Stellar archaeology in the Milky Way Halo Variable stars and stellar populations in the new Milky Way satellites discovered by the SDSS Variable stars

Stellar archaeology Stellar archaeology in the Milky Way Haloin the Milky Way Halo

Variable stars and stellar populations in the Variable stars and stellar populations in the new Milky Way satellites discovered by the new Milky Way satellites discovered by the

SDSSSDSS

Ilaria Musella

INAF – Osservatorio Astronomico di Capodimonte Napoli

Clementini , Dall’Ora, Marconi, Ripepi, Greco, Di Clementini , Dall’Ora, Marconi, Ripepi, Greco, Di Fabrizio, Fabrizio,

Kinemuchi, Smith, Rodgers, Kuehn, Beers, Catelan, Kinemuchi, Smith, Rodgers, Kuehn, Beers, Catelan, Pritzl Pritzl

-CDM hierarchical scenario ---> dSphs as Building Blocks of

larger galaxies (such as the MW)

We should see remnants of this process

MW halo properties homogeneous with MW dSph satellites

-CDM hierarchical scenario ---> dSphs as Building Blocks of

larger galaxies (such as the MW)

We should see remnants of this process

MW halo properties homogeneous with MW dSph satellites

Galaxy formation mechanismsGalaxy formation mechanisms

Sgr dSph

CMa dSph/overdensity (debated)

Substructures in the M31 halo

Sgr dSph

CMa dSph/overdensity (debated)

Substructures in the M31 halo

Dwarf Spheroidal galaxies

Old dSph’s

• Draco• Ursa Minor• Fornax• Carina• Sculptor• LeoI• LeoII• Sextans

• Sagittarius• Canis Major

The impact of SDSS has been dramatic:

16 new objects have been discovered

in the last years.

The most numerous in the LG The most dark matter dominated Complex and unique SFH Metallicity (chemistry) Problem Variable Star Problem Missing Satellite Problem (MSP)

new objects• Bootes • Bootes III• Ursa Major• Ursa Major II• Canes Venatici I• Canes Venatici II• Coma• Leo IV• Leo T• Hercules

• Bootes II• Willman 1• Segue 1• Segue 2

• Koposov I• Koposov II




MW Inner 100 kpc

Milky Way satellites

Leo V

Boo II

Boo III

Old dSph’sGCs

Dimensions -->Dimensions -->

Lu

min

osit

y

-->

Lu

min

osit

y

-->

adapted from Belokurov et al. 2007adapted from Belokurov et al. 2007

BooIBooIII

K1K1

K2K2

And And XIIXII

And And XIIIXIII

And And XIXI

SDSS GCs

And And XVXV And And

XVIXVI

BooIII

Segue 2

SDSS dSph’s







GCs

dSph’s

luminosity and luminosity and mass limit of mass limit of

galaxy galaxy formation? formation?

……. or. ortidally disruptedtidally disrupted

remnants?remnants?

Fainter than previously known dSph’s: V > 28 mag/arcsec-2

Properties intermediate between GCs and dSph’s (M(Mv v ~ -7 mag, r~ -7 mag, rh h ≥ 100 pc)≥ 100 pc)

Darkest known stellar systems (M/L from Darkest known stellar systems (M/L from ~~35 35 to to ~~1000)1000)

Metal poor (…as metal poor as stars in the MW halo)

Irregular shape distorted tidally interacting

Host an ancient population (t ~ 13 gyr)~ 13 gyr) RR Lyrae

Satellite deficit reduced to a factor 4 (Simon & Satellite deficit reduced to a factor 4 (Simon & Geha, 2007)Geha, 2007)

New faint dwarf satellites:“building blocks” of the MW halo?

Looking for the “building blocks” of the MW Looking for the “building blocks” of the MW halohaloIn the MW, most of the GCs

with an RR population sharply divide into two distinct groups, based on <Pab> (Oosterhoff 1939)

Oo I <Pab> = 0.55 dOoII <Pab> = 0.65 d

In the MW, most of the GCs with an RR population sharply divide into two distinct groups, based on <Pab> (Oosterhoff 1939)

Oo I <Pab> = 0.55 dOoII <Pab> = 0.65 d

And outside the Milky Way?And the old dSphs?

And outside the Milky Way?And the old dSphs?

Oo I

Gap

Oo II Oo II

Oo I

Gap

adapted from Catelan, Greco et al. 2009, in preparationadapted from Catelan, Greco et al. 2009, in preparation

Our projects:Which is the Oostehoff type of SDSS faint Which is the Oostehoff type of SDSS faint

dSphs? dSphs?

Telescope time: 1.5m Loiano, 1.8m Lowell, 2.2m ESO, WIRO, INT, TNG,SOAR, WHT

We use time-series photometry for the listed We use time-series photometry for the listed galaxy to study the properties of their variable galaxy to study the properties of their variable starsstars

In progress

• UMa II• Hercules • Bootes II

To observe

• Bootes III

Variable stars in the new SDSS dSph’s

Bootes IDall’Ora et al, 2006, ApJL

Canes Venatici IKuehn et al. 2007, ApJL

Canes Venatici IIGreco et al. 2008, ApJL

ComaMusella et al. 2009, ApJL

Leo IV Moretti et al., 2009, accepted, ApJL

Hercules in progress

Bootes II in progress

Uma II in progress

11 RR Lyrae stars: •5 RRab’s, 5 RRc’s, •1 RRd, 1 LPV

<Pab> =0.69 d<Pc> =0.37 d

OoII

Variable Stars

•RRab (in red)

•RRc (in blue)

•Candidate AC (in purple)

•Variables without periods (in cyan)

Variable Stars

•RRab (in red)

•RRc (in blue)

•Candidate AC (in purple)

•Variables without periods (in cyan)

4 Age Components

• 13 Gyr (red line)

• 5 Gyr (blue line)

• 1.5 Gyr (green line)

• 0.6 Gyr (black line)

4 Age Components

• 13 Gyr (red line)

• 5 Gyr (blue line)

• 1.5 Gyr (green line)

• 0.6 Gyr (black line)

[Fe/H] = -2.1/-2.0

(ZW84/CG97)

[Fe/H] = -2.1/-2.0

(ZW84/CG97)









Uma II in progress

•RRab’s

•RRc •AC

23 RR Lyrae stars: •18 RRab’s, 5 RRc’s•3AC•58 candidate variable (RR Lyrae?)

<Pab> =0.60 d<Pc> =0.38 d

Oosterhoff intermediate

•RRab

•RRc









Uma II in progress __ M15 _ _ M3 __ M15 _ _ M3

2 RR Lyrae stars: •1 RRab, 1 RRc •Several candidate BSSs

<Pab> =0.74 d<Pc> =0.36 d

OoII

__ M68 _ _ M3 __ M68 _ _ M3









Uma II in progress

2 RR Lyrae stars: •V1= RRab, V2= RRc, •V3=short period variable

<Pab> =0.67 d<Pc> =0.32 d

OoII

3 RR Lyrae stars: • 3 RRab’s• 1 SX Phoenicis (V4)

<Pab> =0.66 d

OoII

__ M15 __ M15









Uma II in progress

A Pair with Leo V? (Koch et al. 2008)

A Pair with Leo V? (Koch et al. 2008)









Uma II in progress









Uma II in progress









Uma II in progress

1 Rrab

<Pab> =0.66 d

OoII

Summary:The SDSS new dSph’s in the Oosterhoff

plane• Bootes • Canes Venatici I• Canes Venatici II• Coma• LeoIV• UMa II

Oo IIOo IntermediateOo IIOo IIOo IIOo II

15 RR Lyrae stars48 “ 2 “ 2 “ 2 “ 1 “

The SDSS new dSph’s in the Oosterhoff plane

Oo II

Gap

Oo I

Thank youThank you

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Stellar archaeology in the Milky Way Halo Variable stars and stellar populations in the new Milky Way satellites discovered by the SDSS Variable stars