Ben Burningham
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Ben Burningham
Brown dwarfs in large scale surveys
Brown dwarfs come of ageFuerteventura, 21st 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 dwarf @ ~100 au T5 dwarf @ ~ 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 dwarf @ ~2000 au T5 dwarf @ ~ 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 < 9 - 10 L5 dwarf @ ~10000 au
T 5dwarf @ ~2000 au
Photographic surveys20th 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
The first brown dwarfs - 1995
Rebolo, Zapatero Osorio,& Martin, 1995
Nakajima et al 1995
Kelu - 1 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
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 surveysFacilitated 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 dwarf @ ~40 pc
T5 dwarf @ ~ 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 dwarf @ ~45 pc T5 dwarf @ ~ 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)
SDSSSDSS 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
Brown dwarfs in SDSS381 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 dwarf @ ~175 pc T5 dwarf @ ~ 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 J1458+1013AB (Liu et
al 2011) planetary mass T dwarf CFBDSIR2149-0403 (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 dwarf @ ~80 pc T5 dwarf @ ~ 50 pcY dwarf @ ~12 pc
WISE vs UKIDSS – FIGHT!
J <18.3 18.3 < J <18.8
Survey league table
Survey L dwarfs T dwarfs Y dwarfsDENIS 49 1 02MASS 403 55 0SDSS 381 57 0UKIDSS 50 230 0CFBDS(IR) 170(?) 45 1WISE 10 176 14VISTA-VHS 0 5 0
The immediate futureVISTA:
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~1 MILLI
ON
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 surveysEUCLID: 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!
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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