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J/ApJS/233/3  The VLBA Extragalactic Proper Motion Catalog  (Truebenbach+, 2017)

The VLBA Extragalactic Proper Motion Catalog and a measurement of the secular aberration drift. Truebenbach A.E., Darling J. <Astrophys. J. Suppl. Ser., 233, 3-3 (2017)> =2017ApJS..233....3T (SIMBAD/NED BibCode)
ADC_Keywords: Proper motions ; Active gal. nuclei ; Interferometry ; Spectroscopy ; Redshifts ; Positional data Keywords: astrometry; catalogs; galaxies: distances and redshifts; proper motions; techniques: interferometric Abstract: We present a catalog of extragalactic proper motions created using archival VLBI data and our own VLBA astrometry. The catalog contains 713 proper motions, with average uncertainties of ∼24µas/yr, including 40 new or improved proper motion measurements using relative astrometry with the VLBA. The observations were conducted in the X-band and yielded positions with uncertainties of ∼70µas. We add 10 new redshifts using spectroscopic observations taken at Apache Point Observatory and Gemini North. With the VLBA Extragalactic Proper Motion Catalog, we detect the secular aberration drift-the apparent motion of extragalactic objects caused by the solar system's acceleration around the Galactic center-at a 6.3σ significance. We model the aberration drift as a spheroidal dipole, with the square root of the power equal to 4.89±0.77µas/yr, an amplitude of 1.69±0.27µas/yr, and an apex at (275.2°±10.0°, -29.4°±8.8°). Our dipole model detects the aberration drift at a higher significance than some previous studies, but at a lower amplitude than expected or previously measured. The full aberration drift may be partially removed by the no-net-rotation constraint used when measuring archival extragalactic radio source positions. Like the cosmic microwave background dipole, which is induced by the observer's motion, the aberration drift signal should be subtracted from extragalactic proper motions in order to detect cosmological proper motions, including the Hubble expansion, long-period stochastic gravitational waves, and the collapse of large-scale structure. Description: We created our catalog of extragalactic radio proper motions using the 2017a Goddard VLBI global solution. The 2017a solution is computed from more than 30 years of dual-band VLBI observations --1979 August 3 to 2017 March 27. We also observed 28 objects with either no redshift or a "questionable" Optical Characteristic of Astrometric Radio Sources (OCARS; Malkin 2016ARep...60..996M) redshift at the Apache Point Observatory (APO) 3.5m telescope and/or at Gemini North. We conducted observations on the 3.5m telescope at Apache Point Observatory with the Dual Imaging Spectrograph (DIS) from 2015 April 18 to 2016 June 30. We chose two objects for additional observations with the Gemini Multi-Object Spectrograph-North (GMOS-N) at Gemini North Observatory. 2021+317 was observed on 2016 June 26 and 28, while 0420+417 was observed on 2016 November 8 and 26. We also observed 42 radio sources with the Very Long Baseline Array (VLBA) in the X-band (3.6cm/8.3GHz). Our targets had all been previously observed by VLBI. Our VLBA observations were conducted in two campaigns from 2015 September to 2016 January and 2016 October to November. The final extragalactic proper motion catalog (created primarily from archival Goddard VLBI data, with redshifts obtained from OCARS) contains 713 proper motions with average uncertainties of 24µas/yr. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 99 27 Optical redshifts measured at Apache Point Observatory/Gemini North table2.dat 97 40 Proper motions measured from VLBA astrometry table6.dat 138 713 The VLBA Extragalactic Proper Motion Catalog fig1/* 0 49 *Calibrated, one-dimensional spectra in FITS format obtained from APO fig2/* 0 2 *Flux calibrated spectra in FITS format obtained from Gemini North
Note on fig1/*: All spectra are smoothed by a 3 Angstrom wide boxcar. Some of the spectra lack flux calibration. In the spectra without flux calibration, there is a large dip at ∼5500 Angstroms due to the sensitivity falloff at the edges of the red and blue CCDs. For objects where only the red half of the spectrum is available, the blue continuum was not significantly detected and therefore not included. Note on fig2/*: Jumps in the continua are not real and are due to inexact flux calibration. Several sky absorption features, cosmic rays, and artifacts from the chip gaps are marked in the plots. The night sky absorption feature at ∼7600 Angstroms is also visible in both spectra.
See also: I/251 : VLBI International Celestial Reference Frame (ICRF) (Ma+, 1997) I/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009) VI/137 : GaiaSimu Universe Model Snapshot (Robin+, 2012) V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015) I/337 : Gaia DR1 (Gaia Collaboration, 2016) VII/280 : The Million Quasars (Milliquas) catalog (V5.2) (Flesch, 2017) J/A+A/375/661 : Stability of VLBI reference frame (Gontier+, 2001) J/ApJ/626/95 : Gamma-ray blazar candidates (Sowards-Emmerd+, 2005) J/A+A/493/317 : Radio source selection for the ICRF (Lambert+, 2009) J/A+A/529/A91 : Proper motions of 555 quasars from VLBI (Titov+, 2011) J/ApJ/764/135 : Spectroscopic redshifts of BL Lac objects (Shaw+, 2013) J/MNRAS/430/2633 : The epoch ICRF (Xu+, 2013) J/A+A/559/A95 : Fitted proper motions for the DR solution (Titov+, 2013) J/MNRAS/442/3329 : Rotation measures of 2642 quasars (Xu+, 2014) J/ApJS/215/14 : WISE cand. γ-ray blazar radio sources (D'Abrusco+, 2014) : Pulkovo VLBI analysis center Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Name IVS name (HHMM+DDd; B1950) (1) 10- 13 F4.1 mag mag [15/20.7]? Magnitude of the object from OCARS in Filt 15 A1 --- Filt The optical filter in which the magnitude was measured 17- 22 F6.4 --- z [0.1/2.9]? Redshift of the object if a measurement was possible 24- 29 F6.4 --- e_z [0.0007/0.04]? z uncertainty (2) 30 A1 --- f_z Flag on z (3) 32- 37 A6 --- Obs The observatory where the object was observed (4) 39- 56 A18 --- File1 Name of the fits file (APO red spectrum) in subdirectory fig1 58- 75 A18 --- File2 Name of the fits file (APO blue spectrum) in subdirectory fig1 77- 99 A23 --- File3 Name of the fits file (Gemini spectrum) in subdirectory fig2
Note (1): 2225+033 is a misprint for 2225+003; table corrected at CDS. Note (2): For all of our redshift observations, we also include the associated uncertainty based on the scatter in the line identifications. Note (3): Flag as follows: a = From Shaw et al. (2013, J/ApJ/764/135). b = From Sowards-Emmerd et al. (2005, J/ApJ/626/95). G = only Galactic (z=0) lines were detected, even though we expect all catalog objects to be extragalactic. We were unable to measure optical redshifts for these extragalactic radio sources. Note (4): Both objects observed at Gemini were first observed at APO.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Name Object name 10- 11 I2 h RAh Hour of right ascension (J2000) (1) 13- 14 I2 min RAm Minute of right ascension (J2000) (1) 16- 25 F10.7 s RAs Second of right ascension (J2000) (1) 27- 30 F4.1 us e_RAs [0.2/45] Right ascension uncertainty in µs 32 A1 --- DE- Sign of declination (J2000) (1) 33- 34 I2 deg DEd Degree of declination (J2000) (1) 36- 37 I2 arcmin DEm Arcminute of declination (J2000) (1) 39- 48 F10.7 arcsec DEs Arcsecond of declination (J2000) (1) 50- 54 F5.1 uas e_DEs [2/273] Declination uncertainty in µas 56- 61 F6.1 uas/yr pmRA [-491/71] Proper motion along RA (µα) 63- 67 F5.1 uas/yr e_pmRA [2/207] pmRA uncertainty 69- 74 F6.1 uas/yr pmDE [-52/1329] Proper motion along DEC (µδ) 76- 80 F5.1 uas/yr e_pmDE [2/962] pmDE uncertainty 82- 89 A8 --- Ref Phase references 91- 97 F7.1 d MJD [57282/57700] Average Modified Julian Date of the two observation epochs
Note (1): J2000 average positions derived from the two epochs of CLEANed VLBA images.
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Name Name of the object 10- 11 I2 h RAh Hour of Right Ascension (J2000) (1) 13- 14 I2 min RAm Minute of Right Ascension (J2000) (1) 16- 24 F9.6 s RAs Second of Right Ascension (J2000) (1) 26- 31 F6.3 ms e_RAs [0/14] The 1σ uncertainty in RAs (1) 33 A1 --- DE- Sign of the Declination (J2000) (1) 34- 35 I2 deg DEd Degree of Declination (J2000) (1) 37- 38 I2 arcmin DEm Arcminute of Declination (J2000) (1) 40- 48 F9.6 arcsec DEs Arcsecond of Declination (J2000) (1) 50- 55 F6.2 mas e_DEs [0/207] The 1σ uncertainty in DEs (1) 57- 64 F8.2 uarcsec/yr pmRA [-1360/401] Proper motion in RA 66- 72 F7.2 uarcsec/yr e_pmRA [0.3/1928] The 1σ uncertainty in pmRA 74- 77 I4 --- o_pmRA [2/3797] Number of epochs used to get pmRA 79- 83 F5.1 --- chi2a [0/254]? Reduced chi-squared statistic for pmRA 85- 91 F7.2 uarcsec/yr pmDE [-704/1329] Proper motion in Dec 93- 99 F7.2 uarcsec/yr e_pmDE [0.4/1717] The 1σ uncertainty in pmDE 101-104 I4 --- o_pmDE [2/3797] Number of epochs used to get pmDE 106-110 F5.1 --- chi2d [0.2/315]? Reduced chi-squared statistic for pmDE 112-115 F4.1 yr Length [6.4/27.2] Number of years (2) 117-123 F7.1 d MJD Last observation Modified Julian Date (1) 125 A1 --- Flag New VLBA position measurement flag (3) 127-130 F4.2 --- z [0/4.8]? Redshift; blank=no measurement 132 A1 --- f_z [a-e] Flag on z (4) 134-138 A5 --- r_z Source for z (5)
Note (1): Measured from the most recent VLBA observing epoch. Note (2): Used to measure the proper motion. Note (3): * = a new VLBA position measurement was added by the authors before calculating the proper motions. Note (4): Flag obtained from the OCARS catalog (Malkin 2016ARep...60..996M) as follows: a = photometric; b = unreliable or doubtful identification; c = substantially different estimates in the literature; d = lower limit; e = imaging. Note (5): Either the OCARS catalog, NED, or APO (measured by the authors at Apache Point Observatory).
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Dec-2017
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