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Showing 1-20 of about 104 results.
Trigonometric Parallaxes of Four Star-forming Regions in the Distant Inner GalaxyXu, Y.Bian, S. B.Reid, M. J.Li, J. J.Menten, K. M.Dame, T. M.Zhang, B.Brunthaler, A.Wu, Y. W.Moscadelli, L.Wu, G.Zheng, X. W.DOI: info:10.3847/1538-4365/abd8cfv. 2531
Xu, Y., Bian, S. B., Reid, M. J., Li, J. J., Menten, K. M., Dame, T. M., Zhang, B., Brunthaler, A., Wu, Y. W., Moscadelli, L., Wu, G., and Zheng, X. W. 2021. "Trigonometric Parallaxes of Four Star-forming Regions in the Distant Inner Galaxy." The Astrophysical Journal Supplement Series 253:1.
ID: 159444
Type: article
Authors: Xu, Y.; Bian, S. B.; Reid, M. J.; Li, J. J.; Menten, K. M.; Dame, T. M.; Zhang, B.; Brunthaler, A.; Wu, Y. W.; Moscadelli, L.; Wu, G.; Zheng, X. W.
Abstract: We have measured trigonometric parallaxes for four H2O masers associated with distant massive young stars in the inner regions of the Galaxy using the Very Long Baseline Array as part of the BeSSeL Survey. G026.50 + 0.28 is located at the near end of the Galactic bar, perhaps at the origin of the Norma spiral arm. G020.77−0.05 is in the Galactic Center region and is likely associated with a far-side extension of the Scutum arm. G019.60−0.23 and G020.08−0.13 are likely associated and lie well past the Galactic Center. These sources appear to be in the Sagittarius spiral arm, but an association with the Perseus arm cannot be ruled out.
The Megamaser Cosmology Project - XII. VLBI imaging of H2O maser emission in three active galaxies and the effect of AGN winds on disc dynamicsKuo, C. Y.Braatz, J. A.Impellizzeri, C. M. V.Gao, F.Pesce, Dominic W.Reid, Mark J.Condon, J.Kamali, F.Henkel, C.Greene, J. E.DOI: info:10.1093/mnras/staa2260v. 4981609–1627
Kuo, C. Y., Braatz, J. A., Impellizzeri, C. M. V., Gao, F., Pesce, Dominic W., Reid, Mark J., Condon, J., Kamali, F., Henkel, C., and Greene, J. E. 2020. "The Megamaser Cosmology Project - XII. VLBI imaging of H2O maser emission in three active galaxies and the effect of AGN winds on disc dynamics." Monthly Notices of the Royal Astronomical Society 498:1609– 1627.
ID: 157765
Type: article
Authors: Kuo, C. Y.; Braatz, J. A.; Impellizzeri, C. M. V.; Gao, F.; Pesce, Dominic W.; Reid, Mark J.; Condon, J.; Kamali, F.; Henkel, C.; Greene, J. E.
Abstract: We present very long baseline interferometry (VLBI) images and kinematics of water maser emission in three active galaxies: NGC 5728, Mrk 1, and IRAS 08452-0011. IRAS 08452-0011, at a distance of ∼200 Mpc, is a triple-peaked H2O megamaser, consistent with a Keplerian rotating disc, indicating a black hole mass of (3.3 $\pm 0.2)\times 10^{7}\, \mathrm{ M}_{\odot }$ . NGC 5728 and Mrk 1 display double-peaked spectra, and VLBI imaging reveals complicated gas kinematics that do not allow for a robust determination of black hole mass. We show evidence that the masers in NGC 5728 are in a wind while the Mrk 1 maser system has both disc and outflow components. We also find that disturbed morphology and kinematics are a ubiquitous feature of all double-peaked maser systems, implying that these maser sources may reside in environments where active galactic nucleus (AGN) winds are prominent at ∼1 pc scale and have significant impact on the masing gas. Such AGNs tend to have black hole masses $M_{\rm BH}\, \lt$ 8 × 106 M and Eddington ratios $\lambda _{\rm Edd}\, \gtrsim$ 0.1, while the triple-peaked megamasers show an opposite trend.
SiO maser astrometry of the red transient V838 MonocerotisOrtiz-León, Gisela N.Menten, Karl M.Kamiński, TomaszBrunthaler, AndreasReid, Mark J.Tylenda, RomualdDOI: info:10.1051/0004-6361/202037712v. 638A17
Ortiz-León, Gisela N., Menten, Karl M., Kamiński, Tomasz, Brunthaler, Andreas, Reid, Mark J., and Tylenda, Romuald. 2020. "SiO maser astrometry of the red transient V838 Monocerotis." Astronomy and Astrophysics 638:A17.
ID: 156874
Type: article
Authors: Ortiz-León, Gisela N.; Menten, Karl M.; Kamiński, Tomasz; Brunthaler, Andreas; Reid, Mark J.; Tylenda, Romuald
Abstract: We present multiepoch observations with the Very Long Baseline Array of SiO maser emission in the v = 1, J = 1-0 transition at 43 GHz from the remnant of the red nova V838 Mon. We modeled the positions of maser spots to derive a parallax of 0.166 ± 0.060 mas. Combining this parallax with other distance information results in a distance of 5.6 ± 0.5 kpc, which is in agreement with an independent geometric distance of 6.1 ± 0.6 kpc from modeling polarimetry images of V838 Mon's light echo. Combining these results, and including a weakly constraining Gaia parallax, yields a best estimate of distance of 5.9 ± 0.4 kpc. The maser spots are located close to the peaks of continuum at ∼225 GHz and SiO J = 5-4 thermal emission detected with the Atacama Large (sub)Millimeter Array. The proper motion of V838 Mon confirms its membership in a small open cluster in the Outer spiral arm of the Milky Way.
Fits images associated with Figs. 2-4 are only available at CDS via anonymous ftp to ( or via bin/cat/J/A+A/638/A17
The Megamaser Cosmology Project. XI. A Geometric Distance to CGCG 074-064Pesce, Dominic W.Braatz, J. A.Reid, Mark J.Condon, J. J.Gao, F.Henkel, C.Kuo, C. Y.Lo, K. Y.Zhao, W.DOI: info:10.3847/1538-4357/ab6bcdv. 890118
Pesce, Dominic W., Braatz, J. A., Reid, Mark J., Condon, J. J., Gao, F., Henkel, C., Kuo, C. Y., Lo, K. Y., and Zhao, W. 2020. "The Megamaser Cosmology Project. XI. A Geometric Distance to CGCG 074-064." The Astrophysical Journal 890:118.
ID: 155818
Type: article
Authors: Pesce, Dominic W.; Braatz, J. A.; Reid, Mark J.; Condon, J. J.; Gao, F.; Henkel, C.; Kuo, C. Y.; Lo, K. Y.; Zhao, W.
Abstract: As part of the survey component of the Megamaser Cosmology Project, we have discovered a disk megamaser system in the galaxy CGCG 074-064. Using the Green Bank Telescope and the Very Large Array, we have obtained spectral monitoring observations of this maser system at a monthly cadence over the course of two years. We find that the systemic maser features display line-of-sight accelerations of ∼4.4 km s−1 yr−1 that are nearly constant with velocity, while the high-velocity maser features show accelerations that are consistent with zero. We have also used the High-Sensitivity Array to make a high-sensitivity very long baseline interferometric map of the maser system in CGCG 074-064, which reveals that the masers reside in a thin, edge-on disk with a diameter of ∼1.5 mas (0.6 pc). Fitting a three-dimensional warped disk model to the data, we measure a black hole mass of ${2.42}_{-0.20}^{+0.22}\times {10}^{7}\,{M}_{\odot }$ and a geometric distance to the system of ${87.6}_{-7.2}^{+7.9}$ Mpc. Assuming a cosmic microwave background-frame recession velocity of 7308 ± 150 km s−1, we constrain the Hubble constant to ${H}_{0}={81.0}_{-6.9}^{+7.4}$ (stat.) ± 1.4 (sys.) km s−1 Mpc−1.
The Megamaser Cosmology Project. XIII. Combined Hubble Constant ConstraintsPesce, Dominic W.Braatz, J. A.Reid, Mark J.Riess, A. G.Scolnic, D.Condon, J. J.Gao, F.Henkel, C.Impellizzeri, C. M. V.Kuo, C. Y.Lo, K. Y.DOI: info:10.3847/2041-8213/ab75f0v. 891L1
Pesce, Dominic W., Braatz, J. A., Reid, Mark J., Riess, A. G., Scolnic, D., Condon, J. J., Gao, F., Henkel, C., Impellizzeri, C. M. V., Kuo, C. Y., and Lo, K. Y. 2020. "The Megamaser Cosmology Project. XIII. Combined Hubble Constant Constraints." The Astrophysical Journal 891:L1.
ID: 156700
Type: article
Authors: Pesce, Dominic W.; Braatz, J. A.; Reid, Mark J.; Riess, A. G.; Scolnic, D.; Condon, J. J.; Gao, F.; Henkel, C.; Impellizzeri, C. M. V.; Kuo, C. Y.; Lo, K. Y.
Abstract: We present a measurement of the Hubble constant made using geometric distance measurements to megamaser-hosting galaxies. We have applied an improved approach for fitting maser data and obtained better distance estimates for four galaxies previously published by the Megamaser Cosmology Project: UGC 3789, NGC 6264, NGC 6323, and NGC 5765b. Combining these updated distance measurements with those for the maser galaxies CGCG 074-064 and NGC 4258, and assuming a fixed velocity uncertainty of 250 km s-1 associated with peculiar motions, we constrain the Hubble constant to be H0 = 73.9 ± 3.0 km s-1 Mpc-1 independent of distance ladders and the cosmic microwave background. This best value relies solely on maser- based distance and velocity measurements, and it does not use any peculiar velocity corrections. Different approaches for correcting peculiar velocities do not modify H0 by more than ±1σ, with the full range of best-fit Hubble constant values spanning 71.8-76.9 km s-1 Mpc-1. We corroborate prior indications that the local value of H0 exceeds the early-universe value, with a confidence level varying from 95% to 99% for different treatments of the peculiar velocities.
The Proper Motion of Sagittarius A*. III. The Case for a Supermassive Black HoleReid, Mark J.Brunthaler, A.DOI: info:10.3847/1538-4357/ab76cdv. 89239
Reid, Mark J. and Brunthaler, A. 2020. "The Proper Motion of Sagittarius A*. III. The Case for a Supermassive Black Hole." The Astrophysical Journal 892:39.
ID: 156366
Type: article
Authors: Reid, Mark J.; Brunthaler, A.
Abstract: We report measurements with the Very Long Baseline Array of the proper motion of Sgr A* relative to two extragalactic radio sources spanning 18 yr. The apparent motion of Sgr A* is -6.411 ± 0.008 mas yr-1 along the Galactic plane and -0.219 ± 0.007 mas yr-1 toward the North Galactic Pole. This apparent motion can almost entirely be attributed to the effects of the Sun's orbit about the Galactic center. Removing these effects yields residuals of -0.58 ± 2.23 km s-1 in the direction of Galactic rotation and -0.85 ± 0.75 km s-1 toward the North Galactic Pole. A maximum-likelihood analysis of the motion, both in the Galactic plane and perpendicular to it, expected for a massive object within the Galactic center stellar cluster indicates that the radiative source, Sgr A*, contains more than about 25% of the gravitational mass of 4 × 106 M deduced from stellar orbits. The intrinsic size of Sgr A* is comparable to its Schwarzschild radius, and the implied mass density of ≳ 4× 1023 M pc-3 is very close to that expected for a black hole, providing overwhelming evidence that it is indeed a supermassive black hole. Finally, "intermediate mass" black holes more massive than ≍3 × 104 M between approximately 0.003 and 0.1 pc from Sgr A* are excluded.
The first stellar parallaxes revisitedReid, Mark J.Menten, Karl M.DOI: info:10.1002/asna.202013833v. 341860–869
Reid, Mark J. and Menten, Karl M. 2020. "The first stellar parallaxes revisited." Astronomische Nachrichten 341:860– 869.
ID: 158646
Type: article
Authors: Reid, Mark J.; Menten, Karl M.
Abstract: We have reanalyzed the data used by Bessel, von Struve, and Henderson in the 1830s to measure the first parallax distances to stars. We can generally reproduce their results, although we find that von Struve and Henderson have underestimated some of their measurement errors, leading to optimistic parallax uncertainties. We find that temperature corrections for Bessel's measured positions are larger than anticipated, explaining some systematics apparent in his data. It has long been a mystery as to why von Struve first announced a parallax for Vega of 0."125 only to later revise it to double that value using more data. We resolve this mystery by finding that von Struve's early result used two dimensions of position data, which independently give significantly different parallaxes but, when combined, only fortuitously give the correct result. With later data, von Struve excluded the "problematic" dimension, leading to the larger parallax value. Allowing for likely temperature corrections and using his data from both dimensions reduce von Struve's parallax for Vega to a value consistent with the correct value.
Anomalous peculiar motions of high-mass young stars in the Scutum spiral armImmer, K.Li, J.Quiroga-Nuñez, L. H.Reid, Mark J.Zhang, B.Moscadelli, L.Rygl, K. L. J.DOI: info:10.1051/0004-6361/201834208v. 632A123
Immer, K., Li, J., Quiroga-Nuñez, L. H., Reid, Mark J., Zhang, B., Moscadelli, L., and Rygl, K. L. J. 2019. "Anomalous peculiar motions of high-mass young stars in the Scutum spiral arm." Astronomy and Astrophysics 632:A123.
ID: 154552
Type: article
Authors: Immer, K.; Li, J.; Quiroga-Nuñez, L. H.; Reid, Mark J.; Zhang, B.; Moscadelli, L.; Rygl, K. L. J.
Abstract: We present trigonometric parallax and proper motion measurements toward 22 GHz water and 6.7 GHz methanol masers in 16 high-mass star-forming regions. These sources are all located in the Scutum spiral arm of the Milky Way. The observations were conducted as part of the Bar and Spiral Structure Legacy (BeSSeL) survey. A combination of 14 sources from a forthcoming study and 14 sources from the literature, we now have a sample of 44 sources in the Scutum spiral arm, covering a Galactic longitude range from 0° to 33°. A group of 16 sources shows large peculiar motions of which 13 are oriented toward the inner Galaxy. A likely explanation for these high peculiar motions is the combined gravitational potential of the spiral arm and the Galactic bar.
Accretion disk versus jet orientation in H2O megamaser galaxiesKamali, F.Henkel, C.Koyama, S.Kuo, C. Y.Condon, J. J.Brunthaler, A.Reid, Mark J.Greene, J. E.Menten, K. M.Impellizzeri, C. M. V.Braatz, J. A.Litzinger, E.Kadler, M.DOI: info:10.1051/0004-6361/201834600v. 624A42
Kamali, F., Henkel, C., Koyama, S., Kuo, C. Y., Condon, J. J., Brunthaler, A., Reid, Mark J., Greene, J. E., Menten, K. M., Impellizzeri, C. M. V., Braatz, J. A., Litzinger, E., and Kadler, M. 2019. "Accretion disk versus jet orientation in H2O megamaser galaxies." Astronomy and Astrophysics 624:A42.
ID: 155324
Type: article
Authors: Kamali, F.; Henkel, C.; Koyama, S.; Kuo, C. Y.; Condon, J. J.; Brunthaler, A.; Reid, Mark J.; Greene, J. E.; Menten, K. M.; Impellizzeri, C. M. V.; Braatz, J. A.; Litzinger, E.; Kadler, M.
Abstract: Context. An essential part of the paradigm describing active galactic nuclei is the alignment between the radio jet and the associated rotation axis of the sub-pc accretion disks. Because of the small linear and angular scales involved, this alignment has not yet been checked in a sufficient number of low luminosity active galactic nuclei (LLAGNs). Aims: The project examines the validity of this paradigm by measuring the radio continuum on the same physical scale as the accretion disks to investigate any possible connection between these disks and the radio continuum. Methods: We observed a sample of 18 LLAGNs in the 4.8 GHz (6 cm) radio continuum using the Very Long Baseline Array (VLBA) with 3.3-6.5 ms resolution. The sources were selected to show both an edge-on accretion disk revealed by 22 GHz H2O megamaser emission and signatures of a radio jet. Furthermore, the sources were previously detected in 33 GHz radio continuum observations made with the Very Large Array. Results: Five out of 18 galaxies observed were detected at 8σ or higher levels (Mrk 0001, Mrk 1210, Mrk 1419, NGC 2273, and UGC 3193). While these five sources are known to have maser disks, four of them exhibit a maser disk with known orientation. For all four of these sources, the radio continuum is misaligned relative to the rotation axis of the maser disk, but with a 99.1% confidence level, the orientations are not random and are confined to a cone within 32° of the maser disk's normal. Among the four sources the misalignment of the radio continuum with respect to the normal vector to the maser disk is smaller when the inner radius of the maser disk is larger. Furthermore, a correlation is observed between the 5 GHz VLBA radio continuum and the [OIII] luminosity and also with the H2O maser disk's inner radius.
Resolving the distance controversy for Sharpless 269. A possible kink in the outer armQuiroga-Nuñez, L. H.Immer, K.van Langevelde, H. J.Reid, M. J.Burns, R. A.DOI: info:10.1051/0004-6361/201834726v. 625A70
Quiroga-Nuñez, L. H., Immer, K., van Langevelde, H. J., Reid, M. J., and Burns, R. A. 2019. "Resolving the distance controversy for Sharpless 269. A possible kink in the outer arm." Astronomy and Astrophysics 625:A70.
ID: 151850
Type: article
Authors: Quiroga-Nuñez, L. H.; Immer, K.; van Langevelde, H. J.; Reid, M. J.; Burns, R. A.
Abstract: Context. Sharpless 269 (S 269) is one of a few HII regions in the outer spiral arm of the Milky Way with strong water maser emission. Based on data from the Very Long Baseline Interferometry (VLBI) Exploration of Radio Astrometry (VERA) array, two parallax measurements have been published, which differ by nearly 2σ. Each distance estimate supports a different structure for the outer arm. Moreover, given its large Galactocentric radii, S 269 has special relevance as its proper motion and parallax have been used to constrain the Galactic rotation curve at large radii.
Aims: Using recent Very Long Baseline Array (VLBA) observations, we accurately measure the parallax and proper motion of the water masers in S 269. We interpret the position and motion of S 269 in the context of Galactic structure, and possible optical counterparts.
Methods: S 269's 22 GHz water masers and two close by quasars were observed at 16 epochs between 2015 and 2016 using the VLBA. We calibrated the data by inverse phase referencing using the strongest maser spot. The parallax and proper motion were fitted using the standard protocols of the Bar and Spiral Structure Legacy survey.
Results: We measure an annual parallax for S 269 of 0.241 ± 0.012 mas corresponding to a distance from the Sun of 4.15+0.22-0.20 kpc by fitting four maser spots. The mean proper motion for S 269 was estimated as 0.16 ± 0.26 mas yr-1 and -0.51 ± 0.26 mas yr-1 for μα cosδ and μδ respectively, which corresponds to the motion expected for a flat Galactic rotation curve at large radius. This distance estimate, Galactic kinematic simulations and observations of other massive young stars in the outer region support the existence of a kink in the outer arm at l ≈ 140°. Additionally, we find more than 2000 optical sources in the Gaia DR2 catalog within 125 pc radius around the 3D position of the water maser emission; from those only three sources are likely members of the same stellar association that contains the young massive star responsible for the maser emission (S 269 IRS 2w).
Trigonometric Parallaxes of High-mass Star-forming Regions: Our View of the Milky WayReid, Mark J.Menten, K. M.Brunthaler, A.Zheng, X. W.Dame, Thomas M.Xu, Y.Li, J.Sakai, N.Wu, Y.Immer, K.Zhang, B.Sanna, A.Moscadelli, L.Rygl, K. L. J.Bartkiewicz, A.Hu, B.Quiroga-Nuñez, L. H.van Langevelde, H. J.DOI: info:10.3847/1538-4357/ab4a11v. 885131
Reid, Mark J., Menten, K. M., Brunthaler, A., Zheng, X. W., Dame, Thomas M., Xu, Y., Li, J., Sakai, N., Wu, Y., Immer, K., Zhang, B., Sanna, A., Moscadelli, L., Rygl, K. L. J., Bartkiewicz, A., Hu, B., Quiroga-Nuñez, L. H., and van Langevelde, H. J. 2019. "Trigonometric Parallaxes of High-mass Star-forming Regions: Our View of the Milky Way." The Astrophysical Journal 885:131.
ID: 154604
Type: article
Authors: Reid, Mark J.; Menten, K. M.; Brunthaler, A.; Zheng, X. W.; Dame, Thomas M.; Xu, Y.; Li, J.; Sakai, N.; Wu, Y.; Immer, K.; Zhang, B.; Sanna, A.; Moscadelli, L.; Rygl, K. L. J.; Bartkiewicz, A.; Hu, B.; Quiroga-Nuñez, L. H.; van Langevelde, H. J.
Abstract: We compile and analyze approximately 200 trigonometric parallaxes and proper motions of molecular masers associated with very young high-mass stars. Most of the measurements come from the BeSSeL Survey using the VLBA and the Japanese VERA project. These measurements strongly suggest that the Milky Way is a four-arm spiral, with some extra arm segments and spurs. Fitting log-periodic spirals to the locations of the masers, allowing for "kinks" in the spirals and using well-established arm tangencies in the fourth Galactic quadrant, allows us to significantly expand our view of the structure of the Milky Way. We present an updated model for its spiral structure and incorporate it into our previously published parallax-based distance-estimation program for sources associated with spiral arms. Modeling the three-dimensional space motions yields estimates of the distance to the Galactic center, {R}0=8.15+/- 0.15 {kpc}, the circular rotation speed at the Sun's position, {{{\Theta }}}0=236+/- 7 km s-1, and the nature of the rotation curve. Our data strongly constrain the full circular velocity of the Sun, {{{\Theta }}}0+{V}=247+/- 4 km s-1, and its angular velocity, ({{{\Theta }}}0+{V})/{R}0=30.32+/- 0.27 km s-1 kpc-1. Transforming the measured space motions to a Galactocentric frame which rotates with the Galaxy, we find non- circular velocity components typically ≲10 km s-1. However, near the Galactic bar and in a portion of the Perseus arm we find significantly larger non-circular motions. Young high-mass stars within 7 kpc of the Galactic center have a scale height of only 19 pc, and thus are well suited to define the Galactic plane. We find that the orientation of the plane is consistent with the IAU-defined plane to within ±0.°1, and that the Sun is offset toward the north Galactic pole by {Z}=5.5+/- 5.8 pc. Accounting for this offset places the central supermassive black hole, Sgr A*, in the midplane of the Galaxy. The measured motions perpendicular to the plane of the Galaxy limit precession of the plane to ≲4 km s-1 at the radius of the Sun. Using our improved Galactic parameters, we predict the Hulse-Taylor binary pulsar to be at a distance of 6.54 ± 0.24 kpc, assuming its orbital decay from gravitational radiation follows general relativity.
An Improved Distance to NGC 4258 and Its Implications for the Hubble ConstantReid, Mark J.Pesce, Dominic W.Riess, A. G.DOI: info:10.3847/2041-8213/ab552dv. 886L27
Reid, Mark J., Pesce, Dominic W., and Riess, A. G. 2019. "An Improved Distance to NGC 4258 and Its Implications for the Hubble Constant." The Astrophysical Journal 886:L27.
ID: 154549
Type: article
Authors: Reid, Mark J.; Pesce, Dominic W.; Riess, A. G.
Abstract: NGC 4258 is a critical galaxy for establishing the extragalactic distance scale and estimating the Hubble constant ({H}0). Water masers in the nucleus of the galaxy orbit about its supermassive black hole, and very long baseline interferometric observations of their positions, velocities, and accelerations can be modeled to give a geometric estimate of the angular-diameter distance to the galaxy. We have improved the technique to obtain model parameter values, reducing both statistical and systematic uncertainties compared to previous analyses. We find the distance to NGC 4258 to be 7.576 ± 0.082 (stat.) ± 0.076 (sys.) Mpc. Using this as the sole source of calibration of the Cepheid-SN Ia distance ladder results in {H}0=72.0+/- 1.9 km s−1 Mpc−1, and in concert with geometric distances from Milky Way parallaxes and detached eclipsing binaries in the LMC we find {H}0=73.5 +/- 1.4 km s−1 Mpc−1. The improved distance to NGC 4258 also provides a new calibration of the tip of the red giant branch of {M}F814W=-4.01+/- 0.04 mag, with reduced systematic errors for the determination of {H}0 compared to the LMC-based calibration, because it is measured on the same Hubble Space Telescope (HST) photometric system and through similarly low extinction as SN Ia host halos. The result is {H}0=71.1+/- 1.9 km s−1 Mpc−1, in good agreement with the result from the Cepheid route, and there is no difference in {H}0 when using the same calibration from NGC 4258 and the same SN Ia Hubble diagram intercept to start and end both distance ladders.
Constraining a black hole companion for M87* through imaging by the Event Horizon TelescopeSafarzadeh, MohammadtaherLoeb, AbrahamReid, MarkDOI: info:10.1093/mnrasl/slz108v. 488L90–L93
Safarzadeh, Mohammadtaher, Loeb, Abraham, and Reid, Mark. 2019. "Constraining a black hole companion for M87* through imaging by the Event Horizon Telescope." Monthly Notices of the Royal Astronomical Society 488:L90– L93.
ID: 154420
Type: article
Authors: Safarzadeh, Mohammadtaher; Loeb, Abraham; Reid, Mark
Abstract: The Event Horizon Telescope, a global very long baseline interferometric array observing at a wavelength of 1.3 mm, detected the first image of the M87 supermassive black hole (SMBH). M87 is a giant elliptical galaxy at the centre of the Virgo cluster, which is expected to have formed through merging of cluster galaxies. Consequently M87* hosted mergers of black holes through dynamical friction and could have one or multiple binary companions with a low mass ratio at large separations. We show that a long-term monitoring of the M87 SMBH image over ̃1 yr with absolute positional accuracy of 1 ≈ μas could detect such binary companions and exclude a large parameter space in semimajor axis (a0) and mass ratio (q), which is currently not constrained. Moreover, the presence of the accretion disc around M87* excludes a binary companion with a0 ≈ of the order of a milliparsec, as otherwise the accretion disc would have been tidally disrupted.
Noncircular Motions in the Outer Perseus Spiral ArmSakai, NobuyukiReid, Mark J.Menten, Karl M.Brunthaler, AndreasDame, Thomas M.DOI: info:10.3847/1538-4357/ab12e0v. 87630
Sakai, Nobuyuki, Reid, Mark J., Menten, Karl M., Brunthaler, Andreas, and Dame, Thomas M. 2019. "Noncircular Motions in the Outer Perseus Spiral Arm." The Astrophysical Journal 876:30.
ID: 151847
Type: article
Authors: Sakai, Nobuyuki; Reid, Mark J.; Menten, Karl M.; Brunthaler, Andreas; Dame, Thomas M.
Abstract: We report measurements of parallax and proper motion for five 6.7 GHz methanol maser sources in the outer regions of the Perseus arm as part of the BeSSeL Survey of the Galaxy. By combining our results with previous astrometric results, we determine an average spiral arm pitch angle of 9.°2 ± 1.°5 and an arm width of 0.39 kpc for this spiral arm. For sources on the interior side of the Perseus arm, we find on average a radial inward motion in the Galaxy of 13.3 ± 5.4 km s‑1 and counter to Galactic rotation of 6.2 ± 3.2 km s‑1. These characteristics are consistent with models for spiral arm formation that involve gas entering an arm to be shocked and then to form stars. However, similar data for other spiral arms do not show similar characteristics.
Trigonometric Parallaxes of Star-forming Regions beyond the Tangent Point of the Sagittarius Spiral ArmWu, Y. W.Reid, Mark J.Sakai, N.Dame, Thomas M.Menten, K. M.Brunthaler, A.Xu, Y.Li, J. J.Ho, B.Zhang, B.Rygl, K. L. J.Zheng, X. W.DOI: info:10.3847/1538-4357/ab001av. 87494
Wu, Y. W., Reid, Mark J., Sakai, N., Dame, Thomas M., Menten, K. M., Brunthaler, A., Xu, Y., Li, J. J., Ho, B., Zhang, B., Rygl, K. L. J., and Zheng, X. W. 2019. "Trigonometric Parallaxes of Star-forming Regions beyond the Tangent Point of the Sagittarius Spiral Arm." The Astrophysical Journal 874:94.
ID: 155412
Type: article
Authors: Wu, Y. W.; Reid, Mark J.; Sakai, N.; Dame, Thomas M.; Menten, K. M.; Brunthaler, A.; Xu, Y.; Li, J. J.; Ho, B.; Zhang, B.; Rygl, K. L. J.; Zheng, X. W.
Abstract: As part of the BeSSeL Survey, we report trigonometric parallaxes and proper motions of molecular maser sources associated with 13 distant high-mass star-forming regions in the Sagittarius spiral arm of the Milky Way. In particular, we obtain improved parallax distance estimates for three well-studied regions: {1.9}-0.1+0.1 {kpc} for M17, {5.3}-0.9+1.3 {kpc} for W51, and {7.9}-0.7+0.9 {kpc} for GAL 045.5+00.0. Peculiar motions for all but one source are less than 20 km s-1. We fit a log-periodic spiral to the locations and estimate an average pitch angle of 7.°2 ± 1.°9. We find that the section of the arm beyond the tangent point in the first quadrant of the Milky Way appears 15 pc below the IAU-defined Galactic plane.
Comparison of Gaia DR2 Parallaxes of Stars with VLBI AstrometryXu, ShuangjingZhang, BoReid, Mark J.Zheng, XingwuWang, GuangliDOI: info:10.3847/1538-4357/ab0e83v. 875114
Xu, Shuangjing, Zhang, Bo, Reid, Mark J., Zheng, Xingwu, and Wang, Guangli. 2019. "Comparison of Gaia DR2 Parallaxes of Stars with VLBI Astrometry." The Astrophysical Journal 875:114.
ID: 155250
Type: article
Authors: Xu, Shuangjing; Zhang, Bo; Reid, Mark J.; Zheng, Xingwu; Wang, Guangli
Abstract: We compare the parallaxes of stars from VLBI astrometry in the literature to those in the Gaia DR2 catalog. Our full sample contains young stellar objects, evolved AGB stars, pulsars, and other radio stars. Excluding AGB stars, which show significant discrepancies between Gaia and VLBI parallaxes, and stars in binary systems, we obtain an average, systematic, parallax offset of -75 ± 29 μas for Gaia DR2, consistent with their estimate of a parallax zero-point between -100 and 0 μas.
Parallaxes for Star-forming Regions in the Inner Perseus Spiral ArmZhang, BoReid, Mark J.Zhang, LianWu, YuanweiHu, BoSakai, NobuyukiMenten, Karl M.Zheng, XingwuBrunthaler, AndreasDame, Thomas M.Xu, YeDOI: info:10.3847/1538-3881/ab141dv. 157200
Zhang, Bo, Reid, Mark J., Zhang, Lian, Wu, Yuanwei, Hu, Bo, Sakai, Nobuyuki, Menten, Karl M., Zheng, Xingwu, Brunthaler, Andreas, Dame, Thomas M., and Xu, Ye. 2019. "Parallaxes for Star-forming Regions in the Inner Perseus Spiral Arm." The Astronomical Journal 157:200.
ID: 151849
Type: article
Authors: Zhang, Bo; Reid, Mark J.; Zhang, Lian; Wu, Yuanwei; Hu, Bo; Sakai, Nobuyuki; Menten, Karl M.; Zheng, Xingwu; Brunthaler, Andreas; Dame, Thomas M.; Xu, Ye
Abstract: We report trigonometric parallax and proper motion measurements of 6.7 GHz CH3OH and 22 GHz H2O masers in eight high-mass star-forming regions (HMSFRs) based on Very Long Baseline Array (VLBA) observations as part of the Bar and Spiral Structure Legacy (BeSSeL) Survey. The distances of these HMSFRs combined with their Galactic coordinates, radial velocities, and proper motions, allow us to assign them to a segment of the Perseus arm with ℓ ≲ 70°. These HMSFRs are clustered in Galactic longitude from ≈30° to ≈50° neighboring a dearth of such sources between longitudes ≈50° to ≈90°.
The Evolving Radio Photospheres of Long-period Variable StarsMatthews, L. D.Reid, M. J.Menten, K. M.Akiyama, K.DOI: info:10.3847/1538-3881/aac491v. 15615
Matthews, L. D., Reid, M. J., Menten, K. M., and Akiyama, K. 2018. "The Evolving Radio Photospheres of Long-period Variable Stars." The Astronomical Journal 156:15.
ID: 147922
Type: article
Authors: Matthews, L. D.; Reid, M. J.; Menten, K. M.; Akiyama, K.
Abstract: Observations with the Karl G. Jansky Very Large Array at 46 GHz (lambda ≈ 7 mm) have been used to measure the size and shape of the radio photospheres of four long-period variable stars: R Leonis (R Leo), IRC+10216 (CW Leonis), chi Cygni (chi Cyg), and W Hydrae (W Hya). The shapes of the stars range from nearly round to ellipticities of ~0.15. Comparisons with observations taken several years earlier show that the photospheric parameters (mean diameter, shape, and/or flux density) of each of the stars have changed over time. Evidence for brightness asymmetries and nonuniformities across the radio surfaces is also seen in the visibility domain and in images obtained using a sparse-modeling image reconstruction technique. These trends may be explained as manifestations of large-scale irregular convective flows on the stellar surface, although effects from nonradial pulsations cannot be excluded. Our data also allow a new evaluation of the proper motion of IRC+10216. Our measurement is in agreement with previous values obtained from radio-wavelength measurements, and we find no evidence of statistically significant astrometric perturbations from a binary companion.
Revisiting LS I +61°303 with VLBI astrometryWu, Y. W.Torricelli-Ciamponi, G.Massi, M.Reid, M. J.Zhang, B.Shao, L.Zheng, X. W.DOI: info:10.1093/mnras/stx3003v. 4744245–4253
Wu, Y. W., Torricelli-Ciamponi, G., Massi, M., Reid, M. J., Zhang, B., Shao, L., and Zheng, X. W. 2018. "Revisiting LS I +61°303 with VLBI astrometry." Monthly Notices of the Royal Astronomical Society 474:4245– 4253.
ID: 146138
Type: article
Authors: Wu, Y. W.; Torricelli-Ciamponi, G.; Massi, M.; Reid, M. J.; Zhang, B.; Shao, L.; Zheng, X. W.
Abstract: We conducted multi-epoch Very Long Baseline Array (VLBA) phase-referenced observations of LS I +61°303 in order to study its precessing radio jet. Compared to similar observations in 2006, we find that the observed elliptical trajectory of emission at 8.4 GHz repeats after the 9 yr gap. The accurate alignment of the emission patterns yields a precession period of 26.926 ± 0.005 d, which is consistent with that determined by Lomb-Scargle analysis of the radio light curve. We analytically model the projection on the sky plane of the peak position of a precessing, synchrotron-emitting jet, which traces an elliptical trajectory on the sky. Comparing the simulation with the VLBA astrometry we improve our knowledge of the geometry of the system. We measure the LS I +61°303 absolute proper motion to be -0.150 ± 0.006 mas yr-1 eastward and -0.264 ± 0.006 mas yr-1 northward. Removing Galactic rotation, this reveals a small, northward. Removing Galactic rotation, this reveals a small, -1, non-circular motion, which indicates a very low kick velocity when the black hole was formed.
The Megamaser Cosmology Project. X. High-resolution Maps and Mass Constraints for SMBHsZhao, WeiBraatz, James A.Condon, James J.Lo, K. Y.Reid, Mark J.Henkel, C.Pesce, Dominic W.Greene, J. E.Gao, F.Kuo, C. Y.Impellizzeri, C. M. V.DOI: info:10.3847/1538-4357/aaa95cv. 854124
Zhao, Wei, Braatz, James A., Condon, James J., Lo, K. Y., Reid, Mark J., Henkel, C., Pesce, Dominic W., Greene, J. E., Gao, F., Kuo, C. Y., and Impellizzeri, C. M. V. 2018. "The Megamaser Cosmology Project. X. High-resolution Maps and Mass Constraints for SMBHs." The Astrophysical Journal 854:124.
ID: 145795
Type: article
Authors: Zhao, Wei; Braatz, James A.; Condon, James J.; Lo, K. Y.; Reid, Mark J.; Henkel, C.; Pesce, Dominic W.; Greene, J. E.; Gao, F.; Kuo, C. Y.; Impellizzeri, C. M. V.
Abstract: We present high-resolution (submas) Very Long Baseline Interferometry maps of nuclear H2O megamasers for seven galaxies. In UGC 6093, the well-aligned systemic masers and high-velocity masers originate in an edge-on, flat disk and we determine the mass of the central supermassive black holes (SMBH) to be M SMBH = 2.58 × 107 M (±7%). For J1346+5228, the distribution of masers is consistent with a disk, but the faint high-velocity masers are only marginally detected, and we constrain the mass of the SMBH to be in the range (1.5–2.0) × 107 M . The origin of the masers in Mrk 1210 is less clear, as the systemic and high-velocity masers are misaligned and show a disorganized velocity structure. We present one possible model in which the masers originate in a tilted, warped disk, but we do not rule out the possibility of other explanations including outflow masers. In NGC 6926, we detect a set of redshifted masers, clustered within a parsec of each other, and a single blueshifted maser about 4.4 pc away, an offset that would be unusually large for a maser disk system. Nevertheless, if it is a disk system, we estimate the enclosed mass to be M SMBH 7 M . For NGC 5793, we detect redshifted masers spaced about 1.4 pc from a clustered set of blueshifted features. The orientation of the structure supports a disk scenario as suggested by Hagiwara et al. We estimate the enclosed mass to be M SMBH 7 M . For NGC 2824 and J0350‑0127, the masers may be associated with parsec- or subparsec-scale jets or outflows.