749 research outputs found
Small-scale systems of galaxies. IV. Searching for the faint galaxy population associated with X-ray detected isolated E+S pairs
In hierarchical evolutionary scenarios, isolated, physical pairs may
represent an intermediate phase, or "way station", between collapsing groups
and isolated elliptical (E) galaxies (or fossil groups). We started a
comprehensive study of a sample of galaxy pairs composed of a giant E and a
spiral (S) with the aim of investigating their formation/evolutionary history
from observed optical and X-ray properties. Here we present VLT-VIMOS
observations designed to identify faint galaxies associated with the E+S
systems from candidate lists generated using photometric criteria on WFI images
covering an area of ~ 0.2 h^{-1} Mpc radius around the pairs.
The results are discussed in the context of the evolution of poor galaxy
group associations. A comparison between the Optical Luminosity Functions
(OLFs) of our E+S systems and a sample of X-ray bright poor groups suggest that
the OLF of X-ray detected poor galaxy systems is not universal. The OLF of our
X-ray bright systems suggests that they are more dynamically evolved than our
X-ray faint sample and some X-ray bright groups in the literature. However, we
suggest that the X-ray faint E+S pairs represent a phase in the dynamical
evolution of some X-ray bright poor galaxy groups. The recent or ongoing
interaction in which the E member of the X-ray faint pairs is involved could
have decreased the luminosity of any surrounding X-ray emitting gas.Comment: accepted for publication in Astronomy and Astrophysic
X-ray Tail in NGC 7619
We present new observational results of NGC 7619, an elliptical galaxy with a
prominent X-ray tail and a dominant member of the Pegasus group. With Chandra
and XMM-Newton observations, we confirm the presence of a long X-ray tail in
the SW direction; moreover, we identify for the first time a sharp
discontinuity of the X-ray surface brightness in the opposite (NE) side of the
galaxy. The density, temperature and pressure jump at the NE discontinuity
suggest a Mach number ~1, corresponding to a galaxy velocity of ~500 km s-1,
relative to the surrounding hot gas. Spectral analysis of these data shows that
the Iron abundance of the hot gaseous medium is much higher (1-2 solar) near
the center of NGC 7619 and in the tail extending from the core than in the
surrounding regions (< 1/2 solar), indicating that the gas in the tail is
originated from the galaxy. The possible origin of the head-tail structure is
either on-going ram-pressure stripping or sloshing. The morphology of the
structure is more in line with a ram pressure stripping phenomenon, while the
position of NGC 7619 at the center of the Pegasus I group, and its dominance,
would prefer sloshing.Comment: ApJ accepted to appear in the 2008 December 1 issue; Added discussion
on sloshin
Origin of Radio Emission from Nearby Low-Luminosity Active Galactic Nuclei
We use the observational data in radio, optical and X-ray wavebands, for a
sample of active galactic nuclei (AGNs) with measured black hole masses, to
explore the origin of radio emission from nearby low-luminosity active galactic
nuclei (LLAGNs). We find that the radio luminosities are higher than the
maximal luminosities expected from the ADAF model, for most sources in this
sample. This implies that the radio emission is dominantly from the jets in
these sources. The radio emission from a small fraction of the sources in this
sample can be explained by the ADAF model. However, comparing the observed
multi-band emission data with the spectra calculated for the ADAF or ADIOS
cases, we find that neither ADAF nor ADIOS models can reproduce the observed
multi-band emission simultaneously, with reasonable magnetic field strengths,
for these radio-weak sources. A variety of other possibilities are discussed,
and we suggest that the radio emission is probably dominated by jet emission
even in these radio-weak LLAGNs.Comment: 25 pages, some references were added, accepted for publication in Ap
Effectiveness of Lactobacillus-containing vaginal tablets in the treatment of symptomatic bacterial vaginosis
AbstractThe purpose of this study was to determine the effectiveness of Lactobacillus-containing vaginal tablets in the treatment of bacterial vaginosis (BV) and in the restoration of a healthy vaginal flora. Thirty-nine women with BV were enrolled in a double-blind, placebo-controlled clinical trial. Patients received either one Lactobacillus-containing tablet or placebo daily for 7 days. Clinical criteria, vaginal Gram stain scores and symptoms were compared with those at the initial visit and those at completion of therapy and 2 weeks later. After completion of therapy, all of the patients in the Lactobacillus-treated group (n = 18) were free of BV, showing a normal (83%) or intermediate (17%) vaginal flora, as compared with only two patients free of BV with intermediate flora (12%) from among the 16 placebo-treated women (p <0.001). Two weeks after completion of therapy, treatment was successful (score <7) in 61% of Lactobacillus-treated patients as compared with 19% of those in the placebo group (p <0.05). In the treatment group, the total number of symptomatic patients and the intensity of their symptoms, in particular vaginal malodour, were significantly reduced at both follow-up visits. The data indicate that intravaginal administration of exogenous selected strains of lactobacilli can restore a normal vaginal microbiota and be used in treating bacterial vaginosis
Deep Chandra Monitoring Observations of NGC 4278 : Catalog of Source Properties
We present the properties of the discrete X-ray sources detected in our monitoring program of the globular cluster (GC) rich elliptical galaxy, NGC 4278, observed with Chandra ACIS-S in six separate pointings, resulting in a co-added exposure of 458 ks. From this deep observation, 236 sources have been detected within the region overlapped by all observations, 180 of which lie within the D 25 ellipse of the galaxy. These 236 sources range in L X from 3.5 Ă 1036 erg s-1 (with 3Ï upper limit 1 Ă 1038 erg s-1. From X-ray source photometry, it has been determined that the majority of the 236 point sources that have well-constrained colors have values that are consistent with typical low-mass X-ray binary spectra, with 29 of these sources expected to be background objects from the log N-log S relation. There are 103 sources in this population that exhibit long-term variability, indicating that they are accreting compact objects. Three of these sources have been identified as transient candidates, with a further three possible transients. Spectral variations have also been identified in the majority of the source population, where a diverse range of variability has been identified, indicating that there are many different source classes located within this galaxy.Peer reviewe
An explanation for metallicity effects on X-ray Binary properties
We show that irradiation induced stellar winds can explain two important
metallicity effects in X-ray binaries - the higher numbers and the softer
spectra of the X-ray binaries in metal rich globular clusters compared to the
metal poor ones. As has been previously noted by Iben, Tutukov and Fedorova,
the winds should be stronger at lower metallicity due to less efficient line
cooling. This will speed up the evolution of the LMXBs in metal poor clusters,
hence reducing their numbers. These winds can also provide extra material near
the accreting object which may create an intrinsic absorber to harden the X-ray
spectra of the metal poor cluster systems relative to the metal rich ones, as
suggested by observations. We outline some additional observational predictions
of the model.Comment: 6 pages, no figures, accepted to Ap
ROSAT Evidence for Intrinsic Oxygen Absorption in Cooling Flow Galaxies and Groups
Using spatially resolved, deprojected ROSAT PSPC spectra of 10 of the
brightest cooling flow galaxies and groups with low Galactic column densities
we have detected intrinsic absorption over energies ~0.4-0.8 keV in half of the
sample. Since no intrinsic absorption is indicated for energies below ~0.4 keV,
the most reasonable model for the absorber is collisionally ionized gas at
temperatures T=10^{5-6} K with most of the absorption arising from ionized
states of oxygen but with a significant contribution from carbon and nitrogen.
The soft X-ray emission of this warm gas can explain the sub-Galactic column
densities of cold gas inferred within the central regions of most of the
systems. Attributing the absorption to ionized gas reconciles the large columns
of cold H and He inferred from EINSTEIN and ASCA with the lack of such columns
inferred from ROSAT. Within the central ~10-20 kpc, where the constraints are
most secure, the estimated mass of the ionized absorber is consistent with most
(perhaps all) of the matter deposited by a cooling flow over the lifetime of
the flow. Since the warm absorber produces no significant H or He absorption
the large absorber masses are consistent with the negligible atomic and
molecular H inferred from HI and CO observations of cooling flows. It is also
found that if T > ~2x10^5 K then the optical and UV emission implied by the
warm gas does not violate published constraints. Finally, we discuss how the
prediction of warm ionized gas as the product of mass drop-out in these and
other cooling flows can be verified with new CHANDRA and XMM observations.
(Abridged)Comment: 17 pages (5 figures), Accepted for publication in ApJ, expanded
discussion of multiphase spectral models, theoretical implications of warm
gas in cooling flows, and the statistical significance of the oxygen
absorptio
Static Pressure of Hot Gas: Its Effect on the Gas Disks of Galaxies
The static pressure of the hot gas that fills clusters and groups of galaxies
can affect significantly the volume density and thickness of the gas disks in
galaxies. In combination with the dynamic pressure, the static pressure allows
several observed peculiarities of spiral galaxies surrounded by a hot medium to
be explained.Comment: 9 pages, 2 figures. This is a slightly modified version of the paper
published in Astronomy Letters 2008, Vol. 34, No 11, p. 73
Resistance of uropathogens to antibacterial agents: Emerging threats, trends and treatments
Urinary tract infections are among the most common infectious diseases in humans. Today, resistance to nearly all antimicrobial classes is dramatically growing, and extremely drug-resistant or even pan-drug resistant pathogens are increasingly isolated around the world. It is foreseen that in the next decades the world will be facing a major medical emergency generated by the rapid spread of pathogens carrying resistance determinants of unprecedented power. Carbapenemase-producing Enterobacteriaceae, multidrug-resistant Enterococci and fluoroquinolone resistance determinants in both Gram-negative and Gram-positive uropathogens are among the greatest emergencies. In this article, the major emerging threats of particular interest to urologists are reviewed, worldwide resistance trends are illustrated, and novel and older-but still active-recommended drugs are summarized
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