The First VERA Astrometry Catalog

Abstract

We present the first astrometry catalog from the Japanese VLBI (very long baseline interferometer) project VERA (VLBI Exploration of Radio Astrometry). We have compiled all the astrometry results from VERA, providing accurate trigonometric-annual-parallax and proper-motion measurements. In total, 99 maser sources are listed in the VERA catalog. Among them, 21 maser sources are newly reported, while the rest of the 78 sources are referred to in previously published results or those in preparation for forthcoming papers. The accuracy in the VERA astrometry is revisited and compared with that from the other VLBI astrometry projects such as BeSSeL (The Bar and Spiral Structure Legacy) Survey and GOBELINS (the Gould’s Belt Distances Survey) with the VLBA (Very Long Baseline Array). We have confirmed that most of the astrometry results are consistent with each other, and the largest error sources are due to source structure of the maser features and their rapid variation, along with the systematic calibration errors and different analysis methods. Combined with the BeSSeL results, we estimate the up-to-date fundamental Galactic parameters of $R_{0}=7.92\pm 0.16_{\rm {stat.}}\pm 0.3_{\rm {sys.}}\:$kpc and $\Omega _{\odot }=30.17\pm 0.27_{\rm {stat.}}\pm 0.3_{\rm {sys.}}\:$km$\:$s$^{-1}\:$kpc$^{-1}$, where $R_{0}$ and $\Omega _{\odot }$ are the distance from the Sun to the Galactic center and the Sun’s angular velocity of the Galactic circular rotation, respectively.

The Spiral Structure in the Solar Neighborhood

“…This work opened a new era to accurately reveal the Galaxy's spiral structure through VLBI measurements. Since then, nearly 200 HMSFRs have had measured trigonometric parallaxes (typical accuracy of about ± 0.02 mas) and proper motions, primarily by the Bar And Spiral Structure Legacy (BeSSeL) Survey using the VLBA (Reid et al, 2019) and the Japanese VLBI Exploration of Radio Astrometry (VERA) project (Hirota et al, 2020). Some sources were observed by the European VLBI Network and the Australian Long Baseline Array (e.g., Rygl et al, 2010;Krishnan et al, 2017).…”

“…To depict the local spiral arms with high confidence, only the HMSFRs (Reid et al, 2019;Hirota et al, 2020) with uncertainties of trigonometric distances better than 15% were kept as for GMCs. For the distant sources, we also required that their distance uncertainties were < 0.5 kpc.…”

“…In the past few years, there has been significant progress in observations by taking advantage of the VLBI observations in the radio band (Reid et al, 2019;Hirota et al, 2020) and Gaia astrometry measurements in the optical band (Prusti et al, 2016). Accurate parallaxes and proper motions have been obtained for a large number of HMSFR masers (e.g., Reid et al, 2019), HII regions (e.g., , O-type stars (e.g., Xu et al, 2021), young open clusters (OCs, e.g., Dias et al, 2021), and evolved stars (e.g., Khoperskov et al, 2020).…”

The Science of Fundamental Catalogs

“…Direct astrometric measurements of gravitational waves from a single source are not possible with the current pulsar timing or VLBI technology. However, it was noticed that the stochastic ensemble of these waves produced by various mechanisms can be detected in a roundabout way by studying temporal and angular correlations in the times of arrival (TOA) of radio pulses from the pulsar timing array (PTA) (Hellings and Downs, 1983;Foster and Backer, 1990;van Haasteren et al, 2009;Manchester, 2013;Taylor et al, 2017), or in the redshifts of quasars (Seto and Cooray, 2006), or in the pattern of their proper motions in an astrometric fundamental catalog (Pyne et al, 1996;Gwinn et al, 1997;Kaiser and Jaffe, 1997;Jaffe, 2004;Makarov, 2010;Book and Flanagan, 2011;Bini and Geralico, 2018;Qin et al, 2019).…”

Updated detection prospects for relic neutrinos using coherent scattering

“…We contrast this to the case where neutrinos are clustered, where instead the CνB reference frame is that of the Milky Way. In this scenario, the relative motion of the Earth to the CνB is β MW C » 7.6 ¨10 ´4 [33]. Neutrinos are only able to cluster efficiently if their mean velocity βν does not exceed the escape velocity the galaxy β esc » 1.8 ¨10 ´3 [34].…”