Mario Mateo

University of Michigan–Ann Arbor

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Co-Authors

Edward W. Olszewski

University of Arizona

146

Matthew G. Walker

Carnegie Mellon University

J. Kałużny

Nicolaus Copernicus Astronomical Center

John I. Bailey

University of California, Santa Barbara

A. Udalski

University of Warsaw

M. K. Szymański

University of Warsaw

M. Kubiak

Częstochowa University of Technology

R. C. Dohm‐Palmer

University of Michigan–Ann Arbor

Nelson Caldwell

Center for Astrophysics Harvard & Smithsonian

K. Z. Stanek

The Ohio State University

Cooperative Institutions

Centre National de la Recherche Scientifique

211

University of Oxford

135

Max Planck Society

130

Max Planck Institute for Astronomy

107

California Institute of Technology

UK Astronomy Technology Centre

University of Michigan–Ann Arbor

Laboratoire d’Astrophysique de Marseille

Instituto de Astrofísica de Canarias

Center for Astrophysics Harvard & Smithsonian

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On Kinematic Substructure in the Sextans Dwarf Spheroidal Galaxy

The Astrophysical Journal (2006)

Matthew G. Walker Mario Mateo Edward W. Olszewski Jayanta Kumar Pal Bodhisattva Sen

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 profile of the binned data remains flat to a maximum angular radius of 30'. We introduce a nonparametric technique for estimating the projected velocity dispersion surface and use this to search for kinematic substructure. Our data do not confirm previous reports of a kinematically distinct stellar population at the Sextans center. Instead we detect a region near the Sextans core radius that is kinematically colder than the overall Sextans sample with 95% confidence.

Velocity dispersion

Substructure

Radial velocity

10.1086/504522

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Citations (68)

The Quadruple Gravitational Lens PG 1115+080: Time Delays and Models

The Astrophysical Journal (1997)

Paul L. Schechter C. D. Bailyn Robert C. Barr Richard Barvainis C. M. Becker

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 components ``A1'' and ``A2'' by 9.4 days. A range of models has been fit to the image positions, none of which gives an adequate fit. The best fitting and most physically plausible of these, taking the lensing galaxy and the associated group of galaxies to be singular isothermal spheres, gives a Hubble constant of 42 km/s/Mpc for Omega=1, with an observational uncertainty of 14%, as computed from the B-C time delay measurement. Taking the lensing galaxy to have an approximately E5 isothermal mass distribution yields H0=64 km/sec/Mpc while taking the galaxy to be a point mass gives H0=84 km/sec/Mpc. The former gives a particularly bad fit to the position of the lensing galaxy, while the latter is inconsistent with measurements of nearby galaxy rotation curves. Constraints on these and other possible models are expected to improve with planned HST observations.

Strong gravitational lensing

Mass distribution

10.1086/310478

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Citations (216)

The Binary Fraction of Stars in Dwarf Galaxies: The Case of Leo II

The Astronomical Journal (2017)

M. Spencer Mario Mateo Matthew G. Walker Edward W. Olszewski Alan W. McConnachie

Abstract We combine precision radial velocity data from four different published works of the stars in the Leo II dwarf spheroidal galaxy. This yields a data set that spans 19 years, has 14 different epochs of observation, and contains 372 unique red giant branch stars, 196 of which have repeat observations. Using this multi-epoch data set, we constrain the binary fraction for Leo II. We generate a suite of Monte Carlo simulations that test different binary fractions using Bayesian analysis and determine that the binary fraction for Leo II ranges from to , depending on the distributions of binary orbital parameters assumed. This value is smaller than what has been found for the solar neighborhood (∼0.4–0.6) but falls within the wide range of values that have been inferred for other dwarf spheroidals (0.14–0.69). The distribution of orbital periods has the greatest impact on the binary fraction results. If the fraction we find in Leo II is present in low-mass ultra-faints, it can artificially inflate the velocity dispersion of those systems and cause them to appear more dark matter rich than in actuality. For a galaxy with an intrinsic dispersion of 1 km s −1 and an observational sample of 100 stars, the dispersion can be increased by a factor of 1.5–2 for Leo II-like binary fractions or by a factor of three for binary fractions on the higher end of what has been seen in other dwarf spheroidals.

Velocity dispersion

Radial velocity

10.3847/1538-3881/aa6d51

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Citations (19)

AGB SODIUM ABUNDANCES IN THE GLOBULAR CLUSTER 47 TUCANAE (NGC 104)

The Astronomical Journal (2015)

Christian I. Johnson Iain McDonald C. A. Pilachowski Mario Mateo John I. Bailey

A recent analysis comparing the [Na/Fe] distributions of red giant branch (RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster NGC 6752 found that the ratio of Napoor to Na-rich stars changes from 30:70 on the RGB to 100:0 on the AGB.The surprising paucity of Na-rich stars on the AGB in NGC 6752 warrants additional investigations to determine if the failure of a significant fraction of stars to ascend the AGB is an attribute common to all globular clusters.Therefore, we present radial velocities, [Fe/H], and [Na/Fe] abundances for 35 AGB stars in the Galactic globular cluster 47 Tucanae (47 Tuc; NGC 104), and compare the AGB [Na/Fe] distribution with a similar RGB sample published previously.The abundances and velocities were derived from high resolution spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph on the Magellan-Clay 6.5m telescope.We find the average heliocentric radial velocity and [Fe/H] values to be RV helio.=-18.56 km s -1 (σ=10.21km s -1 ) and [Fe/H] =-0.68 (σ=0.08),respectively, in agreement with previous literature estimates.The average [Na/Fe] abundance is 0.12 dex lower in the 47 Tuc AGB sample compared to the RGB sample, and the ratio of Na-poor to Na-rich stars is 63:37 on the AGB and 45:55 on the RGB.However, in contrast to NGC 6752, the two 47 Tuc populations have nearly identical [Na/Fe] dispersion and interquartile range values.The data presented here suggest that only a small fraction ( 20%) of Na-rich stars in 47 Tuc may fail to ascend the AGB, which is a similar result to that observed in M13.Regardless of the cause for the lower average [Na/Fe] abundance in AGB stars, we find that Na-poor stars and at least some Na-rich stars in 47 Tuc evolve through the early AGB phase.The contrasting behavior of Na-rich stars in 47 Tuc and NGC 6752 suggests that the RGB [Na/Fe] abundance alone is insufficient for predicting if a star will ascend the AGB.

Asymptotic giant branch

Red-giant branch

Giant star

10.1088/0004-6256/149/2/71

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Citations (45)

Mapping the Galactic Halo IV. Searching for Distant Giants with the Washington System

arXiv (Cornell University) (2000)

Helen Morrison Edward W. Olszewski Mario Mateo John E. Norris Paul Harding

Galactic corona

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A radial-velocity study of open clusters containing blue stragglers.

Publications of the Astronomical Society of the Pacific (1984)

M. Bolte Mario Mateo

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Blue straggler

Radial velocity

10.1086/131474

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Citations (0)

Color-Magnitude Diagrams and Luminosity Functions for Four LMC Clusters Ranging in Age from 0.2 to 10 Gyr

Bulletin of the American Astronomical Society (1986)

P. W. Hodge Mario Mateo

Ranging

Source

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Citations (2)

The optical gravitational lensing experiment. Variable stars in globular clusters

Astronomy and Astrophysics Supplement Series (1997)

J. Kałużny M. Kubiak M. K. Szymański A. Udalski W. Krzemiński

We present V-band photometry for 141 variable stars from the field of ω Cen. All but one variables are either RR Lyr stars or Pop. II Cepheids. One object is a distant background RR Lyr star from the galactic halo. The presented sample includes 33 newly identified variables, mostly low amplitude RR Lyr stars. We identified also two Pop. II Cepheids with exceptionally low amplitudes of light variations . The presented data may be used to study period changes of ω Cen variables and/or for Fourier decomposition of light curves.

Variable star

Blue straggler

10.1051/aas:1997376

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Citations (29)

Streaming motion in Leo I

The Annals of Applied Statistics (2009)

Bodhisattva Sen Moulinath Banerjee Michael Woodroofe Mario Mateo Matthew G. Walker

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 center, but the effect appears to be quite modest. Statistical tools include isotonic and split point estimators, asymptotic theory, and resampling methods.

Dwarf spheroidal galaxy

Resampling

10.1214/08-aoas211

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Citations (10)

A SPECTROSCOPIC ANALYSIS OF THE GALACTIC GLOBULAR CLUSTER NGC 6273 (M19)

The Astronomical Journal (2015)

Christian I. Johnson R. Michael Rich C. A. Pilachowski Nelson Caldwell Mario Mateo

A combined effort utilizing spectroscopy and photometry has revealed the existence of a new globular cluster class. These "anomalous" clusters, which we refer to as "iron-complex" clusters, are differentiated from normal clusters by exhibiting large (>0.10 dex) intrinsic metallicity dispersions, complex sub-giant branches, and correlated [Fe/H] and s-process enhancements. In order to further investigate this phenomenon, we have measured radial velocities and chemical abundances for red giant branch stars in the massive, but scarcely studied, globular cluster NGC 6273. The velocities and abundances were determined using high resolution (R~27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph on the Magellan-Clay 6.5m telescope at Las Campanas Observatory. We find that NGC 6273 has an average heliocentric radial velocity of +144.49 km s^-1 (sigma=9.64 km s^-1) and an extended metallicity distribution ([Fe/H]=-1.80 to -1.30) composed of at least two distinct stellar populations. Although the two dominant populations have similar [Na/Fe], [Al/Fe], and [alpha/Fe] abundance patterns, the more metal-rich stars exhibit significant [La/Fe] enhancements. The [La/Eu] data indicate that the increase in [La/Fe] is due to almost pure s-process enrichment. A third more metal-rich population with low [X/Fe] ratios may also be present. Therefore, NGC 6273 joins clusters such as omega centauri, M 2, M 22, and NGC 5286 as a new class of iron-complex clusters exhibiting complicated star formation histories.

Red-giant branch

Red giant

Stellar population

10.1088/0004-6256/150/2/63

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Citations (58)