A5031968960- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Cosmology and Gravitation Theories
- Computational Physics and Python Applications
- Methane Hydrates and Related Phenomena
- Astronomical and nuclear sciences
- Advanced Data Storage Technologies
- Virtual Reality Applications and Impacts
- Distributed and Parallel Computing Systems
- Nonlinear Waves and Solitons
- Scientific Research and Discoveries
- Atmospheric Ozone and Climate
- Scientific Computing and Data Management
- Spectroscopy and Laser Applications
- Digital Games and Media
- Inertial Sensor and Navigation
Indiana University Bloomington
2015-2024
Indiana University
2012-2023
Drexel University
2005-2012
Michigan State University
2003-2006
University of Massachusetts Amherst
1998-2002
Scuola Normale Superiore
1992-1998
International Center for Relativistic Astrophysics
1998
University of Edinburgh
1997
Cornell University
1994
Some globular clusters are observed to host a population of second generation (SG) stars which show chemical anomalies and must have formed from gas containing matter processed in the envelopes first (FG) cluster stars. We study SG formation process by means 1D hydrodynamical simulations, assuming that is ejected AGB This collects cooling flow into core, where it forms star subsystem strongly concentrated innermost regions with structural properties largely independent FG initial properties....
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...
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...
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....
In this paper we show the results of a large set N-body simulations modelling evolution globular clusters driven by relaxation, stellar and disc shocking, including effects tidal field Galaxy. We investigate multi-mass models with power-law initial mass function (IMF) starting different masses, concentrations, slopes IMF located at galactocentric distances. to what extent various evolutionary processes alter shape these changes depend on position cluster in The both global local functions...
A large number of spectroscopic studies have provided evidence the presence multiple populations in globular clusters by revealing patterns stellar chemical abundances. This paper is aimed at studying origin these abundance patterns. We explore a model which second generation (SG) stars form out mix pristine gas and ejecta first asymptotic giant branch stars. study constraints imposed data SG on properties super ejecta. With simple one-zone model, we then formation population focussing our...
Some young star clusters show a degree of mass segregation that is inconsistent with the effects standard two-body relaxation from an initially unsegregated system without substructure, in virial equilibrium, and it unclear whether current cluster formation models can account for this initial significant mass. In Letter we demonstrate mergers small clumps are segregated, or which be produced by before they merge, generically lead to larger systems inherit progenitor clumps' segregation. We...
Numerous spectroscopic and photometric observational studies have provided strong evidence for the widespread presence of multiple stellar populations in globular clusters. In this paper, we study long-term dynamical evolution population clusters, focusing on spatial distributions first- (FG) second-generation (SG) stars. previous studies, suggested that SG stars formed from ejecta FG AGB are expected initially to be concentrated cluster inner regions. Here, by means N-body simulations,...
We present high-precision multi-band photometry for the globular cluster (GC) M2. combine analysis of photometric data obtained from Hubble Space Telescope UV Legacy Survey Galactic GCs GO-13297, with chemical abundances by Yong et al.(2014), and compare models in order to analyze multiple stellar sequences we identified color-magnitude diagram (CMD). find three main components, composed metal-poor, metal-intermediate, metal-rich stars (hereafter referred as population A, B, C,...
We used an appropriate combination of high-resolution Hubble Space Telescope observations and wide-field, ground-based data to derive the radial stellar density profiles 26 Galactic globular clusters from resolved star counts (which can be all freely downloaded on-line). With respect surface brightness (SB) biased by presence sparse, bright stars), are considered most robust reliable tool cluster structural parameters. For each system, a detailed comparison with both King Wilson models has...
The split main sequences (MSs) and extended MS turnoffs (eMSTOs) detected in a few young clusters have demonstrated that these stellar systems host multiple populations differing number of properties such as rotation and, possibly, age.We analyze Hubble Space Telescope photometry for thirteen with ages between ~40 ~1000 Myrs different masses. Our goal is to investigate the first time occurrence large sample clusters. We find all exhibit eMSTO phenomenon stars more massive than ~1.6 solar...
A number of studies based on data collected by the $\textit{Hubble Space Telescope}$ ($\textit{HST}$) GO-13297 program "HST Legacy Survey Galactic Globular Clusters: Shedding UV Light Their Populations and Formation" have investigated photometric properties a large sample globular clusters revolutionized our understanding their stellar populations. In this paper, we expand previous focusing attention clusters' internal kinematics. We computed proper motions for stars in 56 one open combining...
In the past years, we have undertaken an extensive investigation of LMC and SMC star clusters based on HST data. We present photometry astrometry stars in 101 fields observed with WFC/ACS, UVIS/WFC3 NIR/WFC3 cameras. These comprise 113 clusters. provide differential-reddening maps illustrate various scientific outcomes that arise from early inspection photometric catalogs. particular, new insights extended main-sequence turn-off (eMSTO) phenomenon: i) detected eMSTOs two clusters, KMHK361...
Binary stars play a crucial role in our understanding of the formation and evolution star clusters their stellar populations. We use Gaia Data Release 3 to homogeneously analyze 78 Galactic open unresolved binary systems they host, each composed two main sequence (MS) stars. first investigated structural parameters these clusters, such as core radius central density, determined cluster mass function (MF) total by interpolating density profile cluster. measured fraction binaries with large...
In order to account for the chemical composition of a stellar second generation (SG), Globular Clusters (GCs) evolution models based on asymptotic giant branch (AGB) scenario so far included only yields available massive AGB stars, while possible role super-AGB ejecta was either extrapolated or not considered. this work, we explore using recently calculated by Ventura and D'Antona. Models clusters showing extended Na-O anticorrelations, like NGC 2808, indicate that SG formation history...
We present the results of a set N-body simulations aimed at exploring how process mass segregation (as traced by spatial distribution blue straggler stars, BSSs) is affected presence population heavy dark remnants neutron stars and black holes). To this end, clusters characterized different initial concentrations fractions have been modeled. find that an increasing fraction stellar-mass holes significantly delays BSSs visible stellar component. In order to trace evolution BSS segregation, we...
Numerous observational studies have revealed the ubiquitous presence of multiple stellar populations in globular clusters and cast many hard challenges for study formation dynamical history these systems. In this Letter we present results a kinematic properties NGC 2808 based on high-precision Hubble Space Telescope proper-motion measurements. recent study, Milone et al. identified five distinct (A, B, C, D, E) 2808. Populations D E coincide with helium-enhanced middle blue main sequences...
Abstract We present an improved data-reduction technique to obtain high-precision proper motions (PMs) of globular clusters (GCs) using Hubble Space Telescope data. The new reduction is superior the one presented in first paper this series for faintest sources very crowded fields. choose GC NGC 362 as a benchmark test our procedures. measure PMs 117,450 field, showing that we are able PM precision better than 10 μ yr −1 bright stars. make use catalog study cluster’s internal kinematics....
The parameter A+, defined as the area enclosed between cumulative radial distribution of blue straggler stars (BSSs) and that a reference population, is powerful indicator level BSS central segregation. As part Hubble Space Telescope UV Legacy Survey Galactic globular clusters (GCs), here we present population determination A+ in 27 GCs observed out to about one half-mass radius. In combination with 21 additional discussed previous paper this provides us global sample 48 systems...
The dense environment of globular clusters (GCs) can facilitate the formation binary black holes (BBHs), some which merge with gravitational waves (GW) within age Universe. We have performed a survey Monte-Carlo simulations following dynamical evolution GCs different masses, sizes and fractions explored impact host GC properties on BBH mergers. find that number mergers from is determined by GC's initial mass, size primordial fraction. identify two groups mergers: group whose does not depend...
We present the first results of Multi-Instrument Kinematic Survey Galactic Globular Clusters, a project aimed at exploring internal kinematics representative sample globular clusters from radial velocity individual stars, covering entire extension each system. This is achieved by exploiting formidable combination multi-object and integral field unit spectroscopic facilities ESO Very Large Telescope. As step, here we discuss obtained for 11 high medium resolution spectra acquired through...
By means of grid-based, 3D hydrodynamical simulations we study the formation second generation (SG) stars in a young globular cluster (GC) mass 10^7 Msun, possible progenitor an old GC with present ~(1-5) * 10^6 Msun. The accretes external gas as its first (FG) asymptotic giant branch (AGB) release their ejecta and SG form. We consider two models characterised by different densities gas. In both cases, find that very compact subsystem central density >10^5M sun/pc^3 forms innermost regions...
Disentangling distinct stellar populations along the red-giant branches (RGBs) of Globular Clusters (GCs) is possible by using pseudo two-color diagram dubbed chromosome map (ChM). One most intriguing findings that so-called first-generation (1G) stars, characterized same chemical composition their natal cloud, exhibit extended sequences in ChM. Unresolved binaries and internal variations helium or metallicity have been suggested to explain this phenomenon. Here, we derive high-precision...
Many observational studies have revealed the presence of multiple stellar generations in Galactic globular clusters. These suggest that second-generation stars make up a significant fraction current mass clusters, with ranging from ~50 to 80 per cent individual In this Letter we carry out hydrodynamical simulations explore dependence on initial and structural parameters function (IMF) parent cluster. We then use results these estimate fraction, f_{SG,H}, halo composed originated study...