A5010520884- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astronomical and nuclear sciences
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- History and Developments in Astronomy
- Atmospheric Ozone and Climate
- Spectroscopy and Laser Applications
- Pulsars and Gravitational Waves Research
- Impact of Light on Environment and Health
- Nuclear physics research studies
- Scientific Research and Discoveries
- Mechanics and Biomechanics Studies
- Geophysics and Gravity Measurements
- X-ray Spectroscopy and Fluorescence Analysis
- Geology and Paleoclimatology Research
- Geochemistry and Geologic Mapping
- Calibration and Measurement Techniques
- Regional Economics and Spatial Analysis
- Optical Imaging and Spectroscopy Techniques
Osservatorio Astronomico di Padova
2011-2025
National Institute for Astrophysics
2019-2025
University of Padua
2010-2024
Istituto Nazionale di Fisica Nucleare, Galileo Galilei Institute for Theoretical Physics
2021
Australian National University
2013-2018
Mount Stromlo Observatory
2013-2017
Instituto de Astrofísica de Canarias
2009-2014
Universidad de La Laguna
2009-2014
IAC (United States)
2013
Consejo Superior de Investigaciones Científicas
2011
Accurate photometry with HST's ACS shows that the main sequence (MS) of globular cluster NGC 2808 splits into three separate branches. The MS branches may be associated complexities cluster's horizontal branch and its abundance distribution. We attribute to successive rounds star formation, different helium abundances; we discuss possible sources enrichment. Some other massive globulars also appear have complex populations; compare them 2808.
We use high-precision photometry of red-giant-branch (RGB) stars in 57 Galactic globular clusters (GCs), mostly from the ‘Hubble Space Telescope (HST) UV Legacy Survey GCs’, to identify and characterize their multiple stellar populations. For each cluster pseudo-two-colour diagram (or ‘chromosome map’) is presented, built with a suitable combination magnitudes F275W, F336W, F438W, F814W filters that maximizes separation between In chromosome map most GCs (type-I clusters), separate two...
Context. The fraction of binary stars is an important ingredient to interpret globular cluster dynamical evolution and their stellar population.
The ACS Survey of Globular Clusters has used HST's Wide-Field Channel to obtain uniform imaging 65 the nearest globular clusters provide an extensive homogeneous dataset for a broad range scientific investigations. survey goals required not only observing strategy, but also reduction strategy. To this end, we designed sophisticated software program process cluster data in automated way. identifies stars simultaneously multiple dithered exposures each and measures them using best available...
The ACS Survey of Galactic Globular Clusters is a Hubble Space Telescope (HST) Treasury program designed to provide new large, deep and homogeneous photometric database. Based on observations from this program, we have measured precise relative ages for sample 64 globular clusters by comparing the position clusters' main sequence turn offs, using main-sequence fitting cross-compare within sample. This method provides formal precision 2-7%. We demonstrate that calculated are independent...
AIMS. We present abundance analysis based on high resolution spectra of 105 isolated red giant branch (RGB) stars in the Galactic Globular Cluster NGC 6121 (M4). Our aim is to study its star population context multi-population phenomenon recently discovered affect some Clusters. METHODS. The data have been collected with FLAMES+UVES, at ESO/VLT@UT2 telescope. Analysis was performed under LTE approximation for following elements: O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Ba, and NLTE corrections...
The horizontal branch (HB) morphology of globular clusters (GCs) is most strongly influenced by metallicity. second parameter phenomenon, first described in the 1960s, acknowledges that metallicity alone not enough to describe HB all GCs. In particular, astronomers noticed outer Galactic halo contains GCs with redder HBs at a given than are found inside solar circle. Thus, least was required characterize morphology. While term "second parameter" has since come be used broader context, its...
In this paper we describe a new UV-initiative HST project (GO-13297) that will complement the existing F606W and F814W database of ACS Globular Cluster (GC) Treasury by imaging most its clusters through UV/blue WFC3/UVIS filters F275W, F336W F438W. This "magic trio" has shown an uncanny ability to disentangle characterize multiple-population (MP) patterns in GCs way is exquisitely sensitive C, N, O abundance variations. Combination these passbands with those optical also gives best leverage...
We build on the evidence provided by our Legacy Survey of Galactic globular clusters (GC) to submit a crucial test four scenarios currently entertained for formation multiple stellar generations in GCs. The observational constraints be fulfilled are manifold, including GC specificity, ubiquity, variety, predominance, discreteness, supernova avoidance, p-capture processing, helium enrichment and mass budget. argue that appealing supermassive stars, fast rotating massive stars interactive...
<i>Context. <i/>The discovery of multiple main sequences (MS) in the massive clusters NGC 2808 and Omega Centauri, along with subgiant branches 1851 6388 has challenged long-held paradigm that globular consist simple stellar populations. This evolving picture been further complicated by recent photometric studies Large Magellanic Cloud (LMC) intermediate-age clusters, where sequence turn-off (MSTO) was found to be bimodal (NGC 1806 1846) or broadened 1783 2173).<i>Aims. <i/>We undertook a...
Recent work, based on data from the Hubble Space Telescope (HST ) UV Legacy Survey of Galactic Globular Clusters (GCs), has revealed that all analysed clusters host two groups first- (1G) and second-generation (2G) stars. In most GCs, both 1G 2G stars substellar populations with different chemical composition. We compare multiwavelength HST photometry synthetic spectra to determine for first time average helium difference between in a large sample 57 GCs maximum variation within each them....
We review the multiple population (MP) phenomenon of globular clusters (GCs): i.e., evidence that GCs typically host groups stars with different elemental abundances and/or distinct sequences in photometric diagrams. Most Galactic and extragalactic exhibit internal variations He, C, N, O, Na, Al. They two stellar populations: first stars, which resemble field similar metallicities, one or more second populations show signature high-temperature H-burning. In addition, a sub-sample hosts...
Abstract Black holes have been found over a wide range of masses, from stellar remnants with masses 5–150 solar ( M ☉ ), to those at the centres galaxies > 10 5 . However, only few debated candidate black exist between 150 and Determining population these intermediate-mass is an important step towards understanding supermassive hole formation in early universe 1,2 Several studies claimed detection central ω Centauri, most massive globular cluster Milky Way 3–5 questioned because possible...
Photometry with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) reveals that subgiant branch (SGB) of globular cluster NGC 1851 splits into two well-defined branches. If split is due only to an age effect, SGBs would imply star formation episodes separated by ~1 Gyr. We discuss other anomalies in could be interpreted terms a double stellar population. Finally, we compare case globulars known host multiple populations, and show all three clusters differ several important respects.
We use Hubble Space Telescope (HST) and ground-based imaging to study the multiple populations of 47 Tucanae (47 Tuc), combining high-precision photometry with calculations synthetic spectra. Using filters covering a wide range wavelengths, our HST splits main sequence into two branches, we find that this duality is repeated in subgiant red giant regions, on horizontal branch. calculate theoretical stellar atmospheres for main-sequence stars, assuming different chemical composition mixtures,...
AIMS. In this paper we present the chemical abundance analysis from high resolution UVES spectra of seventeen bright giant stars Globular Cluster M~22. RESULTS. We obtained an average iron [Fe/H]=-1.76\pm0.02 (internal errors only) and \alpha enhancement 0.36\pm0.04 only). Na O, Al O follow well known anti-correlation found in many other GCs. identified two groups with significantly different abundances s-process elements Y, Zr Ba. The relative numbers group members are very similar to ratio...
We present a detailed chemical composition analysis of 35 red giant stars in the globular cluster M22. High resolution spectra for this study were obtained at five observatories, and analyzed uniform manner. have determined abundances representative light proton-capture, alpha, Fe-peak neutron-capture element groups. Our aim is to better understand peculiar enrichment history cluster, which two stellar groups are characterized by different content iron, neutron capture elements Y, Zr Ba,...
In this study we present first results from multi-wavelength Hubble Space Telescope (HST) observations of the Galactic globular cluster GC NGC2808 as an extension UV Legacy Survey GCs (GO-13297 and previous proprietary HST archive data). Our analysis allowed us to disclose a multiple-stellar-population phenomenon in even more complex than previously thought. We have separated at least five different populations along main sequence red giant branch (RGB), that name A, B, C, D E (though finer...
Multi-band Hubble Space Telescope photometry reveals that the main sequence, sub-giant, and red-giant branch of globular cluster NGC 6752 splits into three components in close analogy with distinct segments along its horizontal stars. These triple sequences are consistent stellar groups: a population chemical composition similar to field-halo stars (Population a), Population (c) enhanced sodium nitrogen, depleted carbon oxygen, an helium abundance (ΔY ∼ 0.03), (b) intermediate (between...
We present a high resolution spectroscopic analysis of 62 red giants in the Milky Way globular cluster NGC5286. have determined abundances representative light proton-capture, alpha, Fe-peak and neutron-capture element groups, combined them with photometry multiple sequences observed along colour-magnitude diagram. Our principal results are: (i) broad, bimodal distribution s-process abundance ratios, two main s-poor s-rich groups; (ii) substantial star-to-star Fe variations, stars having...