Sydney observatory Galactic survey

Abstract

Context. First Epoch astrometric and radiometric information of a survey in the optical along the Galactic fourth quadrant is archived for further analysis in the time-domain. Aims. A photographic survey of 1.9 × 10 6 stars down to B-magnitude 14 ± 0.5 along the galactic meridian l = (330 ± 5)• , −64• ≤ b ≤ −7• and along the galactic equator 272• , is provided from century old astrographic plates of Sydney Observatory. Stellar candidates to investigate the Galaxy disk kinematics up to a distance of 1 kpc from the Sun are tentatively selected. Methods. The early data are combined with late epoch observations into a set of 4.8 × 10 5 stars with significant proper motion µ ≥ 0.005 yr −1 and approximate color B − V. The selection effects and the kinematical bias on the stellar system are investigated. F-G stellar candidates with a mean transverse velocity dispersion of 45 km s −1 are suggested. Results. The spin rate of 1 2• pc −1 of the velocity ellipsoid along its long axis is observed over half a thickness of 25 pc of the galactic disk for stars at an estimated distance D ≤ 300 pc from the Sun. Conclusions. A catalogue of 4.8 × 10 5 stars is provided for further investigation of the galactic disk heating by transient spiral wave or by GMC encounter.Key words. surveys -stars: kinematics Retrospective of early astrographic surveysFirst epoch observations used in the proper motion (p.m.) determination of faint stars observed in the Tycho-2 catalogue are based on short exposure plates observed for the Astrographic Catalog (AC) at the beginning of the 20th century over a field of view of 2• × 2 • for each of the 4 × 10 4 AC plates at a scale of 1 mm −1 , proving that photographic observations from the past were indeed durable even at the time of space astrometry (Urban et al. 1998). In order to check the quality of the old plates with a fast measuring machine like APM, used for instance to scan large Schmidt plates (Evans 1992), a set of 104 short exposure plates dating from the late 19th century was selected from the plate vault of Sydney Observatory, archived at Macquarie University.The double exposure technique used in the astrophotographic survey is shown in Fig. 1: stars are identified in the image inventory of a plate scanned with APM by the combination of double images. Along with the x, y plate mean coordinates (in mm) and their errors ∆x, ∆y (in microns), an indication of short term magnitude variability ∆m, is also computed for each star: this information is not available from the AC measurements but is usable to search for flare stars (Fresneau et al. 2001). The (ξ, η) plate coordinates (in arcmin) for the Tycho-2 stars The quality of the best linear unbiased estimation of the set of 12 plate constants (A, B, C, D, E, F and A , B , C , D , E , F ) after the weighted least squares fit is measured by the rms error σ T between the computed and observed equatorial coordinates of the set of Tycho-2 stars (a couple of hundreds per 2 • × 2 • field of view). The same stars are also used to derive a calibrat...

Spectrophotometric characterization of high proper motion sources fromWISE

“…Other two attempts to measure the distance from photometry are available from Fresneau et al (2007) and Pickles & Depagne (2010) they obtained 56 pc (no error bars) and 77 +50 −22 pc respectively. Our best SED fit yields 4700 K, in agreement with Ammons et al (2006), but our best spectrum fit is between K0V-K2V.…”

A variability sample catalogue selected from the Sydney Observatory Galactic Survey

“…7 the numbers of foreground stars (those with μ ≥ 0.02 yr −1 ) and background stars (μ ≤ 0.02 yr −1 ) as a function of the (B − V) 0 colour derived using our calibration (B − V) 0 = 0.26 + 0.82(m b −V). We note that Fresneau et al (2007) found no colour effect when deriving p.m. at the level of 0.002 yr −1 by comparing century-old astrographic observations and second-epoch Schmidt telescope ones used in the GSC 1.2 construction. While that result was based on Tycho-2 stars (Hog et al 2000) brighter than m b = 12 (Fresneau et al 2005), we presume it is valid for even fainter stars, and hence no severe systematic effect has been introduced into the data by our proper motion determinations.…”

“…The effect of the los-velocity on w depends on sin b, and our stellar sample along the galactic meridian verifies |b| ≤ 64 • , indicating that the los-velocity needs to be on the order of 75 km s −1 to have an effect on w of 50 km s −1 . We also restrict the analysis to stars with z ≤ 100 pc (a sample of 29 × 10 3 VSC stars), where a thin disk crossing effect has previously been detected (Fresneau et al 2007). Figure 14 shows the trends of σ 1 , σ 2 , and σ 3 as a function of dynamical time t. We observe that, while the σ 3 relation is relatively flat, σ 1 and σ 2 show the same upturn for t ≤ 1 Myr.…”

“…The catalog is available on line through the VizieR system 1 with catalogue identifications J/AJ/130/2701 for the section along the galactic equator and J/A+A/469/1221 for the section along the Data files are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/503/1023 1 http://vizier.u-strasbg.fr/viz-bin/VizieR galactic meridian. Additional details about the SOGS are given in Fresneau et al (2005Fresneau et al ( , 2007.…”

“…Such an effect is suggested by the observed changes in frequency of magnetically active stars with height above the galactic plane (West et al 2006(West et al , 2008. We would like to connect, in the SOGS data, the stellar chromospheric activity in the optical with the orientation of the velocity ellipse of stellar systems that we determined as a function of the altitude over the galactic plane (Fresneau et al 2007). Such a correlation might indicate a star's passage through the dense ISM of the thin disk has an effect on stellar chromospheric activity (seen in the optical), but other causes of chromospheric activity are perhaps more likely (e.g.…”