422 research outputs found
The Nuclear Gas Dynamics and Star Formation of NGC 7469
We report interferometric radio CO2-1 observations at a resolution of 0.7",
and 0.085" resolution adaptive optics K-band spectroscopy of the inner few
arcseconds of NGC7469. The CO2-1 map shows a ring of molecular clouds and a
bright extended nucleus, with a bar or pair of spiral arms between them. The
dynamical structure of both the radio CO2-1 and the K-band H2 1-0S(1) lines can
be reproduced using an axisymmetric mass model comprising 3 components: a broad
disk, a ring 4-5" across, and an inner nuclear ring about 0.5" across. No
non-circular motions faster than the velocity residuals of 25 km/s are seen,
although this may be because in some cases a secondary bar is not expected to
cause gas inflow. From the dynamical mass and estimates of the stellar mass we
find that the CO-to-H_2 conversion is 0.4-0.8 times that for the Milky Way. The
H2 1-0S(1) morphology peaks at the nucleus, although there is no strong nuclear
mass concentration. The 1-0S(1) is likely to originate in X-ray of gas by the
AGN rather than via star formation. Using the 2.3um stellar CO2-0 absorption
and the continuum slope we have directly resolved the nuclear star cluster to
be 0.15-0.20" across, and find that it is asymmetric. This cluster has an age
of less than about 60Myr and contributes 20-30% of the nuclear K-band light,
and about 10% of the nuclear bolometric luminosity. Within a radius of ~4" gas
contributes more than half the total mass; but in the nucleus, within a radius
of 0.1", it is likely that most of the mass is due to starsComment: accepted for publication in ApJ (see their pages for a version with
higher quality figures
Elusive Active Galactic Nuclei
A fraction of active galactic nuclei do not show the classical Seyfert-type
signatures in their optical spectra, i.e. they are optically "elusive". X-ray
observations are an optimal tool to identify this class of objects. We combine
new Chandra observations with archival X-ray data in order to obtain a first
estimate of the fraction of elusive AGN in local galaxies and to constrain
their nature. Our results suggest that elusive AGN have a local density
comparable to or even higher than optically classified Seyfert nuclei. Most
elusive AGN are heavily absorbed in the X-rays, with gas column densities
exceeding 10^24 cm^-2, suggesting that their peculiar nature is associated with
obscuration. It is likely that in elusive AGN, the nuclear UV source is
completely embedded and the ionizing photons cannot escape, which prevents the
formation of a classical Narrow Line Region. Elusive AGN may contribute
significantly to the 30 keV bump of the X-ray background.Comment: accepted for publication in MNRAS Letters, 6 pages, 3 figures, typos
and references correcte
OVI Observations of Galaxy Clusters: Evidence for Modest Cooling Flows
A prediction of the galaxy cluster cooling flow model is that as gas cools
from the ambient cluster temperature, emission lines are produced in gas at
subsequently decreasing temperatures. Gas passing through 10^5.5 K emits in the
lines of OVI 1032,1035, and here we report a FUSE study of these lines in three
cooling flow clusters, Abell 426, Abell 1795, and AWM 7. No emission was
detected from AWM 7, but OVI is detected from the centers of Abell 426 and
Abell 1795, and possibly to the south of the center in Abell 1795, where X-ray
and optical emission line filaments lie. In Abell 426, these line luminosities
imply a cooling rate of 32+/-6 Msolar/yr within the central r = 6.2 kpc region,
while for Abell 1795, the central cooling rate is 26+/-7 Msolar/yr (within r =
22 kpc), and about 42+/-9 Msolar/yr including the southern pointing. Including
other studies, three of six clusters have OVI emission, and they also have star
formation as well as emission lines from 1E4 K gas. These observations are
generally consistent with the cooling flow model but at a rate closer to 30
Msolar/yr than originally suggested values of 100-1000 Msolar/yr.Comment: 17 pages, 6 figures, ApJ, in pres
N-band Imaging of Seyfert Nuclei and the MIR-X-ray correlation
We present new mid-infrared (N-band) images of a sample of eight nearby
Seyfert galaxies. In all of our targets, we detect a central unresolved source,
which in some cases has been identified for the first time. In particular, we
have detected the mid-infrared emission from the active nucleus of NGC 4945,
which previously remained undetected at any wavelength but hard X-rays. We also
detect circumnuclear extended emission in the Circinus galaxy along its major
axis, and find marginal evidence for extended circumnuclear emission in NGC
3281.
The high spatial resolution (1.7") of our data allows us to separate the flux
of the nuclear point sources from the extended circumnuclear starburst (if
present). We complement our sample with literature data for a number of
non-active starburst galaxies, and relate the nuclear N-band flux to published
hard (2-10 kev) X-ray fluxes. We find tight and well-separated correlations
between nuclear N-band flux and X-ray flux for both Seyfert and starburst
nuclei which span over 3 orders of magnitude in luminosity. We demonstrate that
these correlations can be used as a powerful classification tool for galactic
nuclei.
For example, we find strong evidence against NGC 1808 currently harbouring an
active Seyfert nucleus based on its position in the mid-infrared-X-ray diagram.
On the other hand, we confirm that NGC 4945 is in fact a Seyfert 2 galaxy.Comment: 31 pages, incl. 4 figures, uses AASTex. Replaced with accepted
version after minor modifications. To appear in Ap
Integral Field Spectroscopy of a Candidate Disk Galaxy at z~1.5 using Laser Guide Star Adaptive Optics
We present 0.1" resolution near-infrared integral field spectroscopy of
Halpha in a z=1.4781 star forming galaxy, Q2343-BM133. These observations were
obtained with OSIRIS (OH Suppressing Infra-Red Imaging Spectrograph) using the
W.M. Keck Observatory Laser Guide Star Adaptive Optics system. Halpha emission
is resolved over a 0.8" (6.8 kpc) x 0.5" (4.3 kpc) region with a 0.1" spatial
resolution. We find a global flux of 4.2+/-0.6x10^{-16} ergs s^{-1} cm^{-2},
and detect a spatially resolved velocity gradient of ~134 km s^{-1} across the
galaxy and a global velocity dispersion of 73+/-9 km s^{-1}. An upper limit of
NII/Halpha < 0.12 is inferred, which implies that this galaxy is not dominated
by an active galactic nucleus and has a metallicity at or below 1/2 solar
metallicity. We derive a star formation rate (SFR) of 47+/-6 Msun yr^{-1}, and
a dereddened SFR of 66+/-9 Msun yr^{-1}. Two-dimensional kinematics for
Q2343-BM133 fit well with an inclined-disk model, with which we estimate an
enclosed mass of 4.3x10^{9} Msun within 5.5 kpc. A possible merger scenario is
also presented, and can not be fully ruled out. We derive a virial mass of
1.1x10^{10} Msun for a disk geometry, using the observed velocity dispersion.
We propose that Q2343-BM133 is currently at an early stage of disk formation at
a look-back time of 9.3 Gyr.Comment: 21 pages, 5 figures, ApJ accepte
How do Zimbabweans value health states?
Background Quality of life weights based on valuations of health states are often used in cost utility analysis and population health measures. This paper reports on an attempt to develop quality of life weights within the Zimbabwe context. Methods 2,384 residents in randomly selected small residential plots of land in a high-density suburb of Harare valued descriptors of 38 health states based on different combinations of the five domains of the EQ-5D (mobility, self-care, usual activities, pain or discomfort and anxiety or depression). The English version of the EQ-5D was used. The time trade-off method was used to determine the values, and 19,020 individual preferences for health states were analysed. A residual maximum likelihood linear mixed model was used to estimate a function for predicting the values of all possible combinations of levels on the five domains. The model was fit to a random subset of two-thirds of the observations, with the remaining observations reserved for analysis of predictive validity. The results were compared to a similar study undertaken in the United Kingdom. Results A credible model was developed to predict the values of states that were not valued directly. In the subset of observations reserved for validation, the mean absolute difference between predicted and observed values was 0.045. All domains of the EQ-5D were found to contribute significantly to the model, both at the moderate and severe levels. Severe pain was found to have the largest negative coefficient, followed by the inability to wash and dress oneself. Conclusion Despite a generally lower education level than their European counterparts, urban Zimbabweans appear to value health states in a consistent manner, and the determination of a global method of establishing quality of life weights may be feasible and valid. However, as the relative weightings of the different domains, although correlated, differed from the standard set of weights recommended by the EuroQol Group, the locally determined coefficients should be used within the Zimbabwean context
Nuclear mid-infrared properties of nearby low-luminosity AGN
We present ground-based high-spatial resolution mid-infrared (MIR)
observations of 20 nearby low-luminosity AGN (LLAGN) with VLT/VISIR and the
preliminary analysis of a new sample of 10 low-luminosity Seyferts observed
with Gemini/Michelle. LLAGN are of great interest because these objects are the
most common among active galaxies, especially in the nearby universe. Studying
them in great detail makes it possible to investigate the AGN evolution over
cosmic timescale. Indeed, many LLAGN likely represent the final stage of an
AGN's lifetime. We show that even at low luminosities and accretion rates
nuclear unresolved MIR emission is present in most objects. Compared to lower
spatial resolution Spitzer/IRS spectra, the high-resolution MIR photometry
exhibits significantly lower fluxes and different PAH emission feature
properties in many cases. By using scaled Spitzer/IRS spectra of typical
starburst galaxies, we show that the star formation contribution to the 12
micron emission is minor in the central parsecs of most LLAGN. Therefore, the
observed MIR emission in the VISIR and Michelle data is most likely emitted by
the AGN itself, which, for higher luminosity AGN, is interpreted as thermal
emission from a dusty torus. Furthermore, the 12 micron emission of the LLAGN
is strongly correlated with the absorption corrected 2-10 keV luminosity and
the MIR--X-ray correlation found previously for AGN is extended to a range from
10^40 to 10^45 erg/s. This correlation is independent of the object type, and
in particular the low-luminosity Seyferts observed with Michelle fall exactly
on the power-law fit valid for brighter AGN. In addition, no dependency of the
MIR--X-ray ratio on the accretion rate is found. These results are consistent
with the unification model being applicable even in the probed low-luminosity
regime.Comment: to appear in the proceedings of AHAR 2011: The Central Kiloparsec in
Galactic Nucle
A multi-center blinded study on the efficiency of phenotypic screening methods to detect glycopeptide intermediately susceptible Staphylococcus aureus (GISA) and heterogeneous GISA (h-GISA)
Contains fulltext :
52338.pdf (publisher's version ) (Open Access)BACKGROUNDS: To determine the true incidence of hGISA/GISA and its consequent clinical impact, methods must be defined that will reliably and reproducibly discriminate these resistant phenotypes from vancomycin susceptible S. aureus (VSSA). METHODS: This study assessed and compared the ability of eight Dutch laboratories under blinded conditions to discriminate VSSA from hGISA/GISA phenotypes and the intra- and inter-laboratory reproducibility of agar screening plates and the Etest method. A total of 25 blinded and unique strains (10 VSSA, 9 hGISA and 6 GISA) were categorized by the PAP-AUC method and PFGE typed to eliminate clonal duplication. All strains were deliberately added in quadruplets to evaluate intra-laboratory variability and reproducibility of the methods. Strains were tested using three agar screening methods, Brain Heart Infusion agar (BHI) + 6 microg/ml vancomycin, Mueller Hinton agar (MH) + 5 microg/ml vancomycin and MH + 5 microg/ml teicoplanin) and the Etest macromethod using a 2 McFarland inoculum. RESULTS AND DISCUSSION: The ability to detect the hGISA/GISA phenotypes varied significantly between methods and phenotypes. BHI vancomycin and MH vancomycin agar screens lacked the ability to detect hGISA. The MH teicoplanin agar screen was more sensitive but still inferior to Etest that had a sensitivity of 98.5% and 99.5%, for hGISA and GISA, respectively. Intra- and inter-laboratory reproducibility varied between methods with poorest performance seen with BHI vancomycin. CONCLUSION: This is the first multi-center blinded study to be undertaken evaluating various methods to detect GISA and hGISA. These data showed that the ability of clinical laboratories to detect GISA and hGISA varied considerably, and that screening plates with vancomycin have a poor performance in detecting hGISA
Concomitant CIS on TURBT does not impact oncological outcomes in patients treated with neoadjuvant or induction chemotherapy followed by radical cystectomy
© Springer-Verlag GmbH Germany, part of Springer Nature 2018Background: Cisplatin-based neoadjuvant chemotherapy (NAC) for muscle invasive bladder cancer improves all-cause and cancer specific survival. We aimed to evaluate whether the detection of carcinoma in situ (CIS) at the time of initial transurethral resection of bladder tumor (TURBT) has an oncological impact on the response to NAC prior to radical cystectomy. Patients and methods: Patients were identified retrospectively from 19 centers who received at least three cycles of NAC or induction chemotherapy for cT2-T4aN0-3M0 urothelial carcinoma of the bladder followed by radical cystectomy between 2000 and 2013. The primary and secondary outcomes were pathological response and overall survival, respectively. Multivariable analysis was performed to determine the independent predictive value of CIS on these outcomes. Results: Of 1213 patients included in the analysis, 21.8% had concomitant CIS. Baseline clinical and pathologic characteristics of the âCISâ versus âno-CISâ groups were similar. The pathological response did not differ between the two arms when response was defined as pT0N0 (17.9% with CIS vs 21.9% without CIS; p = 0.16) which may indicate that patients with CIS may be less sensitive to NAC or †pT1N0 (42.8% with CIS vs 37.8% without CIS; p = 0.15). On Cox regression model for overall survival for the cN0 cohort, the presence of CIS was not associated with survival (HR 0.86 (95% CI 0.63â1.18; p = 0.35). The presence of LVI (HR 1.41, 95% CI 1.01â1.96; p = 0.04), hydronephrosis (HR 1.63, 95% CI 1.23â2.16; p = 0.001) and use of chemotherapy other than ddMVAC (HR 0.57, 95% CI 0.34â0.94; p = 0.03) were associated with shorter overall survival. For the whole cohort, the presence of CIS was also not associated with survival (HR 1.05 (95% CI 0.82â1.35; p = 0.70). Conclusion: In this multicenter, real-world cohort, CIS status at TURBT did not affect pathologic response to neoadjuvant or induction chemotherapy. This study is limited by its retrospective nature as well as variability in chemotherapy regimens and surveillance regimens.Peer reviewedFinal Accepted Versio
Simultaneous NIR/sub-mm observation of flare emission from SgrA*
We report on a successful, simultaneous observation and modeling of the
sub-millimeter to near-infrared flare emission of the Sgr A* counterpart
associated with the super-massive black hole at the Galactic center. Our
modeling is based on simultaneous observations that have been carried out on 03
June, 2008 using the NACO adaptive optics (AO) instrument at the ESO VLT and
the LABOCA bolometer at the APEX telescope. Inspection and modeling of the
light curves show that the sub-mm follows the NIR emission with a delay of
1.5+/-0.5 hours. We explain the flare emission delay by an adiabatic expansion
of the source components.Comment: 12 pages, 9 figures, 3 tables, in press with A&
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