stellar systems and populations in our galaxy g. micela on behalf of the stellar group istituto...
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Stellar systems and Populations in our Galaxy
G. Micelaon behalf of the stellar group
Istituto Nazionale di AstrofisicaOsservatorio Astronomico di Palermo
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
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 mechanismsand
Coronal Structures
Coronal Evolution
Young stars in Open Clusters
and Star Forming RegionsInitial Mass Function
Young stars in the fieldStar formation history
in the solarneighborhood
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 structuringHinode 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 mechanismsand
Coronal Structures
Coronal Evolution
Young stars in Open Clusters
and Star Forming RegionsInitial Mass Function
Young stars in the fieldStar formation history
in the solarneighborhood
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 nearbystars (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 mechanismsand
Coronal Structures
Coronal Evolution
Young stars in Open Clusters
and Star Forming RegionsInitial Mass Function
Young stars in the fieldStar formation history
in the solarneighborhood
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 mechanismsand
Coronal Structures
Coronal Evolution
Young stars in Open Clusters
and Star Forming RegionsInitial Mass Function
Young stars in the fieldStar formation history
in the solarneighborhood
Interaction with the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
X-ray luminosity evolution
X-ray luminosity functions for several clusters of different ages
Lx depends on rotationRotation evolves with age Lx evolves with age
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
X-ray luminosity evolution
o Sun during the cycle
● stars from the Sun in time project of Ribas et al. (2005)
―clusters from previous slide
X-ray luminosity andcoronal temperature decrease with age during the main sequence lifetime(Micela 2003)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
The Solar Corona The Stellar Coronae Emission mechanismsand
Coronal Structures
Coronal Evolution
Young stars in Open Clusters
and Star Forming RegionsInitial Mass Function
Young stars in the fieldStar formation history
in the solarneighborhood
Interaction with the environment
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Star Forming RegionsX-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 proto-planetary system)
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Star Formation regions:Orion
X-rays penetrate very deep in the interstellar medium and are very efficient in identifying embedded young stars COUP Project
Orion Nebula Cluster:
A laboratory to study the role of high energy radiation during the stellar formation
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.
The aim is to detect member stars down to 0.8 Msun
The IMF in the outer Galaxy: the influence on the environment
~300 stars with IR excess~1000 X-ray sources
Work in progress!!Caramazza et al. in preparation
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
starsFraction 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 mechanismsand
Coronal Structures
Coronal Evolution
Young stars in Open Clusters
and Star Forming RegionsInitial Mass Function
Young stars in the fieldStar formation history
in the solarneighborhood
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 !!! The opposite than in shallow and intermediate surveys !!!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 mechanismsand
Coronal Structures
Coronal Evolution
Young stars in Open Clusters
and Star Forming RegionsInitial Mass Function
Young stars in the fieldStar formation history
in the solarneighborhood
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 StarsPre 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
l
• 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
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
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 et al. 2007)
Interaction star-planet 1 Mjup
1 Mnept
G. Micela – Stellar Systems and Populations in our Galaxy – Palermo 19/12/2007
Interaction star-planetFinal 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
Feigelson et al. 1993Flaccomio et al. 1993Micela et al. 1999Casanova et al. 1995Randich et al. 1996Schmitt 1997Stern et al. 1995
Lx depends on rotationRotation evolves with age Lx evolves with age
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 limitedLow
latitude X-ray
surveysHigh latitude
X-ray surveys