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Protoplanetary discs of isolated VLMOs discovered in the
IPHAS survey
Luisa Valdivielso (IAC)
Collaborators: E. Martín, H. Bouy, E. Solano, J.Drew, R. Greimel, B. Riaz
10/09/2009 [email protected]
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Aims
Search young low mass objects on the IPHAS survey
Spectral type (SpT) classification with low resolution spectroscopy of the targets
Study the chromosferic/accretion activity measuring the Hequivalent width
NaI doublet (818.3nm, 819.5nm) equivalent width as surface gravity indicator
Distance estimation and comparison with known SFR’s
Spitzer photometry, SED’s & disc properties
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Outline
•Introduction
•Data selection & observations
•Results
•Conclusions & perspectives
IntroductionVery low mass objects and brown dwarfs
Many young objects show H emission due to accretion processes
Search in star formation regions such as Chamaeleon, Oph, Orionis, Serpens, Taurus, Trapezium…
Broadband optical surveys have missed strong Halpha emitters as they appear bluer than they are
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Introduction: IPHAS Survey
Observations with WFC (Wide Field Camera) on Isaac Newton Telescope
Filters: r’ (6240 Å), i’ (7743 Å) Sloan, H(6568 Å)
Magnitude limit r’ ~20
1800º2 in the North of the Milky Way: search very low mass objects out of the best known star forming regions
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Data: targets selection
Cross-match of IPHAS with 2MASS (The Two Micron All Sky Survey) catalogue using Aladin: r’, i’, H, J, H, K photometry of the targets
Selection criteria for 2MASS sources:a) 0.7<J-H<1.3 discard strong reddened objects and
red giantsb) 0.5<H-K<1.1 cool photospheres objects and/or
infrared excess IPHAS counterparts:
a) 1.1<r’-H<3.0b) 16<i’<18.5c) 1.2<r’-i’<2.2d) 2.9<i’-J<3.5 red objects
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Data: Observations
WHT/ISIS : - Dates: 2006 August 1-2- 35 targets-texp : 700-1800s
NOT/ALFOSC : Dates: 2006 October 10-14 56 targets texp : 300-2400s
3m-Shane Telescope/KAST: - Dates: 2007 July 2-5- 25 targets texp : 300-2400s
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Results
116 IPHAS targets observed:
48 real candidates according new IPHAS photometry
42 objects show strong Hemission (success rate > 80%)
12 objects M5.5-M7
30 between M0-M5.5
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H vs SpT
Barrado y Navascués & Martín (2003) criteria to study the accretion level of the targets.
All objects with Hemission show accretion
[email protected] L. Valdivielso
NaI doublet measurements
NaI doublet equivalent width measurements between 8172Å and 8207Å
Comparison with field M dwarfs & Upper Sco members (5Myr)
Later type objects show lower surface gravity
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Upper-Sco
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Spectro-photometric distances
Baraffe Nextgen models log g=4 ; age 5Myr and 2Myr to compute distances
SIMBAD search within 30arcmin
16 of them located near molecular clouds, star formation regions and young open clusters: Serpens, North American Nebula, Cep IV, IC1396, Cygnus
Some objects not located to any known young association (free-floating ejected from sfr? member of unknown nearby assoc?)
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Spitzer photometry
Search Spitzer data to compute SED’s
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Data avaliable for 17 objects
Nº objects with 3.6-24 µm: 9
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Spitzer photometry
Search Spitzer data to compute SED’s
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Data avaliable for 17 objects
Nº objects with 3.6-24 µm: 9
Comparison with –Oph members
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Preliminary SED analysis
[email protected] L. Valdivielso
Robitaille SED online-fitting tool for first estimations of disc properties (Robitaille et al. 2007)
Stellar age ~2.5MyrStellar mass ~0.14Msun
Stellar radius ~1.16Rsun
Stellar Temperature ~3063KDisk mass ~1.63e-4Msun
i(deg) ~40-50SpT M6
CONCLUSIONS
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[email protected] L. Valdivielso
VO tools are very efficient to search for very low mass objects and brown dwarfs using large databases
IPHAS survey to detect new objects using optical wavelengths
We spectroscopically detect very low mass objects in different regions studied until now
Most of the objects with H emission show evidences of accretion processes and very low surface density indicative of youth
Spitzer data show infrared excesses due to protoplanetary discs
PERSPECTIVES
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[email protected] L. Valdivielso
Extend this study using the new release of IPHAS
Originally the goal was complement optical surveys but our study proved to be complementary to mid-IR surveys (SPITZER) as well
Study in more detail the properties of the isolated young VLMOs (kinematics, activity, GAIA, HERSCHEL)
This study can be perform in particular regions to see how many objects have been missed
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