First ultracool results from the VISTA Hemisphere Survey

Transcription

1 First ultracool results from the VISTA Hemisphere Survey Nicolas Lodieu (1, 2, 3) (1) Instituto de Astrofisica de Canarias (IAC, Tenerife) (2) Universidad de La Laguna (ULL, Tenerife) (3) Ramon y Cajal fellow at the IAC on behalf of the VISTA Hemisphere Survey UltraCool Dwarf (VHS-UCD) consortium (see list of members at the end of the talk) Cool Stars 17 Splinter session, Barcelona, Spain June 2012

2 The VISTA telescope VISTA = Visible and Infrared Survey Telescope for Astronomy 4-m class telescope equipped with the world largest NIR camera VIRCAM offers a FOV of 1.65 sq. deg. with a pixel scale of 0.34 VISTA started operations on 15 October 2009 ZYJHKs filters + 2 narrow-band filters 75% of VISTA dedicated to ESO public surveys More details at

3 The VISTA Hemisphere Survey Aim: Image the entire Southern sky i.e. ~20000 square degrees 1) 5000 sq. deg. in YJHKs around Galactic Caps 2) 5000 sq. deg. in JHKs linked to the Dark Energy Survey 3) sq. deg. in JKs (rest of the sky) Typical 5σ depths: J~19.5±0.3 mag and Ks~18.5±0.3 mag Science drivers: 1) Low-mass stars and nearby stars 2) Merger history of the Galaxy 3) High-redshift quasars 4) Measuring the properties of Dark Energy Principal Investigator: Richard McMahon, IoA, Cambridge (UK)

4 Project 1 Nearby high proper motion objects

5 High Proper Motion Stars VHS vs 2MASS Aim: Complete census of nearby high proper motion stars of any type Method: Cross-match VHS and 2MASS offering a baseline of >10 years Search limits: 1) Objects brighter than J = 16 mag 2) Proper motions larger than 0.4 arcsec/yr 3) Current overage: 1350 square degrees Results: 172 HPM sources identified 1) 149 known HPM sources 2) 23 new HPM objects, including a few L dwarf candidates Master thesis of Rhys Barnett in collaboration with Subanjoy Mohanty

6 Project 2 T and Y dwarfs

7 Ultracool Brown Dwarf Selection Group 1: Group 2: { { VHS vs WISE (w1-w2) 2.0 mag w2snr 3 VHS non detection No USNO counterpart Matching radius 5 (w1-w2) 0.4 mag WISE χ 2 3 & no bad flags VHS point source within 2 (J-w2) 1.6 mag High galactic latitude only Companions to nearby stars and young objects: Discovery of LHS2803AB pair: dm + T6 at 67 arcsec Béjar et al. (2012, in prep), independently found by Muzic et al. (2012)

8 Photometric follow-up Main goals: 1) Confirm proper motions with a 2 nd epoch 2) Detect objects unseen in the VHS J-band images 3) Additional filter coverage if needed 4) Optical counterparts to the brightest BD candidates IAC80/CAMELOT: 1) 0.8-m telescope on Teide Observatory, Tenerife, Canary Islands 2) FOV ~ 10.4 by 10.4 arcmin, pixel scale of arcsec 3) Sloan i and z-band imaging Calar Alto 3.5-m/Omega2000: 1) 3.5-m telescope in Calar Alto, Almeria, Spain 2) FOV of 15.4 by 15.4 arcmin with pixels of 0.45 arcsec 3) JHK and methane imaging NTT/SofI: 4 visitor nights in May ) 3.5-m telescope in La Silla, Chile 2) FOV of 4.9 by 4.9 arcmin with a arcsec pixel scale 3) JH deep imaging

9 Spectroscopic follow-up VLT/XSHOOTER: 0.3(0.8)-2.3 R~600 down to J~18.5 mag Magellan/FIRE: R~ down to J~19.5 mag XSHOOTER FIRE

10 Conclusions Spectroscopic confirmation of 7 late-t dwarfs identified in VHS/WISE Recovery of known T dwarfs New high proper motion objects in the Southern sky Ultracool substellar companions to nearby stars Ever increasing area from VHS will ultimately led to a complete sample of T dwarfs and high proper motion sources in the entire Southern Hemisphere

11 List of VHS-UCD members Rafael Rebolo (IAC, Tenerife, Spain) Maria Teresa Ruiz (Catolica, Chile) Ben Burningham (Hertfordshire, UK) Philip Lucas (Hertfordshire, UK) David Barrado (Calar Alto Observatory) Victor Bejar (IAC, Tenerife, Spain) Antonio Perez Garrido (Cartagena, Spain) Ralf-Dieter Scholz (Potsdam, Germany) Sergey Koposov (Cambridge, UK) Avril Day-Jones (Chile) Richard McMahon (Cambridge, UK) Simon Hodgkin (Cambridge, UK) Hugh Jones (Hertfordshire, UK) Nigel Hambly (Edinburgh, UK) David Pinfield (Hertfordshire, UK) Steve Boudreault (IAC, Tenerife, Spain) Bartosz Gauza (IAC, Tenerife, Spain) Sarah Casewell (Leicester, UK) Leonardo Testi (ESO) Maria Rosa Zapatero Osorio (CAB, Spain) Jim Emerson (QMUL, UK) Richard Jameson (Leicester, UK)