Steve Boudreault

1
ASTRO DEBATA
Tuesday 24th of February 2009
The formation of brown dwarfs as revealed by the
mass function of IC 2391
Collaborators (MPIA) Coryn Bailer-Jones
Reinhard Mundt Thomas Henning Wei Wang Mario
Gennaro (external) José Caballero, U of
Mardid IAC, Canary Islands Ray Jayawardhana, U of
Toronto

• Steve Boudreault

Postdoctoral researcher at the Max-Planck-Institu
t für Astronomie Heidelberg, Germany
2
Theoretical Background Photometric Survey
Spectroscopic Follow-up Future Work
Today, I will talk about
3
? Compression fragmentation of molecular cloud
(star-like)?? Formation in circumstellar disk
(planet-like)? Interruption of star-like
accretion (ejection, photoevaporation)?
Theoretical Background different formation
mechanisms of brown dwarfs
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
How to form brown dwarfs ?
4
? Compression fragmentation of molecular cloud
(star-like)?? Formation in circumstellar disk
(planet-like)? Interruption of star-like
accretion (ejection, photoevaporation)?
Theoretical Background different formation
mechanisms of brown dwarfs
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Distinction between these scenarios ? presence
/ distribution of binaries ? kinematics /
spatial distribution ? presence of circumstellar
disk ? Mass function (MF)
Grether Lineweaver ( 2006 ) P lt 5 yr ( 3AU for
BD) D 50pc
5
? Compression fragmentation of molecular cloud
(star-like)?? Formation in circumstellar disk
(planet-like)? Interruption of star-like
accretion (ejection, photoevaporation)?
Theoretical Background different formation
mechanisms of brown dwarfs
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Kumar Schmeja (2007)
Distinction between these scenarios ? presence
/ distribution of binaries ? kinematics /
spatial distribution ? presence of circumstellar
disk ? Mass function (MF)
( Taurus star-forming region )
6
? Compression fragmentation of molecular cloud
(star-like)?? Formation in circumstellar disk
(planet-like)? Interruption of star-like
accretion (ejection, photoevaporation)?
Theoretical Background different formation
mechanisms of brown dwarfs
M9.5 M 15 MJ
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Distinction between these scenarios ? presence
/ distribution of binaries ? kinematics /
spatial distribution ? presence of circumstellar
disk ? Mass function (MF)
7
? Compression fragmentation of molecular cloud
(star-like)?? Formation in circumstellar disk
(planet-like)? Interruption of star-like
accretion (ejection, photoevaporation)?
Theoretical Background different formation
mechanisms of brown dwarfs
Bouvier et al. (2008)
Muench et al. (2002)
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Distinction between these scenarios ? presence
/ distribution of binaries ? kinematics /
spatial distribution ? presence of circumstellar
disk ? Mass function (MF)
Briceño et al. (2002)
8
? Compression fragmentation of molecular cloud
(star-like)?? Formation in circumstellar disk
(planet-like)? Interruption of star-like
accretion (ejection, photoevaporation)?
Theoretical Background different formation
mechanisms of brown dwarfs

• Bate Bonnell, 2005, MNRAS, 356, 1201
• Numerical simulation of compression
  fragmentation of a molecular cloud
• ? BDs form via the ejection scenario
• Bonnell et al. 2008, MNRAS, 389, 1556
• Numerical simulation of compression
  fragmentation of a molecular cloud
• ? BDs form like stars in high gas density
• Luhman et al. 2007, Protostar and Planets V
• astro-ph/06085461
• Review of observational signatures
• ? Common formation for BDs and stars

Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Distinction between these scenarios ? presence
/ distribution of binaries ? kinematics /
spatial distribution ? presence of circumstellar
disk ? Mass function (MF)
9
? Compression fragmentation of molecular cloud
(star-like)?? Formation in circumstellar disk
(planet-like)? Interruption of star-like
accretion (ejection, photoevaporation)?
Theoretical Background different formation
mechanisms of brown dwarfs
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Distinction between these scenarios ? presence
/ distribution of binaries ? kinematics /
spatial distribution ? presence of circumstellar
disk ? Mass function (MF)
For our project ? ?
10
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
IC 2391 is an interesting target because
objects in clusters have same metallicity and are
coeval near distance is 146pc ( Robichon et
al., 1999 ) age of 50Myr ( Barrado y Navascués
et al, 2004) ?not too young ( extinction due
to molecular gaz ) ?not too old ( relaxation
time is 104.9Myr, optical data ) low reddening
E(B-V) 0.01 ( Randoch et al., 2001 ) previous
study of MF completness limit of 0.072M? no
radial study of IC 2391 yet
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Why the open cluster IC 2391 ?
11
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
35 ESO/WFI fields of 34x33 ( 10.9 deg2
) Fields chosen to ? avoid bright stars ?
avoid MF gradient due to low galactic
latitude b-6º
12
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Wide bands Rc and J Medium bands at 770, 815,
856 and 914 nm ? ESO/WFI (optical data) ?
CTIO/CPAPIR (IR data) Those bands were chosen
?to sample spectra of M and L-dwarfs ?to
minimize Earth-sky background
13
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
2nd selection - Color-color diagram -
Isochrones - Red giant colors ( Hauschildt et al.
1999 ) - Color VS Teff for G, K, M and L dwarfs
1st selection - Color-magnitude diagram -
Isochrones
14
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
3rd selection - Astrometry (from our 8 years
baseline)
4th selection - M obs VS M model ( from
Teff and mass ) - Errors on age and distance of
IC 2391 - Unresolved binaries
15
? Major radial variation 0.15 M? lt M lt 0.5
M? ? Major no radial variation M 0.11 M?
? Minor long spectral baseline less
M-dwarf contaminants ? Minor medium band
less M-giant contaminants ? Minor colour
variation with E ( B V )
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
16
? Major radial variation 0.15 M? lt M lt 0.5
M? ? Major no radial variation M 0.11 M?
? Minor long spectral baseline less
M-dwarf contaminants ? Minor medium band
less M-giant contaminants ? Minor colour
variation with E ( B V )
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
17
? Major radial variation 0.15 M? lt M lt 0.5
M? ? Major no radial variation M 0.11 M?
? Minor long spectral baseline less
M-dwarf contaminants ? Minor medium band
less M-giant contaminants ? Minor colour
variation with E ( B V )
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Barrado y Navasqués et al. (2004)
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
18
? Major radial variation 0.15 M? lt M lt 0.5
M? ? Major no radial variation M 0.11 M?
? Minor long spectral baseline less
M-dwarf contaminants ? Minor medium band
less M-giant contaminants ? Minor colour
variation with E ( B V )
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
? Jeffries et al. (2004) ? Naylor et al.
(2002)
19
? Major radial variation 0.15 M? lt M lt 0.5
M? ? Major no radial variation M 0.11 M?
? Minor long spectral baseline less
M-dwarf contaminants ? Minor medium band
less M-giant contaminants ? Minor colour
variation with E ( B V )
Photometric Survey determination of the mass
function for very low mass stars and brown dwarfs
population in IC 2391 and look for radial
dependence
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Schlegel et al. (1998)
20
Spectroscopic Follow-up improve candidate
selection and spectral type determination
CTIO / HYDRA 2 Nights in January 2007 ?1st lost
(bad weather) ?2hrs lost (technical) ?Ic18 (
45 MJ ) FINALLY WE HAD 4HRS !! ( out of 12hrs
awarded )
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
21
Spectroscopic Follow-up improve candidate
selection and spectral type determination
?measurement of EW ?SpT determination ?68
contamination ?MF ??? but no red giants.
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
22
Spectroscopic Follow-up improve candidate
selection and spectral type determination
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
23
Spectroscopic Follow-up improve candidate
selection and spectral type determination
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
Vr 16.256.59 km/s
FROM PHOTOMETRY Teff 2791K M0.058M?
815/2017.54
24
Future Work follow-up on brown dwarfs
candidates and survey on other open clusters
Theoretical Background Photometric
Survey Spectroscopic Follow-up Future Work
? Other clusters Praesepe (WFI, O2K, LBTC,
WFC, 45MJ) Coma Ber (O2K, )
Alessi 5 ASCC 24 (WFI
O2K, 20MJ)
Whats next ?
? VLT/VIMOS for IC2391 (April 2008 --- February
2009)
? NTT/SofI (J Ks) for IC2391 (deep fields)
? Numerical simulation evolution of MF of
cluster with sv
25
CONCLUSIONS AND REVIEW
We are interested in the formation and
evolution of BDs population ? Survey in open
cluster to obtain MF of VLMS and BDs
Vr 16.256.59 km/s
Photometric survey of IC 2391 ? MF shows no
variation on the BDs and VLMS regime ? if
formed by ejection, velocity BDs velocity
VLMS ? if velocity BDs gt velocity VLMS and
ejection give high velocity for BDs, then
ejection not dominant formation process
However important contamination spectroscopic
follow-up NEEDED ? Analyses of preliminary
spectroscopic follow-up 32 real members, no
red giants and 7 new brown dwarfs and
additional data from VLT next spring
FROM PHOTOMETRY Teff 2791K M0.058M?
815/2017.54
Still a lot of work and projects