A5067549226- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Dark Matter and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- History and Developments in Astronomy
- Maritime and Coastal Archaeology
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Molecular Spectroscopy and Structure
- Species Distribution and Climate Change
- Pulsars and Gravitational Waves Research
- Meteorological Phenomena and Simulations
- Health and Medical Research Impacts
- Solar and Space Plasma Dynamics
- Advanced Chemical Physics Studies
- Mass Spectrometry Techniques and Applications
- scientometrics and bibliometrics research
- Atmospheric Ozone and Climate
- Data-Driven Disease Surveillance
Center for Astrophysics Harvard & Smithsonian
2018-2024
Carnegie Observatories
2022-2024
Carnegie Institution for Science
2022-2024
Harvard University Press
2018-2021
Harvard University
2017-2020
Yale University
2012-2017
University of Zagreb
2010-2012
Abstract In the ΛCDM paradigm, Galactic stellar halo is predicted to harbor accreted debris of smaller systems. To identify these systems, H3 Spectroscopic Survey, combined with Gaia, gathering 6D phase-space and chemical information in distant Galaxy. Here we present a comprehensive inventory structure within 50 kpc from center using sample 5684 giants at <?CDATA $| b| \gt 40^\circ $?> Z| 2\,\mathrm{kpc}$?> . We known structures including high- α disk, situ (disk stars heated eccentric...
Globular clusters (GCs) formed when the Milky Way experienced a phase of rapid assembly. We use wealth information contained in Galactic GC population to quantify properties satellite galaxies from which assembled. To achieve this, we train an artificial neural network on E-MOSAICS cosmological simulations co-formation and co-evolution GCs their host galaxies. The uses ages, metallicities, orbital that same progenitor predict stellar masses accretion redshifts these progenitors. apply...
Using the example of tidal stream Milky Way globular cluster Palomar 5 (Pal 5), we demonstrate how observational data on streams can be efficiently reduced in dimensionality and modeled a Bayesian framework. Our approach combines detection overdensities by Difference-of-Gaussians process with fast streakline models, continuous likelihood function built from these inference MCMC. By generating $\approx10^7$ model streams, show that geometry Pal debris yields powerful constraints solar...
We present a model for the interaction of GD-1 stellar stream with massive perturber that naturally explains many observed features, including gap and an off-stream spur stars. The involves impulse by fast encounter, after which grows loop stars at different orbital energies. At specific viewing angles, this appears offset from track. A quantitative comparison features prefers models where is in mass range $10^6\,\rm M_\odot$ to $10^8\,\rm M_\odot$. Orbit integrations back time show...
Several lines of evidence suggest the Milky Way underwent a major merger at z~2 with galaxy known as Gaia-Sausage-Enceladus (GSE). Here we use H3 Survey data to argue that GSE entered Galaxy on retrograde orbit based population highly stars chemistry similar largely radial debris. We present first tailored, high-resolution N-body simulations merger. From grid ~500 find $M_{*}=5\times10^{8}\ M_{\odot}, M_{\rm{DM}}=2\times10^{11} M_{\odot}$ (a 2.5:1 total mass merger) best matches data. This...
Abstract Modern theories of galaxy formation predict that the Galactic stellar halo was hierarchically assembled from accretion and disruption smaller systems. This hierarchical assembly is expected to produce a high degree structure in combined phase chemistry space; this should provide relatively direct probe history our Galaxy. Revealing requires precise 3D positions (including distances), velocities, for large samples stars. The Gaia satellite delivering proper motions parallaxes >1...
We announce the discovery of Aquarius~2 dwarf galaxy, a new distant satellite Milky Way, detected on fringes VST ATLAS and SDSS surveys. The object was originally identified as an overdensity Red Giant Branch stars, but chosen for subsequent follow-up based presence strong Blue Horizontal Branch, which also used to measure its distance $\sim 110$ kpc. Using deeper imaging from IMACS camera 6.5m Baade spectroscopy with DEIMOS Keck, we measured satellite's half-light radius $5.1\pm 0.8$...
Abstract The archeological record of stars in the Milky Way opens a uniquely detailed window into early formation and assembly galaxies. Here we use 11,000 main-sequence turn-off with well-measured ages, , orbits from H3 Survey Gaia to time major events Galaxy. Located beyond Galactic plane, this sample contains three chemically distinct groups: low-metallicity population, low- α high- groups at higher metallicity. age orbit distributions these populations show that (1) group, which includes...
The Galactic stellar halo is predicted to have formed at least partially from the tidal disruption of accreted dwarf galaxies. This assembly history should be detectable in orbital and chemical properties stars. H3 Survey obtaining spectra for 200,000 stars, and, when combined with Gaia data, providing detailed Unlike previous surveys halo, target selection based solely on magnitude parallax; survey therefore provides a nearly unbiased view entire high latitudes. In this paper we present...
We use the first Gaia data release, combined with RAVE and APOGEE spectroscopic surveys, to investigate origin of halo stars within <~3 kpc from Sun. identify kinematically, as moving a relative speed at least 220 km/s respect local standard rest. These are in general more metal-poor than disk, but surprisingly, half our sample is comprised [Fe/H]>-1. The orbital directions these metal-rich preferentially aligned disk rotation, sharp contrast isotropic distribution stars. find similar...
Abstract The origins of most stellar streams in the Milky Way are unknown. With improved proper motions provided by Gaia EDR3, we show that orbits 23 Galactic highly clustered orbital phase space. Based on their energies and angular momenta, our sample can plausibly be associated with a specific (disrupted) dwarf galaxy host brought them into Way. For eight also identify likely globular cluster progenitors (four these associations reported here for first time). Some stream surprisingly far...
Abstract The astrophysical origins of r -process elements remain elusive. Neutron star mergers (NSMs) and special classes core-collapse supernovae (rCCSNe) are leading candidates. Due to these channels’ distinct characteristic timescales (rCCSNe: prompt, NSMs: delayed), measuring enrichment in galaxies similar mass but differing formation durations might prove informative. Two recently discovered disrupted dwarfs the Milky Way’s stellar halo, Kraken Gaia-Sausage Enceladus (GSE), afford...
Stellar models generally use simple parametrizations to treat convection. The most widely used parametrization is the so-called "Mixing Length Theory" where convective eddy sizes are described using a single number, \alpha, mixing-length parameter. This free parameter, and general practice calibrate \alpha known properties of Sun apply that all stars. Using data from NASA's Kepler mission we show solar-calibrated not always appropriate, in many cases it would lead estimates initial helium...
We present evidence for a new Milky Way stellar tidal stream in the direction of Andromeda and Triangulum (M31 M33) galaxies. Using matched-filter technique, we search Sloan Digital Sky Survey Data Release 8 by creating density maps which probe halo at distances between 40 kpc. A visual these recovers all major known streams, as well M31/M33 that name stream. The spans 02 12° on sky, or 75 pc 5.5 kpc physical units with best-fitting distance 26 ± 4 width is consistent being remnant globular...
Abstract Stars that escape globular clusters form tidal tails are predominantly shaped by the global distribution of mass in Galaxy, but also preserve a historical record small-scale perturbations. Using deep grz photometry from DECaLS, we present highly probable members associated with evaporating cluster Palomar 5. These data yield cleanest view stellar stream beyond ≈20 kpc and reveal: (1) wide, low surface-brightness extension leading tail; (2) significant density variations along...
Abstract We present MINESweeper , a tool to measure stellar parameters by jointly fitting observed spectra and broadband photometry model isochrones spectral libraries. This approach enables the measurement of spectrophotometric distances, in addition such as T eff <?CDATA $\mathrm{log}g$?> [Fe/H], [ α /Fe], radial velocity. employs Bayesian framework can easily incorporate variety priors, including Gaia parallaxes. Mock data are fit order demonstrate how precision derived depends on...
Abstract Modern Galactic surveys have revealed an ancient merger that dominates the stellar halo of our galaxy (Gaia–Sausage–Enceladus, GSE). Using chemical abundances and kinematics from H3 Survey, we identify 5559 stars this in radial range r Gal = 6–60kpc. We forward model full selection function to infer density profile accreted component halo. consider a general ellipsoid with principal axes allowed rotate respect galactocentric axes, coupled multiply broken power law. The best-fit is...
We use chemistry ([alpha/Fe] and [Fe/H]), main sequence turnoff ages, kinematics determined from H3 Survey spectroscopy Gaia astrometry to identify the birth of Galactic disk. separate in-situ accreted stars on basis angular momenta eccentricities. The high-alpha persists down at least [Fe/H]=-2.5 shows unexpected non-monotonic behavior: with increasing metallicity population first declines in [alpha/Fe], then increases over range -1.3<[Fe/H]<-0.7, again higher metallicities. number rapidly...
ABSTRACT We present the first detailed chemical-abundance analysis of stars from dwarf-galaxy stellar stream Wukong/LMS-1 covering a wide metallicity range ($-3.5 \lt \rm [Fe/H] \lesssim -1.3$). find abundance patterns that are effectively indistinguishable bulk Indus and Jhelum, pair smaller streams proposed to be dynamically associated with Wukong/LMS-1. confirmed carbon-enhanced metal-poor star ($\rm [C/Fe] \gt +0.7$ $\rm \sim -2.9$) in strong enhancements Sr, Y, Zr, which is peculiar...
Abstract Tidally disrupted globular clusters are transformed into thin, dynamically cold streams of stars that extremely valuable tracers the large- and small-scale distribution mass in Galaxy. Using data from Gaia second release combined with Pan-STARRS photometry, we present a sample highly probable members longest stream Milky Way, GD-1. The resulting map GD-1: (1) extends apparent length by 20°, (2) reveals plausible locations for progenitor, (3) detects high-contrast gaps along stream,...
Abstract The 100° long thin stellar stream in the Milky Way halo, GD-1, has an ensemble of features that may be due to dynamical interactions. Using high-resolution MMT/Hectochelle spectroscopy we show a spur GD-1-like stars outside main are kinematically and chemically consistent with stream. In spur, as stream, GD-1 low intrinsic radial velocity dispersion, , is metal-poor, [Fe/H] ≈ −2.3, little spread [ α /Fe] abundances, which point common globular cluster progenitor. At fixed location...
Recent observations of the stellar halo have uncovered debris an ancient merger, Gaia-Sausage-Enceladus, estimated to occurred ~8 Gyr ago. Follow-up studies associated GSE with a large-scale tilt in that links two well-known over-densities diagonally opposing octants Galaxy (the Hercules-Aquila Cloud and Virgo Overdensity; HAC VOD). In this paper, we study plausibility such unmixed merger persisting over several Galactic halo. We employ simulated from Naidu et al. (2021), which reproduces...
The majority of the Milky Way's stellar halo consists debris from our Galaxy's last major merger, Gaia-Sausage-Enceladus (GSE). In past few years, stars GSE have been kinematically and chemically studied in inner $30$ kpc Galaxy. However, simulations predict that accreted could lie at greater distances, forming substructures outer halo. Here we derive metallicities distances using Gaia DR3 XP spectra for an all-sky sample luminous red giant stars, map with kinematics out to $100$ kpc. We...