A 500 Parsec Halo Surrounding the Galactic Globular NGC 1851 (2009)
Olszewski, Edward W., Saha, Abhijit, Knezek, Patricia, Subramaniam, Annapurni, De Boer, Thomas, Seitzer, Patrick
Using imaging that shows four magnitudes of main sequence stars, we have discovered that the Galactic globular cluster NGC 1851 is surrounded by a halo that is visible from the tidal radius of 700...
A Universal Mass Profile for Dwarf Spheroidal Galaxies? (2009)
Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Peñarrubia, Jorge, Evans, N. Wyn, Gilmore, Gerard
(abridged) We apply the Jeans equation to estimate masses for eight of the brightest dSph galaxies. For Fornax we obtain a model-independent constraint on the maximum-circular velocity,...
Mapping the Galactic Halo VIII: Quantifying substructure (2009)
Starkenburg, Else, Helmi, Amina, Morrison, Heather L., Harding, Paul, Van Woerden, Hugo, Mateo, Mario, ...
We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high latitude sky survey. Our sample contains 101...
Leo V: Spectroscopy of a Distant and Disturbed Satellite (2009)
Walker, Matthew G., Belokurov, Vasily, Evans, N. Wyn, Irwin, Michael J., Mateo, Mario, Olszewski, Edward W., ...
We present a spectroscopic study of Leo V, a recently discovered satellite of the Milky Way (MW). From stellar spectra obtained with the MMT/Hectochelle spectrograph we identify seven likely members...
Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Sen, Bodhisattva, Woodroofe, Michael
(abridged) We develop an algorithm for estimating parameters of a distribution sampled with contamination, employing a statistical technique known as ``expectation maximization'' (EM). Given models...
Walker, Matthew G., Mateo, Mario, Olszewski, Edward W.
The transverse motions of nearby dwarf spheroidal (dSph) galaxies contribute line-of-sight components that increase with angular distance from the dSph centers, inducing detectable gradients in...
Mario Mateo, Edward W. Olszewski, K. H. Cook
The High Resolution Echelle Spectrometer on the Keck I telescope has been used to measure nine radial velocities having a median precision of ' 2 km s 1 for seven red giants belonging to the...
Mateo, Mario, Olszewski, Edward W., Walker, Matthew G.
(abridged) We present kinematic results for a sample of 387 stars located near Leo I based on spectra obtained with the MMT's Hectochelle spectrograph near the MgI/Mgb lines. We estimate the mean...
Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies (2007)
Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Gnedin, Oleg Y., Wang, Xiao, Sen, Bodhisattva, ...
We present stellar velocity dispersion profiles for seven Milky Way dwarf spheroidal (dSph) satellite galaxies. We have measured 8394 line-of-sight velocities (+/- 2.5 km/s) for 6804 stars from...
Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Bernstein, Rebecca, Sen, Bodhisattva, Woodroofe, Michael
We introduce a stellar velocity survey of dwarf spheroidal galaxies, undertaken using the Michigan/MIKE Fiber System (MMFS) at the Magellan/Clay 6.5 m telescope at Las Campanas Observatory. As of...
Piatek, Slawomir, Pryor, Carlton, Bristow, Paul, Olszewski, Edward W., Harris, Hugh C., Mateo, Mario, ...
The measured proper motion of Fornax, expressed in the equatorial coordinate system, is $(\mu_{\alpha},\mu_{\delta})=(47.6\pm 4.6,-36.0\pm 4.1)$ mas century$^{-1}$. This proper motion is a weighted...
On Kinematic Substructure in the Sextans Dwarf Spheroidal Galaxy (2006)
Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Pal, Jayanta Kumar, Sen, Bodhisattva, Woodroofe, Michael
We present multifiber echelle radial velocity results for 551 stars in the Sextans dwarf spheroidal galaxy and identify 294 stars as probable Sextans members. The projected velocity dispersion...
Internal Kinematics of the Fornax Dwarf Spheroidal Galaxy (2005)
Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Bernstein, Rebecca A., Wang, Xiao, Woodroofe, Michael
We present new radial velocity results for 176 stars in the Fornax dwarf spheroidal galaxy, of which at least 156 are probable Fornax members. We combine with previously published data to obtain a...
The Nature of the Density Clump in the Fornax Dwarf Spheroidal Galaxy (2005)
Olszewski, Edward W., Mateo, Mario, Harris, Jason, Walker, Matthew G., Coleman, Matthew G., Da Costa, G. S.
We have imaged the recently discovered stellar overdensity located approximately one core radius from the center of the Fornax dwarf spheroidal galaxy using the Magellan Clay 6.5m telescope with the...
Structure of the Draco Dwarf Spheroidal Galaxy (2002)
Piatek, Slawomir, Pryor, Carlton, Armandroff, Taft E., Olszewski, Edward W.
This article studies the structure of the Draco dwarf spheroidal galaxy with an emphasis on the question of whether the spatial distribution of its stars has been affected by the tidal interaction...
Mapping the Galactic Halo III. Simulated Observations of Tidal Streams (2000)
Harding, Paul, Morrison, Heather L., Olszewski, Edward W., Arabadjis, John, Mateo, Mario, Dohm-Palmer, R. C., ...
We have simulated the evolution of tidal debris in the Galactic halo in order to guide our ongoing survey to determine the fraction of halo mass accreted via satellite infall. Contrary to naive...
Stars of the Draco Dwarf Spheroidal Galaxy Beyond its Measured Tidal Boundary (2000)
Piatek, Slawomir, Pryor, Carlton, Armandroff, Taft E., Olszewski, Edward W.
We report R- and V-band photometry derived from CCD imaging for objects in nine fields in and around the Draco dwarf spheroidal galaxy. The most distant fields are about 1.3 degrees from the center....
Mapping the Galactic Halo I. The `Spaghetti' Survey (2000)
Morrison, Heather L., Mateo, Mario, Olszewski, Edward W., Harding, Paul, Dohm-Palmer, R. C., Freeman, Kenneth C., ...
We describe a major survey of the Milky Way halo designed to test for kinematic substructure caused by destruction of accreted satellites. We use the Washington photometric system to identify halo...
Piatek, Slawomir, Pryor, Carlton, Bristow, Paul, Olszewski, Edward W., Harris, Hugh C., Mateo, Mario, ...
This article presents a measurement of the proper motion of the Ursa Minor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope in two distinct fields. Each field...
Mateo, Mario, Olszewski, Edward W., Morrison, Heather L.
We have obtained deep photometric data in 24 fields along the southeast extension of the major axis of the Sagittarius dwarf spheroidal (Sgr dSph) galaxy, and in four fields along the northwest...
Mateo, Mario, Olszewski, Edward W., Vogt, Steven S., Keane, Michael J.
We present radial velocities of 33 red giants in the Leo I dSph galaxy obtained from spectra taken with the HIRES echelle spectrograph on the Keck I telescope. These data have a mean precision of 2.2...
Internal Kinematics of Dward Spheroidal Galaxies (1997)
We discuss the quality of kinematic data in dwarf spheroidal galaxies, the current interpretations of those data, and prospects for actually deriving the mass profile in these galaxies. We then...