A5046316799- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Natural Products and Biological Research
- melanin and skin pigmentation
- Geophysics and Sensor Technology
- Astro and Planetary Science
- Color perception and design
- Spectroscopy and Chemometric Analyses
- Astronomical Observations and Instrumentation
- Color Science and Applications
- History and Developments in Astronomy
Center for Astrophysics Harvard & Smithsonian
2022-2024
Johns Hopkins University
2021
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...
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...
Abstract Our understanding of the assembly timeline Milky Way has been transforming along with dramatic increase in astrometric and spectroscopic data available over past several years. Many substructures chemo-dynamical space have discovered identified as remnants various galactic mergers. To investigate these mergers, we select main-sequence turnoff subgiant stars (MSTOs) from H3 survey, finding members seven metal-poor components halo: Gaia-Sausage/Enceladus (GSE), Helmi Streams, Thamnos,...
ABSTRACT We model the stellar abundances and ages of two disrupted dwarf galaxies in Milky Way halo: Gaia-Sausage Enceladus (GSE) Wukong/LMS-1. Using a statistically robust likelihood function, we fit one-zone models galactic chemical evolution with exponential infall histories to both systems, deriving e-folding time-scales τin = 1.01 ± 0.13 Gyr for GSE $\tau _\text{in} 3.08^{+3.19}_{-1.16}$ formed stars _\text{tot} 5.40^{+0.32}_{-0.31}$ Gyr, sustaining star formation ∼1.5–2 after its first...
The infall of the Large Magellanic Cloud (LMC) is predicted to displace inner Milky Way (MW), imprinting an apparent 'reflex motion' on observed velocities distant halo stars. We construct largest all-sky spectroscopic dataset luminous red giant stars from $50-160$ kpc, including a new survey southern celestial hemisphere. fit full 6D kinematics our data measure amplitude and direction MW's motion towards outer halo. velocity grows with distance such that, relative at $100$ MW lurching...
Abstract Globular clusters can form inside their host galaxies at high redshift when gas densities are higher and gas-rich mergers common. They also lower-mass that have since been accreted tidally disrupted, leaving globular cluster complement bound to higher-mass halos. We argue the age–metallicity–specific orbital energy relation in a galaxy’s system be used identify its origin. Gas-rich should produce tightly systems which metal-rich younger than metal-poor clusters. formed massive disks...
The Milky Way's satellite galaxies ("surviving dwarfs") have been studied for decades as unique probes of chemical evolution in the low-mass regime. Here we extend such studies to "disrupted dwarfs", whose debris constitutes stellar halo. We present abundances ([Fe/H], [$\alpha$/Fe]) and masses nine disrupted dwarfs with $M_{\star}\approx10^{6}-10^{9}M_{\odot}$ from H3 Survey (Sagittarius, $Gaia$-Sausage-Enceladus, Helmi Streams, Sequoia, Wukong/LMS-1, Cetus, Thamnos, I'itoi, Orphan/Chenab)....
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...
Abstract We report the discovery of Specter, a disrupted ultrafaint dwarf galaxy revealed by H3 Spectroscopic Survey. detected this structure via pair comoving metal-poor stars at distance 12.5 kpc, and further characterized it with Gaia astrometry follow-up spectroscopy. Specter is 25° × 1° stream that entirely invisible until strict kinematic cuts are applied to remove Galactic foreground. The spectroscopic members suggest stellar age τ ≳ 12 Gyr mean metallicity <?CDATA $\langle...
ABSTRACT Two decades on, the study of hypervelocity stars is still in its infancy. These can provide novel constraints on total mass Galaxy and dark matter distribution. However how these are accelerated to such high velocities unclear. Various proposed production mechanisms for be distinguished using chemo-dynamic tagging. The advent Gaia other large surveys have provided hundreds candidate hyper velocity objects target ground-based high-resolution follow-up observations. We conduct...
Two decades on, the study of hypervelocity stars is still in its infancy. These can provide novel constraints on total mass Galaxy and Dark Matter distribution. However how these are accelerated to such high velocities unclear. Various proposed production mechanisms for be distinguished using chemo-dynamic tagging. The advent Gaia other large surveys have provided hundreds candidate hyper velocity objects target ground based resolution follow-up observations. We conduct spectroscopic...
Our understanding of the assembly timeline Milky Way has been transforming along with dramatic increase in astrometric and spectroscopic data available over past several years. Many substructures chemo-dynamical space have discovered identified as remnants various galactic mergers. To investigate these mergers we select main sequence turn off & subgiant stars (MSTOs) from H3 survey, finding members seven metal poor components halo: GSE, Helmi Streams, Thamnos, Sequoia, Wukong/LMS-1, Arjuna,...
We model the stellar abundances and ages of two disrupted dwarf galaxies in Milky Way halo: Gaia-Sausage Enceladus (GSE) Wukong/LMS-1. Using a statistically robust likelihood function, we fit one-zone models galactic chemical evolution with exponential infall histories to both systems, deriving e-folding timescales $\tau_\text{in} = 1.01 \pm 0.13$ Gyr for GSE 3.08^{+3.19}_{-1.16}$ formed stars $\tau_\text{tot} 5.40^{+0.32}_{-0.31}$ Gyr, sustaining star formation $\sim$$1.5 - 2$ after its...
We report the discovery of Specter, a disrupted ultrafaint dwarf galaxy revealed by H3 Spectroscopic Survey. detected this structure via pair comoving metal-poor stars at distance 12.5 kpc, and further characterized it with Gaia astrometry follow-up spectroscopy. Specter is $25^\circ \times 1^\circ$ stream that entirely invisible until strict kinematic cuts are applied to remove Galactic foreground. The spectroscopic members suggest stellar age $τ\gtrsim 12$ Gyr mean metallicity...
Modern Galactic surveys have revealed an ancient merger that dominates the stellar halo of our Galaxy (\textit{Gaia}-Sausage-Enceladus, GSE). Using chemical abundances and kinematics from H3 Survey, we identify 5559 stars this in radial range $r_{\text{Gal}}=6-60\text{ kpc}$. 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....
A low-cost computer system for process control and data acquisition in curing bright leaf tobacco was designed, constructed, evaluated. The provides programmed of environment, records data, allows remote inquiry control. It developed tested on a six-unit experimental which is part the research facilities Oxford Tobacco Research Station, Oxford, North Carolina. Up to six alternative schedules, each prescribing different desired air temperature humidity schedule curing, may be defined. These...