410 research outputs found
The properties of active galaxies at the extreme of eigenvector 1
Eigenvector 1 (EV1) is the formal parameter which allows the introduction of
some order in the properties of the unobscured type 1 active galaxies. We aim
to understand the nature of this parameter by analyzing the most extreme
examples of quasars with the highest possible values of the corresponding
eigenvalues . We selected the appropriate sources from the Sloan
Digital Sky Survey (SDSS) and performed detailed modeling, including various
templates for the Fe II pseudo-continuum and the starlight contribution to the
spectrum. Out of 27 sources with larger than 1.3 and with the
measurement errors smaller than 20\% selected from the SDSS quasar catalog,
only six sources were confirmed to have a high value of , defined as
being above 1.3. All other sources have of approximately 1. Three
of the high objects have a very narrow H line, below 2100 km
s but three sources have broad lines, above 4500 km s, that do
not seem to form a uniform group, differing considerably in black hole mass and
Eddington ratio; they simply have a very similar EW([OIII]5007) line.
Therefore, the interpretation of the EV1 remains an open issue.Comment: Astronomy and Astrophysics (in press
SALT long-slit spectroscopy of LBQS 2113-4538: variability of the Mg II and Fe II component
The Mg II line is of extreme importance in intermediate redshift quasars
since it allows us to measure the black hole mass in these sources and to use
these sources as probes of the distribution of dark energy in the Universe, as
a complementary tool to SN Ia. Reliable use of Mg II requires a good
understanding of all the systematic effects involved in the measurement of the
line properties, including the contamination by Fe II UV emission. We performed
three spectroscopic observations of a quasar LBQS 2113-4538 (z = 0.956) with
the SALT telescope separated in time by several months and we analyze in detail
the mean spectrum and the variability in the spectral shape. We show that even
in our good-quality spectra the Mg II doublet is well fit by a single
Lorentzian shape. We tested several models of the Fe II pseudo-continuum and
showed that one of them well represents all the data. The amplitudes of both
components vary in time, but the shapes do not change significantly. The
measured line width of LBQS 2113-4538 identifies this object as a class A
quasar. The upper limit of for the contribution of the Narrow Line Region
(NLR) to Mg II may suggest that the separation of the Broad Line Region (BLR)
and NLR disappears in this class of objects.Comment: 10 pages, 8 figures, accepted to A&
Tracing dark energy with quasars
The nature of dark energy, driving the accelerated expansion of the Universe,
is one of the most important issues in modern astrophysics. In order to
understand this phenomenon, we need precise astrophysical probes of the
universal expansion spanning wide redshift ranges. Quasars have recently
emerged as such a probe, thanks to their high intrinsic luminosities and, most
importantly, our ability to measure their luminosity distances independently of
redshifts. Here we report our ongoing work on observational reverberation
mapping using the time delay of the Mg II line, performed with the South
African Large Telescope (SALT).Comment: 3 pages, 2 figures, submitted as PTA proceeding
The mass of the black hole in RE J1034+396
The black hole mass measurement in active galaxies is a challenge,
particularly in sources where the reverberation method cannot be applied. We
aim to determine the black hole mass in a very special object, RE J1034+396,
one of the two AGN with QPO oscillations detected in X-rays, and a single
bright AGN with optical band totally dominated by starlight. We fit the stellar
content using the code starlight, and the broad band disk contribution to
optical/UV/X-ray emission is modeled with optxagnf. We also determine the black
hole mass using several other independent methods. Various methods give
contradictory results. Most measurements of the blacc hole mass are in the
range 1.e6-1.e7 Msun, and the measurements based on dynamics give higher values
than measurements based on Hbeta and Mg II emission lines.Comment: A&A, in pres
Resistance patterns of selected respiratory tract pathogens in Poland
ABSTRACTThis study presents the results of a survey of the in-vitro susceptibility to antimicrobial agents of major pathogens responsible for community-acquired respiratory tract infections in Poland during 2002–2004. The collection of 1184 bacterial isolates comprised 398 Streptococcus pneumoniae, 344 Haemophilus influenzae, 302 Streptococcus pyogenes and 140 Moraxella catarrhalis. Among the pneumococcal isolates, 16.8% were penicillin-non-susceptible (PNSP), of which 80.6% were identified as multidrug-resistant. Overall, 9.0% of H. influenzae isolates were β-lactamase-positive, although this percentage increased noticeably in the third year of the study. Based on PCR results, 12.8% of H. influenzae isolates were identified as low-level β-lactamase-negative, ampicillin-resistant (BLNAR), and one isolate as low-level β-lactamase-positive, amoxycillin–clavulanic acid-resistant (BLPACR). Pulsed-field gel electrophoresis (PFGE) classified 45 H. influenzae isolates with altered penicillin-binding proteins into 15 PFGE types, including two predominant types (with four and six sub-types) containing 15 and ten isolates, respectively. Resistance to tetracycline, erythromycin and clindamycin was found in 20.9%, 8.9% and 4.6% of S. pyogenes isolates, respectively. The production of β-lactamase characterised 91.4% of M. catarrhalis isolates. In summary, the overall occurrence of PNSP in Poland remains stable, although there was a noticeable increase in the proportion of fully-resistant isolates. A rising trend in the prevalence of β-lactamase producers and low-level BLNAR isolates was observed among Polish isolates of H. influenzae
Multidrug-resistant Streptococcus pneumoniae in Poland: identification of emerging clones
Penicillin resistance among Streptococcus pneumoniae isolates has rapidly
emerged in Poland during the last decade and has reached prevalence levels
of up to 14.4% in 1997. In order to investigate the nature of this
increase, a molecular epidemiological analysis of
non-penicillin-susceptible multidrug-resistant pneumococci isolated in
1995 and 1996 was conducted. Thirty-seven patients who suffered mainly
from upper respiratory tract infections and pneumococcal pneumonia were
enrolled in this study. The medical centers to which the patients were
admitted were located in 16 Polish towns across the country. Eight
distinct BOX PCR types were observed, representing 14 subtypes.
Restriction fragment end labeling (RFEL) analysis divided the pneumococcal
strains into 16 distinct types. By combining the BOX PCR and RFEL data,
four genetically distinct clusters of strains were identified. Two
clusters represented the genetic clones 23F and 9V, which have recently
emerged all over the world. The two other genetic clusters, which
represented serotypes 23F and 6B, clearly predominated in the analyzed
collection of Polish non-penicillin-susceptible pneumococcal strains.
Since the latter clusters did not match any of the 133 RFEL types of
non-penicillin-susceptible pneumococci collected in 15 other countries,
their Polish clonal origin is most likely
Towards equation of state of dark energy from quasar monitoring: reverberation strategy
Context. High-redshift quasars can be used to constrain the equation of state of dark energy. They can serve as a complementary tool to supernovae Type Ia, especially at z > 1
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