Showing papers by "Mark J. Reid published in 2022"
TL;DR: In this paper , the authors focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements and discuss the importance of trying to fit a full array of data with a single model.
335 citations
TL;DR: Inverse multiview as discussed by the authors is a novel very long baseline interferometry (VLBI) calibration method, which uses observations of multiple quasars to accurately model and remove time-variable, directional-dependent changes to the interferometer delay.
Abstract: Very Long Baseline Interferometry (VLBI) astrometry is a well established technique for achieving ±10 μas parallax accuracies at frequencies well above 10 GHz. At lower frequencies, uncompensated interferometer delays associated with the ionosphere play the dominant role in limiting the astrometric accuracy. Multiview is a novel VLBI calibration method, which uses observations of multiple quasars to accurately model and remove time-variable, directional-dependent changes to the interferometer delay. Here we extend the Multiview technique by phase-referencing data to the target source (“inverse Multiview”) and test its performance. Multiple observations with a four-antenna VLBI array operating at 8.3 GHz show single-epoch astrometric accuracies near 20 μas for target–reference quasar separations up to about 7°. This represents an improvement in astrometric accuracy by up to an order of magnitude compared to standard phase-referencing.
5 citations
TL;DR: In this paper , the authors reported VLBA observations of 22 GHz H 2 O and 43 GHz SiO masers toward the Mira variable RR Aql and reported a stellar parallax of 2.44 ± 0.07 mas, corresponding to a distance of 410 + 12 − 11 pc.
Abstract: We report VLBA observations of 22 GHz H 2 O and 43 GHz SiO masers toward the Mira variable RR Aql. By fitting the SiO maser emission to a circular ring, we estimate the absolute stellar position of RR Aql and find agreement with Gaia astrometry to within the joint uncertainty of ≈ 1 mas. Using the maser astrometry we measure a stellar parallax of 2.44 ± 0.07 mas, corresponding to a distance of 410 +12 − 11 pc. The maser parallax deviates significantly from the Gaia EDR3 parallax of 1.95 ± 0.11 mas, indicating a 3 . 8 σ tension between radio and optical measurements. This tension is most likely caused by optical photo-center variations limiting the Gaia astrometric accuracy for this Mira variable. Combining infrared magnitudes with parallaxes for RR Aql and other Miras, we fit a period-luminosity relation using a Bayesian approach with MCMC sampling and a strong prior for the slope of –3.60 ± 0.30 from the LMC. We find a K -band zero-point (defined at logP(days) = 2.30) of –6.79 ± 0.15 mag using VLBI parallaxes and –7.08 ± 0.29 mag using Gaia parallaxes. The Gaia zero-point is statistically consistent with the more accurate VLBI value.
3 citations
TL;DR: In this article , the authors analyze the potential for addressing this need by combining line-of-sight velocities and proper motions to yield three-dimensional kinematic distance estimates.
Abstract: Over the past decade, the BeSSeL Survey and the VERA project have measured trigonometric parallaxes to ≈250 massive, young stars using VLBI techniques. These sources trace spiral arms over nearly half of the Milky Way. What is now needed are accurate distances to such stars that are well past the Galactic center. Here we analyze the potential for addressing this need by combining line-of-sight velocities and proper motions to yield three-dimenensional (3D) kinematic distance estimates. For sources within about 10 kpc of the Sun, significant systematic uncertainties can occur, and trigonometric parallaxes are generally superior. However, for sources well past the Galactic center, 3D kinematic distances are robust and more accurate than can usually be achieved by trigonometic parallaxes.
3 citations
TL;DR: In this article , very long baseline array observations of 22 GHz H2O and 43 GHz SiO masers were used to estimate the absolute stellar position of RR Aql and find agreement with Gaia astrometry to within the joint uncertainty of ≈ 1 mas.
Abstract: We report Very Long Baseline Array observations of 22 GHz H2O and 43 GHz SiO masers toward the Mira variable RR Aql. By fitting the SiO maser emission to a circular ring, we estimate the absolute stellar position of RR Aql and find agreement with Gaia astrometry to within the joint uncertainty of ≈1 mas. Using the maser astrometry we measure a stellar parallax of 2.44 ± 0.07 mas, corresponding to a distance of 410−11+12 pc. The maser parallax deviates significantly from the Gaia EDR3 parallax of 1.95 ± 0.11 mas, indicating a 3.8σ tension between radio and optical measurements. This tension is most likely caused by optical photocenter variations limiting the Gaia astrometric accuracy for this Mira variable. Combining infrared magnitudes with parallaxes for RR Aql and other Miras, we fit a period–luminosity relation using a Bayesian approach with Markov Chain Monte Carlo sampling and a strong prior for the slope of −3.60 ± 0.30 from the Large Magellanic Cloud. We find a K-band zero-point (defined at logP(days) = 2.30) of −6.79 ± 0.15 mag using very long baseline interferometry (VLBI) parallaxes and −7.08 ± 0.29 mag using Gaia parallaxes. The Gaia zero-point is statistically consistent with the more accurate VLBI value.
2 citations
TL;DR: In this article , the absolute position and proper motion of Sgr A*, the radio source at the center of the Milky Way, had been improved by three epochs of phase-referencing observations with the Very Long Baseline Array at 22 and 43 GHz.
Abstract: The absolute position of Sgr A*, the compact radio source at the center of the Milky Way, had been uncertain by several tens of milliarcseconds. Here we report improved astrometric measurements of the absolute position and proper motion of Sgr A*. Three epochs of phase-referencing observations were conducted with the Very Long Baseline Array for Sgr A* at 22 and 43 GHz in 2019 and 2020. Using extragalactic radio sources with submilliarcsecond-accurate positions as reference, we determined the absolute position of Sgr A* at a reference epoch 2020.0 to be at α(J2000) = 17h45m40.ˢ032863 ± 0.ˢ000016 and δ(J2000) = − 29°00′28.″24260± 0.″00047, with an updated proper motion −3.152 ± 0.011 and −5.586 ± 0.006 mas yr−1 in the easterly and northerly directions, respectively.
1 citations
TL;DR: Astrometry at centimeter wavelengths using Very Long Baseline Interferometry is approaching accuracies of ∼1 μas for the angle between a target and a calibrator source separated by ≲1° on the sky as mentioned in this paper .
Abstract: Astrometry at centimeter wavelengths using Very Long Baseline Interferometry is approaching accuracies of ∼1 μas for the angle between a target and a calibrator source separated by ≲1° on the sky. The BeSSeL Survey and the Japanese VERA project are using this to map the spiral structure of the Milky Way by measuring trigonometric parallaxes of hundreds of maser sources associated with massive, young stars. This paper outlines how μas astrometry is done, including details regarding the scheduling of observations, calibration of data, and measuring positions.
1 citations
Peer Review•
07 Dec 2022
TL;DR: In this paper , the first results from the Southern Hemisphere Parallax Interferometric Radio Astrometry Legacy Survey (\spirals): $10\mu$as-accurate parallaxes and proper motions for two southern hemisphere 6.7 GHz methanol masers obtained using the inverse multi-view calibration method.
Abstract: We present the first results from the Southern Hemisphere Parallax Interferometric Radio Astrometry Legacy Survey (\spirals): $10\mu$as-accurate parallaxes and proper motions for two southern hemisphere 6.7 GHz methanol masers obtained using the inverse MultiView calibration method. Using an array of radio telescopes in Australia and New Zealand, we measured the trigonometric parallax and proper motions for the masers associated with the star formation region G232.62+00.99 of $\pi = 0.610\pm0.011$~mas, $\mu_x=-2.266\pm0.021$~mas~y$^{-1}$ and $\mu_y=2.249\pm0.049$~mas~y$^{-1}$, which implies its distance to be $d=1.637\pm0.029$~kpc. These measurements represent an improvement in accuracy by more than a factor of 3 over the previous measurements obtained through Very Long Baseline Array observations of the 12~GHz methanol masers associated with this region. We also measure the trigonometric parallax and proper motion for G323.74--00.26 as $\pi = 0.364\pm0.009$~mas, $\mu_x=-3.239\pm0.025$~mas~y$^{-1}$ and $\mu_y=-3.976\pm0.039$~mas~y$^{-1}$, which implies a distance of $d=2.747\pm0.068$~kpc. These are the most accurate measurements of trigonometric parallax obtained for 6.7~GHz class II methanol masers to date. We confirm that G232.62+00.99 is in the Local arm and find that G323.74--00.26 is in the Scutum-Centaurus arm. We also investigate the structure and internal dynamics of both masers.
TL;DR: This paper measured 16 trigonometric parallaxes and proper motions of molecular masers associated with 14 high-mass star-forming regions in the Scutum arm in the first quadrant of the Milky Way.
Abstract: As part of the BeSSeL Survey, we have used the Very Long Baseline Array to measure 16 trigonometric parallaxes and proper motions of molecular masers associated with 14 high-mass star-forming regions in the Scutum arm in the first quadrant of the Milky Way. This increases the number of maser sources with accurate distances in this arm to 42. The Scutum arm can now be traced over a length of ≈8 kpc and spanning ≈100° of Galactic azimuth. We find that the large inward peculiar motions noted by Immer et al. are concentrated near the end of the Galactic bar, while away from the bar modest peculiar motions more typical of spiral arms are seen, strengthening the suggestion that the large motions are induced by the bar.