Milky Way Tomography with SDSSsdss2008.uchicago.edu/depot/juric-mario.pdf · Mario Juric , Saturday, August 16th, 2008. “SDSS International Symposium: From

Dissecting the Milky Way with SDSSMario Juric <mjuric@ ias.edu>, Saturday, August 16th, 2008.

“ SDSS International Symposium: From Asteroids to Cosmology” , Chicago

DissectingtheMilkyWay withSDSSMapping Galactic density, metallicity and kinematics.

MarioJuric , InstituteforAdvancedStudy Princeton

withZeljko Ivezic, , , … Nick Bond Branimir Sesar Robert Lupton andtheSDSS Collaboration

1 . Directly measure the distribution of stellar , , number density kinematics andmetallicity in a representative volume of the

.Galaxy

2 . [ ] , , Use the distributions to learn about Gg alaxy formation evolution interactions , .with environment and the distribution of darkmatter

Dissecting the Milky Way Program :: Goals

©(~r ;~v; [F e=H ])

Dissecting the Milky Way with SDSSMario Juric <mjuric@ ias.edu> , Saturday, August 16th, 2008.


Mapping the Milky Way with SDSS

:Input : 1SDSS photometry ~ 50 M ugriz , observations of stars

8000deg2, 50 ~ M stars >200 - x larger area than pre SDSS samples

:Data Reduction :Keeping it simple and clean Model-free , mapping first

modeling second : , + Metallicity ug gr calibration fromSDSS spectra : ( )Distances u gri + ( <21 .5 )photometric parallax relation r / : + , +ProperMotions Velocities SDSS POSS SDSS SDSS

:Output Distribution of stars in (X,Y,Z,Mr,[Fe/H],YlY £ b) space



Visualizing the HypercubeR

Z

X

Y

X

YZ

R



:DissectingtheMilky WayDensity

Juric et al. (2008)



: < 3 ( , )Density Maps D kpc Late K M stars

: - Right X Y maps of number density distribution

=+/-900 +/-600 at Z and pcfor1 < - < 1 .1 ( 1 -r i stars ~M

2 )M “ - ” Face on view of the

Galaxy

: Bottom Density contours around the axis of

symmetry



: > 3 ( , , )Density Maps D kpc F G early K

: - Right X Y maps of number density distribution

=5 , 4 , 1 2 , 1 0 at Z kpc for.1 < - < .1 5 ( / r i stars ~F G

)SpT

S ignatures ofoverdensities



- ( - )Edge on View R Z density distribution

: Right e(R, Z) density (“ - distribution edge on

”)view 1 ( ; kpc bottom right M

) 2 0 ( dwarfs to ~ kpc top; ) left F dwarfs scales

Map Analysis Summary: Smooth, axisymmetric,

background consistent with exponentials (disk) and power laws (halo)

Overlayed by localized overdensities: clumps and streams

Most major overdensities at D > 3kpc



Siegel et al. 2002, Figure 1

The SDSS Galactic Density Model

Best fit exponential disk, with all biases accounted for

Comparison with prior measurements

Juric et al. (2008)



: The Value of SDSS I Breaking the Degeneracy

H1=260pc

H2=1000pc =4%f

H1=245pc

H2=750pc =13%f

:NGP line of sight only

Two substantially different fits describe

the NGP line of sight equally well

A number of prior -studies are NGP

only Wide area survey is

necessary to break the degeneracy

, In our case the fitalways converged to

the same minimum( or did not converge

)at all



: / The Value of SDSS II Seeing Avoiding theSubstructure

, If left unremoved overdensities will influence the fits The only way to knowwhere they are is to have a wide area

(survey “Pencil beams considered harmful”) ( … …Overdensity removal is an iterative process Fit check

… … …) remove fit check requiring considerable effort andcare

See also: Heidi Newberg’s talk



:DissectingtheMilky WayMetallicity

Ivezic et al. (2008)



: Photometric Metallicity Calibration

Stellar parameters fromSEGUE ( 2 8 0 ,0 00 ; , spectra ~ stars Beers et al , .)Allende Prieto et al Lee et al

( - , - ) u g g r colors strongly correlate with spectroscopic metallicity and

temperature

:Precision and accuracy 1 0 0Teff ~ K [ / ] 0 .0 9 ( ), Fe H ~ dex calibration per

star estimate bound by ( 0 .2 , photometry ~ dex better than

!)spectroscopic determination

See also: Tim Beers’ 2:55pm talk



Metallicity Map

Metallicity does not follow density Features in density space features inmetallicity↔

space




Vertical Variation ofMetallicit y Distribution

/ Clear disk haloseparation



Halo Metallicity Distribution

:Halo Model Well described by

a Gaussian metallicity

distribution e = -1.46 dex e = 0.3 dex Mean and the

dispersion independent of

position



DiskMetallicity Distribution

Detection ofmetallicitygradient

Diskmetallicity:distribution

Approximately fitted with -a gaussian with Z

, dependentmeane([Fe/H]) ~ G(e D, e =0.16)

Best fit by an asymmetric distribution with a slight

- low metallicity tail

¹ D (Z ) = ¹ 1 + ¢ ¹ exp(¡ jZ j=H ¹ ) dexH ¹ = 1:0kpc; ¹ 1 = ¡ 0:78; ¢ ¹ = 0:35



Metallicity of the Monoceros Stream

Monoceros stream( . 2 0 03 ) Newberg et al

clearly distinct in metallicity space

Metal poor compared , to the disk butmetal

rich compared to the ([ / ] = -0 .9 6 halo Fe H

)dex

Strong evidence for external origin

( , merger remnant as opposed to disk flaring

)or excitation

Alternative view: see Heather Morrison’s

11:35am talk


Disk only Disk w. Mon.



:DissectingtheMilky WayKinematics

Ivezic et al. (2008), Bond et al., in prep.



: Completing the Census ProperMotions

(2 0 04 ) Munn et al catalog Recalibrated POSS astrometry using galaxies :Errors

: 3 / < 1 8 , 6 / =2 0Random mas yr to r mas yr at r : 0 .3 / ( 1 0 0 )Systematic ~ mas yr using k quasars

6Publicly available as part ofDR 30 , Over Mmain sequence stars entire SDSSfootprint

6 (DR sample Dmax ~ 10 kpc) Measure the propermotions towards the NGP :Easy to interpret

ve =e£ b×D is the rotational velocity

~1955 (POSS)

~2002(SDSS)



/ , Halo Disk Components Disk Rotational VelocityLag

: Top panels small dots , are individual stars

large symbols are the median values

: Top left disk stars show clear rotational

velocity lag : Top right halo stars

ve 220 /~ kms, no significant rotation

: Bottom left disk velocity lag not linear

: Bottom right halo velocity dispersion increase consistent

with being due to photometric errors only

HaloHalo

Disk

HaloDisk



- ?Two componentDisk

:Left - Expected rotational velocity metallicity correlation 1 < < 1 .25 ( at kpc Z kpc for a simple gaussian velocity

)model :Right - Observedmetallicity rotational velocitycorrelation

, In general we were unable to find a bimodality in ( , distribution of any property we looked at velocities

. , ).vel dispersions metallicity




Detailedmaps of velocity distribution Bond et al., in preparation



Features in velocity space Bond et al., in preparation

Dehnen (1998)moving groups



…Reduced ProperMotion Diagrams Juric et al., in preparation

Halo

( 200)Local haloLF x

Left: Data

Right: Model (J08 disk/halo model + Disk LF)

Disk

WDs



… Luminosity Functions Juric et al., in preparation

Local diskLF ( 200)Local haloLF x

See also: Independent disk K/M-dwarf LF measurement by Bochanski et al. (4:30pm talk, today)



: - Instead of a Summary SDSS Long termLegacy

+ / : / / SDSS I II SEGUE measurements of density metallicity velocity 2 - distribution with orders ofmagnitude larger samples than pre SDSS

( . ., 1 0% )studies e g in ~ of Galactic disk volume Ahead of theory Setting a benchmark for simulations for the years to come

/ Clumps streams are an integral part , ofMilky Way structure both halo .and the disk

- Methods and codes directly applicable to future wide field surveys( + , , , )SkyMapper RAVE PanSTARRS DES LSST

“The Milky Way Tomography with SDSS. I. Stellar Number Density Distribution”, Juric et al., 2008, ApJ , 673, 864

“The Milky Way Tomography with SDSS. II. Stellar Metallicity”, Ivezic et al., ApJ , in press (arXiv:0804.3850)

“Candidate Wide Binaries in the Sloan Digital Sky Survey”, Sesar et al., ApJ , subm.“The Milky Way Tomography with SDSS. III. Stellar Kinematics”, Bond et al., in prep.“The Luminosity Function of Galactic Disk and Halo”, Juric et al., in prep.

Documents

Milky Way Tomography with SDSSsdss2008.uchicago.edu/depot/juric-mario.pdf · Mario Juric , Saturday, August 16th, 2008. “SDSS International Symposium: From