A5063536774- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Solar and Space Plasma Dynamics
- Scientific Research and Discoveries
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Geophysics and Sensor Technology
- Radio Astronomy Observations and Technology
- Planetary Science and Exploration
- Space Exploration and Technology
- Geophysics and Gravity Measurements
- Spacecraft Design and Technology
- Geomagnetism and Paleomagnetism Studies
- Historical Astronomy and Related Studies
- Spacecraft and Cryogenic Technologies
- Experimental and Theoretical Physics Studies
University of Arizona
2015-2024
Columbia University
2012-2013
Center for Astrophysics Harvard & Smithsonian
2007-2012
Harvard University
2009-2010
University of Toronto
2003-2007
Recent proper motion measurements of the Large and Small Magellanic Clouds (LMC SMC, respectively) by Kallivayalil et al (2006a,b) suggest that 3D velocities are substantially higher (~100 km/s) than previously estimated now approach escape velocity Milky Way (MW). Previous studies have also assumed can be adequately modeled as an isothermal sphere to large distances. Here we re-examine orbital history using new a LCDM-motivated MW model with virial mass Mvir = 1e12 Msun (e.g. Klypin 2002)....
We present proper motions for the Large and Small Magellanic Clouds (LMC SMC) based on three epochs of Hubble Space Telescope data, spanning a ∼7 yr baseline, centered fields with background QSOs. The first two epochs, subject past analyses, were obtained ACS/HRC, have been reanalyzed here. new third epoch WFC3/UVIS increases time baseline provides better control systematics. three-epoch data yield proper-motion random errors only 1%–2% per field. For LMC this is sufficient to constrain...
We present a novel pair of numerical models the interaction history between Large and Small Magellanic Clouds (LMC SMC, respectively) our Milky Way (MW) in light recent high precision proper motions (Kallivayalil et al. 2006a,b). Given new velocities, cosmological simulations structure formation favor scenario where (MCs) are currently on their first infall towards Galaxy (Boylan-Kolchin 2011, Busha 2011). illustrate here that observed irregular morphology internal kinematics MCs (in gas...
A proper understanding of the Milky Way (MW) dwarf galaxies in a cosmological context requires knowledge their 3D velocities and orbits. However, motion (PM) measurements have generally been limited accuracy available only for more massive dwarfs. We therefore present new study kinematics MW galaxies. use Gaia DR2 those dwarfs that spectroscopically observed literature. derive systemic PMs 39 galaxy candidates out to 420 kpc, find good consistency subset with from other studies. implied...
We determine the velocity vector of M31 with respect to Milky Way and use this constrain mass Local Group, based on HST proper-motion measurements presented in Paper I. construct N-body models for correct contributions from stellar motions internal M31. also estimate center-of-mass motion independently, using kinematics satellite galaxies Group. All estimates are mutually consistent, imply a weighted average heliocentric transverse (v_W,v_N) = (-125.2+/-30.8, -73.8+/-28.4) km/s. reflex Sun...
We present N-body simulations of a Sagittarius-like dwarf spheroidal galaxy (Sgr) that follow its orbit about the Milky Way (MW) since first crossing Galaxy's virial radius to day. As Sgr orbits around MW, it excites vertical oscillations, corrugating and flaring Galactic stellar disc. These responses can be understood by two-phase picture in which interaction is dominated torques from wake excited MW dark halo before transitioning tides Sgr's direct impact on disc at late times. show for...
Abstract This paper explores the effect of Large Magellanic Cloud (LMC) on mass estimates obtained from timing argument. We show that accounting for presence LMC systematically lowers Local Group (MLG) derived relative motion Milky Way–Andromeda pair. Motivated by this result, we apply a Bayesian technique devised Peñarrubia et al. to simultaneously fit (i) distances and velocities galaxies within 3 Mpc (ii) between Way Andromeda HST observations, with (MLMC) as free parameter. Our analysis...
Abstract With the release of Gaia DR2, it is now possible to measure proper motions (PMs) lowest-mass, ultrafaint satellite galaxies in Milky Way’s (MW) halo for first time. Many these faint satellites are posited have been accreted as Magellanic Clouds (MCs). Using their six-dimensional phase-space information, we calculate orbital histories 13 and five classical dwarf spheroidals a combined MW+LMC+SMC potential determine which dynamically associated with MCs. These 18 separated into four...
Recent high-precision proper motions from the Hubble Space Telescope suggest that Large and Small Magellanic Clouds (LMC SMC, respectively) are either on their first passage or an eccentric long period (>6 Gyr) orbit about Milky Way (MW). This differs markedly canonical picture in which travel a quasi-periodic MW (period of ∼2 Gyr). Without short-period MW, origin Stream, young (1–2 Gyr old) coherent stream H i gas trails ∼150° across sky, can no longer be attributed to stripping by tides...
Motivated by recent studies suggesting that the Large Magellanic Cloud (LMC) could be significantly more massive than previously thought, we explore whether approximation of an inertial Galactocentric reference frame is still valid in presence such a LMC. We find previous estimates LMC's orbital period and apocentric distance derived assuming fixed Milky Way are shortened for models where allowed to move freely response gravitational pull Holding other parameters fixed, fraction favoring...
We combine our Hubble Space Telescope measurement of the proper motion Leo I dwarf spheroidal galaxy (presented in a companion paper) with highest resolution numerical simulations Galaxy-size dark matter halos existence to constrain mass Milky Way's halo (M_MW). Despite I's large Galacto-centric space velocity (200 km/s) and distance (261 kpc), we show that it is extremely unlikely be unbound if Galactic satellites are associated substructure, as 99.9% subhalos bound their host. The observed...
Recent observations have constrained the orbit and structure of Large Magellanic Cloud (LMC), implying a well-constrained pericentric passage about Milky Way (MW) ~ 50 Myr ago. In this scenario, LMC's gaseous disk has recently experienced maximal ram pressure stripping, suggesting current extent its HI directly probes medium in which it is moving. From observed stellar distributions system we find evidence truncated gas profile along windward ``leading edge' LMC disk, despite far more...
According to LCDM theory, hierarchical evolution occurs on all mass scales, implying that satellites of the Milky Way should also have companions. The recent discovery ultra-faint dwarf galaxy candidates in close proximity Magellanic Clouds provides an opportunity test this theory. We present proper motion (PM) measurements for 13 32 new using Gaia data release 2. All radial velocity measurements. compare measured 3D velocities these dwarfs those expected at corresponding distance and...
We present the first absolute proper motion measurement of Leo I, based on two epochs Hubble Space Telescope ACS/WFC images separated by ∼5 years in time. The average shift I stars with respect to ∼100 background galaxies implies a (μW, μN) = (0.1140 ± 0.0295, −0.1256 0.0293) mas yr−1. implied Galactocentric velocity vector, corrected for reflex Sun, has radial and tangential components Vrad 167.9 2.8 km s−1 Vtan 101.0 34.4 s−1, respectively. study detailed orbital history solving its...
We present N-body and hydrodynamical simulations of the response Milky Way's baryonic disc to presence Large Magellanic Cloud during a first infall scenario. For fiducial galactic model reproducing gross properties Galaxy, we explore set six initial conditions for LMC varying mass which all evolve fit measured constraints on its current position velocity with respect Galactic Center. find that can produce strong disturbances - warping stellar gaseous discs in without violating from...
We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within data from ongoing Survey Magellanic Stellar History conducted with Dark Energy Camera on Blanco 4 m Telescope. The satellite is compact ( ± 11 pc) and faint 0.3), but well realm galaxies. stellar distribution II in color–magnitude diagram well-described by metal-poor () old (13 Gyr) isochrone shows distinct blue horizontal branch, some possible red clump stars, stars that are suggestive stragglers. At...
We introduce TiNy Titans (TNT), the first systematic study of star formation and subsequent processing interstellar medium in interacting dwarf galaxies. Here we present results from a multiwavelength observational program based on sample 104 galaxy pairs selected range environments within spectroscopic portion Sloan Digital Sky Survey caught various stages interaction. The TNT span mass ratios M/M < 10, projected separations <50 kpc, pair member masses 7 log(/) 9.7. dwarf–dwarf merger...
The Milky Way (MW) and M31 both harbor massive satellite galaxies, the Large Magellanic Cloud (LMC) M33, which may comprise up to 10 per cent of their host's total mass. Massive satellites can change orbital barycentre host-satellite system by tens kiloparsecs are cosmologically expected dwarf galaxies own. Assessing impact these effects depends crucially on histories LMC M33. Here, we revisit dynamics MW-LMC present first detailed analysis M31-M33 utilizing high precision proper motions...
We present a new measurement of the systemic proper motion Small Magellanic Cloud (SMC), based on an expanded set 30 fields containing background quasars and spanning $\sim$3 year baseline, using \textit{Hubble Space Telescope} (\textit{HST}) Wide Field Camera 3. Combining this data with our previous 5 \textit{HST} fields, additional 8 measurements from \textit{Gaia}-Tycho Astrometric Solution Catalog, brings us to total 43 SMC fields. measure $\mu_{W}$ = $-0.82$ $\pm$ 0.02 (random) 0.10...
Abstract The 3D velocities of M31 and M33 are important for understanding the evolution cosmological context Local Group. Their most massive stars detected by Gaia , we use Data Release 2 (DR2) to determine galaxy proper motions (PMs). We select members based on, e.g., parallax, PM, color–magnitude diagram location, local stellar density. PM rotation both galaxies is confidently detected, consistent with known line-of-sight curves: <?CDATA ${V}_{\mathrm{rot}}=-206\pm...
Indications of disequilibrium throughout the Milky Way (MW) highlight need for compact,flexible, non-parametric descriptions phase--space distributions galaxies. We present a new representation current Dark Matter (DM) distribution and potential derived from N-body simulations Large Magellanic Cloud (LMC) system using Basis Function Expansions (BFEs). incorporate methods to maximize physical signal in representation. As result, $10^8$ DM particles representing MW--LMC can be described by 354...
We present deep optical images of the Large and Small Magellanic Clouds (LMC SMC) using a low cost telephoto lens with wide field view to explore stellar substructure in outskirts disk LMC (r < 10 degrees from center). These data have higher resolution than existing star count maps, highlight existence arcs multiple spiral arms northern periphery, no comparable counterparts South. compare these detailed simulations outskirts, following interactions its mass companion, SMC. consider...
Abstract We measure homogeneous distances to M31 and 38 associated stellar systems (−16.8 ≤ M V −6.0), using time-series observations of RR Lyrae stars taken as part the Hubble Space Telescope Treasury Survey Satellites. From >700 orbits new/archival Advanced Camera for Surveys imaging, we identify >4700 determine their periods mean magnitudes a typical precision 0.01 day 0.04 mag. Based on period–Wesenheit–metallicity relationships consistent with Gaia eDR3 distance scale, uniformly...