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Register a new userThe extended Gaia-PS1-SDSS (GPS1+) proper motion catalog
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The GPS1 catalog was released in 2017. It delivered precise proper motions for around 350 million sources across three-fourths of the sky down to a magnitude of $rsim20$,mag. In this study, we present GPS1+ the extension GPS1 catalog down to $rsim22.5$,mag, based on {it Gaia} DR2, PS1, SDSS and 2MASS astrometry. The GPS1+ totally provides proper motions for $sim$400 million sources with a characteristic systematic error of less than 0.1masyr. This catalog is divided into two sub-samples, i.e., the primary and secondary parts. The primary $sim$264 million sources have either or both of the {it Gaia} and SDSS astrometry, with a typical precision of 2.0-5.0 masyr. In this part, $sim$160 million sources have {it Gaia} proper motions, we provide another new proper motion for each of them by building a Bayesian model. Relative to {it Gaia}s values, the precision is improved by $sim$0.1,dex on average at the faint end; $sim$50 million sources are the objects whose proper motions are missing in {it Gaia} DR2, we provide their proper motion with a precision of $sim$4.5masyr; the remaining $sim$54 million faint sources are beyond {it Gaia} detecting capability, we provide their proper motions for the first time with a precision of 7.0 masyr. However, the secondary $sim$136 million sources only have PS1 astrometry, the average precision is worse than 15.0 masyr. All the proper motions have been validated using QSOs and the existing {it Gaia} proper motions. The catalog will be released on-line and available via the VO-TAP Service, or via the National Astronomical Data Center serviced by China-VO: https://nadc.china-vo.org/data/data/gps1p/f.
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High proper motion stars probe several extreme stellar populations, including nearby objects, Galactic halo stars, and hyper-velocity stars. Extending the search for high proper motion stars, to faint limits can increase their numbers and help to identify interesting targets. We conduct a search for faint (r>19.5 mag) high proper motion stars (>~200 mas/yr) by comparing the Sloan Digital Sky Survey (SDSS) - Data Release (DR) 10 catalog to the Pan-STARRS1-DR1 stacked image catalog. Our main selection criterion is stars that moved >1.5 arcsec and up to 7 arcsec between the SDSS and PS1 epochs. We identify 2923 high proper motion stars, of which 826 do not have proper motion in the GAIA-DR2 catalog and 565 are not listed in the GAIA-DR2 catalog. Our SDSS-PS1 proper motions are consistent with the GAIA-measured proper motions with a robust rms of about 10 mas/yr.
We present the fourth installment of the Yale/San Juan Southern Proper Motion Catalog, SPM4. The SPM4 contains absolute proper motions, celestial coordinates, and (B,V) photometry for over 103 million stars and galaxies between the south celestial pole and -20 deg declination. The catalog is roughly complete to V=17.5 and is based on photographic and CCD observations taken with the Yale Southern Observatorys double-astrograph at Cesco Observatory in El Leoncito, Argentina. The proper-motion precision, for well-measured stars, is estimated to be 2 to 3 mas/yr, depending on the type of second-epoch material. At the bright end, proper motions are on the International Celestial Reference System by way of Hipparcos Catalog stars, while the faint end is anchored to the inertial system using external galaxies. Systematic uncertainties in the absolute proper motions are on the order of 1 mas/yr.
Astrometric positions of moving objects in the Solar System have been measured using a variety of star catalogs in the past. Previous work has shown that systematic errors in star catalogs can affect the accuracy of astrometric observations. That, in turn, can influence the resulting orbit fits for minor planets. In order to quantify these systematic errors, we compare the positions and proper motion of stellar sources in the most utilized star catalogs to the second release of the Gaia star catalog. The accuracy of Gaia astrometry allows us to unambiguously identify local biases and derive a scheme that can be used to correct past astrometric observations of solar system objects. Here we provide a substantially improved debiasing scheme for 26 astrometric catalogs that were extensively used in minor planet astrometry. Revised corrections near the galactic center eliminate artifacts that could be traced back to reference catalogs used in previous debiasing schemes. Median differences in stellar positions between catalogs now tend to be on the order of several tens of milliarcseconds (mas) but can be as large as 175 mas. Median stellar proper motion corrections scatter around 0.3 mas/yr and range from 1 to 4 mas/yr for star catalogs with and without proper motion, respectively. The tables in this work are meant to be applied to existing optical observations. They are not intended to correct new astrometric measurments as those should make use of the Gaia astrometric catalog. Since previous debiasing schemes already reduced systematics in past observations to a large extent, corrections beyond the current work may not be needed in the foreseeable future.
We use the Gaia data release 1 (DR1) to study the proper motion (PM) fields of the Large and Small Magellanic Clouds (LMC, SMC). This uses the Tycho-Gaia Astrometric Solution (TGAS) PMs for 29 Hipparcos stars in the LMC and 8 in the SMC. The LMC PM in the West and North directions is inferred to be $(mu_W,mu_N) = (-1.872 pm 0.045, 0.224 pm 0.054)$ mas/yr, and the SMC PM $(mu_W,mu_N) = (-0.874 pm 0.066, -1.229 pm 0.047)$ mas/yr. These results have similar accuracy and agree to within the uncertainties with existing Hubble Space Telescope (HST) PM measurements. Since TGAS uses different methods with different systematics, this provides an external validation of both data sets and their underlying approaches. Residual DR1 systematics may affect the TGAS results, but the HST agreement implies this must be below the random errors. Also in agreement with prior HST studies, the TGAS LMC PM field clearly shows the clockwise rotation of the disk, even though it takes the LMC disk in excess of $10^8$ years to complete one revolution. The implied rotation curve amplitude for young LMC stars is consistent with that inferred from line-of-sight (LOS) velocity measurements. Comparison of the PM and LOS rotation curves implies a kinematic LMC distance modulus $m-M = 18.54 pm 0.39$, consistent but not yet competitive with photometric methods. These first results from Gaia on the topic of Local Group dynamics provide an indication of how its future data releases will revolutionize this field.
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