13 research outputs found
Velocity Fields of Spiral Galaxies in z~0.5 Clusters
Spiral galaxies can be affected by interactions in clusters, that also may
distort the internal velocity field. If unrecognized from single-slit
spectroscopy, this could lead to a wrong determination of the maximum rotation
velocity as pointed out by Ziegler et al. (2003). This parameter directly
enters into the Tully-Fisher relation, an important tool to investigate the
evolution of spiral galaxies. To overcome this problem, we measure the
2D-velocity fields by observing three different slit positions per galaxy using
FORS2 at the VLT providing us with full coverage of each galaxy and an adequate
spatial resolution. The kinematic properties are compared to structural
features determined on the HST/ACS images to assess possible interaction
processes. As a next step, the whole analysis will be performed for three more
clusters, so that we will be able to establish a high-accuracy TFR for spirals
at z~0.5.Comment: 2 pages, 2 figures, going to be published in the proceedings of the
IAU Symp. 241, "Stellar Populations as Building Blocks of Galaxies
Determination of masses of the central black holes in NGC524 and NGC2549 using Laser Guide Star Adaptive Optics
[abridged] We present observations of NGC524 and NGC2549 with LGS AO obtained
at GEMINI North telescope using the NIFS IFU in the K band. The purpose of
these observations, together with previously obtained observations with the
SAURON IFU, is to determine the masses (Mbh) of the supermassive black holes
(SMBH). The targeted galaxies were chosen to have central light profiles
showing a core (NGC524) and a cusp (NGC2549), to probe the feasibility of using
the galaxy centre as the NGS required for LGS AO. We employ an innovative `open
loop' technique. The data have spatial resolution of 0.23" and 0.17" FWHM,
showing that high quality LGS AO observations of these objects are possible. We
construct axisymmetric three-integral dynamical models which are constrained
with both the NIFS and SAURON data. The best fitting models yield Mbh=(8.3 +2.7
-1.3) x 10^8 Msun for NGC524 and Mbh=(1.4 +0.2 -1.3) x 10^7 Msun for NGC2549
(all errors are at the 3 sigma CL). We demonstrate that the wide-field SAURON
data play a crucial role in the M/L determination increasing the accuracy of
M/L by a factor of at least 5, and constraining the upper limits on Mbh. The
NIFS data are crucial in constraining the lower limits of Mbh and in
combination with the large scale data reducing the uncertainty by a factor of 2
or more. We find that the orbital structure of NGC524 shows significant
tangential anisotropy, while at larger radii both galaxies are consistent with
having almost perfectly oblate velocity ellipsoids. Tangential anisotropy in
NGC524 coincides with the size of SMBH sphere of influence and the core region
in the light profile. We test the accuracy to which Mbh can be measured using
seeings obtained from typical LGS AO observations, and conclude that for a
typical conditions and Mbh the expected uncertainty is of the order of 50%.Comment: 19 pages, 14 figure
Current star formation in early-type galaxies and the K+A phenomenon
We present the results of an effort to identify and study a sample of the
likely progenitors of elliptical (E) and lenticular (S0) K+A galaxies. To
achieve this, we have searched a sample ~11,000 nearby (m(r)<16) early-type
galaxies selected by morphology from the Sloan Digital Sky Survey (SDSS) Main
spectroscopic sample for actively star-forming E and S0 galaxies. Using
emission line ratios and visual inspection of SDSS g-band images, we have
identified 335 galaxies from the SDSS Fourth Data Release (DR4) as actively
star-forming E and S0 galaxies. These galaxies make up about 3% of the total
early-type sample and less than 1% of all Main galaxies with m(r)<16. We also
identified a sample of ~400 K+A galaxies from DR4 with m(r)<16; more than half
of these are E and S0 galaxies. We find that star-forming early-type galaxies
and K+A galaxies have similar mass distributions; they are on average less
massive than typical early-type galaxies but more massive than the average
star-forming galaxy. Both of these types of galaxies are found in higher
fractions among all galaxies in lower density environments. The fractions of
star-forming E and S0 galaxies and E and S0 K+A galaxies depend on environment
in nearly the same way. Model spectra fit to the stellar continua of the
star-forming E and S0 galaxies showed that their properties are consistent with
star formation episodes of <1 Gyr in duration. The modelling results imply that
on average, the star formation episodes will increase the stellar masses by
about 4%. There is also evidence that the star-forming regions within these
galaxies are rotationally supported.Comment: Accepted to MNRAS, 19 pages, 14 figure
Six new supermassive black hole mass determinations from adaptive-optics assisted SINFONI observations
Different massive black hole mass ā host galaxy scaling relations suggest that the growth of massive black holes is entangled with the evolution of their host galaxies. The number of measured black hole masses is still limited and additional measurements are necessary to understand the underlying physics of this apparent coevolution. We add six new black hole mass (MBH) measurements of nearby fast rotating early-type galaxies to the known black hole mass sample, namely NGC 584, NGC 2784, NGC 3640, NGC 4570, NGC 4281, and NGC 7049. Our target galaxies have effective velocity dispersions (Ļe) between 170 and 245 km sā1, and thus this work provides additional insight into the black hole properties of intermediate-mass early-type galaxies. We combined high-resolution adaptive-optics SINFONI data with large-scale MUSE, VIMOS and SAURON data from ATLAS3D to derive two-dimensional stellar kinematics maps. We then built both Jeans Anisotropic Models and axisymmetric Schwarzschild models to measure the central black hole masses. Our Schwarzschild models provide black hole masses of (1.3ā
Ā±ā
0.5)ā
Ćā
108āMā for NGC 584, (1.0ā
Ā±ā
0.6)ā
Ćā
108āMā for NGC 2784, (7.7ā
Ā±ā
5)ā
Ćā
107āMā for NGC 3640, (5.4ā
Ā±ā
0.8)ā
Ćā
108āMā for NGC 4281, (6.8ā
Ā±ā
2.0)ā
Ćā
107āMā for NGC 4570, and (3.2ā
Ā±ā
0.8)ā
Ćā
108āMā for NGC 7049 at 3Ļ confidence level, which are consistent with recent MBHāĻe scaling relations. NGC 3640 has a velocity dispersion dip and NGC 7049 a constant velocity dispersion in the center, but we can clearly constrain their lower black hole mass limit. We conclude our analysis with a test on NGC 4570 taking into account a variable mass-to-light ratio (M/L) when constructing dynamical models. When considering M/L variations linked mostly to radial changes in the stellar metallicity, we find that the dynamically determined black hole mass from NGC 4570 decreases by 30%. Further investigations are needed in the future to account for the impact of radial M/L gradients on dynamical modeling
Large-Eddy Simulation of the Flow Around a Bluff Body
Large Eddy Simulations of the flow around a surface-mounted cube were made. It was shown that it is possible to obtain accurate results at a computational cost of only 60 CPU hours on a SGI R10000. Two one-equation subgrid models are used for modeling the SGS stress tensor. A series of time-averaged velocities and turbulent stresses are computed and compared with the experiments~\cite{martinuzzi:tropea}, showing good agreement. Global quantities such as drag and lift coefficients are presented. The transfer of the turbulent energy was studied, and the reverse transfer of energy (``backscatter'') was predicted. Coherent structures and other flow features were studied. The results show good agreement with experimental observations
The star formation history and evolution of the circumnuclear region of M100
The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1111/j.1365-2966.2006.10751.xPeer reviewe
European Electronic Personal Health Records initiatives and vulnerable migrants: A need for greater ethical, legal and social safeguards
The effective collection and management of personal data of rapidly migrating populations is important for ensuring adequate healthcare and monitoring of a displaced peoples\u2019 health status. With developments in ICT data sharing capabilities, electronic personal health records (ePHRs) are increasingly replacing less transportable paper records. ePHRs offer further advantages of improving accuracy and completeness of information and seem tailored for rapidly displaced and mobile populations. Various emerging initiatives in Europe are seeking to develop migrant-centric ePHR responses. This paper highlights their importance and benefits, but also identifies a number of significant ethical, legal and social issues (ELSI) and challenges to their design and implementation, regarding (1) the kind of information that should be stored, (2) who should have access to information, and (3) potential misuse of information. These challenges need to be urgently addressed to make possible the beneficial use of ePHRs for vulnerable migrants in Europe
Star formation in nearby early-type galaxies: Mapping in UV, optical and CO
The SAURON integral-field survey reveals that small (ā¼0.1,Re) kinematically decoupled cores (KDCs) in early-type galaxies are increasingly young toward the center and are typically found in fast-rotating galaxies, while large KDCs (ā¼0.5 Re) have homogeneously old stars and are present in non-rotating galaxies (McDermid et al. 2006). GALEX UV imaging further allows the direct identification of regions of recent star formation (0.5 Gyr). In NGC 2974 for example, young stars are identified in the center and an outer ring Jeong et al. 2006). Nuclear and inner ionised-gas rings (Sarzi et al. 2006) then suggest that current star formation is bar-driven. The CO detection rate of SAURON early-type galaxies is 40% (Combes et al. in prep.). Synthesis imaging reveals that it is generally contained in a well-ordered central disk, both in galaxies with a (young) central stellar disk (e.g. NGC 4459, NGC 4526) or a (young) KDC (e.g. NGC 3032, NGC 4150) (Young et al. in prep.). CO also traces well the young stellar populations and ionised gas distribution and kinematics, but in KDCs not always the stellar kinematics Emsellem et al. 2004; Sarzi et al. 2006; Kuntschner et al. 2006). Ā© 2007 International Astronomical Union