iau symp 248: october, 2007proper-motion catalogs1 maintenance and densification: an overview of...

IAU Symp 248: October, 2007

Proper-Motion Catalogs 1

Maintenance and Densification:

An Overview of Current Proper-Motion Catalogs

- T. M. Girard (Yale University)



Importance of proper-motion surveys

Maintain the positional accuracy of an astrometric catalog with time

Provide a means of distance/luminosity estimation and thus discrimination between various classes of objects, (e.g., reduced proper motions)

Provide transverse velocity components, enabling study of the kinematics and equilibrium structure of various Galactic components, (i.e., thin disk, thick disk, halo)



Maintenance: Current astrometric catalogs...



Primary reference catalogs...

Hipparcos (ESA 1997): defines ICRS in the optical► 120,000 objects → ~3 /deg2, V < 7.5 ► @1991 typical pos = 1 mas; @2007 pos = 15 mas

Tycho-2 (Høg et al. 2000): Hipparcos satellite starmapper & 1st-epoch ground-based positions

► 2.5x106 objects → 25 to 150 /deg2, V < 11.5► @2007 typical pos = 25 to 100 mas, depending on magnitude

UCAC2 (Zacharias et al. 2004): USNO CCD Astrograph Catalog & 1st-epoch astrograph data/catalogs

► 48x106 objects, -90°< <+40° to +52°; (soon to be all-sky, UCAC3)► RUCAC < 16, ~85% complete; (to be improved, UCAC3)

► pos = 30 to 70 mas



Currently Available Proper-Motion Catalogs

Catalog N Area Dens Vc(r/a)[mas/

yr]Source Material / Notes

Hipparcos 118K

all-sky 3 7.5 0.9 /0.25

fully satellite-based

Tycho2 2.5M all-sky 62 11.5 2.5 / ? Hipparcos starmapper + ground-based cats

UCAC2

[ UCAC3 ]

48M

[ ? ]

<+45°

[ all-sky ]

1.6K 16.5 ~3 /~3 modern CCD + ground-based plate-catalogs

[ available in the first half of 2008 ]

“The Big Three”

Some

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Currently Available Proper-Motion Catalogs (cont)

Catalog N Area Dens Vc

(r/a)[mas/


USNO-B1.0(Monet et al. 2003 & www)

1046M

all-sky 25K ~21 ~5 / - POSS1, POSS2, ESO, AAO, SERC

GSC II (GSC2.3)(5.1.3 in ~45 min, & www)

945M all-sky 23K ~21†

?? POSS1, POSS2, ESO, AAO, SERC

SuperCOSMOS Sky Survey(Hambly et al. 2001, & www)

>1000M

<+3° >46K

?

~21 10 – 50 / <1 ?

POSS1, POSS2, UKST, ESO

APM Cambridge 166M NGP cap

15000 sq

11K ?? --- POSS1, UKST

APS Luyten P.-M. Project

?? ?? ?? ?? ?? POSS1, POSS2, Luyten

Derivative catalogsSDSS-USNOB1 (Munn et al. 2004)

~8M 2099 sq

3.8K 19.7 3-3.5/ <0.5

SDSS minus USNOB1

Schmidt survey-based

† from the CDS Description of Catalog I/305: “The GSC2.3 has no magnitude limit.”

Some

<





(r/a)[mas/


NOMAD(www)

1100M

all-sky 27K ~21

1 - 5 / 0.2 - ?

HIPPARCOS+Tycho2+UCAC2+USNOB1


(r/a)[mas/


rNLTT(Salim & Gould 2003)

59K 44% sky

3* ~18

3 - 5 NLTT+POSS1+2MASS

LSPM(Lépine et al. 2005)

122K [ all-sky ]

3* 21 ~5 ? >150 mas/yr, [>100 mas/yr ]DSS’s and SUPERBLINK software (+Tycho2)

Proper-motion threshold

Rank merged

Some

<




Catalog N Area Dens Vc(r/a)[mas/


Astrograph-based proper-motion surveysNPM (NPM1+NPM2)(Hanson et al. 2004)

0.4M >-23° 23 --- ~5 / ~1 astrograph plates with objective grating

SPM3(Girard et al. 2004)[SPM4]

10.7M

~ -40°<<-20°

3700 sq[<-20°]

2.9K 17.5

3-5 /0.4 astrograph plates with objective grating

CdC-basedPM2000 Bordeaux(Ducourant et al. 2006)

2.7M +11°<<+18°

0.5K 15.4

Bordeaux Meridian Circle (M2000) +CdC+AC2000+USNOA2+YS3

CdC-SF1(Vicente et al. 2007)

503K -10.5°<<-2.5°

1080 sq

0.5K 15.1

1.1 – 3 /?

San Fernando CdC+UCAC2commercial flatbed scanner

Other useful surveysSome

<



Detecting WD candidates in SDSS-USNOB1(Kilic et al. 2005)

Reduced Proper Motion

Hg = g + 5log + 5



Detecting WD candidates in SDSS-USNOB1(Harris et al. 2005)



Detecting WD candidates in SuperCOSMOS-RECONS(Finch et al. 2007)



Make certain your ’s are appropriate to the task at hand

The central 2°x2° region of a sample southern-sky SPM field. The vector point diagram (VPD) constructed using proper motions from the USNO-B1 (left panel) is compared to that of the SPM3 (right panel) for stars in common.

Note: The majority of the USNO-B1 proper motion values in this field are 0.



Magnitude Equation – the astrometrist’s bane

SPM (and NPM) plates use objective gratings, producing diffraction image pairs which can be compared to the central-order image to deduce the form of the magnitude equation.

A comparison of proper motions derived from uncorrected SPM blue-plate pairs and yellow-plate pairs indicates a significant magnitude equation is present.

Using the grating images to correct each plate’s individual magnitude equation, the resulting proper motions are largely free of bias.



Velocity shear of the thick disk using SPM3

◄ SPM3 stars within 15° of SGP

’s measure transverse motion ►

2MASS photometry to select preferentially thick-disk giants ►

Ngiants ~ 1200

(Girard et al. 2006)



Velocity shear of the thick disk using SPM3 (cont.)

Proper-motion data:

Thick-disk component shows up well, distinct from the faint, nearby dwarfs that show a much larger dispersion.

↓Transverse Velocities

Assume an absolute magnitude distribution as a function of J-K color to convert J,K, to U,V,d. (Integrate under the assumed magnitude distributions.)




(Somewhat equivalent to separation using reduced proper motion.)

◄ Trim conservatively in U,V to eliminate nearby dwarfs.



Velocity shear of the thick disk using SPM3 (cont.) Density and Velocity profiles:

Over the range 1 < z < 4 kpc the observed sample shows an exponential form in number density and roughly linear forms of mean velocity and velocity dispersion as a function of z.

BUT we must correct for systematic biases; (Malmquist and “Lutz-Kelker”-type).

►Use knowledge of our uncertainties and selection criteria to construct Monte-Carlo simulations and derive the intrinsic Thick-disk parameters:

hz = 783 ±48 pc

dV/dz = -30 ±3 km/s/kpc

dV,U/dz = 9 ±3 km/s/kpc

(and 8 ±6 % halo contamination).

[ Figure Key: U-profiles in black, V in gray ]



Velocity shear of the thick disk using SPM3 (cont.)Equilibrium analysis:

Assume a relaxed population of thick-disk stars in equilibrium within the gravitational potential of the Galaxy →

Jeans equation:

Test five model parameters:

1.Halo potential form; Plummer vs isothermal

2.Velocity-dispersion cross-term (<vRvz>)

3.Thick-disk radial scale-length (hR=3.5 – 5.0 kpc)

4.Form of the pressure term (self-gravitating or not)

5.Thin-disk mass surface density (36 – 48 M/pc2)




Figure. The best-fit model’s intrinsic dispersion profile (dashed curve) is convolved with the sampling statistics and proper-motion errors to produce the ±1σ predicted “observed” profile (gray area). Heavy black curve is the actual observed profile for the SGP sample.



Velocity shear from low-mass dwarfs and SDSS-USNOB1(Bochanski et al. 2007, astro-ph)

► Spectroscopic & proper-motion data for ~7400 K and M dwarfs, (l =105°, b = -62°)

► Well-sampled out to 1 kpc

Bochanski et al. Figure 8. Velocity-dispersion profiles for thick-disk stars (squares) compared to the Besançon model prediction (crosses).



A cautionary word of advice...

Dimitri Pourbaix (2007-10-15)

“Someone’s garbage can be science for others.”

The inverse can also be true!



Your catalog will be misused...

iau symp 248: october, 2007proper-motion catalogs1 maintenance and densification: an overview of...

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