Research news
New research grant awarded to the SAGA Team for a collaboration with Lithuanian researchers
This three-year project will be conducted in a collaboration with doc. dr Šarūnas Mikolaitis from the Institute of Theoretical Physics and Astronomy, Vilnius University, Lithuania. The aim of this project is to conduct a comprehensive, homogeneous, and precise analysis of the abundances of carbon, nitrogen, and oxygen (CNO) in a large set of stars belonging to all main Galactic stellar populations. We will use the results to investigate the chemical enrichment history of these elements and explore the effects of evolutionary mixing processes on their abundances in stellar atmospheres. We will announce a post-doc position to work with the team in Warsaw, Poland, soon!
New team member!
Deepak has a Ph.D. in astrophysics from the Indian Institute of Astrophysics (IIA), Bengaluru, India, awarded by the Pondicherry University under an agreement between IIA and the University. Deepak has experience using results from large stellar surveys, like GALAH, LAMOST, and Gaia, and in using such data to determine stellar properties like kinematics, orbits, masses, and ages. He has several works on the topic of Li-rich giants and has also worked on stellar substructures in the Galactic disc and halo. He is joining as a post-doc in the new OPUS/LAP project that is a collaboration with the group of Norbert Christlieb in Heidelberg, Germany. His work will mainly concern the analysis and simulation of (space- and ground-based) flux-calibrated spectra of metal-poor stars, particularly in connection to the CUBES spectrograph.
The "Old Milky Way" project is funded by the National Science Centre, Poland under the OPUS call in the Weave programme, grant number 2022/47/I/ST9/02358.
Modelling CUBES: from instrument simulation to data reduction prototype
This paper presents a comprehensive overview of the collaborative efforts between the End-to-End (E2E) Simulator and the Data Reduction Software (DRS) team, focusing on the modeling of the U-band efficient Cassegrain spectrograph CUBES (ESO-VLT). The E2E model is a Python-based numerical simulator capable of rendering synthetic raw frames with high precision for both astronomical and calibration sources, starting from their 1-d radiation spectra up to the data produced by the detectors. Data from the E2E are processed by the prototype Data Reduction Software (pDRS), a Python library which implements the critical algorithms of the DRS. The PDRS performs wavelength calibration and extracts a 1-d spectrum from one or more reduced science exposures. The 1-d spectrum produced by the extraction routine is meant to be compared directly with the input spectrum fed to the E2E, actually “closing the loop” allowing for a real end-to-end assessment of the instrument capabilities.
The CUBES consortium includes institutes in Italy (leader), Brazil, Germany, Poland, and the UK. Rodolfo Smiljanic, PI of the SAGA Team, is one of the co-PIs of the CUBES consortium.
CUBES paper at SPIE "Astronomical telescopes and instrumentation"
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 instrumental efficiency ( > 37%) observations in the near UV (300-405 nm). We present the CUBES instrument design, currently in Phase-C and approaching the final design review, summarizing the hardware architecture and interfaces between the different subsystems as well as the relevant technical requirements. We describe the optical, mechanical, electrical design of the different subsystems (from the telescope adapter and support structure, through the main opto-mechanical path, including calibration unit, detector devices and cryostat control, main control electronics), detailing peculiar instrument functions like the Active Flexure Compensation (AFC). Installation at the VLT is planned for 2028/2029 and first science operations in late 2029.
The CUBES consortium includes institutes in Italy (leader), Brazil, Germany, Poland, and the UK. Rodolfo Smiljanic, PI of the SAGA Team, is one of the co-PIs of the CUBES consortium.
End-to-end (E2E) simulator for CUBES
End-to-end models (E2E) aim at simulating the expected astronomical observations starting from the radiation of the scientific sources (or calibration sources) up to the raw-frame data produced by the detectors. This paper describes the E2E architecture, computational models, and tools for rendering the simulated frames for three future spectrographs: SOXS, CUBES and ANDES. Of interest to the SAGA Team is CUBES, the Cassegrain U-Band Efficient Spectrograph, a new instrument being developed to be installed at the 8m VLT of the European Southern Observatory. This spectrograph will cover with a high efficiency the UV ground-based wavelength region (300 - 400 nm). It will have two resolution modes: one of low-resolution with R ~ 5000 and one of high-resolution with R > 20 000.
The CUBES consortium includes institutes in Italy (leader), Brazil, Germany, Poland, and the UK. Rodolfo Smiljanic, PI of the SAGA Team, is one of the co-PIs of the CUBES consortium.
New paper accepted for publication
S-PLUS is a photometric survey done in a set of 12 bands (seven narrow and medium-band filters and five broad-band filters) using a 0.826m robotic telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. The data enables a comprehensive characterization of objects by imaging them in different regions of the optical spectra, with the narrow and medium-band filters placed on crucial elemental absorption lines.
The Ultra-Short Survey (USS) is one of many sub-surveys in the S-PLUS project. USS is covering the same area as the overall S-PLUS Main Survey, but with much shorter exposure times. The primary objective of the USS is to identify bright, extremely metal-poor (EMP; [Fe/H] ≤ −3) and ultra metal-poor (UMP; [Fe/H] ≤ −4) stars for further analysis using medium- and high-resolution spectroscopy. This paper presents the first public data release of USS. It contains data for 163 observed fields totalling ∼324 deg2 along the Celestial Equator. By combining colors and magnitudes, 140 candidates for EMP or UMP have been identified for follow-up studies. The USS is an ongoing survey; in the near future, it will provide many more bright metal-poor candidate stars for spectroscopic follow-up.
The paper was lead by Hélio D. Perottoni, a former postdoc at the SAGA Team, and counted with the collaboration of R. Smiljanic, PI of the SAGA Team.
Three-year design study of WST to be funded!
Last March, the WST consortium submitted a grant application for a Horizon Europe call on the topic of "Research infrastructure concept development". The goal was to finance a 3-year conceptual design study for a 12-metre Wide-field Spectroscopic survey Telescope (WST) fully dedicated to multi-object spectroscopy. The funding application has now been approved. It obtained a perfect evaluation score of 15 points out of 15 possible!
WST is currently planned to have a large field-of-view (>2.5 sq. degree). A fibre-fed multi-object spectrograph will be able to obtain, simultaneously, 20,000 spectra in low resolution and 2,000 in high resolution. In addition, a giant 3x3 arcmin integral field spectrograph (IFS) will be at the centre of the field and will be able to patrol an area of 9x9 arcmin. When operating, WST will target 250 million galaxies, 25 million stars at low spectral resolution, and 2 million stars at high resolution in a time frame of 5 years. At the same time, the IFS may obtain 4 billion spectra.
SAGA Team members are involved in the WST Science Team and R. Smiljanic is co-leading the working group responsible for the exoplanet, stellar, and Galactic science case. With the grant, the SAGA Team will be able to fund 18 months of a postdoc position. Together with the WST Science Team, we will help expand and consolidate the Galactic science case that will be addressed by WST.
New Gaia-ESO paper accepted for publication
The light element (anti-)correlations shown by globular clusters (GCs) are the main spectroscopic signature of multiple stellar populations. These internal abundance variations provide us with fundamental constraints on the formation mechanism of stellar clusters. Using Gaia-ESO, the largest and most homogeneous survey of open clusters (OCs), this paper checks whether these stellar aggregates display the same patterns. Based on previous studies of many GCs, several young and massive clusters in the Magellanic Clouds, as well as a few OCs, we do not expect to find any anti-correlation, given the low mass of Milky Way OCs. It was found that the distribution of Na abundances is compatible with a single-value population, within the errors. The few apparent exceptions can be explained by differences in the evolutionary phase (main sequence and giant post first dredge-up episode) or by difficulties in analysing low gravity giants. We did not find any indication of an Na-O anti-correlation in any of the clusters for which O has been derived.
The paper was lead by Angela Bragaglia, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Italy, and counted with the collaboration of R. Smiljanic, PI of the SAGA Team.