reverse chronological order
full texts are gzip-ped PostScript or pdf, abstracts are HTML
Measuring the Atmospheric Attenuation at 47 (and 24) GHz
J.Köppen
DUBUS x/xxxx, xx (20xx)
Summary:
For frequencies above about 20 GHz the attenuation of signals by the Earth atmosphere becomes important. ITU’s Recommendation P.676 predicts for any radio frequency the average attenuation at the
zenith based on local weather data. The actual attenuation we can determine by measuring the noise
from the empty sky at various elevations. We did this on 47 and 24 GHz for various sky situations. If the
sky is clear or blue with only a few white clouds, the measured values agree indeed within ± 0.1 dB with
the results from the ITU formula. Clouds may increase the attenuation appreciably, and if the sky is
covered with grey clouds, the actual attenuation will be substantially greater, by as much as a few dB. In
order to measure the attenuation of the solar noise at various elevations, we tracked the Sun on its daily
path across the sky. This more direct method shows that at lower elevations the Sun noise decreases but
the sky noise increases in the expected way, and in agreement with the sky noise profile. Thus, we can
reliably measure the current attenuation by taking a ‘sky profile’ of the empty sky noise.
Know your Parabolic Antenna better from Measurements of Sun, Moon, and Ground Noise
J.Köppen
DUBUS 1/2024, 14 (2024)
Summary:
With measurements of the noise from the Sun, Moon, and ground, along with the sky noise at the elevations
of the Sun and Moon, we can obtain three estimates for the noise figure or system temperature of a
receiving station which tells about the efficiency of a (parabolic) antenna. Ideally, all three values should
be the same or very close to each other. Should the values differ in a significant way, a measured value
could be in error, or the measuring setup or procedures might need improvement. Three agreeing values
will reveal the overall noise figure of the station. Because the side and rear lobes of the antenna will pick
up noise from the surroundings, this value will be somewhat larger than the noise figure of the receiver on
its own. This gives an idea of the efficiency of the antenna, which can be used to help to optimize the antenna
and the station's overall performance.
Get Atmospheric Attenuation and Noise Figure from a Skyprofile
J.Köppen
DUBUS 4/2023, 7 (2023)
Summary:
Above about 20 GHz, the attenuation by the Earth atmosphere becomes an important parameter in the
EME link budget. It is possible to take the attenuation predicted for the average atmosphere, but this remains
an estimation, and may appreciably differ from the actual atmospheric conditions above the station.
Measuring the noise level of the empty sky at several elevations allows us to determine not only the
actual attenuation but also the noise figure (or system temperature) of the receiving system. A JavaScript
tool to analyse the data is available on the internet at:
http://portia.astrophysik.uni-kiel.de/~koeppen/JS/SkyProfileAnalysis.html
How to Measure the Width of a Narrow Beam Antenna
J.Köppen
DUBUS 3/2023, 5 (2023)
Summary:
The width of the main lobe of a paraboloidal antenna provides a direct measure of the antenna gain.
While it is easy to measure it easily by the width of a drift scan across the Sun or the Moon, this method
no longer works with the narrow beams of large dishes and higher frequencies, because one would only
measure the angular diameter of the celestial body. Fortunately, the discs of both Sun and Moon have
sharp outer edges, which the antenna beam smoothes out into wider rim profiles. This article describes
how we can use the width of the observed rim to determine the antenna beam width.
EME with Narrow Beam Antennas
J.Köppen, G.Ihninger
DUBUS 2/2023, 32 (2023)
Summary:
EME with large parabolic antennas benefits from the higher gain, but is faced with the problem that the
antenna beam widths become comparable or even narrower than the disc of the Moon. In consequence,
the power of the reflected signal is lower than predicted from the radar range equation. We compute numerically
a correcting factor, the Beam Width Factor. Narrow beams also make it possible that the beams
of the participating stations may not or cannot be pointed accurately to the same position on the Moon's
face, resulting in a further loss in signal power. This article explains how these correction factors to the
radar range equation are computed for any arrangement of the beams. A JavaScript tool to perform the
calculations and display the results is available at
http://portia.astrophysik.uni-kiel.de/~koeppen/JS/TwoBeams.html.
Aim a Narrow Beam at the Moon
J.Köppen
DUBUS 1/2023, 72 (2023)
Summary:
EME communications above about 30 GHz need high gain antennas to provide adequate transmission
power as well as strong signals on reception. The associated antenna beams can be as narrow as to cover
only a part of the lunar disc. This places higher demands on the pointing and tracking of the Moon. At
these higher frequencies, the Moon no longer represents a disc of uniform radio brightness. During its
monthly apparent journey around the Earth the Moon is illuminated by the Sun, causing the variation of
the thermal radio emission which is greater at higher frequencies. This also increases the variation of the
noise over the lunar face, which also varies with time. Thus, pointing the antenna at the maximum lunar
noise does not lead to hitting the middle of the disc. Radio images of the Moon can be computed for any
frequency and lunar phase, and the position of the brightest spot can be determined. On 47 GHz and for
antenna beam widths wider than about 0.2° the brightest spot remains always within about 0.05° of the
disc centre, and the search for maximum noise would always lead close to the centre. Only larger antennas
– e.g. HPBW 0.1° – require a greater effort for a more accurate positioning and tracking of the
Moon's middle. With the predicted radio images of the Moon one may determine offsets from the brightest
spot to centre. The interactive JavaScript tool at
http://www.astrophysik.uni-kiel.de/~koeppen/JS/AimRadioMoon.html
allows to predict the orientation of the radio Moon for any given location, time and frequency.
The Arecibo Galaxy Environment Survey XII : Optically dark HI clouds in the Leo I Group
R.Taylor, J.Köppen, P.Jáchym, R.Minchin, J.Palouš, J.L.Rosenberg,
S.Schneider, R.Wünsch, B.Deshev
Astron.J. 164, 233 (2022)
Summary:
Using data from the Arecibo Galaxy Environment Survey, we report the discovery of five HI clouds
in the Leo I group without detected optical counterparts. Three of the clouds are found midway
between M96 and M95, one is only 100 arcmin from the south-east side of the well-known Leo Ring, and
the fifth is relatively isolated. HI masses range from 2.6 E6 - 9.0 E6 Msun and velocity widths (W50)
from 16-42 km/s. Although a tidal origin is the most obvious explanation, this formation mechanism
faces several challenges. For the most isolated cloud, the diffculties are its distance from
neighbouring galaxies and the lack of any signs of disturbance in the HI discs of those systems.
The clouds also follow the baryonic Tully-Fisher relation between mass and velocity width for
normal, stable galaxies which is not expected if they are tidal in origin. By contrast, the
three clouds between M96 and M95 have no optical counterparts even though they have very similar
properties and location to the optically detected galaxy LeG 13. While overall we favour a tidal
debris scenario to explain the clouds, we cannot rule out a primordial origin. If the clouds
were produced in the same event that gave rise to the Leo Ring, they may provide important
constraints on any model attempting to explain that structure.
Lunar Noise at 80 GHz
D.Fedorov, J.Köppen
DUBUS 4/2022, 22 (2022)
Summary:
The expected EME activity in the amateur 4mm (76-80 GHz) band motivates to pay
attention to the Moon’s radiation itself, because the lunar noise is an important
natural factor limiting the receiver system temperature and therefore the real
sensitivity of EME receiving systems. We measured the lunar radio noise at various
times during the Moon's apparent orbit around the Earth with a 0.9 m offset dish
at 80 GHz. Measurements at 80 GHz are faced with several problems: attenuation by
the Earth atmosphere cannot be neglected, the beam of a 1 m diameter antenna is
narrower than the lunar angular size, and the brightness of the lunar surface
changes not only during one lunation but also varies across the lunar face,
similar to the different faces of the Moon at visual wavelengths. These issues
can be solved and are discussed. The results agree very well with previous
radioastronomical measurements. Thus, one can predict with confidence the noise
floor of an EME receiving system.
How to Measure Spillover of a Parabolic Antenna
J.Köppen
DUBUS 1/2022, 63 (2022)
Summary:
If the radiation pattern of the feed is wider than the parabolic dish which it
illuminates, the antenna picks up ground noise from outside the rim of the dish.
This causes the sky noise in the zenith to be higher than at lower elevations.
This article explains how this noise contribution can be computed. From measurements
of the sky noise at different elevation angles we can work out the spill-over
contribution in a quantitative way. This is done by modelling the data with the
aid of the online interactive JavaScript tool at
https://portia.astrophysik.uni-kiel.de/~koeppen/JS/SpillOver.html
A Closer Look at Filling Factors
J.Köppen
DUBUS 4/2021, 15 (2021)
Summary:
A parabolic dish antenna is sensitive only in a narrow beam whose width corresponds to its
size. The efficiency of EME operations depends on how much of the transmitting antenna's
radiated power is concentrated on the Moon, but also how much of the lunar thermal emission
is picked up by the receiving antenna. Likewise, for a sensible interpretation of measurements
in radio astronomy we need to know how much of a source's emssion reaches the radio telescope.
The beam width of a 40 cm dish at 100 GHz is already as narrow as the Sun's angular diameter.
This renders the interpretation of measured solar noise by simple formulae useless. For this
purpose one defines and computes the filling factor as the fraction of the antenna beam which
is filled by the source. In this article we compare simple as well as realistic filling
factor formulations, which can be inspected with the JavaScript tool at
https://portia.astrophysik.uni-kiel.de/~koeppen/JS/FillingFactors.html
Noise from the Moon
J.Köppen
DUBUS 3/2021, 100 (2021)
Summary: At radio frequencies the Moon emits thermal radiation from its
surface which is heated by the Sun. With a model for the heat transport
in the lunar soil it is possible to predict the monthly variation of the
lunar brightness temperature at any frequency. A comparison with radio
measurements of the lunar emission from the professional literature shows
that already a rather simple model is capable of matching the observations
quite well. Thus one may use the Moon as a natural noise generator with
predictable output to measure the sensitivity of a receiving system or
to act as a calibrating source for radioastronomical observations. This
article describes an on-line JavaScript tool that displays the model
predictions and compares them with existing observations.
https://portia.astrophysik.uni-kiel.de/~koeppen/JS/LunarTemps.html.
A Tool to Look at the Feeding of Parabolic Dish Antennas
J.Köppen
DUBUS 1/2021, 8 (2021)
Summary: If one ever wanted to operate a parabolic dish with 100% efficiency,
the feed antenna in its focus would need to illuminate the mirror dish evenly,
but it also must put all the power onto the dish without losing any part by
spilling over the rim of the dish. Real and realistic feeds cannot match these
conflicting requirements. Thus, a compromise must be accepted by the highest
efficiency that a given feed is able to furnish. If the radiation pattern of
the feed is known, one can compute the dish illumination, the efficiency,
and the radiation pattern of the entire assembly. As an extension of the program
Feedpatt by W1GHZ, I wrote for my use an interactive JavaScript tool. The results
are presented graphically and numerically, so that the user can easily evaluate
the properties of the antenna. This online tool is available
https://portia.astrophysik.uni-kiel.de/~koeppen/JS/AntennaFeeds.html.
Radio Observations of the Annular Solar Eclipse of 2012
K.Seki, M.Hidehiko, with J.Köppen
DUBUS 4/2020, 26 (2020)
Summary: A test observation by JJ1NNJ on 2.3 GHz of the annular solar eclipse of
21 may 2012 in Japan gave an interesting but puzzling curve, with two dips near maximum
obscuration which made it look like the letter W. The independent observation on 1.4 GHz
by JH3NYP showed the same features, proving their reality. In the challenging and exciting
process of trying to understand the data, it was realized that the 'W' had a simple origin
in the limb brightening of the Sun at radio wavelengths: When the Moon covers the Sun
centrally, this bright ring is fully seen, but just before and just after maximum obscuration,
the Moon also covers parts of the ring, thus resulting in the reduced signal making the
two dips. A couple of radio-bright active regions associated with the visible sunspots
are responsible for making the data curve unsymmetric and uneven. With the knowledge of
these features of the radio Sun, the recorded data could be very nicely modelled.
We can only strongly encourage anyone who encounters a solar eclipse to record careful
and calibrated measurements. The interpretation is a lot of work … but a lot of fun!
The 2015 Lunar Eclipse Observed at Radio Frequencies
J.Köppen
DUBUS 2/2020, 74 (2020)
Summary: Radio noise from the Moon is thermal emission of its surface, heated by solar
radiation. The signals measured by DL0SHF during the 2015 total lunar eclipse on 1.3, 8.4,
10, and 24 GHz did not show any drop of the noise level during the obscuration of sunlight.
Since the lunar soil is not solid rock but dust, sand, and small pieces of rock, it has a
rather low thermal conductivity. Hence the heat deposited at the surface layer is shared
only slowly with the deeper layers which are responsible for the radio noise in the UHF
and SHF ranges. The rather short interruption of solar irradiation during the eclipse
causes a signal drop too small to be detectable with amateur equipment.
Faint and fading tails: the fate of stripped HI gas in Virgo cluster galaxies
R.Taylor, J.Köppen, P.Jáchym, R.Minchin, J.Palouš, R.Wünsch
Astron.J.159, 218 (2020)
Abstract: Although many galaxies in the Virgo cluster are known to have lost
signifi cant amounts of HI gas, only about a dozen features are known where the HI extends
signif icantly outside its parent galaxy. Previous numerical simulations have predicted that HI
removed by ram pressure stripping should have column densities far in excess of the sensitivity
limits of observational surveys. We construct a simple model to try and quantify how many streams
we might expect to detect. This accounts for the expected random orientation of the streams in
position and velocity space as well as the expected stream length and mass of stripped HI.
Using archival data from the Arecibo Galaxy Environment Survey, we search for any streams which
might previously have been missed in earlier analyses. We report the con fident detection of ten
streams as well as sixteen other less sure detections. We show that these well-match our
analytic predictions for which galaxies should be actively losing gas, however the mass of the
streams is typically far below the amount of missing HI in their parent galaxies, implying that
a phase change and/or dispersal renders the gas undetectable. By estimating the orbital timescales
we estimate that dissolution rates of 1-10 Msun/yr are able to explain both the presence of a
few long, massive streams and the greater number of shorter, less massive features.
The Widefield Arecibo Virgo Extragalactic Survey I: New structures in the Kent cloud complex
and an extended tail on NGC 4522
R.F.Minchin, R.Taylor, J.Köppen, J.I.Davies, W.van Driel, O.Keenan
Astron.J.158, 121 (2019)
Abstract: We are carrying out a sensitive blind survey for neutral hydrogen (HI) in the
Virgo cluster and report here on the first 5° x 1° area covered, which includes
two optically-dark gas features: a fivecloud HI complex (Kent et al. 2007, 2009) and the
stripped tail of NGC 4522 (Kenney et al. 2004). We discover a sixth cloud and low velocity
gas that extends the velocity range of the Kent complex to over 450 km/s, find that around
half of the total HI ux comes from extended emission rather than compact clouds, and see
around 150 percent more gas, raising the total HI mass from 5.1E8 Msun to 1.3E9 Msun.
This makes the identification of NGC 4445 and NGC 4424 by Kent et al. (2009)
as possible progenitors of the complex less likely, as it would require an unusually high
fraction of the gas removed to have been preserved in the complex. We also identify a new
component to the gas tail of NGC 4522 extending to ~200 km/s below the velocity range of
the gas in the galaxy, pointing towards the eastern end of the complex. We consider the
possibility that NGC 4522 may be the parent galaxy of the Kent complex, but the large
velocity separation (~1800 km/s) leads us to rule this out. We conclude that, in the absence
of any better candidate, NGC 4445 remains the most likely parent galaxy, although this requires
it to have been particularly gas-rich prior to the event that removed its
gas into the complex.
The 2-D Radiation Pattern of Parabolic Dish Antennas
J.Köppen
DUBUS 1/2019, 28 (2019)
DUBUS Technik XVII, 19 (2018)
Summary: By measuring the power received at several offset positions from the Sun
one can probe the radiation pattern of an antenna, but this gives only a rough view.
A complete 2-dimensional map of the pattern can easily be obtained by letting the
Sun cross the field of view of the antenna held fixed for a few weeks in spring
or autumn. This makes use of the apparent motion of the Sun via its daily travel
over the sky but also during its slow seasonal rise in spring or fall in autumn.
Such a map shows all the details, such as the shape of the main lobe, the levels
of the side lobes, and any asymmetries and irregularities.
Radio Observations of the Total Solar Eclipse on 20 March 2015
J.Köppen, with J.J.Maintoux
DUBUS 3/2018, 24 (2018)
Summary: The total eclipse on March 20th, 2015 is observed on 1.3, 2.3, 8.4, and 10 GHz
at DL0SHF and on 1.42 GHz at F6KSX. The signal on 8.4 and 10 GHz drops in a way very
similar to that expected for visible light, because radio emission near 10 GHz comes
from the chromosphere, a thin and warm layer just on top of the photosphere which
is responsible for the visible light. On 1.3 and 2.3 GHz the eclipse begins earlier
and lasts longer than the optical eclipse and is less deep, because the radio emission
is produced by the hot corona which extends well above the chromosphere. The curve of
signal level versus time shows a couple of features, which can well be explained by
the presence of several active regions that provide radio-bright spots on the Sun.
Radiation Pattern of a Parabolic Antenna Blocked by its Feed
J.Köppen
DUBUS 1/2018, 15 (2018)
DUBUS Technik XVII, 10 (2018)
Summary: The radiation pattern of a parabolic dish antenna whose central parts are blocked
by the feed assembly differs from the pattern expected for the full dish in these aspects:
The number of side lobes is reduced by suppression of even numbered side lobes and enhancement
of the odd numbered lobes. Depending on the size of the blocking feed, it can result in the
presence of a deep minimum. The width of the main lobe is slightly reduced. This provides
a good explanation of the features seen in the patterns measured with the antennas at DL0SHF.
Ram Pressure Stripping Made Easy: An Analytical Approach
J.Köppen, P.Jáchym, R.Taylor, J.Palouš
MNRAS 479, 4367 (2018)
Abstract: The removal of gas by ram pressure stripping of galaxies is treated by a purely
kinematic description. The solution has two asymptotic limits: if the duration of
the ram pressure pulse exceeds the period of vertical oscillations perpendicular
to the galactic plane, the commonly used quasi-static criterion of Gunn & Gott
is obtained which uses the maximum ram pressure that the galaxy has experienced
along its orbit. For shorter pulses the outcome depends on the time-integrated
ram pressure. This parameter pair fully describes the gas mass fraction that is
stripped from a given galaxy. This approach closely reproduces results from SPH
simulations. We show that typical galaxies follow a very tight relation in this
parameter space corresponding to a pressure pulse length of about 300 Myr.
Thus, the Gunn & Gott criterion provides a good description for galaxies in larger
clusters. Applying the analytic description to a sample of 232 Virgo galaxies
from the GoldMine database, we show that the ICM provides indeed the ram pressures
needed to explain the deficiencies. We also can distinguish current and past strippers,
including objects whose stripping state was unknown.
Several interactive JavaScript tools which evaluate the analytical
considerations of this paper are available at
this URL
Evaluating Parabolic Antennas
J.Köppen
DUBUS 4/2017, 27 (2017)
DUBUS Technik XVI, 68 (2017)
Radio Astronomy (SARA) March-April 2018, 35 (2018)
Summary: The radiation pattern of a parabolic dish antenna, in particular the width of its main
lobe and the spacing and the level of the side lobes, gives essential information of its performance,
and from which the antenna parameters can be determined, such as gain, effective area, and efficiency.
Measurements of the sky noise and the ground noise allow the determination of the system temperature
which describes the overall internal noise level. With these parameters one can predict the
signal-to-noise ratio from a radio source.
How to Measure the Atmospheric Absorption at Radio Wavelengths
J.Köppen
DUBUS 1/2016, 70 (2016)
Summary: Since the Earth atmosphere modifies the strength of radio signals from celestial sources
and space probes by absorption and noise emission, an accurate interpretation of the signal level
requires appropriate correction. Hence one needs to know the atmospheric parameters, the most
important of which is the antenna temperature measured at the zenith. This can be determined by
measuring the sky noise at several elevations. Likewise, measurements of the Sun or the Moon at
several elevations allow to determine the sky absorption. Both methods require some time and care,
but their use at DL0SHF at frequencies between 1.3 and 24 GHz has proven that they give reliable
results, well worth the extra effort. This article explains the procedures of the measurements
and interpretation, and presents some results from DL0SHF.
Pointing Corrections for Large Radio Antennas
J.Köppen
DUBUS 4/2015, 74 (2015)
Summary: The inevitable small errors in the pointing of a large antenna, such
as tilts of the axes or collimation errors, can easily be corrected by software
which applies compensations to the desired values for azimuth and elevation.
These position-dependent corrections are computed by a set of rather simple
formulae which are described by a small number of parameters. The parameters
are derived from the differences of measured and predicted positions of known
celestial sources (Sun, Moon, CasA, etc) and by finding the set of model parameters
whose predicted errors match best the measured differences. This technique is used
at DL0SHF to allow accurate pointing at celestial sources and to ensure accurate
tracking of e.g. the Moon for EME communications. The essential details of such
software are described, along with our experiences and some examples.
Efficiently Measuring Sky Positions for Pointing Corrections
of Radio Telescopes
J.Köppen
DUBUS 3/2015, 17 (2015)
Summary: For optimum EME operations and for radio astronomy a large antenna needs to be
pointed accurately. The basis for a reliable pointing correction scheme are accurate
measurements of the pointing errors, which can be obtained by observing the Sun, Moon,
and other celestial radio sources whose positions can precisely be predicted. The results
of the simple method of searching for the maximum signal can greatly be improved, if one
also uses the information of how the signal decreases as one goes away from the source.
Bracketing the source in horizontal and vertical position by seeking the same signal
level below the maximum is an efficient and accurate approach, as applications at
DL0SHF have shown.
SALT reveals the barium central star of the planetary nebula Hen 2-39
B.Miszalski, H.M.Boffin, D.Jones, A.I.Karakas, J.Köppen,
A.A.Tyndall, S.S.Mohamed, P.Rodrigues-Gil, M.Santander-García
MNRAS 436, 3068 (2013)
IC 4663: The first unambiguous [WN] Wolf-Rayet central
star of a planetary nebula
B.Miszalski, P.A.Crowther, O.DeMarco, J.Köppen,
A.F.J.Moffat, A.Acker, T.C.Hillwig
ASPC 459, 281 (2013)
Abstract
BD-22°3467, a DAO-type star exciting the nebula Abell 35
M.Ziegler, T.Rauch, K.Werner, J.Köppen, J.W.Kruk
Astron.Astrophys. 548, 109 (2012)
A barium central star binary in the Type-I diamond ring planetary
nebula Abell 70
B.Miszalski, H.M.J.Boffin, D.J.Frew, A.Acker, J.Köppen,
A.F.J.Moffat, Q.A.Parker
MNRAS 419, 39 (2012)
PHR1315-6555: a bipolar planetary nebula in the compact Hyades-age
open cluster ESO 96-SC04
Q.A.Parker,D.J.Frew, B.Miszalski, A.V.Kovacevic, P.M.Frinchaboy,
P.D.Dobbie, J.Köppen
MNRAS 413, 1835 (2011)
Abstract
The influence of binarity on dusty obscuration events in the
planetary nebula M 2-29 and its analogues
B.Miszalski, J.Mikolajewska, J.Köppen, T.Rauch, A.Acker,
M.Cohen, D.J.Frew, A.F.J.Moffat, Q.A.Parker, A.F.Jones, A.Udalski
Astron.Astrophys. 528, A39 (2011)
Abstract
Mit Spritzgebäck und Silberscheibe zum eigenen Spektroskop
J.Köppen
Sterne und Weltraum 04/2010
Starbursts in isolated galaxies: I. The influence of stellar birth
function and the IMF
Ch.Theis, J.Köppen
Astron.Astrophys. 502, 486 (2009)
Ram pressure stripping of tilted galaxies
P.Jáchym, J.Köppen, J.Palouš, F.Combes
Astron.Astrophys. 500, 693 (2009)
Abstract
Mit "ESA-Dresden" ins Radiouniversum
J.Köppen
Sterne und Weltraum 03/2009
Gas stripping in galaxy clusters: a new SPH simulation approach
P.Jáchym, J.Palouš, J.Köppen, F.Combes
Astron.Astrophys. 472, 5 (2007)
Abstract
Full paper in gzipped pdf-file (4.4 MB)
A possible origin of the mass-metallicity relation of galaxies
J.Köppen, C.Weidner, P.Kroupa
MNRAS 375, 120 (2007)
Abstract
Full paper in pdf-file (467 kB)
Chemical compositions and plasma parameters of planetary nebulae with
Wolf-Rayet type central stars
P.Girard, J.Köppen, A.Acker
Astron.Astrophys. 463, 265 (2006)
Abstract
Full paper in pdf-file (412 kB)
ASCII file of fluxes and intensities (54 kB)
The Macquarie/AAO/Strasbourg H$\alpha$ Planetary Nebula
Catalogue: MASH
Q.A.Parker, A.Acker, D.J.Frew, M.Hartley, A.E.J.Peyaud, S.Phillipps,
D.Russeil, S.F.Beaulieu, M.Cohen, J.Köppen, J.Marcout, B.Miszalski,
D.H.Morgan, R.A.H.Morris, F.Ochsenbein, M.J.Pierce, A.E.Vaughan
MNRAS 373, 79 (2006)
Abstract
Full paper in pdf-file (1.8 MB)
Effects of episodic gas infall on the chemical abundances in
galaxies
J.Köppen, G.Hensler
Astron.Astrophys. 434, 531 (2005)
Abstract
Full paper in pdf-file (750 kB)
PFP 1: A Large Planetary Nebula Caught in the First
Stages of ISM Interaction
M.J.Pierce, D.J.Frew, Q.A.Parker, J.Köppen
Pub.Astron.Soc.Australia 21, 334 (2004)
Abstract
Full paper (950 kB)
What PNe could tell about extinction inside external galaxies
J.Köppen
Planetary Nebulae beyond the Milky Way,
Proc. ESO Workshop, Garching 19-21 May 2004,
eds. J.R. Walsh, L. Stanghellini, N.G. Douglas,
"ESO Astrophysics Symposia", Springer, (2006), p.217
Abstract
Full paper (1 kB)
Das CDROM Spectroskop
J.Köppen
Sterne und Weltraum 11/2003
Discussion: Between simple and chemodynamical models
J.Köppen
Galaxy Evolution - III. From simple approaches to self-consistent
models, Proc. EuroConference Kiel July 16-20, 2002,
eds. G.Hensler, G.Stasińska, S.Harfst, P.Kroupa, Chr.Theis,
Astrophys. Space Sciences, 284, 881, Kluwer, (2003)
This is the summary of one of the discussions sections of the
conference.
Full paper (100 kB)
A comparison of chemical and chemodynamical models
J.Köppen
Galaxy Evolution - III. From simple approaches to self-consistent
models, Proc. EuroConference Kiel July 16-20, 2002,
eds. G.Hensler, G.Stasińska, S.Harfst, P.Kroupa, Chr.Theis,
Astrophys. Space Sciences, 284, 837, Kluwer, (2003)
Abstract
Full paper (85 kB)
Evolution Chimique des Galaxies
J.Köppen
Formation et évolution des galaxies, Ecole CNRS de
Goutelas XXV, eds. A.Lançon, D.Egret, J.-L.Halbwachs,
Obs.Strasbourg et SFAA, p. 129 (2003)
This is the text (in French) of lectures held in a summer school.
Abstract
Full paper in ps-file (440 kB)
An inverse method to interpret colour-magnitude diagrams
J.-L.Vergely, J.Köppen, D.Egret, O.Bienaymé
Astron.Astrophys. 390, 917 (2002)
Abstract
Full paper in pdf-file (3.7 MB)
PN G291.4-00.3: A new Type I planetary nebula
D.Nürnberger, S.Durand, J.Köppen, Th.Stanke, M.Sterzik, S.Els
Astron.Astrophys. 377, 241 (2001)
Abstract
Full paper (800 kB)
On The Cosmic Origins Of Carbon And Nitrogen
R.B.C.Henry, M.G.Edmunds, J.Köppen
Astrophys.J. 541, 660 (2000)
Abstract
Full paper (pdf) (200 kB)
Planetary Nebulae in Clusters
J.Köppen, A.Acker
Massive Stellar Clusters, Proceedings of the international workshop
held in Strasbourg, France, November 8-11, 1999.
Eds. A.Lançon and C.Boily.
Astronomical Society of the Pacific Conference
Series., p.151 (2000)
Abstract
Full paper (33 kB)
Observations of planetary nebulae in the Galactic bulge
F.Cuisinier, W.J.Maciel, A.Acker, J.Köppen, B.Stenholm
Astron.Astrophys. 353, 543 (2000)
Abstract
Full paper (98 kB)
The hidden past of Sakurai's object:
Stellar properties before the final helium flash
F.Kerber, J.Köppen, M.Roth, S.C.Trager
Astron.Astrophys. 344, L79 (1999)
Abstract
Full paper (144 kB)
HaTr 10, a planetary nebula with extremely strong nitrogen lines
A. Tajitsu, S.Tamura, Y.Yadoumaru, R.Weinberger, J.Köppen
PASP 111, 1157 (1999)
Abstract
Text of paper (30 kB)
Fig.1 (207 kB)
Fig.2 (5 kB)
Fig.3 (7 kB)
Fig.4 (4 kB)
Classification and spectral analysis of faint central stars
of highly excited planetary nebulae
T.Rauch, J.Köppen, R.Napiwotzki, K.Werner
Astron.Astrophys. 347, 169 (1999)
Gas Flows and the Chemical Evolution of Galaxies:
III. Graphical Analysis and Secondary Elements
J.Köppen, M.G.Edmunds
MNRAS 306, 317 (1999)
Abstract
Full paper (492 kB)
There is an interactive
JAVA Applet available which demonstrates the results
of the paper with chemical evolution models with an arbitrary
history of star formation and accretion specified by the user.
The Law of Starformation in Disk Galaxies
J.Köppen
in The Magellanic Clouds and other dwarf galaxies,
Workshop Bonn/Bochum,
eds. T.Richtler, J.M.Braun, Shaker Verlag, in press (1998)
Abstract
Full paper (78 kB)
The Interstellar Extinction in the Solar Neighbourhood
J.-L.Vergely, R.Freire Ferrero, D.Egret, J.Köppen
Astron.Astrophys. 340, 543 (1998)
The Opacity of the Galactic Disk derived with Planetary
Nebulae
J.Köppen, J.-L.Vergely
MNRAS 299, 567 (1998)
Abstract
Full paper (125 kB)
Condensation and evaporation of interstellar clouds in
chemodynamical models of galaxies
J.Köppen, Ch.Theis, G.Hensler
Astron.Astrophys. 331, 524 (1998)
Abstract
Full paper (232 kB)
If you like to have a more detailed description of how the system of
equations was analyzed and what came out, you can get a
rough manuscript here (255 kB)
The star formation law in disk galaxies -
a Bayesian view
J.Köppen, H.-E.Fröhlich
Astron.Astrophys. 325, 961 (1997)
Abstract
Full paper (111 kB)
The variation of abundances in planetary nebulae with height
above the Galactic plane
J.Köppen, F.Cuisinier
Astron.Astrophys. 318, 98 (1996)
Abstract
Full paper (132 kB)
Spectral analysis of the planetary nebula LoTr 4 and its very hot
hydrogen-deficient central star
T.Rauch, J.Köppen, K.Werner
Astron.Astrophys. 310, 613 (1996)
Spectrophotometric observations of planetary nebulae
high above the Galactic plane
F.Cuisinier, A.Acker, J.Köppen
Astron.Astrophys. 307, 217 (1995)
Abstract
Quasar absorption lines: The chemical compositions of the
absorbing clouds
O.J.Dittmann, J.Köppen
Astron.Astrophys. 297, 671 (1995)
Abstract
The self-regulated star formation in chemodynamical models of
galaxies
J.Köppen, C.Theis, G.Hensler
Astron.Astrophys. 296, 99 (1995)
Abstract
Full paper (146 kB)
Chemical evolution in an inhomogeneous interstellar medium
M.Wilmes, J.Köppen
Astron.Astrophys. 294, 47 (1994)
Abstract
Analysis of BD+33 2642 - a newly detected planetary nebula
in the galactic halo and its central star
R.Napiwotzki, U.Heber, J.Köppen
Astron.Astrophys. 292, 239 (1994)
Abstract
Spectral analysis of the planetary nebula K 1-27 and its very hot
hydrogen-deficient central star
T.Rauch, J.Köppen, K.Werner
Astron.Astrophys. 286, 543 (1994)
Abundance gradients from disk planetary nebulae: O, Ne, S, and Ar
W.J.Maciel, J.Köppen
Astron.Astrophys. 282, 436 (1994)
The evolution of abundance gradients in spiral galaxies
J.Köppen
Astron.Astrophys. 281, 26 (1994)
Abstract
Spectrophotometric survey of southern planetary nebulae:
III. Automatic model analysis
M.Samland, J.Köppen, A.Acker, B.Stenholm
Astron.Astrophys. 264, 184 (1991)
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last update: 13 Feb. 2006 J.Köppen