Brown dwarfs and star forming regions in the framework of the Virtual Observatory'

1
Brown dwarfs and star forming regions in the
framework of the Virtual Observatory.

• Enrique Solano, LAEFF / SVO
• Eduardo Martín, IAC / SVO Network
• J. A. Caballero, MPI / SVO Network

• Introduction BDs and VO.
• Discovery of new candidates (field SFR).
• Characterization of SFR
• Testing the BD formation theories.

2
The search for the rare

• The advances in technology (large-scale detector
  arrays, computing capability, highly automated
  pipelines and analysis software,) have undergone
  an explosion of productivity in the search for
  rare objects through large-area surveys.
• From the brightest and most distant quasars (e.g
  Fan et al. 2004)
• to the faintest and nearest stars and brown
  dwarfs (e.g. Burgasser et al. 2002)

• The Virtual Observatory goes a step ahead
  offering
• The possibility of joining these large data sets
  
• The development of tools to facilitate the
  efficient analysis of the contents.

3
Brown dwarfs

• Represent a class of objects linking the
  properties of observable low-mass stars and BD
  with the properties of unobservable
  extrasolar-planets.

4
Brown dwarfs detection methods

• Most of them have been identified using
• Large-area, optical and near-IR surveys
• Color criteria

2MASS
SDSS
DENIS
5
BDs discovered using VO

• However, systematic searches using a VO
  methodology have not been performed so far.

6
Brown dwarfs and star forming regions in the
framework of the Virtual Observatory.

• Enrique Solano, LAEFF / SVO
• Eduardo Martín, IAC / SVO Network
• J. A. Caballero, MPI / SVO Network

• Introduction BDs and VO.
• Discovery of new candidates (field SFR).
• Characterization of SFR
• Testing the BD formation theories.

7
I.- Discovering field BDs with 2MASS/DENIS/SDSS

• DENIS, 2MASS, SDSS/DR5 Millions of objects and
  still new releases to come. (SDSS/DR5 a few
  months ago).
• The South also exists most of the T dwarfs
  were discovered using 2MASS / SDSS ? DENIS
  exploitation.
• Good astrometric (0.5arcsec) and photometry
  accuracy.

• Simulations predict 12 L and 21 T dwarfs
  within the 10 pc horizon, more than twice the
  number so far identified.

• 2MASS/J 10s-limit 15.8
• DENIS/J 3s-limit 16.5
• 2 lt (z-J) lt 4
• SDSS/z limit 20.4
• ? The nearby T dwarf population can be detected.

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using a VO methodology
9
Discovering field BDs with 2MASS/SDSS
Discovering field BDs with 2MASS/DENIS

• Region surveyed
• RA 300 360 / DEC -10 / -34
• RA 210 270 / DEC -1 / -13
• 108 potential candidates
• Follow-up (IR imaging) already done. Analysis
  on-going.

• Region surveyed
• RA 300 360 / DEC 0 20
• Three potential candidates, one of them already
  identified as BD (2004, AJ, 127, 3553)
• Follow-up (IR imaging) foreseen for the coming
  weeks.

10
Whats next?
11
UKIDSS (II)

• z (SDSS) limiting magnitude 20.4
• J (2MASS) limiting magnitude 15.8
• ?Faint SDSS sources do not have 2MASS
  counterparts.

• The discovery of brown dwarfs cooler than T
  dwarfs (the Y dwarfs) is one of the key science
  drivers for UKIDSS.

12
Brown dwarfs and star forming regions in the
framework of the Virtual Observatory.

• Enrique Solano, LAEFF / SVO
• Eduardo Martín, IAC / SVO Network
• J. A. Caballero, MPI / SVO Network

• Introduction BDs and VO.
• Discovery of new candidates (field SFR).
• Characterization of SFR
• Testing the BD formation theories.

13
II.- Characterization of SFRs
14
Characterization of SFRs (II)

• Jumping to the substellar regime
• From 3 to 0.05 solar masses
• 2MASS / DENIS correlation.
• 30 arcmin search radius.
• Selection criteria based on well-known cluster
  members.

• On-going Similar analysis for all the clusters
  of the Orion belt.

15
Brown dwarfs and star forming regions in the
framework of the Virtual Observatory.

• Enrique Solano, LAEFF / SVO
• Eduardo Martín, IAC / SVO Network
• J. A. Caballero, MPI / SVO Network

• Introduction BDs and VO.
• Discovery of new candidates (field SFR).
• Characterization of SFR
• Testing the BD formation theories.

16
Testing the BD formation theories

• The way how BDs are formed is still a matter of
  debate.
• Their masses are two orders of magnitude smaller
  than the average Jeans mass (approximate estimate
  of the lower limit to the stellar mass given a
  density and temperature) in star-forming clouds.
• BUT
• They are as numerous as normal stars.

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The project rationale

• So far, all the surveys for young BDs
  concentrate on the known star-formation regions
  (e.g Taurus-Auriga).
• Depending on the ejection velocity BDs may have
  travelled far from their birth sites and not
  revealed by the previously mentioned surveys.
• Check the ejection model by cross-correlating
  IPHAS and 2MASS to search young BD by their Ha
  emission and IR colors.

• IPHAS
• INT Photometric Ha survey (Drew05)
• 1800 deg²
• -5ltblt5
• r, i, H? filters
• r20 (10 ?), i19
• 80M sources in the Final Catalogue.

18
The project candidates and follow up

• Filtering using appropriate (r-Ha), (I-J),
  (J-H), (H-K) color criteria. ( 300 candidates)

• Low resolution spectroscopic follow-up for a
  proper identification and determination of
  physical parameters.
• WHT 2 nights (Aug 1st-2nd). 35 candidates
  observed.
• NOT/ALFOSC 5 nights granted in Winter 06-07.

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Conclusions

• The scarcity in the number of known brown dwarfs
  has a considerable impact on different fields of
  Astrophysics, in particular on the area of star
  formation.
• This problem has been identified as a key
  VO-Science case both by AstroGrid (included in
  the "Top-Ten" cases) and EURO-VO (through its
  Science Reference Mission).
• Building a census of substellar objects implies
  the discovery of a statistically significant
  number of them through queries that combine
  attributes available from different archives.
• This is an approach out of the scope of the
  "classical" methodology but that perfectly fits
  into the Virtual Observatory.
• The goal of this presentation has been to
  demonstrate the potential of carrying out this
  type of analysis in the VO framework.

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The observational evidences

• Ha double peak ?
  Indicator of accretion.
• Scenario compatible with a disk dissipation in a
  timescale similar to T Tauris.

• A high percentage of BDs found in Star Forming
  Regions show IR excesses ? Existence of
  disks.

21
The theories

• Photoerosion of prestellar cores (Whitworth
  Zinnecker, 2004)
• Turbulent fragmentation (Padoan Nordlund,
  2004)
• Ejection (Reipurth Clarke, 2001)