Download (young) stellar systems and populations of our Galaxy

Istituto Nazionale di Astrofisica
Osservatorio Astronomico di Palermo
Stellar systems and
Populations in our Galaxy
G. Micela
on behalf of the stellar group
From (solar) stellar X-ray
emission to the study of
(young) stellar systems and
populations of our Galaxy
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona
The Stellar Coronae
Emission mechanisms
and
Coronal Structures
Coronal Evolution
Young stars in
Open Clusters
and Star Forming Regions
Initial Mass Function
Young stars in the field
Star formation history
in the solar
neighborhood
Interaction with
the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona :
Space Missions
•Skylab (1973): breakthrough, first monitoring
of the X-ray corona
•SMM (1980-1989): flares and fine X-ray
spectroscopy
•Yohkoh (1991-2001): monitoring and
imaging, flare evolution, hot corona
•SoHO (1995 - ): EUV spectroscopy and
imaging
•TRACE (1998 - ): high resolution EUV imaging
•HINODE (2006 - ): high resolution multiband X-ray
imaging and UV spectroscopy
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The solar corona
• Heating mechanisms of the corona
• Diagnostics: Temperature, Emission
Measure, Spatial and thermal structuring
Hinode observation of an active region (Reale et al.,
2007, Science)
Emission
Temperature
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The solar corona: CMEs
• Strong activity
starting from
SoHO-UVCS
spectra (high
energy
component )
– modeling HPC
MHD
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Sun as a star
• Goal: synthesis of the integrated Sun in
order to simulate stellar observations
Synthesis of the Sun in
several conditions
Solar emission measure
distribution integrated in
space and averaged in time
(Argiroffi et al. in
preparation)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Perspectives
• Reinforcing the Hinode collaboration
• Modeling
• Stellar extrapolation
• Involvement in Solar Orbiter (2015)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona
The Stellar Coronae
Emission mechanisms
and
Coronal Structures
Coronal Evolution
Young stars in
Open Clusters
and Star Forming Regions
Initial Mass Function
Young stars in the field
Star formation history
in the solar
neighborhood
Interaction with
the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The stellar coronae:
Nearby field stars
• The Sun has a quiet corona
• Optical and ‘X-ray’ CM diagram of nearby
stars (data from Schmitt et al. 1995 & Schmitt 1997)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The role of rotation
• For a given mass, rotation
determines the X-ray luminosity
level
• Pluses: field stars
• Squares: cluster stars
(From Pizzolato et al. 2003)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona
The Stellar Coronae
Emission mechanisms
and
Coronal Structures
Coronal Evolution
Young stars in
Open Clusters
and Star Forming Regions
Initial Mass Function
Young stars in the field
Star formation history
in the solar
neighborhood
Interaction with
the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Emission
mechanisms and
coronal
structures
Main tool: the spectrum
• Emission Measure
• Temperature
• Density
• Chemical abundances
AD Leo Chandra/LETG spectrum
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Emission mechanisms and
coronal structures
• Emission Measure reconstruction for several
stars:
Active stars are
hotter than quiet
stars
(Scelsi et al. 2006)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Emission mechanisms and
coronal structures
• Flares are very
common in active
and young stars
Flare frequency of dM stars in
Orion (Caramazza et al. 2007)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Emission mechanisms and
coronal structures
• Variability (flares,
rotational modulation,
eclipses) may
constrain the
geometry of emitting
structures.
• Modeling of a flare in
Prox Cen (Reale et al.
2007)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
LONG TERM VARIABILITY
• Identification of
the X-ray cycle of
the moderately
active star HD
81809 (Favata et
al. in preparation)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Perspectives
• Continuous monitoring with present
instruments Next years
• Relations with optical activity (CoRoT)
Next years
• Hard X-rays, non-thermal emission
(Simbol-X) 2013
• 1eV resolution spectra (XEUS) >2018
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona
The Stellar Coronae
Emission mechanisms
and
Coronal Structures
Coronal Evolution
Young stars in
Open Clusters
and Star Forming Regions
Initial Mass Function
Young stars in the field
Star formation history
in the solar
neighborhood
Interaction with
the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
X-ray luminosity evolution
Lx depends on rotation
Rotation evolves with age  Lx evolves with age
X-ray luminosity
functions for several
clusters of different
ages
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
X-ray luminosity evolution
X-ray luminosity and
coronal temperature
decrease with age during
the main sequence lifetime
(Micela 2003)
o Sun during the cycle
● stars from the Sun
in time project of
Ribas et al. (2005)
―clusters from
previous slide
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona
The Stellar Coronae
Emission mechanisms
and
Coronal Structures
Coronal Evolution
Young stars in
Open Clusters
and Star Forming Regions
Initial Mass Function
Young stars in the field
Star formation history
in the solar
neighborhood
Interaction with
the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Star Forming Regions
X-rays allow the discovery of very young stars
without disks
• Stellar populations ( embedded objects 
starburst galaxies)
• “Unbiased” Initial mass function
• Study of disk frequency and evolution 
angular momentum evolution and formation
of planetary systems ( the early Sun)
• Irradiation in the circumstellar environment
( disk evolution and formation of protoplanetary system)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Star Formation regions:Orion
Orion Nebula
Cluster:
A laboratory to
study the role of
high energy
radiation during
the stellar
formation
X-rays penetrate very deep in the interstellar medium and are
very efficient in identifying embedded young stars
COUP Project
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Other Large Projects on SFRs
• 19 XMM/Newton fields pointed on
formation sites in Taurus (XEST, PI:
Guedel)
• 7 XMM/Newton fields pointed around
ONC (PI: Wolk)
• 500 ksec XMM/Newton pointing on a
core of ρ Oph (DROXO, PI: Sciortino)
• 450 ksec Chandra on NGC 1893 (PI:
Micela)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Membership e mass function in several SFRs
Star formation in different physical environments
NGC 6530: Chandra observation (60 ksec)
(Prisinzano et al. 2005)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Next step: toward the edge of
the Galaxy: The Chandra/Spitzer
observation of NGC 1893
14 kpc from the Galactic
Center.
~300 stars with IR excess
~1000 X-ray sources The aim is to detect member
stars down to 0.8 Msun
Work in progress!!
Caramazza et al.
in preparation
The IMF in the outer Galaxy:
the influence on the
environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Disk frequency in a massive star
forming region: NGC 6611
• Age 1-3 Myr
• Dist. 1750pc
• 56 stars < B5
(with inhomogeneous
distribution)
• >1000 members
(in the red area)
• ~25% disk
Spitzer image at 4.5 μ
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
NGC 6611: disk evaporation
induced by nearby massive stars
Fraction of disks stars as
function of the UV flux
emitted from the massive
stars in the region:
Disks tend to evaporate
near massive stars
(Guarcello et al. 2007)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
PERSPECTIVES
• Other environments (Arches...)
• Old clusters
• Ground based observations (accretion,
lithium, rotation, variability..., XSHOOTER
2009)
• Hard non-thermal emission (SimbolX 2013)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona
The Stellar Coronae
Emission mechanisms
and
Coronal Structures
Coronal Evolution
Young stars in
Open Clusters
and Star Forming Regions
Initial Mass Function
Young stars in the field
Star formation history
in the solar
neighborhood
Interaction with
the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The young population in the
solar neighborhood
• Lx decreases of 3 orders of magnitude
during the main sequence
• We observe young stars at much larger
distances than old stars => Young stars
dominate shallow stellar X-ray samples
while old stars dominate deep high latitude
stellar X-ray samples.
• Comparisons with stellar galactic models
allow us to derive spatial distributions of
stellar populations
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
An intermediate survey: the NEP Rosat
All Sky Survey: Comparison with the
observations (Micela et al. 2007)
• A significant
excess of yellow
stars is present
• Young population
identified through
optical follow-up
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Chandra and XMM/Newton
contribution
• The high sensitivity allows us to go
beyond the scale heights of the
youngest stars
• We may detect all young and
intermediate age stars
• Stellar content of high-latitude deep
X-ray surveys is dominated by old low
mass stars
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The comparison with the observations:
HDFN (Feigelson et al. 2004)
• The predicted yellow stars
are in excess with respect
to the observations
!!! The opposite than in shallow
and intermediate surveys !!!
• We are looking at old stars,
while the previous surveys
were dominated by young
stars => something of
wrong in old star modeling?
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
PERSPECTIVES
• X-ray deep observations of old
clusters
• Optical High Resolution Spectroscopy
• GAIA (2011+)
• Deep surveys (XEUS)
• X-ray Wide Field Camera ???
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona
The Stellar Coronae
Emission mechanisms
and
Coronal Structures
Coronal Evolution
Young stars in
Open Clusters
and Star Forming Regions
Initial Mass Function
Young stars in the field
Star formation history
in the solar
neighborhood
Interaction with
the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Interaction with the
environment
• Pre-main sequence phase interaction star-disk
• Main sequence stars – interaction
star-planetary atmosphere
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Interaction star-disk
Solar-like loops but also very long structures,
possibly connecting the star with the circumstellar
disk (Favata et al. 2005, Flaccomio et al. 2007)
Effects on accretion, disk ionization, chemistry
l
Normal Stars
Pre main sequence
stars with disks
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Evidence for interaction with the
disks: Fluorescence
• Emission of X-ray radiation from
photo-ionized cold material in the
circumstellar disk
• Best observable line is the FeI K line at
6.4 keV
• Mainly detections during flares, some
cases during the quiescent phase
l
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Fluorescence line in X-rays
FeI K fluorescent line is a tracer of a strong
relation between X-rays and cold material
Fluorescence observed
with XMM in EL29 a
PMS star in ρ Oph
(Giardino et al. 2007)
From DROXO
program
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Interaction
star-planet
1 Mjup
X-rays heat significantly
planetary atmospheres
(Cecchi Pestellini et al. 2006)
Planetary Mass loss
induced by X-rays at
very small orbital
distance for different
istance and density (Penz
1 Mnept
et al. 2007)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Interaction star-planet
Final planet mass distribution starting from a flat
initial mass function (Penz et al. 2007)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Interaction star-planet
• Final Mass of a hot Neptune orbiting around a dM star at
0.02 AU: the case of G876d
(Penz & Micela 2007)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
PERSPECTIVES
• X-ray induced fluorescence in IR
• Modeling of fluorescence
• Comparison with mass function of
unbiased observed samples (CoRoT?
Kepler, PLATO)
• Modeling of EUV-UV contribution
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
RESOURCES
• 8 +1.0 staff res. ; 4.5+2 postdoc; 3.5
PhD
• FUNDS (active in 2007):
–
–
–
–
–
1.5 UE ToK programs (4 postdoc+2 senior)
1 UE RTN
ASI (data analysis and theory)
PRIN INAF
MIUR Special Program
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
X-ray luminosity evolution
Lx depends on rotation
Rotation evolves with age  Lx evolves with age
Feigelson et al. 1993
Flaccomio et al. 1993
Micela et al. 1999
Casanova et al. 1995
Randich et al. 1996
Schmitt 1997
Stern et al. 1995
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Next step: toward the edge of
the Galaxy
• NGC 1893, a SFR at 14 kpc from the Galactic Center
• The aim is to detect member stars down to 0.8 Msun
The IMF in the outer Galaxy:
the influence on the environment
•
•
•
•
Low density
Low radiation field
Low metallicity
Less supernovae and spiral arms
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Spatial distribution and star formation
history in the solar
X-ray observations tend to select active and
young stars
Volume limited
Low latitude
X-ray surveys
High latitude
X-ray surveys
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007