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