2,019 research outputs found
The impact of the dynamical state of galaxy groups on the stellar populations of central galaxies
We study the stellar populations of the brightest group galaxies (BGGs) in groups with different dynamical states, using Galaxy And Mass Assembly survey data. We use two independent, luminosity-dependent indicators to probe the relaxedness of their groups: the magnitude gap between the two most luminous galaxies (ΔM 12), and the offset between BGGs and the luminosity center (D offset) of the group. Combined, these two indicators were previously found useful for identifying relaxed and unrelaxed groups. We find that the BGGs of unrelaxed groups have significantly bluer near-ultraviolet-r colors than in relaxed groups. This is also true at the fixed sersic index. We find the bluer colors cannot be explained away by differing dust fraction, suggesting there are real differences in their stellar populations. Star formation rates derived from spectral energy distribution (SED) fitting tend to be higher in unrelaxed systems. This is in part because of a greater fraction of BGGs with non-elliptical morphology, but also because unrelaxed systems have larger numbers of mergers, some of which may bring fuel for star formation. The SED-fitted stellar metallicities of BGGs in unrelaxed systems also tend to be higher by around 0.05 dex, perhaps because their building blocks were more massive. We find that the ΔM 12 parameter is the most important parameter behind the observed differences in the relaxed/unrelaxed groups, in contrast with the previous study of Trevisan et al. We also find that groups selected to be unrelaxed using our criteria tend to have higher velocity offsets between the BGG and their group.Publisher PDFPeer reviewe
Time-delayed Spatial Patterns in a Two-dimensional Array of Coupled Oscillators
We investigated the effect of time delays on phase configurations in a set of
two-dimensional coupled phase oscillators. Each oscillator is allowed to
interact with its neighbors located within a finite radius, which serves as a
control parameter in this study. It is found that distance-dependent
time-delays induce various patterns including traveling rolls, square-like and
rhombus-like patterns, spirals, and targets. We analyzed the stability
boundaries of the emerging patterns and briefly pointed out the possible
empirical implications of such time-delayed patterns.Comment: 5 Figure
Comparison of spatial distributions of Intracluster light and Dark Matter
In a galaxy cluster, the relative spatial distributions of dark matter,
member galaxies, gas, and intracluster light (ICL) may connote their mutual
interactions over the cluster evolution. However, it is a challenging problem
to provide a quantitative measure for the shape matching between two
multi-dimensional scalar distributions. We present a novel methodology, named
the {\em Weighted Overlap Coefficient (WOC)}, to quantify the similarity of
2-dimensional spatial distributions. We compare the WOC with a standard method
known as the Modified Hausdorff Distance (MHD). We find that our method is
robust, and performs well even with the existence of multiple sub-structures.
We apply our methodology to search for a visible component whose spatial
distribution resembled with that of dark matter. If such a component could be
found to trace the dark matter distribution with high fidelity for more relaxed
galaxy clusters, then the similarity of the distributions could also be used as
a dynamical stage estimator of the cluster. We apply the method to six galaxy
clusters at different dynamical stages simulated within the GRT simulation,
which is an N-body simulation using the galaxy replacement technique. Among the
various components (stellar particles, galaxies, ICL), the ICL+ brightest
cluster galaxy (BCG) component most faithfully trace the dark matter
distribution. Among the sample galaxy clusters, the relaxed clusters show
stronger similarity in the spatial distribution of the dark matter and ICL+BCG
than the dynamically young clusters. While the MHD results show weaker trend
with the dynamical stages.Comment: 17 pages, 8 figures, accepted in ApJ
SHELS: Optical Spectral Properties of WISE 22 \mu m-selected Galaxies
We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing
Survey (SHELS), covering a 4 square degree region of a deep imaging survey, the
Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field
Infrared Survey Explorer (WISE) 22 \mu m-selected galaxies. Among 507 WISE 22
\mu m-selected sources with (S/N)_{22\mu m}>3 (\simS_{22\mu m}>2.5 mJy), we
identify the optical counterparts of 481 sources (\sim98%) at R<25.2 in the
very deep, DLS R-band source catalog. Among them, 337 galaxies at R<21 have
SHELS spectroscopic data. Most of these objects are at z<0.8. The infrared (IR)
luminosities are in the range 4.5x10^8 (L_sun) < L_{IR} < 5.4x10^{12} (L_sun).
Most 22 \mu m-selected galaxies are dusty star-forming galaxies with a small
(<1.5) 4000 \AA break. The stacked spectra of the 22 \mu m-selected galaxies
binned in IR luminosity show that the strength of the [O III] line relative to
H\beta grows with increasing IR luminosity. The optical spectra of the 22 \mu
m-selected galaxies also show that there are some (\sim2.8%) unusual galaxies
with very strong [Ne III] \lambda 3869, 3968 emission lines that require hard
ionizing radiation such as AGN or extremely young massive stars. The specific
star formation rates (sSFRs) derived from the 3.6 and 22 \mu m flux densities
are enhanced if the 22 \mu m-selected galaxies have close late-type neighbors.
The sSFR distribution of the 22 \mu m-selected galaxies containing active
galactic nuclei (AGNs) is similar to the distribution for star-forming galaxies
without AGNs. We identify 48 dust-obscured galaxy (DOG) candidates with large
(\gtrsim1000) mid-IR to optical flux density ratio. The combination of deep
photometric and spectroscopic data with WISE data suggests that WISE can probe
the universe to z\sim2.Comment: 18 pages, 17 figures. To appear in Ap
Catheter-associated bacteremia by Mycobacterium senegalense in Korea
BACKGROUND: Rapidly growing mycobacteria is recognized as one of the causative agents of catheter-related infections, especially in immunocompromised hosts. To date, however, Mycobacterium senegalense, which was known as the principal pathogen of bovine farcy, has not been reported in human infection. CASE PRESENTATION: We describe the first case of human infection by M. senegalense, which has caused catheter-related bloodstream infection in a cancer patient in Korea. The microorganism was identified by the 16S rRNA gene, rpoB, and 16S-23S rRNA gene internal transcribed spacer (ITS) sequence analyses. CONCLUSION: Our first report of catheter-associated bacteremia caused by M. senegalense suggests the zoonotic nature of this species and indicates the expansion of mycobacterial species relating to human infection. M. senegalense should be considered as one of the causes of human infections in the clinical practice
Angular analysis of
We present a measurement of angular observables, , , ,
, in the decay , where
is either or . The analysis is performed on
a data sample corresponding to an integrated luminosity of
containing pairs, collected
at the resonance with the Belle detector at the
asymmetric-energy collider KEKB. Four angular observables,
are extracted in five bins of the invariant mass squared of the
lepton system, . We compare our results for with Standard
Model predictions including the region in which the LHCb collaboration
reported the so-called anomaly.Comment: Conference paper for LHC Ski 2016. SM prediction for
corrected and reference for arXiv:1207.2753 adde
Deletion of the Huntingtin Polyglutamine Stretch Enhances Neuronal Autophagy and Longevity in Mice
Expansion of a stretch of polyglutamine in huntingtin (htt), the protein product of the IT15 gene, causes Huntington's disease (HD). Previous investigations into the role of the polyglutamine stretch (polyQ) in htt function have suggested that its length may modulate a normal htt function involved in regulating energy homeostasis. Here we show that expression of full-length htt lacking its polyglutamine stretch (ΔQ-htt) in a knockin mouse model for HD (Hdh140Q/ΔQ), reduces significantly neuropil mutant htt aggregates, ameliorates motor/behavioral deficits, and extends lifespan in comparison to the HD model mice (Hdh140Q/+). The rescue of HD model phenotypes is accompanied by the normalization of lipofuscin levels in the brain and an increase in the steady-state levels of the mammalian autophagy marker microtubule-associate protein 1 light chain 3-II (LC3-II). We also find that ΔQ-htt expression in vitro increases autophagosome synthesis and stimulates the Atg5-dependent clearance of truncated N-terminal htt aggregates. ΔQ-htt's effect on autophagy most likely represents a gain-of-function, as overexpression of full-length wild-type htt in vitro does not increase autophagosome synthesis. Moreover, HdhΔQ/ΔQ mice live significantly longer than wild-type mice, suggesting that autophagy upregulation may be beneficial both in diseases caused by toxic intracellular aggregate-prone proteins and also as a lifespan extender in normal mammals
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