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Ben Burningham

Brown dwarfs in large scale surveys. Ben Burningham. Brown dwarfs come of age Fuerteventura, 21 st May 2013. Plan. a bit of history the recent past the state of the art future challenges. The first wide area surveys. not digital relatively simple data pipeline c 1200 BC 36 stars.

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Ben Burningham

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  1. Brown dwarfs in large scale surveys Ben Burningham Brown dwarfs come of age Fuerteventura, 21st May 2013

  2. Plan • a bit of history • the recent past • the state of the art • future challenges

  3. The first wide area surveys • not digital • relatively simple data pipeline • c 1200 BC • 36 stars L5 dwarf @ ~100 au T5 dwarf @ ~ 100 au

  4. Greek pioneers • Timocharis & Aristillus c300BC • Hipparchus c135BC • 1022 stars • m < 6 • updated in 964 (Sufi) and 1543 (Copernicus) • no brown dwarfs • (but did discover precession of equinox) L5 dwarf @ ~2000 au T5 dwarf @ ~ 1000 au

  5. The next 2000 years…. • Tycho Brahe (1598): • m < 6 • 1004 stars • astrometric accuracy ~2’ • Lalande et al (1801) • 50K stars • m < 9 • Henry Draper (1918 – 1924) • first spectroscopic survey • all sky • m < 10 • Bonner Durchmusterung  (1852 – 1859); Cordoba Durchmusterung (1892); Cape Photographic Durchmusterung (1896) • total 1 million stars  • all sky • m < 9 - 10 L5 dwarf @ ~10000 au T 5dwarf @ ~2000 au

  6. Photographic surveys 20th century dominated by three facilities: • Palomar observatory: • POSS I (1949 – 1958) • -27 to +90 degrees • B ~ 21 • POSS II • Bj < 22.5, Rc < 20.8, Ic < 19.5 • UK & ESO Schmidt telescopes: • ESO/SERC • Bj ~ 22.5, Rc ~ 21 • Ic band • Ic < 19 L5 dwarf @ ~20 pc T5 dwarf @ ~ 4 pc

  7. The first brown dwarfs - 1995 Rebolo, Zapatero Osorio, & Martin, 1995 Nakajima et al 1995

  8. Kelu - 1 Ruiz et al (1997) • L2 dwarf selected by proper motion • 1st epoch: • ESO survey plates • 2nd epoch: • dedicated follow-up of 400 sq degs • examined with a blink comparator

  9. Legacy of photographic surveys • DSS I & II • Catalogues from densitometer scans: • GSC I & II • USNOA, B • superCOSMOS • Proper motion catalogues e.g. LHS, LSPM, PPMXL etc • identification of (ultra) cool >M7 dwarfs • the first L dwarf (Ruiz et al 1997) (the trickle before the flood)

  10. The age of digital sky surveys Facilitated by : • new detectors • improvements in data processing and storage • first brown dwarfs identified in late 1990s (important: allows photometric selection) New generation dominated by 3 surveys: • DENIS • 2MASS • SDSS

  11. DENIS • Overview • southern sky (ESO 1m schmidt) • i < 18.5, J < 16.5 , Ks < 14.0 • finished in 2001 • 355 million sources • Results: • 49 L dwarfs: • Delfosse et al (1997, 1999) • Martin et al (1999) • Bouy et al (2003) • Kendall et al (2004) • Phan-Bao et al (2008) • Martin et al (2010) • 1 T dwarf • Artigua et al (2010) L5 dwarf @ ~40 pc T5 dwarf @ ~ 20 pc

  12. 2MASS • All sky • JHK (J < 16.5; H < 15.7; Ks < 15.2) • >99% complete for J < 15.8, H < 15.1, Ks < 14.3 • game changer for substellar science L5 dwarf @ ~45 pc T5 dwarf @ ~ 20 pc

  13. Brown dwarfs in 2MASS • 2MASS team searched via cross match of 2MASS against USNO for B+R band dropouts • visual inspection to ensure no optical detection • distinguished as L and T candidates based on JHK colours • subsequent searches cross matched 2MASS with e.g. SDSS, and included proper motion searches • 403 L dwarfs identified to-date: • Kirkpatrick et al (1999, 2000, 2008, 2010); Reid et al (2000, 2008); Gizis(2002);Giziset al (2000, 2003); Kendall et al (2003, 2007); Cruz et al (2003, 2007); Burgasser et al (2003, 2004); Wilson et al (2003); Folkes et al (2007); Metchev et al (2008); Looper et al (2008) Sheppard & Cushing (2009); Scholz et al (2009); Geissler et al (2011) • 55 T dwarfs: • Kirkpatrick et al (2000, 2010); Burgasser et al (1999, 2000, 2002, 2003, 2004, ); Cruz et al (2004) Tinney et al (2005); Looper et al (2007); Reid et al (2008)

  14. SDSS SDSS DR9: • 14,555 square degrees • 932,891,133 “sources” • 1.7 million extragalactic spectra • 700K stellar spectra • z’ < 20.8ish • “arguably the most successful scientific project ever undertaken” L5 dwarf @ ~75 pc T5 dwarf @ ~ 40 pc

  15. Brown dwarfs in SDSS 381 L dwarfs to-date: • photometric selection: • Fan et al (2000) Hawley et al (2002); Geballeet al (2002); Schneider et al (2002); Knapp et al (2004); Chiu et al (2006); Zhang et al (2009); Scholz et al (2009) • spectroscopic selection: Schmidt et al (2010) • highlights risky nature of photometric selection 57 T dwarfs: • Leggett et al (2000); Geballe et al (2002); Knapp et al (2004); Chiu et al (2006)

  16. Highlights from the end of the beginning • definition of the “L” spectral class • 830 L dwarfs discovered • extended to halo population and young moving groups • definition of the “T” spectral class • 113 T dwarfs discovered • extended sequence to Teff ~ 700K (T8) • diversity of properties beyond Teff sequence apparent • gravity? • metallicity? • dust properties? Kirkpatrick et al 1999, 2000 Burgasser et al 2006

  17. Beyond stamp collecting • luminosity function of L dwarfs • Cruz et al (2007) • space density of T dwarfs  constraining the IMF • Allen et al (2005) • Metchev et al (2008) • binary statistics (e.g. Burgasser et al 2003) • benchmarks (e.g. G570D, HD3651B) • weather!!! (e.g. Radigan et al 2012; Buenzli et al 2012)

  18. Photometric survey exploitation cookbook Select candidates from survey(s) using colours e.g. z’ – J > 2.5 Follow-up photometry to remove contaminants e.g. scattered M dwarfs; SSOs Spectroscopic confirmation SCIENCE

  19. UKIRT Infrared Deep Sky Survey (UKIDSS)Lawrence et al 2007 • UKIDSS consists of 5 surveys • Large Area Survey (LAS) • 3600 sq. degs, J = 19.6 • 2 epoch for ~1500 sq degs • Galactic Plane Survey (GPS) • 1800 sq. degs, K=19 • Galactic Clusters Survey (GCS) • 1400 sq. degs K=18.7 • Deep Extragalactic Survey (DXS) • 35 sq. degs, K=21.0 • Ultra Deep Survey (UDS) • 0.77 sq. degs, K=23.0 L5 dwarf @ ~175 pc T5 dwarf @ ~ 110 pc Casali et al 2007

  20. 171 T dwarfs identified (Lodieu et al 2007; Pinfield et al 2008; Burningham et al (2008, 2009, 2010a,b, 2013) • ~70 (+) L dwarfs • (Day-Jones et al 2013) • extended T sequence to Teff ~ 500K (Lucas et al 2011) • halo T dwarfs (Smith et al – today!) • more young L dwarfs (see Marocco et al poster)

  21. CFBDS(IR) • ~1000 sq degs in i & z (+NIR sections) • early T8+ discovery (CFBDS 0059; Delorme et al 2008) • L5 – T8 luminosit function (Reyle et al 2010) • extremely cool binary CFBDSIR J1458+1013AB (Liu et al 2011) • planetary mass T dwarf CFBDSIR2149-0403 (Delorme et al 2012)

  22. WISE – another leap forwards Kirkpatrick et al (2011) • all sky • 3.4, 4.6, 12, and 22μm • Y dwarfs (Cushing et al 2011; Kirkpatrick et al 2012) • seriously, Teff ~ 300K brown dwarfs!! • halo(?) T dwarfs (Gomes et al – today!) • buckets of bright T dwarfs (Mace et al 2013) • complementary data facilitating all sorts of cool science with UKIDSS, 2MASS etc L5 dwarf @ ~80 pc T5 dwarf @ ~ 50 pc Y dwarf @ ~12 pc

  23. WISE vs UKIDSS – FIGHT! J <18.3 18.3 < J <18.8

  24. Survey league table

  25. The immediate future ~1 MILLION BROWN DWARFS!!!! VISTA: • VISTA Hemisphere Survey (VHS) • (Y)J(H)Ks • J < 19.6 • ~100K L0 – T5 • ~2000 late-T dwarfs • VIKING • 1500 sq degs • ZYJHK • J < 21.0 Dark Energy Survey: • 4000 sq degs • grizy (z < 24.7, y < 23.0) PanStarrs (+UKIRT Hemisphere Survey): • griz (+J) • z < 23.0 (+ J < 19.6) L5 dwarf @ ~330 pc T5 dwarf @ ~200 pc …and that’s before LSST

  26. What’s the point? • rare objects: • benchmarks • halo T dwarfs/subdwarfs • young objects • improved space density • scale height for BDs (as a function of spectral type) need kinematic data need to use survey data for more than candidate selection

  27. Photometric redshifts spectral types Skrzypek & Warren (poster here!)

  28. Large scale spectroscopic surveys EUCLID: • VIS (<24.5 AB) + YJH (<24 AB) wide imaging survey over 15000 sq deg • YJH < 26.5 (AB) over 40 sq degs, • slitless spectroscopy (J ~ 19?) VLT-MOONS (proposed): • 500 sq arcminute, 500 object NIR MOS • deep survey key element of science case • scale height for LT dwarfs • c.f SDSS for M dwarfs!

  29. What do we want next? • proper motions (PanStarrs; LSST; 2nd epoch of VHS !?) • deep spectroscopic survey (VLT-MOONS; EUCLID) • what about photometric surveys? • best colours for characterisation?

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