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Photometric and spectroscopic properties of stellar populations in the Carina dSph galxy

This study focuses on the photometric and spectroscopic properties of stellar populations in the Carina dwarf spheroidal galaxy. The observational issues, complex star formation history, and the presence of anomalous Cepheids and RR Lyrae variables are explored. Different approaches, including 4m telescopes with wide-field imagers and 8m telescopes with medium-field cameras, are used to understand the global properties of nearby galaxies.

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Photometric and spectroscopic properties of stellar populations in the Carina dSph galxy

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  1. Photometric and spectroscopic properties of stellar populations in the Carina dSph galxy M. Monelli Instituto de Astrofìsica de Canarias Concepcion, Jan 8-14, 2007

  2. Spirals • dSph/dE • dSph/dIrr • dIrr S. Hidalgo

  3. An example: the field of IC1613 Rt~15' ACS

  4. I. Drozdovski An example: the field of IC1613 Rt~15' ACS + Subaru

  5. An example: the field of IC1613 Rt~15' ACS + Subaru + CFHT

  6. D~200Kpc, (m-M)=21.5  mv(TO)~25 D~770Kpc, (m-M)=24.5  mv(TO)~28 D~2Mpc, (m-M)=26.5  mv(TO)~30 TO star, Mv~3.5 S. Hidalgo

  7. Use different approaches! • 4m telescopes + wide-field imagers • 8m telescopes + medium-field cameras • HST • + spectroscopy (8m + multi-object spect.) Global understanding of the properties of nearby galaxies (SFH, variables, radial gradients, tidal interactions…)

  8. 1°x1° DSS Carina: Observational issues • Extended • low surface brightness • low central density (m-M)0 ~ 20.15 D ~ 100 Kpc Mv~ -9.3 Rcore ~ 9 Rtidal ~ 29 (47’) (Mateo 1998) WIDE FIELD OBSERVATIONS!!

  9. Why Carina? • complexstar formation history (Smecker-Hane et al. 1996) • ( mix of stellar populations) • recentepisode (<1Gyr) (Monelli et al. 2003) • sizable sample of variable stars (Dall’Ora et al. 2003) • high M/L ( ~30 M☼ /L☼)  DM? • controversial evidence of extra-tidal stars: tidalinteractions with the Galaxy or extendedhalo?(Hayashi et al 2003, Kazantzidis et al 2004, Monelli et al. 2004, Munoz et al. 2006)

  10. The Carina Project:Longtermphotometricandspetroscopicproject aimed at studying the stellar content of the Carina dSph galaxy • G. Bono,R. Buonanno, V. Castellani, C.E. Corsi, F. Caputo, • L. Pulone (INAF-Rome Obs.) • A.R. Walker (CTIO) • M. Dall’Ora, V. Ripepi (INAF-Capodimonte Obs.) • A. Munteanu (Univ. Pompeu Fabra) • P.B. Stetson (DAO) • H.A Smith (MSU) • A. Aparicio, C. Gallart (IAC) • M. Nonino(INAF-Trieste) • F. Thévenin (Nice Obs.) • P. Francois (Paris Obs.)

  11. WARNING!!! CAREFUL WITH THE CALIBRATION!! The data set: central region • Photometric reduction with DAOPHOTII/ALLFRAME • (Stetson 1987, 1994)  ~2,900 frames

  12. Results: color-magnitude diagram ~30000 stars (|sharp|<0.2) DM = 20.24 E(B-V) = 0.03 Z = 0.004 [Fe/H] = -1.7  isochrones superposition: Old population ~11Gyr Intermediatepop. ~3-7 Gyr Youngpop ~0.6-1 Gyr

  13. Results: spatial distribution The intermediate-age stellar population is more concentrated toward the centre; old stars are distributed in a sort of diffused halo. The peak of the distribution of the old stars is offset by ~2´.

  14. Spectroscopic data sets

  15. FLAMES (archive): based on EIS photometry (Koch et al. 2006) FORS2: based on our photometry Complementary samples

  16. Two main questions: 1)Do the different populations present different kinematical properties? 2) Is there any spread in the chemical composition among different populations?

  17. WARNING!! FLAMES: Uncertainties in sky subtraction: partially masked in the vr determination but show up with the individual abundance determination • FORS2: • day/night mask positioning  abundances • Centroid positioning in the slit  vr

  18. FLAMES (1095) FORS2 (150) Work in progress… Different peak?? Hidden systematics??

  19. Variable Stars • Multiple stellar populations  different families of • variable stars present in the same system, both in • H- and He-burning phases • Bright variables as tracers of stellar populations

  20. 19 Anomalous Cepheids

  21. 19 Anomalous Cepheids 79 RRLyrae

  22. 19 Anomalous Cepheids 79 RRLyrae 13 binaries

  23. 19 Anomalous Cepheids 79 RRLyrae 13 binaries 270 candidates/unclassified

  24. Outer fields: tidal tails? We observed selected regions around Carina. Deep images were collected in order to use Main Sequence stars as tracers of the stellar content. CTIO 4m 2.2m ESO

  25. Conclusions • USE DIFFERENT APPROACHES!!

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