8 research outputs found
The SAURON project. II. Sample and early results
Early results are reported from the SAURON survey of the kinematics and
stellar populations of a representative sample of nearby E, S0 and Sa galaxies.
The survey is aimed at determining the intrinsic shape of the galaxies, their
orbital structure, the mass-to-light ratio as a function of radius, the age and
metallicity of the stellar populations, and the frequency of kinematically
decoupled cores and nuclear black holes. The construction of the representative
sample is described, and its properties are illustrated. A comparison with
long-slit spectroscopic data establishes that the SAURON measurements are
comparable to, or better than, the highest-quality determinations. Comparisons
are presented for NGC 3384 and NGC 4365 where stellar velocities and velocity
dispersions are determined to a precision of 6 km/s, and the h3 and h4
parameters of the line-of-sight velocity distribution to a precision of better
than 0.02. Extraction of accurate gas emission-line intensities, velocities and
line widths from the datacubes is illustrated for NGC 5813. Comparisons with
published line-strengths for NGC 3384 and NGC 5813 reveal uncertainties of <
0.1 A on the measurements of the Hbeta, Mgb and Fe5270 indices. Integral-field
mapping uniquely connects measurements of the kinematics and stellar
populations to the galaxy morphology. The maps presented here illustrate the
rich stellar kinematics, gaseous kinematics, and line-strength distributions of
early-type galaxies. The results include the discovery of a thin, edge-on, disk
in NGC 3623, confirm the axisymmetric shape of the central region of M32,
illustrate the LINER nucleus and surrounding counter-rotating star-forming ring
in NGC 7742, and suggest a uniform stellar population in the decoupled core
galaxy NGC 5813.Comment: 20 pages, 17 figures. To be published in MNRAS. Version with full
resolution images available at
http://www.strw.leidenuniv.nl/~dynamics/Instruments/Sauron/pub_list.htm
The Atlas3D project -- XIII. Mass and morphology of HI in early-type galaxies as a function of environment
We present the Atlas3D HI survey of 166 nearby early-type galaxies (ETGs)
down to M(HI)~10^7 M_sun. We detect HI in ~40% of all ETGs outside the Virgo
cluster and in ~10% of all ETGs inside it. This demonstrates that it is common
for non-cluster ETGs to host HI. The HI morphology varies from regular
discs/rings (the majority of the detections) to unsettled gas distributions.
The former are either small discs (M(HI)<10^8 M_sun) confined within the
stellar body and sharing the same kinematics of the stars, or large discs/rings
(M(HI) up to 5x10^9 M_sun) extending to tens of kpc from the host galaxy and
frequently kinematically decoupled from the stars. Neutral hydrogen provides
material for star formation in ETGs. Galaxies with central HI exhibit
signatures of star formation in ~70% of the cases, ~5 times more frequently
than galaxies without central HI. The central ISM is dominated by molecular
gas. In ETGs with a small gas disc the conversion of HI into H_2 is as
efficient as in spirals. The ETG HI mass function has M*~2x10^9 M_sun and
slope=-0.7. ETGs host much less HI than spirals as a family. However, a
significant fraction of them is as HI-rich as spirals. The main difference
between ETGs and spirals is that the former lack the high-column-density HI
typical of the bright stellar disc of the latter. We find an envelope of
decreasing M(HI) with increasing environment density. The gas-richest ETGs live
in the poorest environments (where star-formation is more common), galaxies in
the centre of Virgo have the lowest HI content, and the cluster outskirts are a
transition region. We find an HI morphology-density relation. At low
environment density HI is mostly distributed on large discs/rings. More
disturbed HI morphologies dominate environment densities typical of rich
groups, confirming the importance of processes occurring on a galaxy-group
scale for the evolution of ETGs.Comment: Accepted for publication on MNRA
The ATLAS project - X. On the origin of the molecular and ionized gas in early-type galaxies
The definitive version can be found at: http://onlinelibrary.wiley.com/ Copyright Royal Astronomical SocietyWe make use of interferometric CO and Hi observations, and optical integral-field spectroscopy from the ATLAS survey, to probe the origin of the molecular and ionized interstellar medium (ISM) in local early-type galaxies. We find that 36 ± 5 per cent of our sample of fast-rotating early-type galaxies have their ionized gas kinematically misaligned with respect to the stars, setting a strong lower limit on the importance of externally acquired gas (e.g. from mergers and cold accretion). Slow rotators have a flat distribution of misalignments, indicating that the dominant source of gas is external. The molecular, ionized and atomic gas in all the detected galaxies are always kinematically aligned, even when they are misaligned from the stars, suggesting that all these three phases of the ISM share a common origin. In addition, we find that the origin of the cold and warm gas in fast-rotating early-type galaxies is strongly affected by environment, despite the molecular gas detection rate and mass fractions being fairly independent of group/cluster membership. Galaxies in dense groups and the Virgo cluster nearly always have their molecular gas kinematically aligned with the stellar kinematics, consistent with a purely internal origin (presumably stellar mass loss). In the field, however, kinematic misalignments between the stellar and gaseous components indicate that at least 42 ± 5 per cent of local fast-rotating early-type galaxies have their gas supplied from external sources. When one also considers evidence of accretion present in the galaxies' atomic gas distributions, ≳46 per cent of fast-rotating field ETGs are likely to have acquired a detectable amount of ISM from accretion and mergers. We discuss several scenarios which could explain the environmental dichotomy, including preprocessing in galaxy groups/cluster outskirts and the morphological transformation of spiral galaxies, but we find it difficult to simultaneously explain the kinematic misalignment difference and the constant detection rate. Furthermore, our results suggest that galaxy mass may be an important independent factor associated with the origin of the gas, with the most massive fast-rotating galaxies in our sample (M≲-24mag; stellar mass of ≈8 × 10 M) always having kinematically aligned gas. This mass dependence appears to be independent of environment, suggesting it is caused by a separate physical mechanism.Peer reviewe
Use of Telehealth for Research and Clinical Measures in Cochlear Implant Recipients: A Validation Study
Tunable and reversible drug control of protein production via a self-excising degron
An effective method for direct chemical control over the production of specific proteins would be widely useful. We describe Small Molecule-Assisted Shutoff (SMASh), a technique in which proteins are fused to a degron that removes itself in the absence of drug, leaving untagged protein. Clinically tested HCV protease inhibitors can then block degron removal, inducing rapid degradation of subsequently synthesized protein copies. SMASh allows reversible and dose-dependent shutoff of various proteins in multiple mammalian cell types and in yeast. We also used SMASh to confer drug responsiveness onto a RNA virus for which no licensed inhibitors exist. As SMASh does not require permanent fusion of a large domain, it should be useful when control over protein production with minimal structural modification is desired. Furthermore, as SMASh only involves a single genetic modification and does not rely on modulating protein-protein interactions, it should be easy to generalize to multiple biological contexts