Roberto Abuter

SINFONI integral field spectroscopy of z ~ 2 UV-selected galaxies: rotation curves and dynamical evolution

We present ~0.5 resolution near-infrared integral field spectroscopy of the Hα line emission of 14 z ~ 2 UV-selected BM/BX galaxies, obtained with SINFONI at the ESO Very Large Telescope. The average Hα half-light radius is r_(1/2)≈ 4 h^(-1)_(70) kpc, and line emission is detected over ≳20 h^(-1)_(70)kpc in several sources. In nine galaxies, we detect spatially resolved velocity gradients, from 40 to 410 km s^(-1) over ~10 h^(-1)_(70) kpc. The kinematics of the larger systems are generally consistent with orbital motions. Four galaxies are well described by rotating clumpy disks, and we extracted rotation curves out to radii ≳10 h^(-1)_(70) kpc. One or two galaxies exhibit signatures more consistent with mergers. Analyzing all 14 galaxies in the framework of rotating disks, we infer mean inclination- and beam-corrected maximum circular velocities of v_c ~ 180 ± 90 km s^(-1) and dynamical masses from ~0.5 to 25 × 10^(10) h^(-1)_(70) M_☉ within r_(1/2). The specific angular momenta of our BM/BX galaxies are similar to those of local late-type galaxies. Moreover, the specific angular momenta of their baryons are comparable to those of their dark matter halos. Extrapolating from the average vc at 10 himg1.gif kpc, the virial mass of the typical halo of a galaxy in our sample is 10^(11.7±0.5) h^(-1)_(70) M_☉. Kinematic modeling of the three best cases implies a ratio of v_c to local velocity dispersion v_(c)/σ ~ 2-4 and, accordingly, a large geometric thickness. We argue that this suggests a mass accretion (alternatively, gas exhaustion) timescale of ~500 Myr. We also argue that if our BM/BX galaxies were initially gas-rich, their clumpy disks would subsequently lose their angular momentum and form compact bulges on a timescale of ~1 Gyr.

The rapid formation of a large rotating disk galaxy three billion years after the Big Bang.

Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks—the primary components of present-day galaxies—were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger.

SINFONI: integral field spectroscopy at 50-milli-arcsecond resolution with the ESO VLT

SINFONI is an adaptive optics assisted near-infrared integral field spectrometer for the ESO VLT. The Adaptive OPtics Module (built by the ESO Adaptive Optics Group) is a 60-elements curvature-sensor based system, designed for operations with natural or sodium laser guide stars. The near-infrared integral field spectrometer SPIFFI (built by the Infrared Group of MPE) provides simultaneous spectroscopy of 32 x 32 spatial pixels, and a spectral resolving power of up to 3300. The adaptive optics module is in the phase of integration; the spectrometer is presented tested in the laboratory. We provide an overview of the project, with particular emphasis on the problems encountered in designing and building an adaptive optics assisted spectrometer.

Very high contrast integral field spectroscopy of AB Doradus C: 9-mag contrast at 0.2 arcsec without a coronagraph using spectral deconvolution

We present an extension of the spectral deconvolution (SD) method to achieve very high contrast at small inner working radii. We apply the method to the specific case of ground-based adaptive optics fed integral field spectroscopy (without a coronagraph). Utilizing the wavelength dependence of the Airy and speckle patterns, we make an accurate estimate of the point spread function that can be scaled and subtracted from the data cube. The residual noise in the resulting spectra is very close to the photon noise from the starlight halo. We utilize the technique to extract a very high signal-to-noise ratio H- and K-band spectrum of AB Doradus (AB Dor) C, the low-mass companion to AB Dor A. By effectively eliminating all contamination from AB Dor A, the extracted spectrum retains both continuum and spectral features. The achieved 1σ contrast is 9 mag at 0.2xa0arcsec, 11 mag at 0.5xa0arcsec, in 20 min exposure time, at an effective spectral bandwidth of 5.5 nm, proving that the method is applicable even in low-Strehl regimes. n n n nThe SD method clearly demonstrates the efficacy of image slicer based integral field units in achieving very high contrast imaging spectroscopy at small angular separations, validating their use as high-contrast spectrographs/imagers for extreme adaptive optics systems.

SPIFFI Observations of the Starburst SMM J14011+0252:Already Old, Fat, and Rich by z = 2.565

Using the SPectrometer for Infrared Faint Field Imaging on the ESO Very Large Telescope, we have obtained J-, H-, and K-band integral field spectroscopy of the luminous submillimeter galaxy SMM J140110252. z p 2.565 A global spectrum reveals the brighter of this spatially resolved system’s two components as an intense starburst that is remarkably old, massive, and metal-rich for the early epoch at which it is observed. We see a strong Balmer break implying a ≥100 Myr timescale for continuous star formation as well as nebular emission-line ratios implying a supersolar oxygen abundance on large spatial scales. Overall, the system is rapidly converting a large baryonic mass into stars over the course of only a few hundred megayears. Our study thus adds new arguments to the growing evidence that submillimeter galaxies are more massive than Lyman break galaxies and more numerous at high redshift than predicted by current semianalytic models of galaxy evolution. Subject headings: galaxies: abundances — galaxies: evolution — galaxies: formation

Test performance of the PARSEC laser system

The PARSEC laser system is designed for the VLT Laser Guide Star Facility to deliver a high power cw laser beam at 589nm, in order to create an artificial guide star in the mesospheric Sodium layer. The laser consists of a resonant, dye based power amplifier which is injection seeded with 589nm, single frequency radiation from a master oscillator. We report on the performance of the system both during the European Acceptance tests, and that which has been achieved in the laboratory. The maximum power we have obtained amounts to 20W cw laser light in a single mode and a single frequency at 589nm. With a beam quality of M2 of 1.05-1.15 and a long term stability without manual intervention, the laser suits all the demands for operation at the VLT.

On-sky performance of SPIFFI: the integral field spectrometer for SINFONI at the VLT

SPIFFI (SPectrometer for Infrared Faint Field Imaging) is a fully cryogenic, near-infrared imaging spectrograph built at the Max-Planck-Institute for Extraterrestrial Physics (MPE) and upgraded with a new detector and spectrograph camera by ASTRON/NOVA, ESO and MPE. The upgraded instrument will become a facility instrument for the ESO VLT in summer 2004 as part of the SINFONI (SINgle Faint Object Near-IR Investigation) project, which is the combination of SPIFFI and ESOs adaptive optics module MACAO (Multiple Application Curvature Adaptive Optics), at the Cassegrain focus of Yepun (UT4). In spring 2003 we had the opportunity to observe with SPIFFI as a guest instrument without the AO-module at the Cassegrain focus of UT2 of the VLT. In this paper we discuss the performance of SPIFFI during the guest-instrument phase. First we summarize the technical performance of SPIFFI like the spatial and spectral resolution, the detector performance and the instruments throughput. Afterwards we illustrate the power of integral field spectroscopy by presenting data and results of the Galactic Center.

SPIFFI image slicer: high-precision optics at cryogenic temperatures

SPIFFI is the near-infrared integral field spectrograph of the SINFONI VLT instrument. SPIFFI uses an image slicer with plane mirrors as its integral field unit. The integral field unit consists of two stacks of mirrors, each with 32 mirrors, rearranging a two-dimensional field-of-view of 32 x 32 pixels into a one-dimensional pseudo slit, which is fed into a long-slit spectrograph. The image slicer is constructed solely from Zerodur and is operated at a cryogenic temperature of 77 Kelvin. Only optical contacting is used for the assembly of the individual slicer mirrors and the image slicer on its base-plate. The special slicer mount holds the image slicer stress-free and compensates for the different thermal coefficients of expansion of the Zerodur image slicer and the Aluminium mount. Tests at room and cryogenic temperatures show the performance of the image slicer, the durability of the optical contacting technique, and the accuracy of the slicer mount.

VLTI - PRIMA fringe tracking testbed

One of the key components of the planned VLTI dual feed facility PRIMA is the Fringe Sensor Unit (FSU). Its basic function is the instantaneous measurement of the Optical Path Difference (OPD) between two beams. The FSU acts as the sensor for a complex control system involving optical delay lines and laser metrology with the aim of removing any OPD introduced by the atmosphere and the beam relay. We have initiated a cooperation between ESO and MPE with the purpose of systematically testing this Fringe Tracking Control System in a laboratory environment. This testbed facility is being built at MPE laboratories with the aim to simulate the VLTI and includes FSUs, OPD controller, metrology and in-house built delay lines. In this article we describe this testbed in detail, including the environmental conditions in the laboratory, and present the results of the testbed subsystem characterisation.

New direction in the development of the observation software framework (BOSS)

The Observation Software (OS) of astronomical instruments, which lie directly beneath the instructions of astronomers, carrying out exposures and calibrations is the supervisor of the multi-process and multi-layer instrument software package. The main responsibility of the OS is the synchronization of the subsystems (detectors and groups of mechanical devices) and the telescope during exposures. At ESO a software framework Base Observation Software Stub (BOSS) takes care of the common functionalities of all OS of various instruments at the various sites VLT, VLTI, La Silla and Vista. This paper discusses the latest applications and how their new generic requirements contributes to the BOSS framework. The paper discusses the resolution of problems of event queues, interdependent functionalities, parallel commands and asynchronous messages in the OS using OO technologies.