Brown dwarfs in large scale surveys Ben Burningham
Brown dwarfs in large scale surveys Ben Burningham Brown dwarfs come of age Fuerteventura, 21 st May 2013
Plan Ü a bit of history Ü the recent past Ü the state of the art Ü future challenges
The first wide area surveys Ü not digital Ü relatively simple data pipeline Ü c 1200 BC Ü 36 stars L 5 dwarf @ ~100 au T 5 dwarf @ ~ 100 au
Greek pioneers Ü Timocharis & Aristillus c 300 BC Ü Hipparchus c 135 BC Ü 1022 stars Ü m < 6 Ü updated in 964 (Sufi) and 1543 (Copernicus) Ü no brown dwarfs Ü (but did discover precession of equinox) L 5 dwarf @ ~2000 au T 5 dwarf @ ~ 1000 au
The next 2000 years…. Ü Tycho Brahe (1598): Ü Ü Ü m < 6 1004 stars astrometric accuracy ~2’ Ü Lalande et al (1801) Ü Ü 50 K stars m < 9 Ü Henry Draper (1918 – 1924) Ü Ü Ü first spectroscopic survey all sky m < 10 Ü Bonner Durchmusterung (1852 – 1859); Cordoba Durchmusterung (1892); Cape Photographic Durchmusterung (1896) Ü Ü Ü total 1 million stars all sky m < 9 - 10 L 5 dwarf @ ~10000 au T 5 dwarf @ ~2000 au
Photographic surveys 20 th century dominated by three facilities: Ü Palomar observatory: Ü POSS I (1949 – 1958) Ü -27 to +90 degrees Ü B ~ 21 Ü POSS II Ü Bj < 22. 5, Rc < 20. 8, Ic < 19. 5 Ü UK & ESO Schmidt telescopes: Ü ESO/SERC Ü Bj ~ 22. 5, Rc ~ 21 Ü Ic band Ü Ic < 19 L 5 dwarf @ ~20 pc T 5 dwarf @ ~ 4 pc
The first brown dwarfs - 1995 Rebolo, Zapatero Osorio, & Martin, 1995 Nakajima et al 1995
Kelu - 1 Ruiz et al (1997) Ü L 2 dwarf selected by proper motion Ü 1 st epoch: Ü ESO survey plates Ü 2 nd epoch: Ü dedicated follow-up of 400 sq degs Ü examined with a blink comparator
Legacy of photographic surveys Ü DSS I & II Ü Catalogues from densitometer scans: Ü GSC I & II Ü USNOA, B Ü super. COSMOS Ü Proper motion catalogues e. g. LHS, LSPM, PPMXL etc Ü identification of (ultra) cool >M 7 dwarfs Ü the first L dwarf (Ruiz et al 1997) (the trickle before the flood)
The age of digital sky surveys Facilitated by : Ü new detectors Ü improvements in data processing and storage Ü first brown dwarfs identified in late 1990 s (important: allows photometric selection) New generation dominated by 3 surveys: Ü DENIS Ü 2 MASS Ü SDSS
DENIS Ü Overview Ü southern sky (ESO 1 m schmidt) Ü i < 18. 5, J < 16. 5 , Ks < 14. 0 Ü finished in 2001 Ü 355 million sources Ü Results: Ü 49 L dwarfs: Ü Delfosse et al (1997, 1999) Ü Martin et al (1999) Ü Bouy et al (2003) Ü Kendall et al (2004) Ü Phan-Bao et al (2008) Ü Martin et al (2010) Ü 1 T dwarf Ü Artigua et al (2010) L 5 dwarf @ ~40 pc T 5 dwarf @ ~ 20 pc
2 MASS Ü All sky Ü JHK (J < 16. 5; H < 15. 7; Ks < 15. 2) Ü >99% complete for J < 15. 8, H < 15. 1, Ks < 14. 3 Ü game changer for substellar science L 5 dwarf @ ~45 pc T 5 dwarf @ ~ 20 pc
Brown dwarfs in 2 MASS Ü 2 MASS team searched via cross match of 2 MASS against USNO for B+R band dropouts Ü Ü visual inspection to ensure no optical detection distinguished as L and T candidates based on JHK colours Ü subsequent searches cross matched 2 MASS with e. g. SDSS, and included proper motion searches Ü 403 L dwarfs identified to-date: Ü Ü Kirkpatrick et al (1999, 2000, 2008, 2010); Reid et al (2000, 2008); Gizis (2002); Gizis et 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: Ü 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)
SDSS DR 9: Ü 14, 555 square degrees Ü 932, 891, 133 “sources” Ü 1. 7 million extragalactic spectra Ü 700 K stellar spectra Ü z’ < 20. 8 ish Ü “arguably the most successful scientific project ever undertaken” L 5 dwarf @ ~75 pc T 5 dwarf @ ~ 40 pc
Brown dwarfs in SDSS 381 L dwarfs to-date: Ü photometric selection: Ü Fan et al (2000) Hawley et al (2002); Geballe et al (2002); Schneider et al (2002); Knapp et al (2004); Chiu et al (2006); Zhang et al (2009); Scholz et al (2009) Ü spectroscopic selection: Schmidt et al (2010) Ü highlights risky nature of photometric selection 57 T dwarfs: Ü Leggett et al (2000); Geballe et al (2002); Knapp et al (2004); Chiu et al (2006)
Highlights from the end of the beginning Ü definition of the “L” spectral class Ü Ü 830 L dwarfs discovered extended to halo population and young moving groups Ü definition of the “T” spectral class Ü Ü 113 T dwarfs discovered extended sequence to Teff ~ 700 K (T 8) Ü diversity of properties beyond Teff sequence apparent Ü Ü Ü gravity? metallicity? dust properties? Kirkpatrick et al 1999, 2000 Burgasser et al 2006
Beyond stamp collecting Ü luminosity function of L dwarfs Ü Cruz et al (2007) Ü space density of T dwarfs constraining the IMF Ü Allen et al (2005) Ü Metchev et al (2008) Ü binary statistics (e. g. Burgasser et al 2003) Ü benchmarks (e. g. G 570 D, HD 3651 B) Ü weather!!! (e. g. Radigan et al 2012; Buenzli et al 2012)
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
UKIRT Infrared Deep Sky Survey (UKIDSS) Lawrence et al 2007 Ü UKIDSS consists of 5 surveys Ü Large Area Survey (LAS) Ü 3600 sq. degs, J = 19. 6 Ü 2 epoch for ~1500 sq degs Ü Galactic Plane Survey (GPS) Ü 1800 sq. degs, K=19 Ü Galactic Clusters Survey (GCS) Ü 1400 sq. degs K=18. 7 Ü Deep Extragalactic Survey (DXS) Ü 35 sq. degs, K=21. 0 Ü Ultra Deep Survey (UDS) Ü 0. 77 sq. degs, K=23. 0 Casali et al 2007 L 5 dwarf @ ~175 pc T 5 dwarf @ ~ 110 pc
Ü 171 T dwarfs identified (Lodieu et al 2007; Pinfield et al 2008; Burningham et al (2008, 2009, 2010 a, b, 2013) Ü ~70 (+) L dwarfs Ü (Day-Jones et al 2013) Ü extended T sequence to Teff ~ 500 K (Lucas et al 2011) Ü halo T dwarfs (Smith et al – today!) Ü more young L dwarfs (see Marocco et al poster)
CFBDS(IR) Ü ~1000 sq degs in i & z (+NIR sections) Ü early T 8+ discovery (CFBDS 0059; Delorme et al 2008) Ü L 5 – T 8 luminosit function (Reyle et al 2010) Ü extremely cool binary CFBDSIR J 1458+1013 AB (Liu et al 2011) Ü planetary mass T dwarf CFBDSIR 2149 -0403 (Delorme et al 2012)
WISE – another leap forwards Kirkpatrick et al (2011) Ü all sky Ü 3. 4, 4. 6, 12, and 22 μm Ü Y dwarfs (Cushing et al 2011; Kirkpatrick et al 2012) Ü seriously, Teff ~ 300 K brown dwarfs!! Ü halo(? ) T dwarfs (Gomes et al – today!) Ü buckets of bright T dwarfs (Mace et al 2013) Ü complementary data facilitating all sorts of cool science with UKIDSS, 2 MASS etc L 5 dwarf @ ~80 pc T 5 dwarf @ ~ 50 pc Y dwarf @ ~12 pc
WISE vs UKIDSS – FIGHT! J <18. 3 < J <18. 8
Survey league table Survey L dwarfs T dwarfs Y dwarfs DENIS 49 1 0 2 MASS 403 55 0 SDSS 381 57 0 UKIDSS 50 230 0 CFBDS(IR) 170(? ) 45 1 WISE 10 176 14 VISTA-VHS 0 5 0
The immediate future VISTA: Ü VISTA Hemisphere Survey (VHS) Ü Ü (Y)J(H)Ks J < 19. 6 ~100 K L 0 – T 5 ~2000 late-T dwarfs Ü VIKING Ü Ü Ü 1500 sq degs ZYJHK J < 21. 0 Dark Energy Survey: Ü Ü N O I L L I N L 5 dwarf @ ~330 pc M OW !!!! T 5 dwarf @ ~200 pc 1 ~ R FS B R A DW 4000 sq degs grizy (z < 24. 7, y < 23. 0) Pan. Starrs (+UKIRT Hemisphere Survey): Ü griz (+J) Ü z < 23. 0 (+ J < 19. 6) …and that’s before LSST
What’s the point? Ü rare objects: Ü benchmarks Ü halo T dwarfs/subdwarfs need kinematic data Ü young objects Ü improved space density Ü scale height for BDs (as a function of spectral type) need to use survey data for more than candidate selection
Photometric redshifts spectral types Skrzypek & Warren (poster here!)
Large scale spectroscopic surveys EUCLID: Ü VIS (<24. 5 AB) + YJH (<24 AB) wide imaging survey over 15000 sq deg Ü YJH < 26. 5 (AB) over 40 sq degs, Ü slitless spectroscopy (J ~ 19? ) VLT-MOONS (proposed): Ü 500 sq arcminute, 500 object NIR MOS Ü deep survey key element of science case Ü scale height for LT dwarfs Ü c. f SDSS for M dwarfs!
What do we want next? Ü proper motions (Pan. Starrs; LSST; 2 nd epoch of VHS !? ) Ü deep spectroscopic survey (VLT-MOONS; EUCLID) Ü what about photometric surveys? Ü best colours for characterisation?
- Slides: 29