Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array Detection of Exoplanets and Brown Dwarfs with ALMA (and EVLA) Bryan Butler National Radio Astronomy Observatory

ALMA The Centimeter to Submillimeter Spectrum EVLA

Probe through heavy dust obscuration Direct (and indirect) probe of magnetic fields Direct measure of emission from exoplanets and BDs No problems with primary contrast or exozodiacal contamination Superb sensitivity High resolution Access to unique emission mechanisms (gyrocyclotron, e.g.) Why Long Wavelengths?

We measure emission at radio wavelengths with large (generally a few m to a few hundred m) telescopes. Measuring the Radiation

 ~ Typical values are ~ 1 cm, D ~ 20 m, so  ~ 100". Even for ~ 1 mm,  ~ 10" This is not enough spatial resolution for many (most?) astrophysical questions. D D Resolution

How do we get the necessary resolution? With an interferometer: D B >> D Increasing Resolution

Current Interferometers Centimeter - Very Large Array Millimeter/submm - PdB, CARMA, SMA

Improving Millimeter Interferometers Despite their utility, current millimeter and submillimeter interferometers have limited resolution (of order 0.5”), sensitivity (total collecting area < 1000 m 2 ), and frequency coverage Decadal panel of 2000 recognized the need for a next generation mm/submm interferometer, and ranked NRAO’s proposed MilliMeter Array (MMA) one of the highest of ground-based facilities NSF funded a much more ambitious version in collaboration with European partners - the Atacama Large Millimeter Array (ALMA) in Japan joined in More partners have joined since, including Taiwan (ASIAA).

What is ALMA? m antennas, with extremely accurate surfaces and pointing. 4 additional 12-m antennas and 12 additional 7-m antennas for imaging large spatial scales wavelengths from 6mm to 350  m, with incredibly sensitive receivers. antenna separations from 15m to 15km. powerful and flexible correlator; bandwidths to 16 GHz. on an extremely high and dry site in the Chilean Andes. Sensitivity of ~ 200  Jy/min at main bands ( GHz).

ALMA Site High (5000 m), dry site in the northern Chilean Andes (Atacama desert)

ALMA Antennas 12-m diameter 20 micron rms surface accuracy Move 1 deg/s 4 different types

ALMA Receivers Cover all atmospheric windows from GHz Extremely sensitive (quantum limited) and stable

ALMA Configurations The ALMA antennas are mobile and will be configured in “zoom spirals” (Conway 2001) These configurations will cover all but the most compact configuration and out to 5 km maximum antenna separation For highest resolution, a special configuration of antennas is designed with maximum baseline of 15 km, constrained by the extent of the science preserve allocated to ALMA

Linear Resolution ALMA, at 345 GHz in the 15 km configuration, has a resolution of ~12 masec, or in linear extent: So,  l ~ pc (TW Hya,  Pic, AU Microscopium Fomalhaut)  l ~ pc (  Oph, Taurus, Coal Sack, Chameleon, Lupus)  l ~ pc (Orion)

The imaging of protoplanetary disks (in dust and molecular transitions) is one of the three highest level science goals of ALMA, and hence it will be a fantastic instrument for imaging these disks, including early condensations and the gaps cleared by them. Similarly, debris disks are a primary scientific target of ALMA. I will be discussing neither of these today. Protoplanetary and Debris Disks

Extrasolar Solar Systems Hundreds now known, via: – Radial velocity – Direct imaging – Astrometry – Transit – Microlensing – Timing Tens of multiple planet systems Surprising number very close in Selection effects important

EGPs - ALMA Direct Detection Expected flux density at 345 GHz: Distance (pc)JupiterGl229BProto-Jupiter Details in Butler, Wootten, & Brown 2003

Contrast Since we are on the Rayleigh-Jeans tail of emission from the star and exoplanet (or BD), we have little problem with contrast between them, which goes like: Even with a 200 K Jupiter and 6000 K central star, this is only a factor of 3000 in contrast, which is trivial to achieve (heterodyne interferometers routinely achieve thousands to 1, and at radio wavelengths we relatively easily achieve :1, even in the presence of very bright sources, which these stars are not)

EGPs - ALMA Indirect Detection Reflex motion of star: Astrometric resolution of ALMA: Planet is detected at 345 GHz with 15 km baselines if: This is the key!

EGPs - ALMA Indirect Detection Gliese’s 3rd catalog of nearby stars and the Hipparcos catalog reject multiples and variables; those with unknown spectral class; those with dec > 40 o use spectral class and subclass and luminosity class to determine T eff and R Assume planet is in orbit at 5 AU Calculate for 3 planet masses: 5 X Jovian, Jovian, Neptunian Assume 10 minutes of integration Catalog5 X JovianJovianNeptunian Gliese200 (100)120 (30)30 (0) Hipparcos

ALMA Status 12 antennas now on site First ALMA production receivers on site (not yet tested) First quarter of the correlator installed on site Concrete poured for 10’s of antenna pads Two antenna transporters on site Operations Support Facility (OSF) technical buildings built and occupied Array Operation Site (AOS) building built Roads, antenna buildings, etc., built and being used Software tested on ALMA Test Facility at VLA site Early science observing to commence in full operations in 2013

The EVLA will upgrade: Front Ends (feeds + Rx) LO Data transmission Correlator Software Main result is increased sensitivity: 25  Jy/min The VLA is the world’s most powerful radio wavelength interferometer, but was designed and built in the 1960’s/70’s, and completed in the dark ages relative to “modern” electronics! But the infrastructure (antennas, rails, buildings, etc…) are sound. Improving the VLA

Flare Quiescent Upper Limit White et al Krishnamurthi et al White et al Krishnamurthi et al Berger et al Berger 2002 Burgasser & Putman 2005 Berger 2006 McLean et al 2009 (in prep) VLA Observations of Brown Dwarfs

There are now several examples of Ultracool Dwarfs (UCDs) observed with the VLA which have regular pulses, which are used to infer rotation rates (v sin(i)). The pulses repeat over long periods (years), and are completely polarized. Emission mechanisms are being studied. Unique to radio wavelengths! Berger et al. 2009

EVLA Observations of Brown Dwarfs EVLA will allow observation of fainter BDs, including L and T dwarfs, and M dwarfs to much larger distances, potentially allowing a solution to the rotation-age-activity question Wider simultaneous frequency coverage will yield information on emission mechanism(s) (pulsed and not) and magnetic field strengths and topologies

Summary ALMA and the EVLA will be revolutionary ground-based astronomical facilities for the next decade Both to start operating soon (EVLA next year, ALMA in 2011) Open skies (for NA portion anyway)! They will both provide new and exciting results in the areas of extrasolar planets and brown dwarfs: – ALMA will potentially be able to astrometrically detect planets around hundreds of stars (10’s of them solar analogs) – ALMA will potentially be able to directly detect emission from young, hot Jupiters (or Y dwarfs?) out to the nearest star forming regions – EVLA will be able to detect emission from ultracool dwarfs, providing unique information on rotation rates and atmospheric conditions