20 research outputs found
Evidence for Low Extinction in Actively Star Forming Galaxies at z6.5
We present a search for the [CII] 158micron fine structure line (a main
cooling line of the interstellar medium) and the underlying far-infrared (FIR)
continuum in three high-redshift (6.6<z<8.2) star-forming galaxies using the
IRAM Plateau de Bure interferometer. We targeted two Lyman-Alpha-selected
galaxies (Lyman-Alpha-Emitters, LAEs) with moderate UV-based star formation
rates (SFR~20 M_sun/yr; Himiko at z=6.6 and IOK-1 at z=7.0) and a Gamma Ray
Burst (GRB) host galaxy (GRB 090423 at z~8.2). Based on our 3 sigma rest-frame
FIR continuum limits, previous (rest-frame) UV continuum measurements and
spectral energy distribution (SED) fitting, we rule out SED shapes similar to
highly obscured galaxies (e.g. Arp220, M82) and less extreme dust-rich nearby
spiral galaxies (e.g. M51) for the LAEs. Conservatively assuming a SED shape
typical of local spiral galaxies we derive upper limits for the FIR-based star
formation rates (SFRs) of ~70 M_sun/yr, ~50 M_sun/yr and ~40 M_sun/yr for
Himiko, IOK-1 and GRB 090423, respectively. For the LAEs these limits are only
a factor ~3 higher than the published UV-based SFRs (uncorrected for
extinction). This indicates that the dust obscuration in the z>6 LAEs studied
here is lower by a factor of a few than what has recently been found in some
LAEs at lower redshift (2<z<3.5) with similar UV-based SFRs. A low obscuration
in our z>6 LAE sample is consistent with recent rest-frame UV studies of z~7
Lyman-Break-Galaxies (LBGs).Comment: Accepted for publication in the Astrophysical Journa
Disk, merger, or outflow ? Molecular gas kinematics in two powerful obscured QSOs at z>3.4
We report on the detection of bright CO(4-3) line emission in two powerful,
obscured quasars discovered in the SWIRE survey, SW022513 and SW022550 at
z>3.4. We analyze the line strength and profile to determine the gas mass,
dynamical mass and the gas dynamics for both galaxies. In SW022513 we may have
found the first evidence for a molecular, AGN-driven wind in the early
Universe. The line profile in SW022513 is broad (FWHM = 1000 km/s) and
blueshifted by -200 km/s relative to systemic (where the systemic velocity is
estimated from the narrow components of ionized gas lines, as is commonly done
for AGN at low and high redshifts). SW022550 has a more regular, double-peaked
profile, which is marginally spatially resolved in our data, consistent with
either a merger or an extended disk. The molecular gas masses, 4x10^10 Msun,
are large and account for <30% of the stellar mass, making these obscured QSOs
as gas rich as other powerful CO emitting galaxies at high redshift, i.e.,
submillimeter galaxies. Our sources exhibit relatively lower star-formation
efficiencies compared to other dusty, powerful starburst galaxies at high
redshift. We speculate that this could be a consequence of the AGN perturbing
the molecular gas.Comment: Accepted for publication in A&
The properties of (sub)millimetre-selected galaxies as revealed by CANDELS HST WFC3/IR imaging in GOODS-South
We have exploited the HST CANDELS WFC3/IR imaging to study the properties of
(sub-)mm galaxies in GOODS-South. After using the deep radio and Spitzer
imaging to identify galaxy counterparts for the (sub-)mm sources, we have used
the new CANDELS data in two ways. First, we have derived improved photometric
redshifts and stellar masses, confirming that the (sub-)mm galaxies are massive
(=2.2x10^11 M_solar) galaxies at z=1-3. Second, we have exploited the depth
and resolution of the WFC3/IR imaging to determine the sizes and morphologies
of the galaxies at rest-frame optical wavelengths, fitting two-dimensional
axi-symmetric Sersic models. Crucially, the WFC3/IR H-band imaging enables
modelling of the mass-dominant galaxy, rather than the blue high-surface
brightness features which often dominate optical (rest-frame UV) images of
(sub-)mm galaxies, and can confuse visual morphological classification. As a
result of this analysis we find that >95% of the rest-frame optical light in
almost all of the (sub-)mm galaxies is well-described by either a single
exponential disk, or a multiple-component system in which the dominant
constituent is disk-like. We demonstrate that this conclusion is consistent
with the results of high-quality ground-based K-band imaging, and explain why.
The massive disk galaxies which host luminous (sub-)mm emission are reasonably
extended (r_e=4 kpc), consistent with the sizes of other massive star-forming
disks at z~2. In many cases we find evidence of blue clumps within the sources,
with the mass-dominant disk becoming more significant at longer wavelengths.
Finally, only a minority of the sources show evidence for a major galaxy-galaxy
interaction. Taken together, these results support the view that most (sub-)mm
galaxies at z~2 are simply the most extreme examples of normal star-forming
galaxies at that era.Comment: 30 pages, 9 figure
ALMA constraints on star-forming gas in a prototypical z=1.5 clumpy galaxy: the dearth of CO(5-4) emission from UV-bright clumps
We present deep ALMA CO(5-4) observations of a main sequence, clumpy galaxy at z = 1.5 in the HUDF. Thanks to the âŒ0.500 resolution of the ALMA data, we can link stellar population properties to the CO(5-4) emission on scales of a few kpc. We detect strong CO(5-4) emission from the nuclear region of the galaxy, consistent with the observed LIRâL 0 CO(5â4) correlation and indicating on-going nuclear star formation. The CO(5-4) gas component appears more concentrated than other star formation tracers or the dust distribution in this galaxy. We discuss possible implications of this difference in terms of star formation efficiency and mass build-up at the galaxy centre. Conversely, we do not detect any CO(5-4) emission from the UV-bright clumps. This might imply that clumps have a high star formation efficiency (although they do not display unusually high specific star formation rates) and are not entirely gas dominated, with gas fractions no larger than that of their host galaxy (âŒ50%). Stellar feedback and disk instability torques funnelling gas towards the galaxy centre could contribute to the relatively low gas content. Alternatively, clumps could fall in a more standard star formation efficiency regime if their actual star-formation rates are lower than generally assumed. We find that clump star-formation rates derived with several different, plausible methods can vary by up to an order of magnitude. The lowest estimates would be compatible with a CO(5-4) non-detection even for main-sequence like values of star formation efficiency and gas content
CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey
The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS)
is designed to document the first third of galactic evolution, over the
approximate redshift (z) range 8--1.5. It will image >250,000 distant galaxies
using three separate cameras on the Hubble Space Telescope, from the
mid-ultraviolet to the near-infrared, and will find and measure Type Ia
supernovae at z>1.5 to test their accuracy as standardizable candles for
cosmology. Five premier multi-wavelength sky regions are selected, each with
extensive ancillary data. The use of five widely separated fields mitigates
cosmic variance and yields statistically robust and complete samples of
galaxies down to a stellar mass of 10^9 M_\odot to z \approx 2, reaching the
knee of the ultraviolet luminosity function (UVLF) of galaxies to z \approx 8.
The survey covers approximately 800 arcmin^2 and is divided into two parts. The
CANDELS/Deep survey (5\sigma\ point-source limit H=27.7 mag) covers \sim 125
arcmin^2 within GOODS-N and GOODS-S. The CANDELS/Wide survey includes GOODS and
three additional fields (EGS, COSMOS, and UDS) and covers the full area to a
5\sigma\ point-source limit of H \gtrsim 27.0 mag. Together with the Hubble
Ultra Deep Fields, the strategy creates a three-tiered "wedding cake" approach
that has proven efficient for extragalactic surveys. Data from the survey are
nonproprietary and are useful for a wide variety of science investigations. In
this paper, we describe the basic motivations for the survey, the CANDELS team
science goals and the resulting observational requirements, the field selection
and geometry, and the observing design. The Hubble data processing and products
are described in a companion paper.Comment: Submitted to Astrophysical Journal Supplement Series; Revised
version, subsequent to referee repor
CUBES : the Cassegrain U-band Efficient Spectrograph
In the era of Extremely Large Telescopes, the current generation of 8-10m facilities are likely to remain competitive at ground-UV wavelengths for the foreseeable future. The Cassegrain U-Band Efficient Spectrograph (CUBES) has been designed to provide high-efficiency (> 40%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R >20, 000 (with a lower-resolution, sky-limited mode of R ~7, 000). With the design focusing on maximizing the instrument throughput (ensuring a Signal to Noise Ratio (SNR) ~20 per high-resolution element at 313 nm for U ~18.5 mag objects in 1h of observations), it will offer new possibilities in many fields of astrophysics, providing access to key lines of stellar spectra: a tremendous diversity of iron-peak and heavy elements, lighter elements (in particular Beryllium) and light-element molecules (CO, CN, OH), as well as Balmer lines and the Balmer jump (particularly important for young stellar objects). The UV range is also critical in extragalactic studies: the circumgalactic medium of distant galaxies, the contribution of different types of sources to the cosmic UV background, the measurement of H2 and primordial Deuterium in a regime of relatively transparent intergalactic medium, and follow-up of explosive transients. The CUBES project completed a Phase A conceptual design in June 2021 and has now entered the detailed design and construction phase. First science operations are planned for 2028
Virtual Redundancy and Barrier Functions for Collision Avoidance in Robotic Manufacturing
In some robotic manufacturing processes, a displacement between the nominal tool trajectory and the actual can be tolerated, provided that the displacement occurs along a specific direction/rotation axis. For instance, in wire sawing, a translation along the wire axis is permitted. Such an admissible displacement can be thought of as an additional degree of freedom that could be exploited for accomplishing further tasks, e.g., collision avoidance. In the case of offline programming, the operator can manually adapt the trajectory in order to exploit such additional degree of freedom. However, when the tool trajectory is automatically generated, as in modern flexible automation systems, an automatic way to adjust the displacement is needed. We propose an approach that, based on virtual redundancy (introduced originally for singularity avoidance purposes) and barrier functions, can automatically exploit the additional degree of freedom while satisfying the constraints on the admissible displacement
APPARATO E PROCEDIMENTO PER LA PROGRAMMAZIONE DI ROBOT PER MEZZO DI DIMOSTRAZIONE
The present invention relates to an apparatus for programming robots based on a novel passive pointing device including fiducial markers which enables interaction with one or more cameras through a computer implemented method. By taking advantage of a camera integral to the robot, the computer implemented method and the pointing device enable a tracking mechanism that during robot programming makes possible to change the position of the robot in real time in order to maintain substantially constant the relative pose between the on-board camera and the pointing device
In this way, the human operator can advantageously set the poses of the robot tool by means of demonstration i.e., by placing the pointer in the desired position and orientation during execution of the computer implemented method.
In the preferred embodiment, the apparatus includes a passive pointer (i.e. without electronic unit to detect the pose) and a camera mounted on the robotâs wrist.
Thanks to the tracking mechanism, the programming apparatus and method achieves higher precision than known systems and larger working-space. The precision is advantageously adjustable according to needs
Singularity Avoidance for Cart-Mounted Hand-Guided Collaborative Robots: A Variational Approach
Most collaborative robots (cobots) can be taught by hand guiding: essentially, by manually jogging the robot, an operator teaches some configurations to be employed as via points. Based on those via points, Cartesian end-effector trajectories such as straight lines, circular arcs or splines are then constructed. Such methods can, in principle, be employed for cart-mounted cobots (i.e., when the jogging involves one or two linear axes, besides the cobot axes). However, in some applications, the sole imposition of via points in Cartesian space is not sufficient. On the contrary, albeit the overall system is redundant, (i) the via points must be reached at the taught joint configurations, and (ii) the undesirable singularity (and near-singularity) conditions must be avoided. The naive approach, consisting of setting the cart trajectory beforehand (for instance, by imposing a linear-in-time motion law that crosses the taught cart configurations), satisfies the first need, but does not guarantee the satisfaction of the second. Here, we propose an approach consisting of (i) a novel strategy for decoupling the planning of the cart trajectory and that of the robot joints, and (ii) a novel variational technique for computing the former in a singularity-aware fashion, ensuring the avoidance of a class of workspace singularity and near-singularity configurations
Data from: Emergence of transformation-tolerant representations of visual objects in rat lateral extrastriate cortex
Rodents are emerging as increasingly popular models of visual functions. Yet, evidence that rodent visual cortex is capable of advanced visual processing, such as object recognition, is limited. Here we investigate how neurons located along the progression of extrastriate areas that, in the rat brain, run laterally to primary visual cortex, encode object information. We found a progressive functional specialization of neural responses along these areas, with: (1) a sharp reduction of the amount of low-level, energy-related visual information encoded by neuronal firing; and (2) a substantial increase in the ability of both single neurons and neuronal populations to support discrimination of visual objects under identity-preserving transformations (e.g., position and size changes). These findings strongly argue for the existence of a rat object-processing pathway, and point to the rodents as promising models to dissect the neuronal circuitry underlying transformation-tolerant recognition of visual objects