Pascale Hibon

First light of the Gemini Planet Imager

Bruce Macintosh a , James R. Graham , Patrick Ingraham b , Quinn Konopacky , Christian Marois , Marshall Perrin f , Lisa Poyneer a , Brian Bauman a , Travis Barman , Adam Burrows , Andrew Cardwell , Jeffrey Chilcote j , Robert J. De Rosa , Daren Dillon , Rene Doyon , Jennifer Dunn e , Darren Erikson e , Michael Fitzgerald j , Donald Gavel l , Stephen Goodsell i , Markus Hartung i , Pascale Hibon i , Paul G. Kalas c , James Larkin j , Jerome Maire d , Franck Marchis , Mark Marley , James McBride c , Max Millar-Blanchaer d , Katie Morzinski , Andew Norton l B. R. Oppenheimer , Dave Palmer a , Jennifer Patience k , Laurent Pueyo f , Fredrik Rantakyro i , Naru Sadakuni i , Leslie Saddlemyer e , Dmitry Savransky , Andrew Serio i , Remi Soummer f Anand Sivaramakrishnan f , q Inseok Song , Sandrine Thomas , J. Kent Wallace , Sloane Wiktorowicz l , and Schuyler Wolff vSignificance Direct detection—spatially resolving the light of a planet from the light of its parent star—is an important technique for characterizing exoplanets. It allows observations of giant exoplanets in locations like those in our solar system, inaccessible by other methods. The Gemini Planet Imager (GPI) is a new instrument for the Gemini South telescope. Designed and optimized only for high-contrast imaging, it incorporates advanced adaptive optics, diffraction control, a near-infrared spectrograph, and an imaging polarimeter. During first-light scientific observations in November 2013, GPI achieved contrast performance that is an order of magnitude better than conventional adaptive optics imagers. The Gemini Planet Imager is a dedicated facility for directly imaging and spectroscopically characterizing extrasolar planets. It combines a very high-order adaptive optics system, a diffraction-suppressing coronagraph, and an integral field spectrograph with low spectral resolution but high spatial resolution. Every aspect of the Gemini Planet Imager has been tuned for maximum sensitivity to faint planets near bright stars. During first-light observations, we achieved an estimated H band Strehl ratio of 0.89 and a 5-σ contrast of 106 at 0.75 arcseconds and 105 at 0.35 arcseconds. Observations of Beta Pictoris clearly detect the planet, Beta Pictoris b, in a single 60-s exposure with minimal postprocessing. Beta Pictoris b is observed at a separation of 434 ± 6 milliarcseconds (mas) and position angle 211.8 ± 0.5°. Fitting the Keplerian orbit of Beta Pic b using the new position together with previous astrometry gives a factor of 3 improvement in most parameters over previous solutions. The planet orbits at a semimajor axis of 9.0−0.4+0.8 AU near the 3:2 resonance with the previously known 6-AU asteroidal belt and is aligned with the inner warped disk. The observations give a 4% probability of a transit of the planet in late 2017.

Discovery and spectroscopy of the young jovian planet 51 Eri b with the Gemini Planet Imager

An exoplanet extracted from the bright Direct imaging of Jupiter-like exoplanets around young stars provides a glimpse into how our solar system formed. The brightness of young stars requires the use of next-generation devices such as the Gemini Planet Imager (GPI). Using the GPI, Macintosh et al. discovered a Jupiter-like planet orbiting a young star, 51 Eridani (see the Perspective by Mawet). The planet, 51 Eri b, has a methane signature and is probably the smallest exoplanet that has been directly imaged. These findings open the door to understanding solar system origins and herald the dawn of a new era in next-generation planetary imaging. Science, this issue p. 64; see also p. 39 The Gemini Planet Imager detects a Jupiter-like exoplanet orbiting the young star 51 Eridani. [Also see Perspective by Mawet] Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the Gemini Planet Imager, we discovered a planet orbiting the ~20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10−6 and an effective temperature of 600 to 750 kelvin. For this age and luminosity, “hot-start” formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the “cold-start” core-accretion process that may have formed Jupiter.

Gemini Planet Imager observational calibrations I: Overview of the GPI data reduction pipeline

The Gemini Planet Imager (GPI) has as its science instrument an infrared integral field spectrograph/polarimeter (IFS). Integral field spectrographs are scientificially powerful but require sophisticated data reduction systems. For GPI to achieve its scientific goals of exoplanet and disk characterization, IFS data must be reconstructed into high quality astrometrically and photometrically accurate datacubes in both spectral and polarization modes, via flexible software that is usable by the broad Gemini community. The data reduction pipeline developed by the GPI instrument team to meet these needs is now publicly available following GPI’s commissioning. This paper, the first of a series, provides a broad overview of GPI data reduction, summarizes key steps, and presents the overall software framework and implementation. Subsequent papers describe in more detail the algorithms necessary for calibrating GPI data. The GPI data reduction pipeline is open source, available from planetimager.org, and will continue to be enhanced throughout the life of the instrument. It implements an extensive suite of task primitives that can be assembled into reduction recipes to produce calibrated datasets ready for scientific analysis. Angular, spectral, and polarimetric differential imaging are supported. Graphical tools automate the production and editing of recipes, an integrated calibration database manages reference files, and an interactive data viewer customized for high contrast imaging allows for exploration and manipulation of data.

Evolution of the observed Lyα luminosity function from z = 6.5 to z = 7.7: evidence for the epoch of reionization?

Aims. Lyα emitters (LAEs) can be detected out to very high redshifts during the epoch of reionization. The evolution of the LAE luminosity function with redshift is a direct probe of the Lyα transmission of the intergalactic medium (IGM), and therefore of the IGM neutral-hydrogen fraction. Measuring the Lyα luminosity function (LF) of Lyα emitters at redshift z = 7.7 therefore allows us to constrain the ionizing state of the Universe at this redshift. Methods. We observed three 7. 5 × 7. 5 fields with the HAWK-I instrument at the VLT with a narrow band filter centred at 1.06 μm and targeting Lyα emitters at redshift z ∼ 7.7. The fields were chosen for the availability of multiwavelength data. One field is a galaxy cluster, the Bullet Cluster, which allowed us to use gravitational amplification to probe luminosities that are fainter than in the field. The two other fields are subareas of the GOODS Chandra Deep Field South and CFHTLS-D4 deep field. We selected z = 7.7 LAE candidates from a variety of colour criteria, in particular from the absence of detection in the optical bands. Results. We do not find any LAE candidates at z = 7.7 in ∼2.4 × 104 Mpc3 down to a narrow band AB magnitude of ∼26, which allows us to infer robust constraints on the Lyα LAE luminosity function at this redshift. Conclusions. The predicted mean number of objects at z = 6.5, derived from somewhat different luminosity functions of Hu et al. (2010, ApJ, 725, 394), Ouchi et al. (2010, ApJ, 723, 869), and Kashikawa et al. (2011, ApJ, 734, 119) are 2.5, 13.7, and 11.6, respectively. Depending on which of these luminosity functions we refer to, we exclude a scenario with no evolution from z = 6.5 to z = 7.7 at 85% confidence without requiring a strong change in the IGM Lyα transmission, or at 99% confidence with a significant quenching of the IGM Lyα transmission, possibly from a strong increase in the high neutral-hydrogen fraction between these two redshifts.

A narrow-band search for Lyα emitting galaxies at z= 8.8 ⋆

Aims: The first star forming galaxies in the early universe should be copious Ly alpha emitters, and may play a significant role in ionizing the intergalactic medium (IGM). It has been proposed that the luminosity function of Lya emitting galaxies beyond z~6 may be used to constrain the neutral fraction of the IGM during this epoch. In this work we report on a search for Ly alpha emitters at redshift 8.8. Methods: We performed a narrow band imaging programme using ISAAC at the ESO VLT. Seven fields, covering a total area of 31sq. arcmin and for which optical and broad band infra-red images have been obtained in the GOODS survey, were imaged to a limiting flux (respectively luminosity) of ~ 1.3 x 10^{-17} ergs.s^{-1}.cm^{-2} (respectively ~ 1.3 x 10^{43} ergs.s^{-1} in a narrow band filter centered in a region of low OH sky emission at 1.19 micron. Candidate Lyman alpha emitters are objects that are detected in the ISAAC NB images and undetected in the visible broad band images. Results: No z=8.8 Ly alpha emitting galaxies were detected to a limit approaching recent estimates of the luminosity function at z ~ 6. Our results do suggest, however, that detections or substantial constraints could be achieved by this method in the near future with larger field instruments planned for various telescopes.

β PICTORIS' INNER DISK in POLARIZED LIGHT and NEW ORBITAL PARAMETERS for β PICTORIS b

© 2015. The American Astronomical Society. All rights reserved. We present H-band observations of β Pic with the Gemini Planet Imagers (GPIs) polarimetry mode that reveal the debris disk between ∼0.″3 (6 AU) and ∼1.″7 (33 AU), while simultaneously detecting β Pic b. The polarized disk image was fit with a dust density model combined with a Henyey-Greenstein scattering phase function. The best-fit model indicates a disk inclined to the line of sight () with a position angle (PA) (slightly offset from the main outer disk, ), that extends from an inner disk radius of to well outside GPIs field of view. In addition, we present an updated orbit for β Pic b based on new astrometric measurements taken in GPIs spectroscopic mode spanning 14 months. The planet has a semimajor axis of , with an eccentricity The PA of the ascending node is offset from both the outer main disk and the inner disk seen in the GPI image. The orbital fit constrains the stellar mass of β Pic to Dynamical sculpting by β Pic b cannot easily account for the following three aspects of the inferred disk properties: (1) the modeled inner radius of the disk is farther out than expected if caused by β Pic b; (2) the mutual inclination of the inner disk and β Pic b is when it is expected to be closer to zero; and (3) the aspect ratio of the disk () is larger than expected from interactions with β Pic b or self-stirring by the disks parent bodies.

Searching for z 7.7 Lyα emitters in the cosmos field with newfirm

The study of Ly-alpha emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Ly-alpha line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Ly-alpha emitters in the COSMOS field. We have used two ultra-narrowband filters (filter width of ~8-9 {\deg}A) on the NEWFIRM camera, installed on the Mayall 4m telescope at Kitt Peak National Observatory, in order to isolate Ly-alpha emitters at z = 7.7; such ultra-narrowband imaging searches have proved to be excellent at detecting Ly-alpha emitters. We found 5-sigma detections of four candidate Ly-alpha emitters in a survey volume of 2.8 x 10^4 Mpc^3 (total survey area ~760 arcmin^2). Each candidate has a line flux greater than 8 x 10^-18 erg s^-1 cm^-2. Using these results to construct a luminosity function and comparing to previously established Ly-alpha luminosity functions at z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of the luminosity function between z = 5.7 and z = 7.7. Statistical Monte Carlo simulations suggest that half of these candidates are real z = 7.7 targets, and spectroscopic follow-up will be required to verify the redshift of these candidates. However, our results are consistent with no strong evolution in the neutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if only one or two of the z = 7.7 candidates are spectroscopically confirmed.

Gemini planet imager observational calibrations VIII: characterization and role of satellite spots

The Gemini Planet Imager (GPI) combines extreme adaptive optics, an integral field spectrograph, and a high performance coronagraph to directly image extrasolar planets in the near-infrared. Because the coronagraph blocks most of the light from the star, it prevents the properties of the host star from being measured directly. Instead, satellite spots, which are created by diffraction from a square grid in the pupil plane, can be used to locate the star and extract its spectrum. We describe the techniques implemented into the GPI Data Reduction Pipeline to measure the properties of the satellite spots and discuss the precision of the reconstructed astrometry and spectrophotometry of the occulted star. We find the astrometric precision of the satellite spots in an H-band datacube to be 0.05 pixels and is best when individual satellite spots have a signal to noise ratio (SNR) of > 20. In regards to satellite spot spectrophotometry, we find that the total flux from the satellite spots is stable to ~7% and scales linearly with central star brightness and that the shape of the satellite spot spectrum varies on the 2% level.

The integral field spectrograph for the Gemini planet imager

The Gemini Planet Imager (GPI) is a complex optical system designed to directly detect the self-emission of young planets within two arcseconds of their host stars. After suppressing the starlight with an advanced AO system and apodized coronagraph, the dominant residual contamination in the focal plane are speckles from the atmosphere and optical surfaces. Since speckles are diffractive in nature their positions in the field are strongly wavelength dependent, while an actual companion planet will remain at fixed separation. By comparing multiple images at different wavelengths taken simultaneously, we can freeze the speckle pattern and extract the planet light adding an order of magnitude of contrast. To achieve a bandpass of 20%, sufficient to perform speckle suppression, and to observe the entire two arcsecond field of view at diffraction limited sampling, we designed and built an integral field spectrograph with extremely low wavefront error and almost no chromatic aberration. The spectrograph is fully cryogenic and operates in the wavelength range 1 to 2.4 microns with five selectable filters. A prism is used to produce a spectral resolution of 45 in the primary detection band and maintain high throughput. Based on the OSIRIS spectrograph at Keck, we selected to use a lenslet-based spectrograph to achieve an rms wavefront error of approximately 25 nm. Over 36,000 spectra are taken simultaneously and reassembled into image cubes that have roughly 192x192 spatial elements and contain between 11 and 20 spectral channels. The primary dispersion prism can be replaced with a Wollaston prism for dual polarization measurements. The spectrograph also has a pupil-viewing mode for alignment and calibration.

THE ORBIT and TRANSIT PROSPECTS for β PICTORIS b CONSTRAINED with ONE MILLIARCSECOND ASTROMETRY

Gemini Observatory; National Science Foundation [NSF AST-1518332]; NASA [NNX15AC89G, NNX15AD95G]; U.S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC52-07NA27344]