1,502 research outputs found
SINFONI Observations of Starclusters in Starburst Galaxies
We have used ESO's new NIR IFS SINFONI during its Science Verification period
to observe the central regions of local starburst galaxies. Being Science
Verification observations, the aim was two-fold: to demonstrate SINFONI's
capabilities while obtaining information on the nature of starclusters in
starburst galaxies. The targets chosen include a number of the brighter
clusters in NGC1808 and NGC253. Here we present first results.Comment: Submitted to "Adaptive Optics-Assisted Integral-Field Spectroscopy",
Rutten R.G.M., Benn C.R., Mendez J., eds., May 2005, La Palma (Spain), New
Astr. Re
NIR spectroscopy of the most massive open cluster in the Galaxy: Westerlund 1
Using ISAAC/VLT, we have obtained individual spectra of all NIR-bright stars
in the central 2'x2' of the cluster Westerlund 1 (Wd 1) with a resolution of
R~9000 at a central wavelength of 2.30 micron. This allowed us to determine
radial velocities of ten post-main-sequence stars, and from these values a
velocity dispersion. Assuming virial equilibrium, the dispersion of sigma=8.4
km/s leads to a total dynamical cluster mass of 1.25x10^5 solar masses,
comparable to the photometric mass of the cluster. There is no extra-virial
motion which would have to be interpreted as a signature of cluster expansion
or dissolution.Comment: To appear in the proceedings of IAU 246: "Dynamical Evolution of
Dense Stellar Systems" (E. Vesperini, M. Giersz, A. Sills, eds.
Stellar and Molecular Gas Kinematics of NGC1097: Inflow Driven by a Nuclear Spiral
We present spatially resolved distributions and kinematics of the stars and
molecular gas in the central 320pc of NGC1097. The stellar continuum confirms
the previously reported 3-arm spiral pattern extending into the central 100pc.
The stellar kinematics and the gas distribution imply this is a shadowing
effect due to extinction by gas and dust in the molecular spiral arms. The
molecular gas kinematics show a strong residual (i.e. non-circular) velocity,
which is manifested as a 2-arm kinematic spiral. Linear models indicate that
this is the line-of-sight velocity pattern expected for a density wave in gas
that generates a 3-arm spiral morphology. We estimate the inflow rate along the
arms. Using hydrodynamical models of nuclear spirals, we show that when
deriving the accretion rate into the central region, outflow in the disk plane
between the arms has to be taken into account. For NGC1097, despite the inflow
rate along the arms being ~1.2Msun/yr, the net gas accretion rate to the
central few tens of parsecs is much smaller. The numerical models indicate that
the inflow rate could be as little as ~0.06Msun/yr. This is sufficient to
generate recurring starbursts, similar in scale to that observed, every
20-150Myr. The nuclear spiral represents a mechanism that can feed gas into the
central parsecs of the galaxy, with the gas flow sustainable for timescales of
a Gigayear.Comment: accepted by Ap
Duration of air leak is reduced after awake nonresectional lung volume reduction surgery
OBJECTIVE:
Prolonged air leak occurs frequently after lung volume reduction surgery (LVRS) and can negatively affect both morbidity and hospital stay. We hypothesised that awake nonresectional LVRS could reduce the duration of air leak in emphysema patients.
METHODS:
This analysis included 66 patients undergoing awake, unilateral plication of the most emphysematous lung regions under sole epidural anaesthesia. Primary outcome measure was the rate of prolonged (>7 days) air leak; secondary outcome measures included the mean duration of air leak, hospital stay and early discharges (<or=4 days). All results were retrospectively compared with those of a similar control group undergoing resectional LVRS under general anaesthesia.
RESULTS:
Intergroup comparisons showed that demographics and baseline data were well matched. Prolonged air leak occurred in 12 patients (18%) in the awake group versus 27 patients (40%) in the control group (p=0.007) with a mean duration of 5.2+/-6.5 days versus 7.9+/-7.6 days (p<0.0002). Mean hospital stay was significantly shorter in the awake group (6.3+/-2.8 days vs 9.2+/-5.6 days, p<0.0001). At univariate analysis, resectional LVRS (p=0.007), higher severity of emphysema (p<0.0001) and lower diffusion capacity for carbon monoxide (p=0.0001) correlated with occurrence of prolonged air leak; however, logistic regression indicated high severity of emphysema as the most important factor predicting prolonged air leak (odds ratio=4.85, p<0.0001). At 6 months, dyspnoea index, FEV1 and 6 min walking test improved significantly in both study groups.
CONCLUSIONS:
In this study, awake nonresectional LVRS was associated with a lower rate of prolonged air leak and a shorter hospital stay than the standard resectional technique
The Molecular Gas in the Circumnuclear Region of Seyfert Galaxies
Sub-arcsecond IRAM Plateau de Bure mm-interferometric observations of the
12CO (2-1) line emission in the Seyfert~1 NGC 3227 and the Seyfert~2 NGC 1068
have revealed complex kinematic systems in the inner 100 pc to 300 pc that are
not consistent with pure circular motion in the host galaxies. Modeling of
these kinematic systems with elliptical orbits in the plane of the host galaxy
(representing gas motion in a bar potential) is a possible solution but does
not reproduce all features observed. A better description of the complex
kinematics is achieved by circular orbits which are tilted out of the plane of
the host galaxy. This could indicate that the thin circumnuclear gas disk is
warped. In the case of NGC 1068 the warp model suggests that at a radius of
about 70 pc, the gas disk is oriented edge-on providing material for the
obscuration of the AGN nucleus. The position-velocity diagrams show rising
rotation curves at r 2
x 10^7 M_solar for NGC 3227 and > 10^8 M_solar for NGC 1068 within the central
25 pc.Comment: 14 pages, Ap.J. letter, accepte
ALFA & 3D: integral field spectroscopy with adaptive optics
One of the most important techniques for astrophysics with adaptive optics is
the ability to do spectroscopy at diffraction limited scales. The extreme
difficulty of positioning a faint target accurately on a very narrow slit can
be avoided by using an integral field unit, which provides the added benefit of
full spatial coverage. During 1998, working with ALFA and the 3D integral field
spectrometer, we demonstrated the validity of this technique by extracting and
distinguishing spectra from binary stars separated by only 0.26". The
combination of ALFA & 3D is also ideally suited to imaging distant galaxies or
the nuclei of nearby ones, as its field of view can be changed between
1.2"x1.2" and 4"x4", depending on the pixel scale chosen. In this contribution
we present new results both on galactic targets, namely young stellar objects,
as well as extra-galactic objects including a Seyfert and a starburst nucleus.Comment: SPIE meeting 4007 on Adaptive Optical Systems Technology, March 200
Low, Milky-Way like, Molecular Gas Excitation of Massive Disk Galaxies at z~1.5
We present evidence for Milky-Way-like, low-excitation molecular gas
reservoirs in near-IR selected massive galaxies at z~1.5, based on IRAM Plateau
de Bure Interferometer CO[3-2] and NRAO Very Large Array CO[1-0] line
observations for two galaxies that had been previously detected in CO[2-1]
emission. The CO[3-2] flux of BzK-21000 at z=1.522 is comparable within the
errors to its CO[2-1] flux, implying that the CO[3-2] transition is
significantly sub-thermally excited. The combined CO[1-0] observations of the
two sources result in a detection at the 3 sigma level that is consistent with
a higher CO[1-0] luminosity than that of CO[2-1]. Contrary to what is observed
in submillimeter galaxies and QSOs, in which the CO transitions are thermally
excited up to J>=3, these galaxies have low-excitation molecular gas, similar
to that in the Milky Way and local spirals. This is the first time that such
conditions have been observed at high redshift. A Large Velocity Gradient
analysis suggests that molecular clouds with density and kinetic temperature
comparable to local spirals can reproduce our observations. The similarity in
the CO excitation properties suggests that a high, Milky-Way-like, CO to H_2
conversion factor could be appropriate for these systems. If such
low-excitation properties are representative of ordinary galaxies at high
redshift, centimeter telescopes such as the Expanded Very Large Array and the
longest wavelength Atacama Large Millimeter Array bands will be the best tools
for studying the molecular gas content in these systems through the
observations of CO emission lines.Comment: 5 pages, 4 figures. ApJ Letters in pres
Local Swift-BAT active galactic nuclei prefer circumnuclear star formation
We use Herschel data to analyze the size of the far-infrared 70micron
emission for z<0.06 local samples of 277 hosts of Swift-BAT selected active
galactic nuclei (AGN), and 515 comparison galaxies that are not detected by
BAT. For modest far-infrared luminosities 8.5<log(LFIR)<10.5, we find large
scatter of half light radii Re70 for both populations, but a typical Re70 <~ 1
kpc for the BAT hosts that is only half that of comparison galaxies of same
far-infrared luminosity. The result mostly reflects a more compact distribution
of star formation (and hence gas) in the AGN hosts, but compact AGN heated dust
may contribute in some extremely AGN-dominated systems. Our findings are in
support of an AGN-host coevolution where accretion onto the central black hole
and star formation are fed from the same gas reservoir, with more efficient
black hole feeding if that reservoir is more concentrated. The significant
scatter in the far-infrared sizes emphasizes that we are mostly probing spatial
scales much larger than those of actual accretion, and that rapid accretion
variations can smear the distinction between the AGN and comparison categories.
Large samples are hence needed to detect structural differences that favour
feeding of the black hole. No size difference AGN host vs. comparison galaxies
is observed at higher far-infrared luminosities log(LFIR)>10.5 (star formation
rates >~ 6 Msun/yr), possibly because these are typically reached in more
compact regions in the first place.Comment: 7 pages, 3 figures, accepted for publication in Astronomy &
Astrophysic
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