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Nicolas Lodieu

Low-mass stars and brown dwarfs in open clusters. Nicolas Lodieu. SAAO, 28 September 2005. Head: Richard Jameson Post-docs: Paul Dobbie & Nicolas Lodieu PhD student: Sarah Casewell. The BD group @ Leicester. Pleiades, α Per IC2391, Collinder 359 Coma Ber, Praesepe. {.

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Nicolas Lodieu

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  1. Low-mass stars and brown dwarfs in open clusters Nicolas Lodieu SAAO, 28 September 2005

  2. Head: Richard Jameson Post-docs: Paul Dobbie & Nicolas Lodieu PhD student: Sarah Casewell The BD group @ Leicester • Pleiades, α Per • IC2391, Collinder 359 • Coma Ber, Praesepe { • BDs in open clusters • BDs in the field: UKIDSS Large Area Survey

  3. α Per

  4. The α Per cluster: previous work • Analogue to the Pleiades • Distance = 182 pc (Hipparcos) • Low galactic latitude (b = -7°) • Little extinction 0.3 mag • Extended 6°6° • PM and photometric surveys • Heckmann et al. (1956) • Stauffer et al. (1985, 1989) • Prosser (1992, 1994) • Down to V = 19; SpT ~ M5 • Lithium test (Stauffer et al. 1999) Age =90 10 Myr • Deep optical wide-field survey • Barrado y Navascués et al. (2002) • ~ 100 new candidates • dN/dM αM-0.590.05 • Mass range 0.3-0.035 Msun

  5. Our wide-field near-infrared survey I • Wide-field survey conducted with the infrared Omega-Prime camera on the Calar Alto 3.5-m telescope • Five optical KPNO/MOSA frames covered in the infrared Total area of 0.7 deg2covered in K' in Per (Lodieu et al. 2005) • Total of 22129 objects common to the optical and to the infrared • More than 100 new candidates selected from the colour-magnitude (K', I-K') and colour-colour (Rc-Ic, Ic-K') diagrams • About 70% are contaminating distant background giants • 1 non-member (Barrado y Navascués et al. 2002) • 16 probable members (Barrado y Navascués et al. 2002) • 16 new infrared-selected candidate members • 4 new brown dwarf candidates • Spectroscopy needed to ascertain the membership

  6. Our wide-field near-infrared survey II • Crosses: distant giants • Open hexagons: new infrared-selected candidates (Lodieu et al. 2005) • Filled symbols: probable candidates from Barrado y Navascués et al. (2002) 50 Myr 100 Myr Colour-colour diagram Colour-magnitude diagram

  7. Follow-up optical spectroscopy • Optical spectroscopy (5800-8800 Å) conducted with the Twin spectrograph at Calar Alto • 24 probable members (Barrado et al. 2002) • 1 possible member (Barrado et al. 2002) • 4 non-members (Barrado et al. 2002) • 4 new infrared-selected candidates • All optically-selected candidates with masses 0.4-0.12 Msun are genuine cluster members • Spectral types • Fluxes consistent with I magnitudes • Hαin emission (EW = 4-15 Å) • Gravity (KI and NaI doublets) • Possible and non-members are rejected • 4 new infrared-selected candidates are rejected as cluster members

  8. Collinder 359

  9. The CFHT Key Programme • CFHTKP: wide-field optical observations: • PI: Bouvier in collaboration with the EC network • 30 nights over 2 years • CFH12K camera offers a 42'*28' FOV with 0.206 arcsec/pix • I and z CFH12K filters • Completeness and detection limits of 22 and 24 mag in I and z filters • Targets (age < 200 Myr, d < 500 pc, visible from Hawai'i) • SFRs: Perseus, Taurus, Ophiuchus, and Serpens • PMS clusters: IC4665, Collinder 359, Stephenson 1 • The Hyades • Main goals of the CFHTKP programme: • How do brown dwarfs form and at which rate? • Is the Initial Mass Function sensitive to the environment? • How do substellar objects evolve with time? • What is the mass distribution of low-mass stars and brown dwarfs?

  10. Collinder 359: presentation • Unstudied cluster • RA=17h58m, Dec=+02°54' • Constellation Ophiuchus • Located around 67 Oph(Melotte 1915) • Galactic latitude = +12.5 • Age = 32 Myr(Wielen 1971) • Distance = 435 pc [200,650] (Hipparcos) • Diameter = 240 arcmin (~ 20 pc) Location of the CFH12K FOV • 13 members belonging to the cluster • Collinder (1931) • 6 of them confirmed as members • Rucínski (1980; 1987),Van't Veer (1980) • Latest estimates(Kharchenko et al. 2004) • Age = 30 Myr • Distance = 650 pc

  11. Age of Collinder 359 • Girardi tracks (Girardi et al. 2002) • Solar metallicity • Moderate overshoot • Alpha Persei (open square): • 50 Myr (Stauffer et al. 2003) • Membership of 67 Ophiuchus: • P  75% (Baumgardt et al. 2000) • P  95% (Kharchenko et al. 2004) • 67 Ophiuchus (filled hexagon): • 60  20 Myr • Lithium test age  2

  12. Optical and NIR Observations 1) Optical wide-field survey within the framework of the CFHTKP • 5 CFH12K fields-of-view covering 42 arcmin x 28 arcmin • 1.6 square degree area surveyed in Collinder 359 • I and z filters • Completeness limits of I, z22.0 mag (30 MJup at 450 pc and 60 Myr) • Detection limits of I, z24.0 mag (< 30 MJup at 450 pc and 60 Myr) 2) Near-infrared follow-up photometry of candidates • 2MASS counterparts down to I = 17.0 mag • K'-band follow-up: CFHT 3.6-m/CFHTIR + CAHA 2.2-m/MAGIC • 29 + 36 objects spanning I = 17.0-22.0 mag

  13. (I-z,I) CMD • Theoretical Isochrones • NextGen + Dusty • Age = 60 Myr • Distance = 450 pc • Mass scale in solar masses • HBL @ I = 19.75 mag • Mass range: 1.3-0.03 Msun

  14. Optical and NIR Observations 1) Optical wide-field survey within the framework of the CFHTKP • 5 CFH12K fields-of-view covering 42 arcmin x 28 arcmin • 1.6 square degree are surveyed in Collinder 359 • I and z filters • Completeness limits of I, z22.0 mag (30 MJup at 450 pc and 60 Myr) • Detection limits of I, z24.0 mag (< 30 MJup at 450 pc and 60 Myr) 2) Near-infrared follow-up photometry of candidates • 2MASS counterparts down to I = 17.0 mag • K'-band follow-up: CFHT 3.6-m/CFHTIR + CAHA 2.2-m/MAGIC • 29 + 36 objects spanning I = 17.0-22.0 mag

  15. (I-K,I) CMD • Isochrones • NextGen + Dusty • Age = 60 Myr • Distance = 450 pc • Crosses = 2MASS • Filled circles = CFHT + CAHA

  16. Optical spectroscopy: H • Tests for membership: • Spectral typing • Chromospheric activity: Hα EW • Surface gravity: KI and NaI doublets • Magnitude vs. SpT relationship • Spectroscopic observations: • TNG/DOLORES: 48 candidates • WHT/AF2/WYFFOS: 33 candidates • CAHA 3.5-m/Twin: 74 candidates • AAT/2dF: several hundreds • Caveat: What criterion for M  0.3 Msun? Lithium? Radial velocity? ==> A dozen candidates confirmed as members out of 100 candidates with optical spectroscopy

  17. Collinder 359 & IC4665 Red dots have proper motion consistent with cluster membership Green squares represent a control sample Black boxes represent the coverage in Collinder 359 & IC4665

  18. Collinder 359 & IC4665 Red dots have proper motion consistent with cluster membership Green squares represent a control sample Blue dots are within a 2 degree area around Collinder 359 & (B-V) < 1.0 Blue triangles are within a 2 degree area around IC4665 & (B-V) < 1.0

  19. Coma Ber

  20. Coma Berenices open star cluster • 45 known cluster members • Selected via proper motion using the USNO B1.0 catalogue • Photometric selection using 2MASS Point-Source Catalogue • 60 new possible members • Stars down to 0.25 M found • Control field used to estimate membership probability • 15 square degrees of cluster surveyed in I and Z • 13 brown dwarf candidates • Awaiting UKIRT/WFCAM data

  21. Red: NEXTGEN model Green:Dusty model Blue: Known members Black: Our members Magenta: Brown dwarf candidates

  22. Future prospects • Collinder 359: • AAT/2dF low-resolution optical spectroscopy (August 2005) • UKIDSS Galactic Cluster Survey: • UKIRT/WFCAM with ~0.8 square degree field-of-view • 10 open clusters and star-forming regions in ZYJHK • 5-σ completeness limits of J = 19.7, H = 18.8, K = 18.4 • αPer: proper motion + larger coverage • Pleiades: proper motion + deeper observations • IC4665: infrared counterparts of optically-selected cluster candidates • Coma Ber: new candidates over a larger area

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