stellar systems and populations in our galaxy g. micela on behalf of the stellar group istituto...

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


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


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


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


The solar corona: CMEs

• Strong activity starting from SoHO-UVCS spectra (high energy component )– modeling HPC

MHD


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)


Perspectives

• Reinforcing the Hinode collaboration• Modeling• Stellar extrapolation• Involvement in Solar Orbiter (2015)



Coronal Structures

Coronal Evolution







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)


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)



Coronal Structures

Coronal Evolution







Emission mechanisms and

coronal structures

Main tool: the spectrum

• Emission Measure• Temperature• Density• Chemical

abundances

AD Leo Chandra/LETG spectrum


Emission mechanisms and coronal structures

• Emission Measure reconstruction for several stars:

Active stars are hotter than quiet stars

(Scelsi et al. 2006)



• Flares are very common in active and young stars

Flare frequency of dM stars in Orion (Caramazza et al. 2007)



• Variability (flares, rotational modulation, eclipses) may constrain the geometry of emitting structures.

• Modeling of a flare in Prox Cen (Reale et al. 2007)


LONG TERM VARIABILITY

• Identification of the X-ray cycle of the moderately active star HD 81809 (Favata et al. in preparation)


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



Coronal Structures

Coronal Evolution







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



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)



Coronal Structures

Coronal Evolution







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)


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


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)


Membership e mass function in several SFRs

Star formation in different physical environments

NGC 6530: Chandra observation (60 ksec) (Prisinzano et al. 2005)


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


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


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)


PERSPECTIVES

• Other environments (Arches...)• Old clusters• Ground based observations (accretion,

lithium, rotation, variability..., XSHOOTER 2009)

• Hard non-thermal emission (SimbolX -2013)



Coronal Structures

Coronal Evolution







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


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


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


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?


PERSPECTIVES• X-ray deep observations of old

clusters• Optical High Resolution

Spectroscopy• GAIA (2011+)• Deep surveys (XEUS)• X-ray Wide Field Camera ???



Coronal Structures

Coronal Evolution








• Pre-main sequence phase - interaction star-disk

• Main sequence stars – interaction star-planetary atmosphere


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


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


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


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


Interaction star-planetFinal planet mass distribution starting from a flat initial mass function (Penz et al. 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)


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


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



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


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


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

stellar systems and populations in our galaxy g. micela on behalf of the stellar group istituto...

Documents

micela stellar systems

galaxy slide

galaxy palermo

palermo slide

solar stellar xray emission

study of young stellar

stellar observations

environment slide