45 research outputs found
Multicolor single-molecule spectroscopy with alternating laser excitation for the investigation of interactions and dynamics
No full textRoss J, Buschkamp P, Fetting D, Donnermeyer A, Roth CM, Tinnefeld P. Multicolor single-molecule spectroscopy with alternating laser excitation for the investigation of interactions and dynamics. Journal of Physical Chemistry B. 2007;111(2):321-326.We have developed confocal multicolor single-molecule spectroscopy with optimized detection sensitivity on three spectrally distinct channels for the study of biomolecular interactions and FRET between more than two molecules. Using programmable acousto-optical devices as beamsplitter and excitation filter, we overcome some of the limitations of conventional multichroic beamsplitters and implement rapid alternation between three laser lines. This enables to visualize the synthesis of DNA three-way junctions on a single-molecule basis and to resolve seven stoichiometric subpopulations as well as to quantify FRET in the presence of competing energy transfer pathways. Furthermore, the ability to study correlated molecular movements by monitoring several distances within a biomolecular complex simultaneously is demonstrated
The LUCIFER multi-object spectroscopy unit and line excitation, metallicity, and dust extinction in massive star-forming galaxies at high redshift
Get PDFLBT/ARGOS adaptive optics observations of z ∼ 2 lensed galaxies
No full textAims. Gravitationally lensed systems allow a detailed view of galaxies at high redshift. High spatial-and spectral-resolution measurements of arc-like structures can offer unique constraints on the physical and dynamical properties of high-z systems. Methods. We present near-infrared spectra centred on the gravitational arcs of six known z ∼ 2 lensed star-forming galaxies of stellar masses of 109-11 M⊙ and star formation rate (SFR) in the range between 10 and 400 M⊙ yr-1. Ground layer adaptive optics (AO)-Assisted observations are obtained at the Large Binocular Telescope (LBT) with the LUCI spectrographs during the commissioning of the ARGOS facility. We used MOS masks with curved slits to follow the extended arched structures and study the diagnostic emission lines. LBT observations are used to demonstrate the spectroscopic capabilities of ARGOS. Results. Combining spatially resolved kinematic properties across the arc-like morphologies, emission line diagnostics and archival information, we distinguish between merging and rotationally supported systems, and reveal the possible presence of ejected gas. For galaxies that have evidence for outflows, we derive outflow energetics and mass-loading factors compatible with those observed for stellar winds in local and high-z galaxies. We also use flux ratio diagnostics to derive gas-phase metallicities. The low signal-To-noise ratio in the faint Hβ and nitrogen lines allows us to derive an upper limit of 0.15 dex for the spatial variations in metallicity along the slit for the lensed galaxy J1038. Conclusions. Analysed near-infrared spectra presented here represent the first scientific demonstration of performing AO-Assisted multi-object spectroscopy with narrow curved-shape slits. The increased angular and spectral resolution, combined with the binocular operation mode with the 8.4 m wide eyes of LBT, will allow the characterisation of kinematic and chemical properties of a large sample of galaxies at high-z in the near future
The SINS Survey: Modeling the dynamics of z ~ 2 galaxies and the high-z Tully-Fisher relation
No full textWe present the modeling of SINFONI integral field dynamics of 18 star-forming galaxies at z ~ 2 from Halpha line emission. The galaxies are selected from the larger sample of the SINS survey, based on the prominence of ordered rotational motions with respect to more complex merger-induced dynamics. The quality of the data allows us to carefully select systems with kinematics dominated by rotation, and to model the gas dynamics across the whole galaxy using suitable exponential disk models. We obtain a good correlation between the dynamical mass and the stellar mass, finding that large gas fractions (M gas ââ°Ë M *) are required to explain the difference between the two quantities. We use the derived stellar mass and maximum rotational velocity V max from the modeling to construct for the first time the stellar mass Tully-Fisher relation at z ~ 2.2. The relation obtained shows a slope similar to what is observed at lower redshift, but we detect an evolution of the zero point. We find that at z ~ 2.2 there is an offset in log(M *) for a given rotational velocity of 0.41 ± 0.11 with respect to the local universe. This result is consistent with the predictions of the latest N-body/hydrodynamical simulations of disk formation and evolution, which invoke gas accretion onto the forming disk in filaments and cooling flows. This scenario is in agreement with other dynamical evidence from SINS, where gas accretion from the halo is required to reproduce the observed properties of a large fraction of the z ~ 2 galaxies. Based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory, Paranal, Chile, in the context of guaranteed time programs 073.B-9018, 074.A-9011, 075.A-0466, 076.A-0527, 077.A-0576, 078.A-0600, 078.A-0055, 079.A-0341, 080.A-0330, and 080.A-0635
From rings to bulges: evidence for rapid secular galaxy evolution at z 2 from integral field spectroscopy in the SINS survey
Get PDFWe present Hα integral field spectroscopy of well-resolved, UV/optically selected z ~ 2 star-forming galaxies as part of the SINS survey with SINFONI on the ESO VLT. Our laser guide star adaptive optics and good seeing data show the presence of turbulent rotating star-forming outer rings/disks, plus central bulge/inner disk components, whose mass fractions relative to the total dynamical mass appear to scale with the [N II]/Hα flux ratio and the star formation age. We propose that the buildup of the central disks and bulges of massive galaxies at z ~ 2 can be driven by the early secular evolution of gas-rich proto-disks. High-redshift disks exhibit large random motions. This turbulence may in part be stirred up by the release of gravitational energy in the rapid "cold" accretion flows along the filaments of the cosmic web. As a result, dynamical friction and viscous processes proceed on a timescale of <1 Gyr, at least an order of magnitude faster than in z ~ 0 disk galaxies. Early secular evolution thus drives gas and stars into the central regions and can build up exponential disks and massive bulges, even without major mergers. Secular evolution along with increased efficiency of star formation at high surface densities may also help to account for the short timescales of the stellar buildup observed in massive galaxies at z ~ 2
LBT/ARGOS adaptive optics observations of z lensed galaxies
Get PDFpeer reviewedAims. Gravitationally lensed systems allow a detailed view of galaxies at high redshift. High spatial- and spectral-resolution measurements of arc-like structures can offer unique constraints on the physical and dynamical properties of high-z systems.
Methods. We present near-infrared spectra centred on the gravitational arcs of six known z ∼ 2 lensed star-forming galaxies of stellar masses of 109−11 M⊙ and star formation rate (SFR) in the range between 10 and 400 M⊙ yr−1. Ground layer adaptive optics (AO)-assisted observations are obtained at the Large Binocular Telescope (LBT) with the LUCI spectrographs during the commissioning of the ARGOS facility. We used MOS masks with curved slits to follow the extended arched structures and study the diagnostic emission lines. LBT observations are used to demonstrate the spectroscopic capabilities of ARGOS.
Results. Combining spatially resolved kinematic properties across the arc-like morphologies, emission line diagnostics and archival information, we distinguish between merging and rotationally supported systems, and reveal the possible presence of ejected gas. For galaxies that have evidence for outflows, we derive outflow energetics and mass-loading factors compatible with those observed for stellar winds in local and high-z galaxies. We also use flux ratio diagnostics to derive gas-phase metallicities. The low signal-to-noise ratio in the faint Hβ and nitrogen lines allows us to derive an upper limit of ≈0.15 dex for the spatial variations in metallicity along the slit for the lensed galaxy J1038.
Conclusions. Analysed near-infrared spectra presented here represent the first scientific demonstration of performing AO-assisted multi-object spectroscopy with narrow curved-shape slits. The increased angular and spectral resolution, combined with the binocular operation mode with the 8.4 m wide eyes of LBT, will allow the characterisation of kinematic and chemical properties of a large sample of galaxies at high-z in the near future
The SINS survey: broad emission lines in high-redshift star-forming galaxies
Get PDFHigh signal-to-noise, representative spectra of star-forming galaxies at z ~ 2, obtained via stacking, reveal a high-velocity component underneath the narrow Hα and [NII] emission lines. When modeled as a single Gaussian, this broad component has FWHM 1500 km s–1; when modeled as broad wings on the Hα and [N II] features, it has FWHM ≳ 500 km s^(–1). This feature is preferentially found in the more massive and more rapidly star-forming systems, which also tend to be older and larger galaxies. We interpret this emission as evidence of either powerful starburst-driven galactic winds or active supermassive black holes (SMBHs). If galactic winds are responsible for the broad emission, the observed luminosity and velocity of this gas imply mass outflow rates comparable to the star formation rate. On the other hand, if the broad-line regions of active black holes account for the broad feature, the corresponding black holes masses are estimated to be an order of magnitude lower than those predicted by local scaling relations, suggesting a delayed assembly of SMBHs with respect to their host bulges
A frequent variant in the human bile salt export pump gene ABCB11 is associated with hepatitis C virus infection, but not liver stiffness in a German population
No full textBackground: The human ATP-binding cassette, subfamily B, member 11 (ABCB11) gene encodes the bile salt export pump, which is exclusively expressed at the canalicular membrane of hepatocytes. A frequent variant in the coding region, c.1331 T > C, leading to the amino acid exchange p.V444A, has been associated with altered serum bile salt levels in healthy individuals and predisposes homozygous carriers of the [C] allele for obstetric cholestasis. Recently, elevated bile salt levels were shown to be significantly associated with rates and risk of cirrhosis in patients with chronic hepatitis C virus (HCV) infection treated with pegylated interferon-alpha2 and ribavirin, suggesting a potential role for bile salt levels in HCV treatment outcomes and in the fibrogenic evolution of HCV-related liver disease. The aim of this study was to investigate a possible association of ABCB11 c.1331 T > C with hepatitis C virus (HCV) infection and fibrosis stages as assessed by non-invasive transient elastography in a German cohort of patients.
Methods: ABCB11 c.1331 T > C genotype was determined by allelic discrimination assay in 649 HCV infected cases and 413 controls. Overall, 444 cases were staged for fibrotic progression by measurement of liver stiffness.
Results: Homo- or heterozygous presence of the frequent [C] allele was associated with HCV positivity (OR = 1.41, CI = 1.02 - 1.95, p = 0.037). No association was detectable between the ABCB11 c.1331 T > C genotype and increased liver stiffness.
Conclusions: Our data confirm that homozygous presence of the major [C] allele of ABCB11 c.1331 T > C is a genetic susceptibility factor for HCV infection, but not for liver fibrosis
