M. J. Reid

Center for Astrophysics Harvard & Smithsonian

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Papers

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i-10 index

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Document Type

Co-Authors

K. M. Menten

Max Planck Institute for Radio Astronomy

201

J. M. Moran

Center for Astrophysics Harvard & Smithsonian

144

A. Brunthaler

Max Planck Institute for Radio Astronomy

121

C. Henkel

Max Planck Institute for Radio Astronomy

J. A. Braatz

National Radio Astronomy Observatory

L. J. Greenhill

Center for Astrophysics Harvard & Smithsonian

Ye Xu

University of Science and Technology of China

L. Moscadelli

Arcetri Astrophysical Observatory

Bo Zhang

Shanghai Astronomical Observatory

J. J. Condon

National Radio Astronomy Observatory

Cooperative Institutions

Max Planck Society

203

Center for Astrophysics Harvard & Smithsonian

158

Max Planck Institute for Radio Astronomy

146

National Radio Astronomy Observatory

100

Harvard University

California Institute of Technology

Centre National de la Recherche Scientifique

Max Planck Innovation

Max Planck Institute for Astronomy

University of California, Berkeley

Author Statistics

Papers

Citation

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Science with the ngVLA: H$_2$O Megamaser Cosmology

arXiv (Cornell University) (2018)

J. A. Braatz Dominic W. Pesce J. J. Condon M. J. Reid

In combination with observations of the Cosmic Microwave Background, a measurement of the Hubble Constant provides a direct test of the standard $Λ$CDM cosmological model and a powerful constraint on the equation of state of dark energy. Observations of circumnuclear water vapor megamasers at 22 GHz in nearby active galaxies can be used to measure their distances, geometrically, and thereby provide a direct, one step measurement of the Hubble Constant. The measurement is independent of distance ladders and standard candles. With present-day instrumentation, the Megamaser Cosmology Project is expected to reach a $\sim$4% measurement using the megamaser technique, based on distances to fewer than 10 megamaser systems. A goal of the observational cosmology community is to reach a percent-level measurement of H$_0$ from several independent astrophysical measurements to minimize the systematics. The ngVLA will provide the sensitivity at 22 GHz required to discover and measure the additional megamaser disks that will enable an H$_0$ measurement at the $\sim$1% level.

Megamaser

Cosmic distance ladder

Observational cosmology

10.48550/arxiv.1810.06686

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Citations (1)

Microarcsecond astrometry using the SKA

New Astronomy Reviews (2004)

E. B. Fomalont M. J. Reid

Astrometry

Proper motion

Nutation

Ephemeris

10.1016/j.newar.2004.09.037

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Citations (49)

A preliminary distance to W 75N in the Cygnus X star-forming region

arXiv (Cornell University) (2010)

K. L. J. Rygl A. Brunthaler K. M. Menten M. J. Reid H. J. van Langevelde

Cygnus X is one of the closest giant molecular cloud complexes and therefore an extensively studied region of ongoing high mass star formation. However, the distance to this region has been a long-standing issue, since sources at galactic longitude of ~80 degrees could be in the Local Arm nearby (1-2 kpc), in the Perseus Arm at ~5 kpc, or even in the outer arm (~10 kpc). We use combined observations of the EVN plus two Japanese stations to measure very accurate parallaxes of methanol masers in five star-forming regions in Cygnus X to understand if they belong to one large star-forming complex or if they are separate entities located at different distances. Here we report our preliminary result for W75N based on six epochs of VLBI observations: we find that W75N is at a distance of 1.32^{+0.11}_{-0.09} kpc, which is significantly closer than the reported values in the literature (1.5-2 kpc).

Star (game theory)

Longitude

Very-long-baseline interferometry

10.48550/arxiv.1011.5042

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Citations (2)

THE PROPER MOTION OF THE GALACTIC CENTER PULSAR RELATIVE TO SAGITTARIUS A*

The Astrophysical Journal (2015)

Geoffrey C. Bower Adam T. Deller Paul Demorest A. Brunthaler H. Falcke

We measure the proper motion of the pulsar PSR J1745-2900 relative to the Galactic center massive black hole, Sgr A*, using the Very Long Baseline Array (VLBA). The pulsar has a transverse velocity of 236 ± 11 km s−1 at position angle 22 ± 2 deg east of north at a projected separation of 0.097 pc from Sgr A*. Given the unknown radial velocity, this transverse velocity measurement does not conclusively prove that the pulsar is bound to Sgr A*; however, the probability of chance alignment is very small. We do show that the velocity and position are consistent with a bound orbit originating in the clockwise disk of massive stars orbiting Sgr A* and a natal velocity kick of ≲ 500 km s−1. An origin among the isotropic stellar cluster is possible but less probable. If the pulsar remains radio-bright, multiyear astrometry of PSR J1745-2900 can detect its acceleration and determine the full three-dimensional orbit. We also demonstrate that PSR J1745-2900 exhibits the same angular broadening as Sgr A* over a wavelength range of 3.6 cm to 0.7 cm, further confirming that the two sources share the same interstellar scattering properties. Finally, we place the first limits on the presence of a wavelength-dependent shift in the position of Sgr A*, i.e., the core shift, one of the expected properties of optically thick jet emission. Our results for PSR J1745-2900 support the hypothesis that Galactic center pulsars will originate from the stellar disk and deepen the mystery regarding the small number of detected Galactic center pulsars.

Proper motion

Position angle

Sagittarius A*

10.1088/0004-637x/798/2/120

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Citations (46)

Sub-luminal Motion in M87

Symposium - International Astronomical Union (1988)

J. A. Biretta M. J. Reid W. Junor R. E. Spencer T. W. B. Muxlow

The galaxy M87 (3C274, NGC4486) contains one of the nearest jet sources in the northern hemisphere, and one of our best opportunities to study a jet in detail. We have made MkII VLBI observations of the nuclear jet at 1.66 GHz using 18 stations of the “World Array.” The array included Arecibo which greatly improved the north-south resolution. The data were global fringe fitted, and self-calibrated to remove both antenna and baseline amplitude and phase errors. The resulting map (Fig. 1) has a dynamic range of 2300:1 and reveals a very complex structure. At distances ≥50 mas from the core, the jet is resolved across its width and appears limb-brightened. The brightness centroid oscillates from side to side by an amount roughly equal to the jet's width; this may be caused by brightness variations at the edges of a limb-brightened jet. Within 50 mas of the core the opening angle (at the FWHM points) is 6.5°±0.3°; this is larger than that of the 20″ jet, and suggests there is recollimation between the pc and kpc scales. The jet is aligned within 1° of the 20″ jet. There is no evidence for a counter-jet; the jet/counter-jet brightness ratio is R≥200.

Very-long-baseline interferometry

Proper motion

10.1017/s0074180900133893

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Citations (0)

The Structure of Hydroxyl Masers and Circumstellar Envelopes of Long Period Variable Stars

M. J. Reid

Long period variable stars with envelopes of circumstellar dust and gas often exhibit strong hydroxyl (OH) maser emission. This emission is characterized by two emission line complexes typically separated by 20 km/s. While the OH maser spectra suggest well defined dynamical properties of the circumstellar material, the crucial observations required to determine these properties have been lacking. This thesis is primarily concerned with determining the radial velocity of the central star and the spatial distribution of the maser emission in the circumstellar material. The radial velocity of the central star can be determined by a statistical analysis of spectral line velocities in an ensemble of stars. Such an analysis is presented in Chapter I for optical emission and absorption lines and for radio OH maser emission lines. The results indicate that, contrary to currently accepted theories, the optical absorption line velocities and the high velocity OH emission line velocities are red-shifted with respect to the stellar radial velocity. This argues against models of the OH emission which involve shock fronts or emission from the limb of a spherically expanding circumstellar shell. The spatial distribution of the maser emission can be determined from radio interferometric observations. Spectral-line very long baseline (VLB) interferometric observations of the OH maser emission in long period variable stars such as IRC+F10011, U Ori and R Aql are presented in Chapter II. The primary result of these observations is that the apparent sizes of the OH maser components in long period variable stars are greater than or about 5 x 1015 cm. These large apparent sizes argue strongly against either gravitational collapse or rotation as the dominant dynamical process in the circumstellar envelope. Analysis of data obtained on IRC+10011 and VY CMa (discussed in Chapter III) indicate that the two emission complexes probably are separated by distances less than, or comparable to, the extent of the emission in either complex. These and other findings suggest that OH emission from long period variable stars comes from a series of concentric, inhomogeneous, circumstellar shells expanding from the central star. The origin of these shells is probably a result of condensation of dust followed by radiative acceleration away from the star during the stellar light cycle. A direct Fourier inversion of VLB data is presented in Chapter III for the 1612 MHz OH emission of VY CMa. This is the first attempt at such an analysis procedure for any VLB observations. This work demonstrates that Fourier inversion of spectral-line VLB data, even with very limited u-v coverage, is more efficient and less biased than direct model fitting for the resolution of complex source structures.

Circumstellar envelope

Line (geometry)

Variable star

Circumstellar dust

10.7907/4egt-tw53.

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Citations (0)

The Distance to the Galactic Center: R 0

Springer eBooks (1989)

M. J. Reid

Center (category theory)

Value (mathematics)

10.1007/978-94-009-2362-1_3

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Citations (13)

HIGH-PRECISION RADIO AND INFRARED ASTROMETRY OF LSPM J1314+1320AB. I. PARALLAX, PROPER MOTIONS, AND LIMITS ON PLANETS

The Astrophysical Journal (2016)

Jan Forbrich Trent J. Dupuy M. J. Reid E. Berger Aaron C. Rizzuto

We present multi-epoch astrometric radio observations with the Very Long Baseline Array (VLBA) of the young ultracool-dwarf binary LSPM J1314+1320AB . The radio emission comes from the secondary star. Combining the VLBA data with Keck near-infrared adaptive-optics observations of both components, a full astrometric fit of parallax ($\pi_{\rm abs}=57.975\pm0.045$ mas, corresponding to a distance of $d=17.249\pm0.013$ pc), proper motion ($\mu_{\rm \alpha cos \delta}=-247.99\pm0.10$ mas yr$^{-1}$, $\mu_{\delta}=-183.58\pm0.22$ mas yr$^{-1}$), and orbital motion is obtained. Despite the fact that the two components have nearly identical masses to within $\pm2$%, the secondary's radio emission exceeds that of the primary by a factor of $\gtrsim$30, suggesting a difference in stellar rotation history, which could result in different magnetic field configurations. Alternatively, the emission could be anisotropic and beamed toward us for the secondary but not for the primary. Using only reflex motion, we exclude planets of mass 0.7 to 10 $M_{\rm jup}$ with orbital periods of 600 to 10 days, respectively. Additionally, we use the full orbital solution of the binary to derive an upper limit for the semi-major axis of 0.23 AU for stable planetary orbits within this system. These limits cover a parameter space that is inaccessible with, and complementary to, near-infrared radial velocity surveys of ultracool dwarfs. Our absolute astrometry will constitute an important test for the astrometric calibration of Gaia.

Astrometry

Proper motion

Parallax

Orbital motion

Orbital inclination

10.3847/0004-637x/827/1/22

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Citations (17)

Atmosphere-Corrected Phase-Referencing

A. Brunthaler M. J. Reid H. Falcke

One major problem of phase-referencing VLBI observations are phase errors due to the unknown tropospheric zenith delay at each antenna. These errors degrade the quality of the phase-referenced image and limit the achievable astrometric accuracy. We will present and compare two independent methods to estimate the zenith delay offset at each antenna. The zenith delay offsets can then be used to correct the data. These corrections improve the quality of the phase-referenced image and an astrometric accuracy of 10 muas can be achieved. With this accuracy, measurements of proper motions in the Local Group become feasible.

Zenith

Source

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Citations (4)

SiO and H₂O Masers in the Central Parsec of the Galaxy

International Astronomical Union Colloquium (1998)

K. M. Menten M. J. Reid

Abstract We have discovered maser emission from SiO and H 2 O molecules toward a number of evolved stars within the central parsec of our Galaxy. The maser positions can be registered with milliarcsecond precision relative to the radio continuum emission of the nonthermal Galactic center source Sgr A*. Since the masing stars are prominent infrared sources, our data can be used to locate the position of Sgr A* on infrared images of the Galactic center region. Using VLBA observations it will be possible to measure proper motions of the maser stars, which can be used to put constraints on the mass distribution in the central parsec.

Parsec

10.1017/s0252921100045334

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Citations (1)