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Stellar systems and Populations in our Galaxy

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From (solar) stellar X-ray emission to the study of (young) stellar systems and ... HINODE (2006 - ): high resolution multiband X-ray imaging and UV spectroscopy ... – PowerPoint PPT presentation

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Title: Stellar systems and Populations in our Galaxy


1
Stellar systems and Populations in our Galaxy
Istituto Nazionale di AstrofisicaOsservatorio
Astronomico di Palermo
  • G. Micela
  • on behalf of the stellar group

2
  • From (solar) stellar X-ray emission to the
    study of (young) stellar systems and populations
    of our Galaxy

3
Emission mechanisms and Coronal Structures
The Solar Corona
The Stellar Coronae
Coronal Evolution
Young stars in the field Star formation history
in the solar neighborhood
Young stars in Open Clustersand Star Forming
Regions Initial Mass Function
Interaction with the environment
4
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

5
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
6
The solar corona CMEs
  • Strong activity starting from SoHO-UVCS spectra
    (high energy component )
  • modeling HPC MHD

7
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)
8
Perspectives
  • Reinforcing the Hinode collaboration
  • Modeling
  • Stellar extrapolation
  • Involvement in Solar Orbiter (2015)

9
Emission mechanisms and Coronal Structures
The Solar Corona
The Stellar Coronae
Coronal Evolution
Young stars in the field Star formation history
in the solar neighborhood
Young stars in Open Clustersand Star Forming
Regions Initial Mass Function
Interaction with the environment
10
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)

11
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)

12
Emission mechanisms and Coronal Structures
The Solar Corona
The Stellar Coronae
Coronal Evolution
Young stars in the field Star formation history
in the solar neighborhood
Young stars in Open Clustersand Star Forming
Regions Initial Mass Function
Interaction with the environment
13
Emission mechanisms and coronal structures
  • Main tool the spectrum
  • Emission Measure
  • Temperature
  • Density
  • Chemical abundances
  • AD Leo Chandra/LETG spectrum

14
Emission mechanisms and coronal structures
  • Emission Measure reconstruction for several
    stars
  • Active stars are
  • hotter than quiet
  • stars
  • (Scelsi et al. 2006)

15
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)

16
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)

17
LONG TERM VARIABILITY
  • Identification of the X-ray cycle of the
    moderately active star HD 81809 (Favata et al. in
    preparation)

18
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) gt2018

19
Emission mechanisms and Coronal Structures
The Solar Corona
The Stellar Coronae
Coronal Evolution
Young stars in the field Star formation history
in the solar neighborhood
Young stars in Open Clustersand Star Forming
Regions Initial Mass Function
Interaction with the environment
20
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

21
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

22
Emission mechanisms and Coronal Structures
The Solar Corona
The Stellar Coronae
Coronal Evolution
Young stars in the field Star formation history
in the solar neighborhood
Young stars in Open Clustersand Star Forming
Regions Initial Mass Function
Interaction with the environment
23
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 proto-planetary
    system)

24
Star Formation regionsOrion
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
25
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 ? Oph
    (DROXO, PI Sciortino)
  • 450 ksec Chandra on NGC 1893 (PI Micela)

26
Membership e mass function in several SFRs Star
formation in different physical environments
  • NGC 6530 Chandra observation (60 ksec)
    (Prisinzano et al. 2005)

27
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
28
Disk frequency in a massive star forming region
NGC 6611
  • Age 1-3 Myr
  • Dist. 1750pc
  • 56 stars lt B5
  • (with inhomogeneous distribution)
  • gt1000 members (in the red area)
  • 25 disk
  • Spitzer image at 4.5 µ

29
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)
30
PERSPECTIVES
  • Other environments (Arches...)
  • Old clusters
  • Ground based observations (accretion, lithium,
    rotation, variability..., XSHOOTER 2009)
  • Hard non-thermal emission (SimbolX -2013)

31
Emission mechanisms and Coronal Structures
The Solar Corona
The Stellar Coronae
Coronal Evolution
Young stars in the field Star formation history
in the solar neighborhood
Young stars in Open Clustersand Star Forming
Regions Initial Mass Function
Interaction with the environment
32
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 gt 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

33
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

34
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

35
The comparison with the observationsHDFN
(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 gt
    something of wrong in old star modeling?

36
PERSPECTIVES
  • X-ray deep observations of old clusters
  • Optical High Resolution Spectroscopy
  • GAIA (2011)
  • Deep surveys (XEUS)
  • X-ray Wide Field Camera ???

37
Emission mechanisms and Coronal Structures
The Solar Corona
The Stellar Coronae
Coronal Evolution
Young stars in the field Star formation history
in the solar neighborhood
Young stars in Open Clustersand Star Forming
Regions Initial Mass Function
Interaction with the environment
38
Interaction with the environment
  • Pre-main sequence phase - interaction star-disk
  • Main sequence stars interaction star-planetary
    atmosphere

39
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
Pre main sequence stars with disks
Normal Stars
l
40
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
41
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 ? Oph (Giardino et al. 2007)
From DROXO program
42
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
et al. 2007)
1 Mnept
43
Interaction star-planet
  • Final planet mass distribution starting from a
    flat initial mass function (Penz et al. 2007)

44
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)

45
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

46
RESOURCES
  • 8 1.0 staff res. 4.52 postdoc 3.5 PhD
  • FUNDS (active in 2007)
  • 1.5 UE ToK programs (4 postdoc2 senior)
  • 1 UE RTN
  • ASI (data analysis and theory)
  • PRIN INAF
  • MIUR Special Program

47
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

48
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

49
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
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