305 research outputs found
Evidence for a 3 x 10^8 solar mass black hole in NGC 7052 from HST observations of the nuclear gas disk
We present an HST study of the nuclear region of the E4 radio galaxy NGC
7052, which has a nuclear disk of dust and gas. The WFPC2 was used to obtain B,
V and I broad-band images and an H_alpha+[NII] narrow-band image. The FOS was
used to obtain H_alpha+[NII] spectra along the major axis, using a 0.26 arcsec
diameter circular aperture. The observed rotation velocity of the ionized gas
is V = 155 +/- 17 km/s at r = 0.2 arcsec from the nucleus. The Gaussian
dispersion of the emission lines increases from sigma = 70 km/s at r=1 arcsec,
to sigma = 400 km/s on the nucleus.
To interpret the gas kinematics we construct axisymmetric models in which the
gas and dust reside in a disk in the equatorial plane of the stellar body. It
is assumed that the gas moves on circular orbits, with an intrinsic velocity
dispersion due to turbulence. The circular velocity is calculated from the
combined gravitational potential of the stars and a possible nuclear black hole
(BH). Models without a BH predict a rotation curve that is shallower than
observed (V_pred = 92 km/s at r = 0.2 arcsec), and are ruled out at > 99%
confidence. Models with a BH of 3.3^{+2.3}_{-1.3} x 10^8 solar masses provide
an acceptable fit.
NGC 7052 can be added to the list of active galaxies for which HST spectra of
a nuclear gas disk provide evidence for the presence of a central BH. The BH
masses inferred for M87, M84, NGC 6251, NGC 4261 and NGC 7052 span a range of a
factor 10, with NGC 7052 falling on the low end. By contrast, the luminosities
of these galaxies are identical to within 25%. Any relation between BH mass and
luminosity, as suggested by independent arguments, must therefore have a
scatter of at least a factor 10.Comment: 39 pages, LaTeX, with 16 PostScript figures. Submitted to the
Astronomical Journal. Postscript version with higher resolution figures
available from http://sol.stsci.edu/~marel/abstracts/abs_R22.htm
A new population of recently quenched elliptical galaxies in the SDSS
We use the Sloan Digital Sky Survey to investigate the properties of massive
elliptical galaxies in the local Universe (z\leq0.08) that have unusually blue
optical colors. Through careful inspection, we distinguish elliptical from
non-elliptical morphologies among a large sample of similarly blue galaxies
with high central light concentrations (c_r\geq2.6). These blue ellipticals
comprise 3.7 per cent of all c_r\geq2.6 galaxies with stellar masses between
10^10 and 10^11 h^{-2} {\rm M}_{\sun}. Using published fiber spectra
diagnostics, we identify a unique subset of 172 non-star-forming ellipticals
with distinctly blue urz colors and young (< 3 Gyr) light-weighted stellar
ages. These recently quenched ellipticals (RQEs) have a number density of
2.7-4.7\times 10^{-5}\,h^3\,{\rm Mpc}^{-3} and sufficient numbers above
2.5\times10^{10} h^{-2} {\rm M}_{\sun} to account for more than half of the
expected quiescent growth at late cosmic time assuming this phase lasts 0.5
Gyr. RQEs have properties that are consistent with a recent merger origin
(i.e., they are strong `first-generation' elliptical candidates), yet few
involved a starburst strong enough to produce an E+A signature. The preferred
environment of RQEs (90 per cent reside at the centers of < 3\times
10^{12}\,h^{-1}{\rm M}_{\sun} groups) agrees well with the `small group scale'
predicted for maximally efficient spiral merging onto their halo center and
rules out satellite-specific quenching processes. The high incidence of Seyfert
and LINER activity in RQEs and their plausible descendents may heat the
atmospheres of small host halos sufficiently to maintain quenching.Comment: 26 pages, 9 figures. Revised version; accepted for publication in
MNRA
WFPC2 Images of the Central Regions of Early-Type Galaxies - I. The Data
We present high resolution R-band images of the central regions of 67
early-type galaxies obtained with the Wide Field and Planetary Camera 2 (WFPC2)
aboard the Hubble Space Telescope (HST). Our sample strikingly confirms the
complex morphologies of the central regions of early-type galaxies. In
particular, we detect dust in 43 percent of all galaxies, and evidence for
embedded stellar disks in a remarkably large fraction of 51 percent. In 14 of
those galaxies the disk-like structures are misaligned with the main galaxy,
suggesting that they correspond to stellar bars in S0 galaxies. We analyze the
luminosity profiles of the galaxies in our sample, and classify galaxies
according to their central cusp slope. To a large extent we confirm the clear
dichotomy found in previous HST surveys: bright, boxy ellipticals with shallow
inner cusps (`core' galaxies) on one hand and faint, disky ellipticals with
steep central cusps (`power-law' galaxies) on the other hand. The advantages
and shortcomings of classification schemes utilizing the extrapolated central
cusp slope are discussed, and it is shown that this cusp slope might be an
inadequate representation for galaxies whose luminosity profile slope changes
smoothly with radius rather than resembling a broken power-law. In fact, we
find evidence for an `intermediate' class of galaxies, that cannot
unambiguously be classified as either core or power-law galaxies, and which
have central cusp slopes and absolute magnitudes intermediate between those of
core and power-law galaxies.Comment: 44 pages, 7 Postscript figures. Accepted for publication in the
Astronomical Journal. The associated Appendix with figures of luminosity
profiles, contour plots and isophotal parameters for all galaxies is
available at http://www.astro.washington.edu/rest/centralpro
Scaling Relations of Spiral Galaxies
We construct a large data set of global structural parameters for 1300 field
and cluster spiral galaxies and explore the joint distribution of luminosity L,
optical rotation velocity V, and disk size R at I- and 2MASS K-bands. The I-
and K-band velocity-luminosity (VL) relations have log-slopes of 0.29 and 0.27,
respectively with sigma_ln(VL)~0.13, and show a small dependence on color and
morphological type in the sense that redder, early-type disk galaxies rotate
faster than bluer, later-type disk galaxies for most luminosities. The VL
relation at I- and K-bands is independent of surface brightness, size and light
concentration. The log-slope of the I- and K-band RL relations is a strong
function of morphology and varies from 0.25 to 0.5. The average dispersion
sigma_ln(RL) decreases from 0.33 at I-band to 0.29 at K, likely due to the
2MASS selection bias against lower surface brightness galaxies. Measurement
uncertainties are sigma_ln(V)~0.09, sigma_ln(L)~0.14 and somewhat larger and
harder to estimate for ln(R). The color dependence of the VL relation is
consistent with expectations from stellar population synthesis models. The VL
and RL residuals are largely uncorrelated with each other; the RV-RL residuals
show only a weak positive correlation. These correlations suggest that scatter
in luminosity is not a significant source of the scatter in the VL and RL
relations. The observed scaling relations can be understood in the context of a
model of disk galaxies embedded in dark matter halos that invokes low mean spin
parameters and dark halo expansion, as we describe in our companion paper
(Dutton et al. 2007). We discuss in two appendices various pitfalls of standard
analytical derivations of galaxy scaling relations, including the Tully-Fisher
relation with different slopes. (Abridged).Comment: Accepted for publication at ApJ. The full document, with
high-resolution B&W and colour figures, is available at
http://www.astro.queensu.ca/~courteau/papers/VRL2007ApJ.pdf . Our data base
for 1303 spiral galaxies is also available at
http://www.astro.queensu.ca/~courteau/data/VRL2007.da
White Blood Cell Scintigraphy for Fracture-Related Infection:Is Semiquantitative Analysis of Equivocal Scans Accurate?
Purpose: White blood cell (WBC) scintigraphy is considered the gold-standard nuclear imaging technique for diagnosing fracture-related infection (FRI). Correct interpretation of WBC scans in FRI is important since a false positive or false negative diagnosis has major consequences for the patient in terms of clinical decision-making. The European Association of Nuclear Medicine (EANM) guideline for correct analysis and interpretation of WBC scans recommends semiquantitative analysis of visually equivocal scans. Therefore, this study aims to assess the diagnostic accuracy of semiquantitative analysis of visually equivocal WBC scans for diagnosing FRI. Methods: A retrospective single-center study was performed in consecutive patients who received WBC scintigraphy in the diagnostic work-up for FRI between February 2012 and January 2017. All the visually equivocal scans were analysed using semiquantitative analysis by comparing leukocyte uptake in the manually selected suspected infection focus with the contralateral bone marrow (L/R ratio). Cut-off points for a ‘positive’ scan result of >0%, >10% and >20% leukocyte increase between the early and late scans were used in separate analyses. The discriminative ability was quantified by calculating the sensitivity, specificity and diagnostic accuracy. Results: In total, 153 WBC scans were eligible for inclusion. After visual assessment of all the scans, 28 visually equivocal scans were included. Dichotomization of the ratios using the cut-off of >0% resulted in a sensitivity of 30%, a specificity of 45% and a diagnostic accuracy of 40%. The >10% cut-off point resulted in a sensitivity of 18%, a specificity of 82% and a diagnostic accuracy of 66%. The >20% cut-off point resulted in a sensitivity of 0%, a specificity of 89% and a diagnostic accuracy of 67%. Conclusion: Semiquantitative analysis of visually equivocal WBC scans is insufficient for correctly diagnosing FRI
Spatial and kinematic alignments between central and satellite halos
Based on a cosmological N-body simulation we analyze spatial and kinematic
alignments of satellite halos within six times the virial radius of group size
host halos (Rvir). We measure three different types of spatial alignment: halo
alignment between the orientation of the group central substructure (GCS) and
the distribution of its satellites, radial alignment between the orientation of
a satellite and the direction towards its GCS, and direct alignment between the
orientation of the GCS and that of its satellites. In analogy we use the
directions of satellite velocities and probe three further types of alignment:
the radial velocity alignment between the satellite velocity and connecting
line between satellite and GCS, the halo velocity alignment between the
orientation of the GCS and satellite velocities and the auto velocity alignment
between the satellites orientations and their velocities. We find that
satellites are preferentially located along the major axis of the GCS within at
least 6 Rvir (the range probed here). Furthermore, satellites preferentially
point towards the GCS. The most pronounced signal is detected on small scales
but a detectable signal extends out to 6 Rvir. The direct alignment signal is
weaker, however a systematic trend is visible at distances < 2 Rvir. All
velocity alignments are highly significant on small scales. Our results suggest
that the halo alignment reflects the filamentary large scale structure which
extends far beyond the virial radii of the groups. In contrast, the main
contribution to the radial alignment arises from the adjustment of the
satellite orientations in the group tidal field. The projected data reveal good
agreement with recent results derived from large galaxy surveys. (abridged)Comment: accepted for publication in Ap
Semi-Analytical Models for the Formation of Disk Galaxies II. Dark Matter versus Modified Newtonian Dynamics
We present detailed semi-analytical models for the formation of disk galaxies
both in a Universe dominated by dark matter (DM), and in one for which the
force law is given by modified Newtonian dynamics (MOND). We tune the models to
fit the observed near-infrared Tully-Fisher (TF) relation, and compare numerous
predictions of the resulting models with observations. The DM and MOND models
are almost indistinguishable. They both yield gas mass fractions and dynamical
mass-to-light ratios which are in good agreement with observations. Both models
reproduce the narrow relation between global mass-to-light ratio and central
surface brightness, and reveal a characteristic acceleration, contrary to
claims that these relations are not predicted by DM models. Both models require
SN feedback in order to reproduce the lack of high surface brightness dwarf
galaxies. However, the introduction of feedback to the MOND models steepens the
TF relation and increases the scatter, making MOND only marginally consistent
with observations. The most serious problem for the DM models is their
prediction of steep central rotation curves. However, the DM rotation curves
are only slightly steeper than those of MOND, and are only marginally
inconsistent with the poor resolution data on LSB galaxies.Comment: 26 pages, 11 figures. Accepted for publication in Ap
Evidence for a massive BH in the S0 galaxy NGC 4342
We present axisymmetric dynamical models of the edge-on S0 galaxy NGC 4342. A
combination of observations from the ground and with the Hubble Space Telescope
(HST) has shown that NGC 4342 rotates rapidly and has a strong central increase
in velocity dispersion. We construct simple two-integral Jeans models as well
as fully general, three-integral models. The latter are built using a modified
version of Schwarzschild's orbit-superposition technique. The two-integral
Jeans models suggest a black hole (BH) mass between 3 and 6x10^8 Msun,
depending on the data set used to constrain the model, but they fail to fit the
details of the observed kinematics. The three-integral models can fit all
ground-based and HST data simultaneously, but only when a central BH is
included. Models without BH are ruled out to a confidence level better than
99.73 per cent. We determine a BH mass of 3x10^8 Msun. This corresponds to 2.6
per cent of the total mass of the bulge, making NGC 4342 one of the galaxies
with the highest BH mass to bulge mass ratio currently known. The models that
best fit the data do not have a two-integral phase-space distribution function.
They have rather complex dynamical structures: the velocity anisotropies are
strong functions of radius reflecting the multi-component structure of this
galaxy. The best fit model without BH tries to fit the high central velocity
dispersion by placing stars on radial orbits. The measured rotation velocities,
however, restrict the amount of radial anisotropy such that the central
velocity dispersion measured with the HST can only be fit when a massive BH is
included in the models.Comment: 47 pages, 14 figures (postscript). Submitted to Ap
Effectiveness of adalimumab in treating patients with active psoriatic arthritis and predictors of good clinical responses for arthritis, skin and nail lesions
International audienceObjectives: To evaluate the effectiveness of adalimumab in patients with psoriatic arthritis (PsA) and identify predictors of good clinical response for joint and skin lesions. Methods: Patients received adalimumab 40 mg every other week in addition to standard therapy in this prospective, 12-week, open-label, uncontrolled study. Four definitions of good clinical response were used: >= 50% improvement in American College of Rheumatology response criteria (ACR50), good response according to European League Against Rheumatism (EULAR) guidelines, a >= 3-grade improvement in Physician Global Assessment of psoriasis (PGA) and a >= 50% improvement in the Nail Psoriasis Severity Index (NAPSI). Response predictors were determined by logistic regression with backward elimination (selection level was 5%). Results: Of 442 patients, 94% completed 12 weeks of treatment. At week 12, 74%, 51% and 32% of the patients had achieved ACR20, 50 and 70, respectively; 87% and 61% experienced moderate and good responses according to EULAR criteria, respectively. The percentage of patients with PGA results of "clear/almost clear'' increased from 34% (baseline) to 68%. The mean NAPSI score was reduced by 44%. No new safety signals were detected. A lower Health Assessment Questionnaire Disability Index (HAQ-DI) score, greater pain assessment, male sex and absence of systemic glucocorticoid therapy were strongly associated with achievement of ACR50 and good response according to EULAR criteria. In addition, greater C-reactive protein concentration and polyarthritis predicted ACR50, and non-involvement of large joints predicted a good response according to EULAR criteria. Conclusions: Adalimumab was effective in patients with PsA. Lower impairment of physical function, greater pain, male sex and no systemic treatment with glucocorticoids were factors that increased the chance of achieving a good clinical response
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