86 research outputs found
RX J1548.9+0851, a fossil cluster?
Fossil galaxy groups are spatially extended X-ray sources with X-ray
luminosities above L_X,bol > 10^42 h_50^-2 ergs s^-1 and a central elliptical
galaxy dominating the optical, the second-brightest galaxy being at least 2
magnitudes fainter in the R band. Whether these systems are a distinct class of
objects resulting from exceptional formation and evolution histories is still
unclear, mainly due to the small number of objects studied so far, mostly
lacking spectroscopy of group members for group membership confirmation and a
detailed kinematical analysis. To complement the scarce sample of
spectroscopically studied fossils down to their faint galaxy populations, the
fossil candidate RX J1548.9+0851 (z=0.072) is studied in this work. Our results
are compared with existing data from fossils in the literature. We use ESO VLT
VIMOS multi-object spectroscopy to determine redshifts of the faint galaxy
population and study the luminosity-weighted dynamics and luminosity function
of the system. The full-spectrum fitting package ULySS is used to determine
ages and metallicities of group members. VIMOS imaging data are used to study
the morphology of the central elliptical. We identify 40 group members
spectroscopically within the central ~300 kpc of the system and find 31
additional redshifts from the literature, resulting in a total number of 54
spectroscopically confirmed group members within 1 Mpc. RX J1548.9+0851 is made
up of two bright ellipticals in the central region with a magnitude gap of
m_1,2 = 1.34 in the SDSS r' band leaving the definition of RX J1548.9+0851
being a fossil to the assumption of the virial radius. We find a
luminosity-weighted velocity dispersion of 568 km s^-1 and a mass of ~2.5 x
10^14 M_sun for the system confirming previous studies that revealed fossils to
be massive. (abridged)Comment: 13 pages, 13 figures, accepted for publication in A&
Infection of Human Coronary Artery Endothelial Cells by Group B Streptococcus Contributes to Dysregulation of Apoptosis, Hemostasis, and Innate Immune Responses
Early onset sepsis due to group B streptococcus leads to neonatal morbidity, increased mortality, and long-term neurological deficencies. Interaction between septicemic GBS and confluent monolayers of human coronary artery endothelial cells (HCAECs) was analyzed by genome wide expression profiling. In total, 124 genes were differentially expressed (89 upregulated, 35 downregulated) based on a more than 3-fold difference to control HCAEC. Regulated genes are involved in apoptosis, hemostasis, oxidative stress response, infection, and inflammation. Regulation of selected genes and proteins identified in the gene array analysis was confirmed by Real-time RT-PCR assay (granulocyte chemotactic protein 2), ELISA (urokinase, cyclooxygenase 2, granulocyte chemotactic protein 1), and western blotting (Heme oxygenase1, BCL2 interacting protein) at various time points between 4 and 24 hours. These results indicate that GBS infection might influence signalling pathways leading to impaired function of the innate immune system and hemorrhagic and inflammatory complications during GBS sepsis
Unveiling a Rich System of Faint Dwarf Galaxies in the Next Generation Fornax Survey
We report the discovery of 158 previously undetected dwarf galaxies in the
Fornax cluster central regions using a deep coadded and -band image
obtained with the DECam wide-field camera mounted on the 4-meter Blanco
telescope at the Cerro Tololo Interamerican Observatory as part of the {\it
Next Generation Fornax Survey} (NGFS). The new dwarf galaxies have
quasi-exponential light profiles, effective radii kpc and
average effective surface brightness values mag
arcsec. We confirm the existence of ultra-diffuse galaxies (UDGs) in the
Fornax core regions that resemble counterparts recently discovered in the Virgo
and Coma galaxy clusters.~We also find extremely low surface brightness NGFS
dwarfs, which are several magnitudes fainter than the classical UDGs. The
faintest dwarf candidate in our NGFS sample has an absolute magnitude of
\,mag. The nucleation fraction of the NGFS dwarf galaxy sample
appears to decrease as a function of their total luminosity, reaching from a
nucleation fraction of at luminosities brighter than
mag to at luminosities fainter than
mag. The two-point correlation function analysis of the
NGFS dwarf sample shows an excess on length scales below kpc,
pointing to the clustering of dwarf galaxies in the Fornax cluster core.Comment: 6 pages, 3 figures. Accepted for publication in The Astrophysical
Journal Letters. Download the high-resolution version of the paper from the
following link: https://www.dropbox.com/s/xb9vz8s29wlzjgf/ms.pdf?dl=
The Next Generation Virgo Cluster Survey - Infrared (NGVS-IR): I. A new Near-UV/Optical/Near-IR Globular Cluster selection tool
The NGVS-IR project (Next Generation Virgo Survey - Infrared) is a contiguous
near-infrared imaging survey of the Virgo cluster of galaxies. It complements
the optical wide-field survey of Virgo (NGVS). The current state of NGVS-IR
consists of Ks-band imaging of 4 deg^2 centered on M87, and J and Ks-band
imaging of 16 deg^2 covering the region between M49 and M87. In this paper, we
present the observations of the central 4 deg^2 centered on Virgo's core
region. The data were acquired with WIRCam on the Canada-France-Hawaii
Telescope and the total integration time was 41 hours distributed in 34
contiguous tiles. A survey-specific strategy was designed to account for
extended galaxies while still measuring accurate sky brightness within the
survey area. The average 5\sigma limiting magnitude is Ks=24.4 AB mag and the
50% completeness limit is Ks=23.75 AB mag for point source detections, when
using only images with better than 0.7" seeing (median seeing 0.54"). Star
clusters are marginally resolved in these image stacks, and Virgo galaxies with
\mu_Ks=24.4 AB mag arcsec^-2 are detected. Combining the Ks data with optical
and ultraviolet data, we build the uiK color-color diagram which allows a very
clean color-based selection of globular clusters in Virgo. This diagnostic plot
will provide reliable globular cluster candidates for spectroscopic follow-up
campaigns needed to continue the exploration of Virgo's photometric and
kinematic sub-structures, and will help the design of future searches for
globular clusters in extragalactic systems. Equipped with this powerful new
tool, future NGVS-IR investigations based on the uiK diagram will address the
mapping and analysis of extended structures and compact stellar systems in and
around Virgo galaxies.Comment: 23 pages, 18 figures. Accepted for publication in ApJ
Revisiting the low-luminosity galaxy population of the NGC 5846 group with SDSS
Low-luminosity galaxies are known to outnumber the bright galaxy population
in poor groups and clusters of galaxies. Yet, the investigation of
low-luminosity galaxy populations outside the Local Group remains rare and the
dependence on different group environments is still poorly understood. Previous
investigations revealed photometric scaling relations for early-type dwarfs and
a strong dependence of morphology with environment.
The present study aims to analyse the photometric and spectroscopic
properties of the low-luminosity galaxy population in the nearby, well-evolved
and early-type dominated NGC 5846 group of galaxies. It is the third most
massive aggregate of early-type galaxies after the Virgo and Fornax clusters in
the local universe. Photometric scaling relations and the distribution of
morphological types as well as the characteristics of emission-line galaxies
are investigated.
Spectroscopically selected low-luminosity group members from the Sloan
Digital Sky Survey with cz<3000 km/s within a radius of 2 deg=0.91 Mpc around
NGC 5846 are analysed. Surface brightness profiles of early-type galaxies are
fit by a Sersic model r^(1/n). Star formation rates, oxygen abundances and
emission characteristics are determined for emission-line galaxies. [abridged]Comment: 13 pages, 10 figures; accepted for publication in A&
RVSPY -- Radial Velocity Survey for Planets around Young Stars. Target characterization and high-cadence survey
We introduce our Radial Velocity Survey for Planets around Young stars
(RVSPY), characterise our target stars, and search for substellar companions at
orbital separations smaller than a few au from the host star. We use the FEROS
spectrograph to obtain high signal-to-noise spectra and time series of precise
radial velocities (RVs) of 111 stars most of which are surrounded by debris
discs. Our target stars have spectral types between early F and late K, a
median age of 400 Myr, and a median distance of 45 pc. We determine for all
target stars their basic stellar parameters and present the results of the
high-cadence RV survey and activity characterization. We achieve a median
single-measurement RV precision of 6 m/s and derive the short-term intrinsic RV
scatter of our targets (median 22 m/s), which is mostly caused by stellar
activity and decays with age from >100 m/s at 500 Myr.
We discover six previously unknown close companions with orbital periods
between 10 and 100 days, three of which are low-mass stars, and three are in
the brown dwarf mass regime. We detect no hot companion with an orbital period
<10 days down to a median mass limit of ~1 M_Jup for stars younger than 500
Myr, which is still compatible with the established occurrence rate of such
companions around main-sequence stars. We find significant RV periodicities
between 1.3 and 4.5 days for 14 stars, which are, however, all caused by
rotational modulation due to starspots. We also analyse the TESS photometric
time series data and find significant periodicities for most of the stars. For
11 stars, the photometric periods are also clearly detected in the RV data. We
also derive stellar rotation periods ranging from 1 to 10 days for 91 stars,
mostly from TESS data. From the intrinsic activity-related short-term RV
jitter, we derive the expected mass-detection thresholds for longer-period
companions.Comment: 24 pages, 14 figures, 4 tables; Accepted for publication in A&
Globular cluster systems in fossil groups: NGC6482, NGC1132 and ESO306-017
We study the globular cluster (GC) systems in three representative fossil
group galaxies: the nearest (NGC6482), the prototype (NGC1132) and the most
massive known to date (ESO306-017). This is the first systematic study of GC
systems in fossil groups. Using data obtained with the Hubble Space Telescope
Advanced Camera for Surveys in the F475W and F850LP filters, we determine the
GC color and magnitude distributions, surface number density profiles, and
specific frequencies. In all three systems, the GC color distribution is
bimodal, the GCs are spatially more extended than the starlight, and the red
population is more concentrated than the blue. The specific frequencies seem to
scale with the optical luminosities of the central galaxy and span a range
similar to that of the normal bright elliptical galaxies in rich environments.
We also analyze the galaxy surface brightness distributions to look for
deviations from the best-fit S\'ersic profiles; we find evidence of recent
dynamical interaction in all three fossil group galaxies. Using X-ray data from
the literature, we find that luminosity and metallicity appear to correlate
with the number of GCs and their mean color, respectively. Interestingly,
although NGC6482 has the lowest mass and luminosity in our sample, its GC
system has the reddest mean color, and the surrounding X-ray gas has the
highest metallicity.Comment: 16 pages, 13 figures. Accepted for publication in A&
Quantification of cAMP and cGMP analogs in intact cells: pitfalls in enzyme immunoassays for cyclic nucleotides
Immunoassays are routinely used as research tools to measure intracellular cAMP and cGMP concentrations. Ideally, this application requires antibodies with high sensitivity and specificity. The present work evaluates the cross-reactivity of commercially available cyclic nucleotide analogs with two non-radioactive and one radioactive cAMP and cGMP immunoassay. Most of the tested cyclic nucleotide analogs showed low degree competition with the antibodies; however, with Rp-cAMPS, 8-Br-cGMP and 8-pCPT-cGMP, a strong cross-reactivity with the corresponding cAMP and cGMP, respectively, immunoassays was observed. The determined EIA-binding constants enabled the measurement of the intracellular cyclic nucleotide concentrations and revealed a time- and lipophilicity-dependent cell membrane permeability of the compounds in the range of 10–30% of the extracellular applied concentration, thus allowing a more accurate prediction of the intracellular analog levels in a given experiment
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