arXiv subjects

Marco Azzaro

Publications and source records attributed to Marco Azzaro.

7 recordsLinked to original sources

arXiv2026

The ORCA-TWIN qCMOS Experiment I. Science case and commissioning at Calar Alto Observatory

We describe a pilot study to explore a new generation of fast and low noise CMOS image sensors for time domain astronomy, using two remote telescopes with a baseline of 1635 km. The experiment involves direct imaging with novel qCMOS image sensor technology that combines fast readout with sub-electron readout noise. Moreover, synchronized observations from two remote telescope sites will be used to explore new approaches for measuring Solar System bodies, precision stellar photometry, and speckle imaging. A fast-track installation of an ORCA-Quest2 camera at the Calar Alto Observatory 1.23m telescope has demonstrated the potential of the qCMOS technology for time domain astronomy. Numerical simulations suggest that owing to sub-electron readout noise, qCMOS sensors outperform classical CCDs for high-cadence imaging on 1m-class telescopes. The small penalty for post-readout binning, that is almost insignificant in comparison to higher readout noise detectors, opens interesting applications for scene-dependent data processing in direct imaging, and potentially even for spectroscopy.

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arXiv2024

CAVITY: Calar Alto Void Integral-field Treasury surveY. I. First public data release

The Calar Alto Void Integral-field Treasury surveY (CAVITY) is a legacy project aimed at characterising the population of galaxies inhabiting voids, which are the most under-dense regions of the cosmic web, located in the Local Universe. This paper describes the first public data release (DR1) of CAVITY, comprising science-grade optical data cubes for the initial 100 out of a total of $\sim$300 galaxies in the Local Universe ($0.005 < z < 0.050$). These data were acquired using the integral-field spectrograph PMAS/PPak mounted on the 3.5m telescope at the Calar Alto observatory. The DR1 galaxy sample encompasses diverse characteristics in the color-magnitude space, morphological type, stellar mass, and gas ionisation conditions, providing a rich resource for addressing key questions in galaxy evolution through spatially resolved spectroscopy. The galaxies in this study were observed with the low-resolution V500 set-up, spanning the wavelength range 3745-7500 Å, with a spectral resolution of 6.0 Å (FWHM). Here, we describe the data reduction and characteristics and data structure of the CAVITY datasets essential for their scientific utilisation, highlighting such concerns as vignetting effects, as well as the identification of bad pixels and management of spatially correlated noise. We also provide instructions for accessing the CAVITY datasets and associated ancillary data through the project's dedicated database.

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arXiv2022

The Robotic Multi-Object Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)

A system of 5,020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically re-target their optical fibers every 10 - 20 minutes, each to a precision of several microns, with a reconfiguration time less than 2 minutes. Over the next five years, they will enable the newly-constructed Dark Energy Spectroscopic Instrument (DESI) to measure the spectra of 35 million galaxies and quasars. DESI will produce the largest 3D map of the universe to date and measure the expansion history of the cosmos. In addition to the 5,020 robotic positioners and optical fibers, DESI's Focal Plane System includes 6 guide cameras, 4 wavefront cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. The system also includes associated structural, thermal, and electrical systems. In all, it contains over 675,000 individual parts. We discuss the design, construction, quality control, and integration of all these components. We include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multi-object, fiber-fed spectrographs.

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arXiv2011

Fiber Assignment in Next-generation Wide-field Spectrographs

We present an optimized algorithm for assigning fibers to targets in next-generation fiber-fed multi-object spectrographs. The method, that we named draining algorithm, ensures that the maximum number of targets in a given target field is observed in the first few tiles. Using randomly distributed targets and mock galaxy catalogs we have estimated that the gain provided by the draining algorithm as compared to a random assignment can be as much as 2% for the first tiles. This would imply for a survey like BigBOSS saving for observation several hundred thousand objects or, alternatively, reducing the covered area in ~350 sq. deg. An important advantage of this method is that the fiber collision problem can be solved easily and in an optimal way. We also discuss additional optimizations of the fiber positioning process. In particular, we show that allowing for rotation of the focal plane can improve the efficiency of the process in ~3.5-4.5% even if only small adjustments are permitted (up to 2 deg). For instruments that allow large rotations of the focal plane the expected gain increases to ~5-6%. These results, therefore, strongly support focal plane rotation in future spectrographs, as far as the efficiency of the fiber positioning process is concerned. Finally, we discuss on the implications of our optimizations and provide some basic hints for an optimal survey strategy based on the number of targets per positioner.

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arXiv2010

A Fiber Positioner Robot for the Gran Telescopio Canarias

Fiber-fed spectrographs dedicated to observing massive portions of the sky are increasingly being more demanded within the astronomical community. For all the fiber-fed instruments, the primordial and common problem is the positioning of the fiber ends, which must match the position of the objects of a target field on the sky. Amongst the different approaches found in the state of the art, actuator arrays are one of the best. Indeed, an actuator array is able to position all the fiber heads simultaneously, thus making the reconfiguration time extremely short and the instrument efficiency high. The SIDE group (see http://side.iaa.es) at the Instituto de Astrofísica de Andalucía, together with the industrial company AVS and the University of Barcelona, has been developing an actuator suitable for a large and scalable array. A real-scale prototype has been built and tested in order to validate its innovative design concept, as well as to verify the fulfillment of the mechanical requirements. The present article describes both the concept design and the test procedures and conditions. The main results are shown and a full justification of the validity of the proposed concept is provided.

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arXiv2006

Angular distribution of satellite galaxies from the Sloan Digital Sky Survey Data Release 4

We explore the angular distribution of two samples of satellite galaxies orbiting isolated hosts extracted from the Sloan Digital Sky Survey Data Release 4. We find a clear alignment of the satellites along the major axis of their hosts when restricting the analysis to red hosts. The anisotropy is most pronounced for red satellites of red hosts. We find that the distribution of the satellites about blue, isolated hosts is consistent with isotropy. We show that under the assumption that the true, underlying distribution of satellites of blue hosts exhibits the same anisotropy as the satellites of red hosts, the sample of blue hosts is too small to measure this anisotropy at a statistically-significant level. The anisotropy that we detect for satellites about red primaries is independent of the projected radius. In particular, it is evident at large projected distances from primaries (300 < r_p < 500 kpc).

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arXiv2003

Star Formation in Satellite Galaxies

The study of satellite galaxies can provide information on the merging and aggregation processes which, according to the hierarchical clustering models, form the larger spiral galaxies we observe. With the aim of testing hierarchical models of galaxy formation, we have conducted an observational program which comprises H$α$ imaging for both the parent and the satellite galaxies, taken from the compilation by Zaritsky et al. (1997) that contains 115 galaxies orbiting 69 primary isolated spiral galaxies. We have observed a subsample of 37 spiral and irregular galaxies taken from the compilation mentioned above. The aim of this study is to determine star formation properties of the sample galaxies. In this work we present the preliminary results of this program that we have carried out with the 1.8-m Vatican Telescope (VATT).

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