Mario L. Mateo

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We present new kinematic results for a sample of 387 stars located in and around the Milky Way satellite dwarf spheroidal galaxy Leo I. These spectra were obtained with the Hectochelle multi-object echelle spectrograph on the MMT, and cover the MgI/Mgb lines at about 5200Å. Based on 297 repeat measurements of 108 stars, we estimate the mean velocity error(More)
We apply the Jeans equation to estimate masses for eight of the brightest dwarf spheroidal (dSph) galaxies. For Fornax, the dSph with the largest kinematic data set, we obtain a model-independent constraint on the maximum-circular velocity, Vmax = 20 +4 −3 km s . Although we obtain only lowerlimits of Vmax & 10 km s −1 for the remaining dSphs, we find that(More)
We report the discovery of a new Milky Way satellite in the constellation Leo, identified in data from the Sloan Digital Sky Survey. It lies at a distance of ∼ 180 kpc, and is separated by . 3 from another recent discovery, Leo IV. We present follow-up imaging from the Isaac Newton Telescope and spectroscopy from the Hectochelle fiber spectrograph at the(More)
I review observational data on the kinematic properties of dwarf spheroidal galaxies in the halo of the Milky Way and beyond. The present data confirm previous claims that these small galaxies have unusually large central velocity dispersions. ‘Simple’ sources of bias such as binary stars, internal atmospheric motions, measurement errors and small sample(More)
We present a systematic and homogeneous analysis of population gradients for the Local Group dwarf spheroidals (dSphs) Carina, Sculptor, Sextans, Tucana, Andromeda I-III, V, and VI. For all of the Milky Way companions studied here we find significant population gradients. The same is true for the remote dSph Tucana located at the outskirts of the LG. Among(More)
We have compiled a new sample of 240 halo objects with accurate distance and radial velocity measurements, including globular clusters, satellite galaxies, field blue horizontal branch stars and red giant stars from the Spaghetti survey. The new data lead to a significant increase in the number of known objects for Galactocentric radii beyond 50 kpc, which(More)
Optical photometry is presented for the quadruple gravitational lens PG1115+080. A preliminary reduction of data taken from November 1995 to June 1996 gives component “C” leading component “B” by 23.7± 3.4 days and Department of Physics, Massachusetts Institute of Technology, Cambridge MA 02138 Department of Astronomy, Yale University, New Haven CT(More)
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 isolated dwarf spheroidal galaxy Andromeda II (And II). We find a weighted mean radial velocity of vr = –188±3 km s−1 and a central velocity dispersion of σ0 = 9.3 −2.6(More)
Whether a dwarf spheroidal galaxy is in equilibrium or being tidally disrupted by the Milky Way is an important question for the study of its dark matter content and distribution. This question is investigated using 328 recent observations from the dwarf spheroidal Leo I. For Leo I, tidal disruption is detected, at least for stars sufficiently far from the(More)
We present the second part of the OGLE Catalog of Periodic Variable Stars in the Galactic bulge. 800 variable stars found in four Baade’s Window fields BW1, BW2, BW3 and BW4 are presented. Among them 71 are classified as pulsating, 465 as eclipsing and 264 as miscellaneous type. The Catalog and individual observations are available in digital form from the(More)