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 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 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)

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

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 2007L5 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 dwarfs

DENIS 49 1 0

2MASS 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 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 MILL

ION

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?