Ben Burningham Brown dwarfs in large scale surveys 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 L5 ~100 au T5 ~ 100 au

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 ~2000 au T5 ~ 1000 au

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 < L5 ~10000 au T ~2000 au

Photographic surveys 20 th 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 ~20 pc T5 ~ 4 pc

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

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

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)

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

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 ~40 pc T5 ~ 20 pc

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 ~45 pc T5 ~ 20 pc

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); 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:  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 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 ~75 pc T5 ~ 40 pc

Brown dwarfs in SDSS 381 L dwarfs to-date:  photometric selection:  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)  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)

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

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)

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

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 Casali et al 2007 L5 ~175 pc T5 ~ 110 pc

 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)

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 J AB (Liu et al 2011)  planetary mass T dwarf CFBDSIR (Delorme et al 2012)

WISE – another leap forwards  all sky  3.4, 4.6, 12, and 22 μm  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 Kirkpatrick et al (2011) L5 ~80 pc T5 ~ 50 pc Y ~12 pc

WISE vs UKIDSS – FIGHT! J < < J <18.8

Survey league table SurveyL dwarfsT dwarfsY dwarfs DENIS4910 2MASS SDSS UKIDSS CFBDS(IR)170(?)451 WISE VISTA-VHS050

The immediate future 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 ~330 pc T5 ~200 pc ~1 MILLION BROWN DWARFS!!!! …and that’s before LSST

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

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

Large scale spectroscopic surveys EUCLID:  VIS (<24.5 AB) + YJH (<24 AB) wide imaging survey over 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!

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