1 / 49

Stellar systems and Populations in 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. Emission mechanisms

lampe
Télécharger la présentation

Stellar systems and Populations in our Galaxy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Istituto Nazionale di AstrofisicaOsservatorio Astronomico di Palermo Stellar systems and Populations in our Galaxy 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 TheSolarCorona 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 TheSolarCorona The StellarCoronae 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) >2018

  19. Emission mechanisms and CoronalStructures TheSolarCorona The StellarCoronae 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 oSun during the cycle ● stars from the Sun in time project of Ribas et al. (2005) ―clusters from previous slide X-ray luminosity and coronal temperature decrease with age during the main sequence lifetime (Micela 2003)

  22. Emission mechanisms and CoronalStructures TheSolarCorona The StellarCoronae 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 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

  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 ρ Oph (DROXO, PI: Sciortino) • 450 ksec Chandra on NGC 1893 (PI: Micela)

  26. Membership e mass function in several SFRsStar 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 < B5 (with inhomogeneous distribution) • >1000 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 CoronalStructures TheSolarCorona The StellarCoronae 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 => 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. A significant excess of yellow stars is present Young population identified through optical follow-up An intermediate survey: the NEP Rosat All Sky Survey: Comparison with the observations (Micela et al. 2007)

  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 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?

  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 CoronalStructures TheSolarCorona The StellarCoronae 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 ρ 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. ; 4.5+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

  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 Lowlatitude X-ray surveys High latitude X-ray surveys

More Related