146 research outputs found
The Munich Near-Infrared Cluster Survey -- IV. Biases in the Completeness of Near-Infrared Imaging Data
We present the results of completeness simulations for the detection of point
sources as well as redshifted elliptical and spiral galaxies in the K'-band
images of the Munich Near-Infrared Cluster Survey (MUNICS). The main focus of
this work is to quantify the selection effects introduced by threshold-based
object detection algorithms used in deep imaging surveys. Therefore, we
simulate objects obeying the well-known scaling relations between effective
radius and central surface brightness, both for de Vaucouleurs and exponential
profiles. The results of these simulations, while presented for the MUNICS
project, are applicable in a much wider context to deep optical and
near-infrared selected samples. We investigate the detection probability as
well as the reliability for recovering the true total magnitude with Kron-like
(adaptive) aperture photometry. The results are compared to the predictions of
the visibility theory of Disney and Phillipps in terms of the detection rate
and the lost-light fraction. Additionally, the effects attributable to seeing
are explored. The results show a bias against detecting high-redshifted massive
elliptical galaxies in comparison to disk galaxies with exponential profiles,
and that the measurements of the total magnitudes for intrinsically bright
elliptical galaxies are systematically too faint. Disk galaxies, in contrast,
show no significant offset in the magnitude measurement of luminous objects.
Finally we present an analytic formula to predict the completeness of
point-sources using only basic image parameters.Comment: 13 pages, 11 figures, accepted for publication in MNRA
Large-Scale Structure in the NIR-Selected MUNICS Survey
The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep,
photometric survey selected in the K' band. The project's main scientific aims
are the identification of galaxy clusters up to redshifts of unity and the
selection of a large sample of field early-type galaxies up to z < 1.5 for
evolutionary studies. We created a Large Scale Structure catalog, using a new
structure finding technique specialized for photometric datasets, that we
developed on the basis of a friends-of-friends algorithm. We tested the
plausibility of the resulting galaxy group and cluster catalog with the help of
Color-Magnitude Diagrams (CMD), as well as a likelihood- and Voronoi-approach.Comment: 4 pages, to appear in "The Evolution of Galaxies III. From Simple
Approaches to Self-Consistent Models", proceedings of the 3rd EuroConference
on the evolution of galaxies, held in Kiel, Germany, July 16-20, 200
The Munich Near-Infrared Cluster Survey - I. Field selection, object extraction, and photometry
The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep,
photometric survey selected in the K' band. It covers an area of roughly one
square degree in the K' and J near-IR pass-bands. The survey area consists of
16 6' x 6' fields targeted at QSOs with redshifts 0.5 < z < 2 and 7 28' x 13'
stripes targeted at `random' high Galactic latitude fields. Ten of the QSO
fields were additionally imaged in R and I, and 0.6 square degrees of the
randomly selected fields were also imaged in the V, R, and I bands. The
resulting object catalogues were strictly selected in K', having a limiting
magnitude (50 per cent completeness) of K' ~ 19.5 mag and J ~ 21 mag,
sufficiently deep to detect passively evolving systems up to a redshift of z ~
1.5 and luminosity of 0.5 L*. The optical data reach a depth of roughly R ~
23.5 mag. The project's main scientific aims are the identification of galaxy
clusters at redshifts around unity and the selection of a large sample of field
early-type galaxies at 0 < z < 1.5 for evolutionary studies. In this paper -
the first in a series - we describe the survey's concept, the selection of the
survey fields, the near-IR and optical imaging and data reduction, object
extraction, and the construction of photometric catalogues. Finally, we show
the J-K' vs. K' colour-magnitude diagramme and the R-J vs. J-K', V-I vs. J-K',
and V-I vs. V-R colour-colour diagrammes for MUNICS objects, together with
stellar population-synthesis models for different star-formation histories, and
conclude that the data set presented is suitable for extracting a catalogue of
massive field galaxies in the redshift range 0.5 < z < 1.5 for evolutionary
studies and follow-up observations.Comment: Accepted for publication in MNRA
Immunotherapeutic targeting of membrane Hsp70-expressing tumors using recombinant human granzyme B
Background: We have previously reported that human recombinant granzyme B (grB) mediates apoptosis in membrane heat shock protein 70 (Hsp70)-positive tumor cells in a perforin-independent manner
Microlens OGLE-2005-BLG-169 Implies Cool Neptune-Like Planets are Common
We detect a Neptune mass-ratio (q~8e-5) planetary companion to the lens star
in the extremely high-magnification (A~800) microlensing event
OGLE-2005-BLG-169. If the parent is a main-sequence star, it has mass M~0.5
M_sun implying a planet mass of ~13 M_earth and projected separation of ~2.7
AU. When intensely monitored over their peak, high-magnification events similar
to OGLE-2005-BLG-169 have nearly complete sensitivity to Neptune mass-ratio
planets with projected separations of 0.6 to 1.6 Einstein radii, corresponding
to 1.6--4.3 AU in the present case. Only two other such events were monitored
well enough to detect Neptunes, and so this detection by itself suggests that
Neptune mass-ratio planets are common. Moreover, another Neptune was recently
discovered at a similar distance from its parent star in a low-magnification
event, which are more common but are individually much less sensitive to
planets. Combining the two detections yields 90% upper and lower frequency
limits f=0.37^{+0.30}_{-0.21} over just 0.4 decades of planet-star separation.
In particular, f>16% at 90% confidence. The parent star hosts no Jupiter-mass
companions with projected separations within a factor 5 of that of the detected
planet. The lens-source relative proper motion is \mu~7--10 mas/yr, implying
that if the lens is sufficiently bright, I<23.8, it will be detectable by HST
by 3 years after peak. This would permit a more precise estimate of the lens
mass and distance, and so the mass and projected separation of the planet.
Analogs of OGLE-2005-BLG-169Lb orbiting nearby stars would be difficult to
detect by other methods of planet detection, including radial velocities,
transits, or astrometry.Comment: Submitted to ApJ Letters, 9 text pages + 4 figures + 1 tabl
A wide angle tail radio galaxy in the COSMOS field: evidence for cluster formation
We have identified a complex galaxy cluster system in the COSMOS field via a
wide angle tail (WAT) radio galaxy consistent with the idea that WAT galaxies
can be used as tracers of clusters. The WAT galaxy, CWAT-01, is coincident with
an elliptical galaxy resolved in the HST-ACS image. Using the COSMOS
multiwavelength data set, we derive the radio properties of CWAT-01 and use the
optical and X-ray data to investigate its host environment. The cluster hosting
CWAT-01 is part of a larger assembly consisting of a minimum of four X-ray
luminous clusters within ~2 Mpc distance. We apply hydrodynamical models that
combine ram pressure and buoyancy forces on CWAT-01. These models explain the
shape of the radio jets only if the galaxy's velocity relative to the
intra-cluster medium (ICM) is in the range of about 300-550 km/s which is
higher than expected for brightest cluster galaxies (BCGs) in relaxed systems.
This indicates that the CWAT-01 host cluster is not relaxed, but is possibly
dynamically young. We argue that such a velocity could have been induced
through subcluster merger within the CWAT-01 parent cluster and/or
cluster-cluster interactions. Our results strongly indicate that we are
witnessing the formation of a large cluster from an assembly of multiple
clusters, consistent with the hierarchical scenario of structure formation. We
estimate the total mass of the final cluster to be approximately 20% of the
mass of the Coma cluster.Comment: 18 pages, 13 figures; accepted for publication in ApJS, COSMOS
special issue; added color figure (Fig. 13) which was previously unavailabl
Identifying dynamically young galaxy groups via wide-angle tail galaxies: A case study in the COSMOS field at z=0.53
We present an analysis of a wide-angle tail (WAT) radio galaxy located in a
galaxy group in the COSMOS field at a redshift of z=0.53 (hereafter CWAT-02).
We find that the host galaxy of CWAT-02 is the brightest galaxy in the group,
although it does not coincide with the center of mass of the system. Estimating
a) the velocity of CWAT-02, relative to the intra-cluster medium (ICM), and b)
the line-of-sight peculiar velocity of CWAT-02's host galaxy, relative to the
average velocity of the group, we find that both values are higher than those
expected for a dominant galaxy in a relaxed system. This suggests that
CWAT-02's host group is dynamically young and likely in the process of an
ongoing group merger. Our results are consistent with previous findings showing
that the presence of a wide-angle tail galaxy in a galaxy group or cluster can
be used as an indicator of dynamically young non-relaxed systems. Taking the
unrelaxed state of CWAT-02's host group into account, we discuss the impact of
radio-AGN heating from CWAT-02 onto its environment, in the context of the
missing baryon problem in galaxy groups. Our analysis strengthens recent
results suggesting that radio-AGN heating may be powerful enough to expel
baryons from galaxy groups.Comment: 8 pages, 6 figures, 1 table. Accepted for publication in Ap
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