Simonetta Chinellato

Formation and evolution of early-type galaxies: spectro-photometry from cosmo-chemo-dynamical simulations

One of the major challenges in modern astrophysiscs is to understand the origin and the evolution of galaxies, the bright Early-Type Galaxies (ETGs) in particular, in the context of a Universe dominated by Cold Dark Matter (CDM), with some kind of Dark Energy in form of the Cosmological Constant ?. These spheroidal systems are of interest in their own right as they contain more than half of the total stellar mass in the local Universe (Fukugita et al 1998). Giant elliptical galaxies are the most massive stellar systems and they appear to define a homogeneous class of objects which predominantly consist of uniformly old and red populations, which implies that they must have formed at high redshift, have negligible amounts of gas and very little star formation (Bressan et al. 1993). There is strong observational evidence that ellipticals are already in place at z ~ 2-3 and that formed most of their stars well before a redshift z=1 (Searle et al. 1973; Brinchmann & Ellis 2000; Treu et al. 2005; van der Wel et al. 2005). These galaxies are therefore likely to be good probes of galaxy evolution, star formation and metal enrichment in the early Universe. The main goal of this PhD thesis is the derivation of a tool that combines the results derived from the cosmo-chemo-dynamical models of elliptical galaxies obtained from N-body simulations, together with the spectro-photometric models computed from the stellar Evolutionary Population Synthesis (EPS) technique. The aim is to reproduce the observational integrated properties of early-type galaxies in any photometric bandpass, and in particular in the systems used by the modern imaging surveys of observational cosmology, that cover any spectral range. The EPS technique is based on Simple Stellar Populations (SSPs) due to their characteristics, these are suitable for purposes of population synthesis of more complex systems of stellar populations, such as simulated ETGs derived from numerical simulations, and so are suitable for the modelling of the integrated properties (light), and allow easy testing for different input prescriptions in the description of a galaxy (different masses, star formation, initial mass functions, physical processes, etc.) and reproduction of basic observational constraints. In the present work, the approach allows the computation of spectroscopic and photometric quantities by combining the EPS technique to three-dimensional self-consistent cosmo-chemo-dynamical Tree-SPH numerical simulations, carried on in the last years by the Padova group (Merlin & Chiosi 2006, 2007), that follow the evolution of ETGs from the epoch of their complex formation to the present. The method has been tested so far on three simulated galaxies: these models have different cosmological metrics, both cold dark matter (CDM) scenarios, one in the SCDM and two in the ?CDM cosmologies. In the first part of the thesis we consider the template galaxies, which have been dynamically simulated with a detailed chemical evolution, and recover their spectro-photometric evolution in the rest-frame and the integrated properties, such as magnitudes and colors, at the different epochs through the entire history of the Universe up to the formation of present-day ellipticals. This is done in particluar for two inportant photometric systems, the Bessell-Brett passbands and the Sloan Digital Sky Survey (SDSS). The advent of the modern giant telescope facilities has opened a new era in observational cosmology and galaxy evolution can be traced back to its early stages. In this sense, deep multicolor imaging surveys are established as a powerful tool to access the population of faint galaxies with relatively high efficiency. These surveys sample the whole spectral range from the UV to the near-IR bands, enabling galaxy evolution to be followed on a wider range of redshifts. Starting from the evolutionary synthesis results we compute the evolutionary and cosmological corrections, along with magnitudes and colors and their evolution at different redshifts for the simulated galaxies at our disposal. We consider the COSMOS (Giavalisco et al. 2004) and the GOODS (Scoville et al 2007) databases, which allow us to select a sample of galaxies that are catalogued as early-type and to make a qualitative and quantitative comparison between the theoretical results obtained from our model galaxies and the observational data. For the COSMOS database we find that the models follow the general trend for all data at high redshift and, in particular, are in good agreement with those galaxies selected as ellipticals. For the galaxies selected from the GOODS database, theoretical colors seem to match better with data than what found for the COSMOS data. Having a better morphological classificator, the selection is done by eye and by correlating a catalog of photometric and spectroscopic redshifts with a morphological one for GOODS in contrast to the selection derived from the automated pipelines used for COSMOS, is certainly discriminating in favour of the GOODS database. For both datasets our findings show that simulated colors for the different cosmological scenarios follow the general trend at lower redshifts and are in good agreement with the data up to z ~ 1, where the number of early-type galaxies observed falls abruptly. In conclusion, within the redshift range considered, all the simulated colors reproduce quite well the observational data. The dynamical and geometrical informations, derived from the numerical simulations, and the spectro-photometric properties, recovered from our tool, combined together, allow to tackle in some detail important physical issues that deal with the scaling relations governing the photometric and structural parameters of ETGs, and in particluar with the Kormendy relation that allows a comparison with observables in the luminosity-radius plane. The method we introduced for the derivation of the parameters that enter the scaling laws deals with the construction of artificial images in a bi-dimensional plane, starting from the three-dimensional structure of the simulated galaxies. By matching the population synthesis models with the three-dimensional geometric information of the galaxys structure along with the chemical details, both provided by the N-body simulations, we create synthetic images of a galaxy in a given photometric system, from which we derive the structural and morphological parameters, such as the galaxys effective radius and the luminosity within this, the shape indices through Fourier and Sersic analysis, color profiles, and radial profiles of most of the parameters that define the structure of galaxies. The most interesting aspect of these results is that the investigation of the simulated galaxies, via the photometric analysis of the artificial images, led us to recover properties that resemble those of observed galaxies. The results obtained in this way are studied and compared within the scaling laws, the Kormendy relation in particular, as it is the only one we can construct so far, due to the limited resolution of our simulations. The observational data with which we compare our simulated results have been selected form the SDSS database. We separate a subsample of elliptical galaxies, and our findings show that the values of luminosities and effective radii, the two parameters that compare in the Kormendy relation, measured for our model galaxies are consistent with the archivial data from the SDSS.

PLATO: a multiple telescope spacecraft for exo-planets hunting

PLATO stands for PLAnetary Transits and Oscillation of stars and is a Medium sized mission selected as M3 by the European Space Agency as part of the Cosmic Vision program. The strategy behind is to scrutinize a large fraction of the sky collecting lightcurves of a large number of stars and detecting transits of exo-planets whose apparent orbit allow for the transit to be visible from the Earth. Furthermore, as the transit is basically able to provide the ratio of the size of the transiting planet to the host star, the latter is being characterized by asteroseismology, allowing to provide accurate masses, radii and hence density of a large sample of extra solar bodies. In order to be able to then follow up from the ground via spectroscopy radial velocity measurements these candidates the search must be confined to rather bright stars. To comply with the statistical rate of the occurrence of such transits around these kind of stars one needs a telescope with a moderate aperture of the order of one meter but with a Field of View that is of the order of 50 degrees in diameter. This is achieved by splitting the optical aperture into a few dozens identical telescopes with partially overlapping Field of View to build up a mixed ensemble of differently covered area of the sky to comply with various classes of magnitude stars. The single telescopes are refractive optical systems with an internally located pupil defined by a CaF2 lens, and comprising an aspheric front lens and a strong field flattener optical element close to the detectors mosaic. In order to continuously monitor for a few years with the aim to detect planetary transits similar to an hypothetical twin of the Earth, with the same revolution period, the spacecraft is going to be operated while orbiting around the L2 Lagrangian point of the Earth-Sun system so that the Earth disk is no longer a constraints potentially interfering with such a wide field continuous uninterrupted survey.

Extending the pyramid WFS to LGSs: the INGOT WFS

Laser Guide Stars are, in spite of their name, all but “stars”. They do not stand at infinite distance, neither on a plane. If fired from the side of a large telescope their characteristics as seen from various points on the apertures changes dramatically. As they extend in a 3D world, there is need of a WFS that deploy in a similar 3D manner, in the conjugated volume, resembling the approach that MCAO required long time ago to overcome the usual limitations of conventional AO. We describe a class of a novel kind of WFS that employ a combination of refraction and reflection, such that they can convey the light from an LGS into a limited number of pupils, making the device compact, doable with a single piece of glass, and able to feed a minimum sized format detector where the information is collected maximizing the information depending from which part of the LGS the light is coming from, and on which portion of the telescope aperture the light is landing. They represent, in our opinion, the best-known adaptation of the pyramid WFS for NGS to the LGS world. As in the natural reference case the practical advantages come along with some fundamental advantages. Being a pupil plane WFS with the perturbator placed on the (3D) loci of focus of the various portions of the source of light they have the potentiality to extend WFS to a number of issues, including the ability to sense the islands effect, where non-contiguous portions of the main apertures are optically displaced. Further to their description and the main recipes we speculate onto possible variations on cases where the LGS is fired from the back of the secondary mirror and we exploit some potential features when implementing onto an extremely large aperture.

Manufacturing and alignment tolerance analysis through Montecarlo approach for PLATO

The project PLAnetary Transits and Oscillations of stars (PLATO) is one of the selected medium class (M class) missions in the framework of the ESA Cosmic Vision 2015-2025 program. The main scientific goal of PLATO is the discovery and study of extrasolar planetary systems by means of planetary transits detection. According to the current baseline, the scientific payload consists of 34 all refractive telescopes having small aperture (120mm) and wide field of view (diameter greater than 37 degrees) observing over 0.5-1 micron wavelength band. The telescopes are mounted on a common optical bench and are divided in four families of eight telescopes with an overlapping line-of-sight in order to maximize the science return. Remaining two telescopes will be dedicated to support on-board star-tracking system and will be specialized on two different photometric bands for science purposes. The performance requirement, adopted as merit function during the analysis, is specified as 90% enclosed energy contained in a square having size 2 pixels over the whole field of view with a depth of focus of +/-20 micron. Given the complexity of the system, we have followed a Montecarlo analysis approach for manufacturing and alignment tolerances. We will describe here the tolerance method and the preliminary results, speculating on the assumed risks and expected performances.

The AIV concept of SHARK-NIR, a new coronagraph for the Large Binocular Telescope

SHARK-NIR is one of the forthcoming instruments of the Large Binocular Telescope second generation instruments. Due to its coronagraphic nature, coupled with low resolution spectroscopy capabilities, it will be mainly devoted to exoplanetary science, but its FoV of 18 x 18 arcsec and very high contrast imaging capabilities will allow to exploit also other intriguing scientific cases. The instrument has been conceived and designed to fully exploit the exquisite adaptive optics correction delivered by the FLAO module, which will be improved with the SOUL upgrade, and will implement different coronagraphic techniques, with contrast as high as 10-6 up to 65 mas from the star. Despite the wavelength range of SHARK-NIR is 0.96-1.7 um, the instrument is designed to work in synergy with SHARK-VIS and with LMIRcam, on board of LBTI. The contemporary acquisition from these instruments will extend the wavelength coverage from M band down to the visible radiation. The physical location of the instrument, at the entrance of LBTI, imposes dimensional constraints to the instrument, which had been kept very compact. The folded optical design includes more than 50 optical elements, among which 4 Off-Axis Parabolas, 1 Deformable Mirror for the compensation of the Non Common Path Aberrations from the FLAO Wavefront Sensor, 2 detectors and 3 different kinds of coronagraph: Gaussian Lyot, Shaped Pupil and Four Quadrant Pupil Mask. Most of these optics are located onto an optical bench 500 x 400 mm, which makes SHARK-NIR an extremely dense instrument. This, together with the presence of 4 off-axis parabolas and of coronagraphs, such as the Four Quadrant, poorly tolerant to misalignments, requires a careful alignment and test phase, which needs the fine adjustement of many hundreds of degrees of freedom. We will give here an overview of the opto-mechanical layout of SHARK-NIR and of the identified alignment procedure, mostly optical, planned to take place in 2018.

The Copernico Telescope testing facility for AO on-sky demonstrations

We present a new testing facility hosted at the Coude focus of the INAF-Padova Copernico Telescope, a project carried on within the ADaptive Optics National Italian laboratories - ADONI. A permanent laboratory for on-sky experimentation accessible to the AO community, with the aim of hosting visiting multi-purpose instrumentation that may be directly tested on sky. We will give an overview of the activities carried on, describing the refurbishment activities at the hosting structure that allowed the opening of the facility: the implementation of the opto-mechanical train down to the Coude focus, and the creation of the laboratory. This facility provides a powerful scientific and technical test bench for new instrumental concepts, which may eventually be incorporated later in the next generation ELTs telescopes.

SHARK-NIR: the coronagraphic camera for LBT in the AIV phase at INAF-Padova

Exo-Planets search and characterization has been the science case driving the SHARK-NIR design, which is one of the two coronagraphic instruments proposed for the Large Binocular Telescope. In fact, together with SHARK-VIS (working in the visible domain), it will offer the possibility to do binocular observations combining direct imaging, coronagraphic imaging and coronagraphic low resolution spectroscopy in a wide wavelength domain, going from 0.5μm to 1.7μm. Additionally, the contemporary usage of LMIRCam, the coronagraphic LBTI NIR camera, working from K to L band, will extend even more the covered wavelength range. The instrument has been designed with two intermediate pupil planes and three focal planes, in order to give the possibility to implement a certain number of coronagraphic techniques, with the purpose to select a few of them matching as much as possible the requirements of the different science cases in terms of contrast at various distances from the star and in term of required field of view. SHARK-NIR has been approved by the LBT board in June 2017, and the procurement phase started just after. We report here about the project status, which is currently at the beginning of the AIV phase at INAF-Padova, and should last about one year. Even if exo-planets is the main science case, the SOUL upgrade of the LBT AO will increase the instrument performance in the faint end regime, allowing to do galactic (jets and disks) and extra-galactic (AGN and QSO) science on a relatively wide sample of targets, normally not reachable in other similar facilities.

Exploring the performance of a GMCAO-equipped ELT within the deep field surveys strategy

As the deep field surveys strategy represents a well popular way to study the cosmology and the formation and evolution of galaxies, we investigated how the new generation of extremely large telescopes (ELTs) will perform in this field of research. Our simulations, which combine a number of technical, tomographic and astrophysical information, take advantages of the Global-MCAO approach, a well demonstrated method that can be applied in absence of laser guide stars because it exploits only natural references. A statistics of the expected performance in a sub-sample of 22 well-known surveys are presented here.

Thermal effects on PLATO point spread function

Thermal effects in PLATO are analyzed in terms of uniform temperature variations, longitudinal and lateral temperature gradients. We characterize these effects by evaluating the PSF centroid shifts and the Enclosed Energy variations across the whole FoV. These patterns can then be used to gauge the thermal behavior of each individual telescope in order to improve the local photometric calibration across the PLATO field of view.

Radiation, Thermal Gradient and Weight: a threefold dilemma for PLATO

The project PLAnetary Transits and Oscillations of stars (PLATO) is one of the selected medium class (M class) missions in the framework of the ESA Cosmic Vision 2015-2025 program. The mean scientific goal of PLATO is the discovery and study of extrasolar planetary systems by means of planetary transits detection. The opto mechanical subsystem of the payload is made of 32 normal telescope optical units (N-TOUs) and 2 fast telescope optical units (FTOUs). The optical configuration of each TOU is an all refractive design based on six properly optimized lenses. In the current baseline, in front of each TOU a Suprasil window is foreseen. The main purposes of the entrance window are to shield the following lenses from possible damaging high energy radiation and to mitigate the thermal gradient that the first optical element will experience during the launch from ground to space environment. In contrast, the presence of the window increases the overall mass by a non-negligible quantity. We describe here the radiation and thermal analysis and their impact on the quality and risks assessment, summarizing the trade-off process with pro and cons on having or dropping the entrance window in the optical train.