105 research outputs found
Long Period Variables in Local Group Dwarf Galaxies
No full textIn this work the results are presented of an extensive search for Long Period Variables stars (LPVs) in a sample of Local Group irregular dwarf galaxies. The methods applied for the detection and the extraction of the variable sources are explained. Extensive completeness simulations were carried out to asses the impact on the resulting catalog caused by the observing pattern and algorithms used.
The resulting catalog of LPVs was together with color-magnitude diagrams used to draw conclusions on the star-formation history in these galaxies
The evolution of the luminosity functions in the FORS Deep Field from low to high redshift. I. The blue bands
No full textWe use the very deep and homogeneous I-band selected
dataset of the FORS Deep Field (FDF) to trace the evolution of the
luminosity function over the redshift range .
We show that the FDF I-band selection down to misses
of the order of 10% of the galaxies that would be detected in a
K-band selected survey with magnitude limit (like
FIRES). Photometric redshifts for 5558 galaxies are estimated based
on the photometry in 9 filters (U, B, Gunn g, R, I, SDSS z, J, K and a special filter centered at 834 nm). A comparison with 362 spectroscopic redshifts shows that the achieved accuracy of the
photometric redshifts is
with only ~1% outliers. This allows us to derive luminosity
functions with a reliability similar to spectroscopic surveys. In
addition, the luminosity functions can be traced to objects of lower
luminosity which generally are not accessible to spectroscopy. We
investigate the evolution of the luminosity functions evaluated in
the restframe UV (1500 Å and 2800 Å), u', B, and g' bands.
Comparison with results from the literature shows the reliability of
the derived luminosity functions. Out to redshifts of
the data are consistent with a slope of the luminosity function
approximately constant with redshift, at a value of
in the UV (1500 Å, 2800 Å) as well as u', and
in the blue (g', B). We do not see evidence for a very steep slope
() in the UV at and favoured by other
authors. There may be a tendency for the faint-end slope to become
shallower with increasing redshift but the effect is marginal. We
find a brightening of and a decrease of with
redshift for all analyzed wavelengths. The effect is systematic and
much stronger than what can be expected to be caused by cosmic
variance seen in the FDF. The evolution of and
from to is well described by the simple approximations
and for and . The
evolution is very pronounced at shorter wavelengths
(, and for 1500 Å rest wavelength) and
decreases systematically with increasing wavelength, but is also
clearly visible at the longest wavelength investigated here
(, and for g'). Finally we show a
comparison with semi-analytical galaxy formation models
The evolution of the luminosity functions in the FORS deep field from low to high redshift - II. The red bands
No full textWe present the redshift evolution of the restframe galaxy
luminosity function (LF) in the red r', i', and z' bands, as derived
from the FORS Deep Field (FDF), thus extending our earlier results
to longer wavelengths. Using the deep and
homogeneous I-band selected dataset of the FDF, we were able to follow
the red LFs over the redshift range . The
results are based on photometric redshifts for 5558 galaxies derived
from the photometry in 9 filters and achieving an accuracy of
with only ~%
outliers. A comparison with results from the literature shows the
reliability of the derived LFs. Because of the depth of the FDF, we
can give relatively tight constraints on the faint-end slope α of the LF; the faint-end of the red LFs does not show a
large redshift evolution and is compatible within to with a constant slope over the redshift range 0.5
\la z \la 2.0. Moreover, the slopes in r', i', and z' are
very similar to a best-fitting value of
for the combined bands. There is a clear trend of α to
steepen with increasing wavelength:
. We
subdivided our galaxy sample into four SED types and determined the
contribution of a typical SED type to the overall LF. We show that
the wavelength dependence of the LF slope can be explained by the
relative contribution of different SED-type LFs to the overall LF,
as different SED types dominate the LF in the blue and red bands.
Furthermore we also derived and analyzed the luminosity density
evolution of the different SED types up to .
We investigated the evolution of and by means of
the redshift parametrization and .
Based on the FDF data, we found only a mild brightening
of (, and ) and
a decreasing () with increasing
redshift. Therefore, from to
the characteristic luminosity
increases by ~0.8, ~0.4, and ~0.4 mag in
the r', i', and z' bands, respectively. Simultaneously the
characteristic density decreases by about 40% in all analyzed
wavebands.
A comparison of the LFs with semi-analytical galaxy formation models
by Kauffmann et al. (1999) shows a similar result to the blue bands:
the semi-analytical models predict LFs that describe the data at
low redshift very well, but show growing disagreement with
increasing redshifts.
The FORS Deep Field: Field selection, photometric observations and photometric catalog
No full textThe FORS Deep Field project is a multi-colour,
multi-object spectroscopic investigation of a ~
7arcmin x 7arcmin region near the south
galactic pole based mostly on observations
carried out with the FORS instruments attached
to the VLT telescopes. It includes the QSO Q
0103-260 (z = 3.36). The goal of this study is to
improve our understanding of the formation and
evolution of galaxies in the young Universe. In
this paper the field selection, the photometric
observations, and the data reduction are
described. The source detection and photometry
of objects in the FORS Deep Field is discussed in
detail. A combined B and I selected UBgRIJKs
photometric catalog of 8753 objects in the FDF
is presented and its properties are briefly
discussed. The formal 50% completeness limits
for point sources, derived from the co-added
images, are 25.64, 27.69, 26.86, 26.68, 26.37,
23.60 and 21.57 in U, B, g, R, I, J and Ks
(Vega-system), respectively. A comparison of the
number counts in the FORS Deep Field to those
derived in other deep field surveys shows very
good agreement
Wendelstein observatory control software
No full textLMU München operates an astrophysical observatory on Mt. Wendelstein (Hopp et al. 2008). The 2m Fraunhofer telescope (Thiele et al. 2012; Hopp et al. 2012) is equipped with a 0.5 × 0.5 square degree field-of-view wide field camera (Gössl et al. 2012) and a 3 channel optical/NIR camera (Lang-Bardl et al. 2010, 2016). Two fiber coupled spectrographs (Fabricius et al. 2012; Pfeiffer et al. 1998; Brucalassi et al. 2012) and a wavefront sensor will be added in the near future. The observatory hosts a multitude of supporting hardware, i.e. allsky cameras, webcams, meteostation, air conditioning etc. All scientific hardware can be controlled through a single, central “Master Control Program” (MCP). At the ADASS conference in 2014 we presented the overall Wendelstein Observatory software concept (Gössl et al. 2014). Here we explain concept and implementation of the MCP as a multi-threaded Python daemon in the area of conflict between debuggability and Don't Repeat Yourself (DRY)
Finding structures in photometric redshift galaxy surveys: an extended friends-of-friends algorithm
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