23 research outputs found
The LUCIFER multi-object spectroscopy unit and line excitation, metallicity, and dust extinction in massive star-forming galaxies at high redshift
Star-Forming Galaxies at z~2: An Emerging Picture of Galaxy Dynamics and Assembly
In these proceedings, we summarize recent results from our "SINS" VLT/SINFONI
integral-field survey, focusing on the 52 detected UV/optically-selected
star-forming galaxies at z~2. Our H-alpha emission-line imaging and kinematic
data of these systems illustrates that a substantial fraction (> 1/3) of these
galaxies are large, rotating disks and that these disks are clumpy, thick, and
forming stars rapidly. We compare these systems to local disk scaling relations
and find that the backbones of these relations are already in place at z~2.
Detailed analysis of the large disks in our sample provides strong evidence
that this population cannot result from a merger-dominated formation history
and instead must be assembled by the smooth but rapid inflow of gas along
filaments. These systems will then secularly evolve from clump-dominated disks
to bulge-dominated disks on short timescales, a phenomenon that is observed in
our SINS observations and is consistent with predictions from numerical
simulations. These results provide new and exciting insights into the formation
of bulge-dominated galaxies in the local Universe.Comment: 7 pages, to appear in the proceedings of "Galaxy Evolution: Emerging
Insights and Future Challenges," Austin, TX, 11-14 Nov 200
LBT/LUCIFER Observations of the z~2 Lensed Galaxy J0900+2234
We present rest-frame optical images and spectra of the gravitationally
lensed, star-forming galaxy J0900+2234 (z=2.03). The observations were
performed with the newly commissioned LUCIFER1 near-infrared instrument mounted
on the Large Binocular Telescope (LBT). We fit lens models to the rest-frame
optical images and find the galaxy has an intrinsic effective radius of 7.4 kpc
with a lens magnification factor of about 5 for the A and B components. We also
discovered a new arc belonging to another lensed high-z source galaxy, which
makes this lens system a potential double Einstein ring system. Using the high
S/N rest-frame optical spectra covering H+K band, we detected Hbeta, OIII,
Halpha, NII and SII emission lines. Detailed physical properties of this high-z
galaxy were derived. The extinction towards the ionized HII regions (E_g(B-V))
is computed from the flux ratio of Halpha and Hbeta and appears to be much
higher than that towards stellar continuum (E_s(B-V)), derived from the optical
and NIR broad band photometry fitting. The metallicity was estimated using N2
and O3N2 indices. It is in the range of 1/5-1/3 solar abundance, which is much
lower than the typical z~2 star-forming galaxies. From the flux ratio of SII
6717 and 6732, we found that the electron number density of the HII regions in
the high-z galaxy were >1000 cm^-3, consistent with other z~2 galaxies but much
higher than that in local HII regions. The star-formation rate was estimated
via the Halpha luminosity, after correction for the lens magnification, to be
about 365\pm69 Msun/yr. Combining the FWHM of Halpha emission lines and the
half-light radius, we found the dynamical mass of the lensed galaxy is
5.8\pm0.9x10^10 Msun. The gas mass is 5.1\pm1.1x10^10~Msun from the H\alpha
flux surface density by using global Kennicutt-Schmidt Law, indicating a very
high gas fraction of 0.79\pm0.19 in J0900+2234.Comment: 11 pages, 6 figures accepted by ApJ, revised based on referee repor
Mergers and Mass Accretion Rates in Galaxy Assembly: The Millennium Simulation Compared to Observations of z~2 Galaxies
Recent observations of UV-/optically selected, massive star forming galaxies
at z~2 indicate that the baryonic mass assembly and star formation history is
dominated by continuous rapid accretion of gas and internal secular evolution,
rather than by major mergers. We use the Millennium Simulation to build new
halo merger trees, and extract halo merger fractions and mass accretion rates.
We find that even for halos not undergoing major mergers the mass accretion
rates are plausibly sufficient to account for the high star formation rates
observed in z~2 disks. On the other hand, the fraction of major mergers in the
Millennium Simulation is sufficient to account for the number counts of
submillimeter galaxies (SMGs), in support of observational evidence that these
are major mergers. When following the fate of these two populations in the
Millennium Simulation to z=0, we find that subsequent mergers are not frequent
enough to convert all z~2 turbulent disks into elliptical galaxies at z=0.
Similarly, mergers cannot transform the compact SMGs/red sequence galaxies at
z~2 into observed massive cluster ellipticals at z=0. We argue therefore, that
secular and internal evolution must play an important role in the evolution of
a significant fraction of z~2 UV-/optically and submillimeter selected galaxy
populations.Comment: 5 pages, 4 figures, Accepted for publication in Ap
The SINS Survey: Broad Emission Lines in High-Redshift Star-Forming Galaxies
High signal-to-noise, representative spectra of star-forming galaxies at z~2,
obtained via stacking, reveal a high-velocity component underneath the narrow
H-alpha and [NII] emission lines. When modeled as a single Gaussian, this broad
component has FWHM > 1500 km/s; when modeled as broad wings on the H-alpha and
[NII] features, it has FWHM > 500 km/s. 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. 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 supermassive black holes
with respect to their host bulges.Comment: 11 pages, 5 figures. Accepted version, incorporating referee
comments, including changes to title, abstract, figures, and discussion
sectio
The SINS/zC-SINF survey of z~2 galaxy kinematics: Outflow properties
Based on SINFONI Ha, [NII] and [SII] AO data of 30 z \sim 2 star-forming
galaxies (SFGs) from the SINS and zcSINF surveys, we find a strong correlation
of the Ha broad flux fraction with the star formation surface density of the
galaxy, with an apparent threshold for strong outflows occurring at 1 Msun
yr^-1 kpc^-2. Above this threshold, we find that SFGs with logm_\ast>10 have
similar or perhaps greater wind mass loading factors (eta = Mdotout/SFR) and
faster outflow velocities than lower mass SFGs. This trend suggests that the
majority of outflowing gas at z \sim 2 may derive from high-mass SFGs, and that
the z \sim 2 mass-metallicity relation is driven more by dilution of enriched
gas in the galaxy gas reservoir than by the efficiency of outflows. The mass
loading factor is also correlated with the SFR and inclination, such that more
star-forming and face-on galaxies launch more powerful outflows. For galaxies
that have evidence for strong outflows, we find that the broad emission is
spatially extended to at least the half-light radius (\sim a few kpc). We
propose that the observed threshold for strong outflows and the observed mass
loading of these winds can be explained by a simple model wherein break-out of
winds is governed by pressure balance in the disk. Using the ratio of the [SII]
doublet in a broad and narrow component, we find that outflowing gas has a
density of \sim10-100 cm^-3, significantly less than that of the star forming
gas (600 cm^-3).Comment: 7 pages, 3 figures, accepted by Ap
LBT/ARGOS adaptive optics observations of z lensed galaxies
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. We present near-infrared spectra centred on the
gravitational arcs of six known z ~ 2 lensed star-forming galaxies of stellar
masses of 10^9-10^11 Msun and star formation rate (SFR) in the range between 10
and 400 Msun/yr. 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. 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 H 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. 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.Comment: 18 pages, 13 figures, accepted for publication in A&
Multicolor single-molecule spectroscopy with alternating laser excitation for the investigation of interactions and dynamics
Ross 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