556 research outputs found
Tracing the Peculiar Dark Matter Structure in the Galaxy Cluster CL 0024+17 with Intracluster Stars and Gas
ICL is believed to originate from the stars stripped from cluster galaxies.
They are no longer gravitationally bound to individual galaxies, but to the
cluster, and their smooth distribution potentially makes them serve as much
denser tracers of the cluster dark matter than the sparsely distributed cluster
galaxies. We present our study of the ICL in Cl 0024+17 using both ACS and
Subaru data, where we previously reported discovery of a ringlike dark matter
structure with gravitational lensing. The ACS images provide much lower sky
levels than ground data, and enable us to measure relative variation of surface
brightness reliably. This analysis is repeated with the Subaru images to
examine if consistent features are recovered despite different reduction scheme
and instrumental characteristics. We find that the ICL profile clearly
resembles the peculiar mass profile, which stops decreasing at r~50" (~265 kpc)
and slowly increases until it turns over at r~75" (~397 kpc). This feature is
seen in both ACS and Subaru images for nearly all available passband images
while the features are stronger in red filters. The consistency across
different filters and instruments strongly rules out the possibility that the
feature might come from any residual, uncorrected calibration errors. In
addition, our re-analysis of the cluster X-ray data shows that the peculiar
mass structure is also indicated by a non-negligible bump in the intracluster
gas profile when the geometric center of the dark matter ring, not the peak of
the X-ray emission, is chosen as the center of the radial bin. The location of
the gas ring is closer to the center by ~15" (~80 kpc), raising an interesting
possibility that the ring-like structure is expanding and the gas ring is
lagging behind perhaps because of the ram pressure if both features in mass and
gas share the same dynamical origin.Comment: Accepted to ApJ for publicatio
The Burrell-Optical-Kepler-Survey (BOKS). I. Survey Description and Initial Results
We present the initial results of a 40 night contiguous ground-based campaign of time series photometric observations of a 1.39 deg^2 field located within the NASA Kepler Mission field of view. The goal of this pre-launch survey was to search for transiting extrasolar planets and to provide independent variability information of stellar sources. We have gathered a data set containing light curves of 54,687 stars from which we have created a statistical sub-sample of 13,786 stars between 14 < r < 18.5 and have statistically examined each light curve to test for variability. We present a summary of our preliminary photometric findings including the overall level and content of stellar variability in this portion of the Kepler field and give some examples of unusual variable stars found within. We present a preliminary catalog of 2,457 candidate variable stars, of which 776 show signs of periodicity. We also present three potential exoplanet candidates, all of which should be observable by the Kepler mission
Diffuse light and galaxy interactions in the core of nearby clusters
The kinematics of the diffuse light in the densest regions of the nearby
clusters can be unmasked using the planetary nebulae (PNs) as probes of the
stellar motions. The position-velocity diagrams around the brightest cluster
galaxies (BCGs) identify the relative contributions from the outer halos and
the intracluster light (ICL), defined as the light radiated by the stars
floating in the cluster potential. The kinematics of the ICL can then be used
to asses the dynamical status of the nearby cluster cores and to infer their
formation histories. The cores of the Virgo and Coma are observed to be far
from equilibrium, with mergers currently on-going, while the ICL properties in
the Fornax and Hydra clusters show the presence of sub-components being
accreted in their cores, but superposed to an otherwise relaxed population of
stars. Finally the comparison of the observed ICL properties with those
predicted from Lambda-CDM simulations indicates a qualitative agreement and
provides insights on the ICL formation. Both observations and simulations
indicate that BCG halos and ICL are physically distinct components, with the
``hotter" ICL dominating at large radial distances from the BCGs halos as the
latter become progressively fainter.Comment: 14 pages, 5 figures. Invited review to appear in the proceedings of
"Galaxies and their masks" eds. Block, D.L., Freeman, K.C. and Puerari, I.,
2010, Springer (New York
Glycine receptor in rat hippocampal and spinal cord neurons as a molecular target for rapid actions of 17-β-estradiol
Glycine receptors (GlyRs) play important roles in regulating hippocampal neural network activity and spinal nociception. Here we show that, in cultured rat hippocampal (HIP) and spinal dorsal horn (SDH) neurons, 17-β-estradiol (E2) rapidly and reversibly reduced the peak amplitude of whole-cell glycine-activated currents (IGly). In outside-out membrane patches from HIP neurons devoid of nuclei, E2 similarly inhibited IGly, suggesting a non-genomic characteristic. Moreover, the E2 effect on IGly persisted in the presence of the calcium chelator BAPTA, the protein kinase inhibitor staurosporine, the classical ER (i.e. ERα and ERβ) antagonist tamoxifen, or the G-protein modulators, favoring a direct action of E2 on GlyRs. In HEK293 cells expressing various combinations of GlyR subunits, E2 only affected the IGly in cells expressing α2, α2β or α3β subunits, suggesting that either α2-containing or α3β-GlyRs mediate the E2 effect observed in neurons. Furthermore, E2 inhibited the GlyR-mediated tonic current in pyramidal neurons of HIP CA1 region, where abundant GlyR α2 subunit is expressed. We suggest that the neuronal GlyR is a novel molecular target of E2 which directly inhibits the function of GlyRs in the HIP and SDH regions. This finding may shed new light on premenstrual dysphoric disorder and the gender differences in pain sensation at the CNS level
Excessive Biologic Response to IFNβ Is Associated with Poor Treatment Response in Patients with Multiple Sclerosis
Interferon-beta (IFNβ) is used to inhibit disease activity in multiple sclerosis (MS), but its mechanisms of action are incompletely understood, individual treatment response varies, and biological markers predicting response to treatment have yet to be identified.he relationship between the molecular response to IFNβ and treatment response was determined in 85 patients using a longitudinal design in which treatment effect was categorized by brain magnetic resonance imaging as good (n = 70) or poor response (n = 15). Molecular response was quantified using a customized cDNA macroarray assay for 166 IFN-regulated genes (IRGs).The molecular response to IFNβ differed significantly between patients in the pattern and number of regulated genes. The molecular response was strikingly stable for individuals for as long as 24 months, however, suggesting an individual ‘IFN response fingerprint’. Unexpectedly, patients with poor response showed an exaggerated molecular response. IRG induction ratios demonstrated an exaggerated molecular response at both the first and 6-month IFNβ injections.MS patients exhibit individually unique but temporally stable biological responses to IFNβ. Poor treatment response is not explained by the duration of biological effects or the specific genes induced. Rather, individuals with poor treatment response have a generally exaggerated biological response to type 1 IFN injections. We hypothesize that the molecular response to type I IFN identifies a pathogenetically distinct subset of MS patients whose disease is driven in part by innate immunity. The findings suggest a strategy for biologically based, rational use of IFNβ for individual MS patients
The outer halos of elliptical galaxies
Recent progress is summarized on the determination of the density
distributions of stars and dark matter, stellar kinematics, and stellar
population properties, in the extended, low surface brightness halo regions of
elliptical galaxies. With integral field absorption spectroscopy and with
planetary nebulae as tracers, velocity dispersion and rotation profiles have
been followed to ~4 and ~5-8 effective radii, respectively, and in M87 to the
outer edge at ~150 kpc. The results are generally consistent with the known
dichotomy of elliptical galaxy types, but some galaxies show more complex
rotation profiles in their halos and there is a higher incidence of
misalignments, indicating triaxiality. Dynamical models have shown a range of
slopes for the total mass profiles, and that the inner dark matter densities in
ellipticals are higher than in spiral galaxies, indicating earlier assembly
redshifts. Analysis of the hot X-ray emitting gas in X-ray bright ellipticals
and comparison with dynamical mass determinations indicates that non-thermal
components to the pressure may be important in the inner ~10 kpc, and that the
properties of these systems are closely related to their group environments.
First results on the outer halo stellar population properties do not yet give a
clear picture. In the halo of one bright galaxy, lower [alpha/Fe] abundances
indicate longer star formation histories pointing towards late accretion of the
halo. This is consistent with independent evidence for on-going accretion, and
suggests a connection to the observed size evolution of elliptical galaxies
with redshift.Comment: 8 pages. Invited review to appear in the proceedings of "Galaxies and
their Masks" eds. Block, D.L., Freeman, K.C. & Puerari, I., 2010, Springer
(New York
The merger history, AGN and dwarf galaxies of Hickson Compact Group 59
Compact group galaxies often appear unaffected by their unusually dense
environment. Closer examination can, however, reveal the subtle, cumulative
effects of multiple galaxy interactions. Hickson Compact Group (HCG) 59 is an
excellent example of this situation. We present a photometric study of this
group in the optical (HST), infrared (Spitzer) and X-ray (Chandra) regimes
aimed at characterizing the star formation and nuclear activity in its
constituent galaxies and intra-group medium. We associate five dwarf galaxies
with the group and update the velocity dispersion, leading to an increase in
the dynamical mass of the group of up to a factor of 10 (to 2.8e13 Msun), and a
subsequent revision of its evolutionary stage. Star formation is proceeding at
a level consistent with the morphological types of the four main galaxies, of
which two are star-forming and the other two quiescent. Unlike in some other
compact groups, star-forming complexes across HCG 59 closely follow mass-radius
scaling relations typical of nearby galaxies. In contrast, the ancient globular
cluster populations in galaxies HCG 59A and B show intriguing irregularities,
and two extragalactic HII regions are found just west of B. We age-date a faint
stellar stream in the intra-group medium at ~1 Gyr to examine recent
interactions. We detect a likely low-luminosity AGN in HCG 59A by its ~10e40
erg/s X-ray emission; the active nucleus rather than star formation can account
for the UV+IR SED. We discuss the implications of our findings in the context
of galaxy evolution in dense environments.Comment: 38 pages, 17 figures. Please visit "http://tinyurl.com/isk-hcg59" for
a full-resolution PDF. Accepted for publication in the Astrophysical Journa
The Stellar Halos of Massive Elliptical Galaxies
We use the Mitchell Spectrograph (formerly VIRUS-P) on the McDonald
Observatory 2.7m Harlan J. Smith Telescope to search for the chemical
signatures of massive elliptical galaxy assembly. The Mitchell Spectrograph is
an integral-field spectrograph with a uniquely wide field of view (107x107 sq
arcsec), allowing us to achieve remarkably high signal-to-noise ratios of
~20-70 per pixel in radial bins of 2-2.5 times the effective radii of the eight
galaxies in our sample. Focusing on a sample of massive elliptical galaxies
with stellar velocity dispersions sigma* > 150 km/s, we study the radial
dependence in the equivalent widths (EWs) of key metal absorption lines. By
twice the effective radius, the Mgb EWs have dropped by ~50%, and only a weak
correlation between sigma* and Mgb EW remains. The Mgb EWs at large radii are
comparable to those seen in the centers of elliptical galaxies that are
approximately an order of magnitude less massive. We find that the well-known
metallicity gradients often observed within an effective radius continue
smoothly to 2.5R_e, while the abundance ratio gradients remain flat. Much like
the halo of the Milky Way, the stellar halos of our galaxies have low
metallicities and high alpha-abundance ratios, as expected for very old stars
formed in small stellar systems. Our observations support a picture in which
the outer parts of massive elliptical galaxies are built by the accretion of
much smaller systems whose star formation history was truncated at early times.Comment: To appear in ApJ, 15 pages, 9 figure
Acute pancreatitis following medical abortion: Case report
BACKGROUND: Acute pancreatitis rarely complicates pregnancy. Although most pregnant women with acute pancreatitis have associated gallstones, less common causes such as drugs have been reported. CASE PRESENTATION: We report the case of a 34-year-old woman who underwent medical abortion with mifepristone and gemeprost and received codeine as pain-relief during the induction of abortion. She developed a severe acute necrotizing pancreatitis which required 14 days of intensive care. Other possible etiological factors, i.e. gallstone, alcohol intake and hyperlipidemia, were excluded. CONCLUSIONS: The reported case of acute pancreatitis was most likely drug-induced
Industrial methodology for process verification in research (IMPROVER): toward systems biology verification
Motivation: Analyses and algorithmic predictions based on high-throughput data are essential for the success of systems biology in academic and industrial settings. Organizations, such as companies and academic consortia, conduct large multi-year scientific studies that entail the collection and analysis of thousands of individual experiments, often over many physical sites and with internal and outsourced components. To extract maximum value, the interested parties need to verify the accuracy and reproducibility of data and methods before the initiation of such large multi-year studies. However, systematic and well-established verification procedures do not exist for automated collection and analysis workflows in systems biology which could lead to inaccurate conclusions
- …