119 research outputs found
The infrared imaging spectrograph (IRIS) for TMT: the science case
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument being
designed for the Thirty Meter Telescope (TMT). IRIS is a combination of an
imager that will cover a 16.4" field of view at the diffraction limit of TMT (4
mas sampling), and an integral field unit spectrograph that will sample objects
at 4-50 mas scales. IRIS will open up new areas of observational parameter
space, allowing major progress in diverse fields of astronomy. We present the
science case and resulting requirements for the performance of IRIS.
Ultimately, the spectrograph will enable very well-resolved and sensitive
studies of the kinematics and internal chemical abundances of high-redshift
galaxies, shedding light on many scenarios for the evolution of galaxies at
early times. With unprecedented imaging and spectroscopy of exoplanets, IRIS
will allow detailed exploration of a range of planetary systems that are
inaccessible with current technology. By revealing details about resolved
stellar populations in nearby galaxies, it will directly probe the formation of
systems like our own Milky Way. Because it will be possible to directly
characterize the stellar initial mass function in many environments and in
galaxies outside of the the Milky Way, IRIS will enable a greater understanding
of whether stars form differently in diverse conditions. IRIS will reveal
detailed kinematics in the centers of low-mass galaxies, allowing a test of
black hole formation scenarios. Finally, it will revolutionize the
characterization of reionization and the first galaxies to form in the
universe.Comment: to appear in Proc. SPIE 773
Gemini Planet Imager Observational Calibrations VI: Photometric and Spectroscopic Calibration for the Integral Field Spectrograph
The Gemini Planet Imager (GPI) is a new facility instrument for the Gemini
Observatory designed to provide direct detection and characterization of
planets and debris disks around stars in the solar neighborhood. In addition to
its extreme adaptive optics and corona graphic systems which give access to
high angular resolution and high-contrast imaging capabilities, GPI contains an
integral field spectrograph providing low resolution spectroscopy across five
bands between 0.95 and 2.5 m. This paper describes the sequence of
processing steps required for the spectro-photometric calibration of GPI
science data, and the necessary calibration files. Based on calibration
observations of the white dwarf HD 8049B we estimate that the systematic error
in spectra extracted from GPI observations is less than 5%. The flux ratio of
the occulted star and fiducial satellite spots within coronagraphic GPI
observations, required to estimate the magnitude difference between a target
and any resolved companions, was measured in the -band to be in laboratory measurements and using
on-sky observations. Laboratory measurements for the , , and
filters are also presented. The total throughput of GPI, Gemini South and the
atmosphere of the Earth was also measured in each photometric passband, with a
typical throughput in -band of 18% in the non-coronagraphic mode, with some
variation observed over the six-month period for which observations were
available. We also report ongoing development and improvement of the data cube
extraction algorithm.Comment: 15 pages, 6 figures. Proceedings of the SPIE, 9147-30
Constraints on the architecture of the HD 95086 planetary system with the Gemini Planet Imager
We present astrometric monitoring of the young exoplanet HD 95086 b obtained
with the Gemini Planet Imager between 2013 and 2016. A small but significant
position angle change is detected at constant separation; the orbital motion is
confirmed with literature measurements. Efficient Monte Carlo techniques place
preliminary constraints on the orbital parameters of HD 95086 b. With 68%
confidence, a semimajor axis of 61.7^{+20.7}_{-8.4} au and an inclination of
153.0^{+9.7}_{-13.5} deg are favored, with eccentricity less than 0.21. Under
the assumption of a co-planar planet-disk system, the periastron of HD 95086 b
is beyond 51 au with 68% confidence. Therefore HD 95086 b cannot carve the
entire gap inferred from the measured infrared excess in the SED of HD 95086.
We use our sensitivity to additional planets to discuss specific scenarios
presented in the literature to explain the geometry of the debris belts. We
suggest that either two planets on moderately eccentric orbits or three to four
planets with inhomogeneous masses and orbital properties are possible. The
sensitivity to additional planetary companions within the observations
presented in this study can be used to help further constrain future dynamical
simulations of the planet-disk system.Comment: Accepted for publication in ApJ
The Peculiar Debris Disk of HD 111520 as Resolved by the Gemini Planet Imager
Using the Gemini Planet Imager (GPI), we have resolved the circumstellar
debris disk around HD 111520 at a projected range of ~30-100 AU in both total
and polarized -band intensity. The disk is seen edge-on at a position angle
of ~165 along the spine of emission. A slight inclination or
asymmetric warping are covariant and alters the interpretation of the observed
disk emission. We employ 3 point spread function (PSF) subtraction methods to
reduce the stellar glare and instrumental artifacts to confirm that there is a
roughly 2:1 brightness asymmetry between the NW and SE extension. This specific
feature makes HD 111520 the most extreme examples of asymmetric debris disks
observed in scattered light among similar highly inclined systems, such as HD
15115 and HD 106906. We further identify a tentative localized brightness
enhancement and scale height enhancement associated with the disk at ~40 AU
away from the star on the SE extension. We also find that the fractional
polarization rises from 10 to 40% from 0.5" to 0.8" from the star. The
combination of large brightness asymmetry and symmetric polarization fraction
leads us to believe that an azimuthal dust density variation is causing the
observed asymmetry.Comment: 9 pages, 8 Figures, 1 table, Accepted to Ap
Improving and Assessing Planet Sensitivity of the GPI Exoplanet Survey with a Forward Model Matched Filter
We present a new matched filter algorithm for direct detection of point
sources in the immediate vicinity of bright stars. The stellar Point Spread
Function (PSF) is first subtracted using a Karhunen-Lo\'eve Image Processing
(KLIP) algorithm with Angular and Spectral Differential Imaging (ADI and SDI).
The KLIP-induced distortion of the astrophysical signal is included in the
matched filter template by computing a forward model of the PSF at every
position in the image. To optimize the performance of the algorithm, we conduct
extensive planet injection and recovery tests and tune the exoplanet spectra
template and KLIP reduction aggressiveness to maximize the Signal-to-Noise
Ratio (SNR) of the recovered planets. We show that only two spectral templates
are necessary to recover any young Jovian exoplanets with minimal SNR loss. We
also developed a complete pipeline for the automated detection of point source
candidates, the calculation of Receiver Operating Characteristics (ROC), false
positives based contrast curves, and completeness contours. We process in a
uniform manner more than 330 datasets from the Gemini Planet Imager Exoplanet
Survey (GPIES) and assess GPI typical sensitivity as a function of the star and
the hypothetical companion spectral type. This work allows for the first time a
comparison of different detection algorithms at a survey scale accounting for
both planet completeness and false positive rate. We show that the new forward
model matched filter allows the detection of fainter objects than a
conventional cross-correlation technique with a Gaussian PSF template for the
same false positive rate.Comment: ApJ accepte
Dynamical Mass Measurement of the Young Spectroscopic Binary V343 Normae AaAb Resolved With the Gemini Planet Imager
We present new spatially resolved astrometry and photometry from the Gemini
Planet Imager of the inner binary of the young multiple star system V343
Normae, which is a member of the beta Pictoris moving group. V343 Normae
comprises a K0 and mid-M star in a ~4.5 year orbit (AaAb) and a wide 10" M5
companion (B). By combining these data with archival astrometry and radial
velocities we fit the orbit and measure individual masses for both components
of M_Aa = 1.10 +/- 0.10 M_sun and M_Ab = 0.290 +/- 0.018 M_sun. Comparing to
theoretical isochrones, we find good agreement for the measured masses and JHK
band magnitudes of the two components consistent with the age of the beta Pic
moving group. We derive a model-dependent age for the beta Pic moving group of
26 +/- 3 Myr by combining our results for V343 Normae with literature
measurements for GJ 3305, which is another group member with resolved binary
components and dynamical masses.Comment: 12 pages, 7 figures. Accepted to A
GPI spectra of HR 8799 c, d, and e from 1.5 to 2.4m with KLIP Forward Modeling
We explore KLIP forward modeling spectral extraction on Gemini Planet Imager
coronagraphic data of HR 8799, using PyKLIP and show algorithm stability with
varying KLIP parameters. We report new and re-reduced spectrophotometry of HR
8799 c, d, and e in H & K bands. We discuss a strategy for choosing optimal
KLIP PSF subtraction parameters by injecting simulated sources and recovering
them over a range of parameters. The K1/K2 spectra for HR 8799 c and d are
similar to previously published results from the same dataset. We also present
a K band spectrum of HR 8799 e for the first time and show that our H-band
spectra agree well with previously published spectra from the VLT/SPHERE
instrument. We show that HR 8799 c and d show significant differences in their
H & K spectra, but do not find any conclusive differences between d and e or c
and e, likely due to large error bars in the recovered spectrum of e. Compared
to M, L, and T-type field brown dwarfs, all three planets are most consistent
with mid and late L spectral types. All objects are consistent with low gravity
but a lack of standard spectra for low gravity limit the ability to fit the
best spectral type. We discuss how dedicated modeling efforts can better fit HR
8799 planets' near-IR flux and discuss how differences between the properties
of these planets can be further explored.Comment: Accepted to AJ, 25 pages, 16 Figure
Performance of the Gemini Planet Imager Non-Redundant Mask and spectroscopy of two close-separation binaries HR 2690 and HD 142527
The Gemini Planet Imager (GPI) contains a 10-hole non-redundant mask (NRM),
enabling interferometric resolution in complement to its coronagraphic
capabilities. The NRM operates both in spectroscopic (integral field
spectrograph, henceforth IFS) and polarimetric configurations. NRM observations
were taken between 2013 and 2016 to characterize its performance. Most
observations were taken in spectroscopic mode with the goal of obtaining
precise astrometry and spectroscopy of faint companions to bright stars. We
find a clear correlation between residual wavefront error measured by the AO
system and the contrast sensitivity by comparing phase errors in observations
of the same source, taken on different dates. We find a typical 5-
contrast sensitivity of at . We explore the
accuracy of spectral extraction of secondary components of binary systems by
recovering the signal from a simulated source injected into several datasets.
We outline data reduction procedures unique to GPI's IFS and describe a newly
public data pipeline used for the presented analyses. We demonstrate recovery
of astrometry and spectroscopy of two known companions to HR 2690 and HD
142527. NRM+polarimetry observations achieve differential visibility precision
of in the best case. We discuss its limitations on
Gemini-S/GPI for resolving inner regions of protoplanetary disks and prospects
for future upgrades. We summarize lessons learned in observing with NRM in
spectroscopic and polarimetric modes.Comment: Accepted to AJ, 22 pages, 14 figure
Characterizing 51 Eri b from 1-5 m: a partly-cloudy exoplanet
We present spectro-photometry spanning 1-5 m of 51 Eridani b, a 2-10
M planet discovered by the Gemini Planet Imager Exoplanet Survey.
In this study, we present new (1.90-2.19 m) and (2.10-2.40
m) spectra taken with the Gemini Planet Imager as well as an updated
(3.76 m) and new (4.67 m) photometry from the NIRC2 Narrow
camera. The new data were combined with (1.13-1.35 m) and
(1.50-1.80 m) spectra from the discovery epoch with the goal of better
characterizing the planet properties. 51 Eri b photometry is redder than field
brown dwarfs as well as known young T-dwarfs with similar spectral type
(between T4-T8) and we propose that 51 Eri b might be in the process of
undergoing the transition from L-type to T-type. We used two complementary
atmosphere model grids including either deep iron/silicate clouds or
sulfide/salt clouds in the photosphere, spanning a range of cloud properties,
including fully cloudy, cloud free and patchy/intermediate opacity clouds.
Model fits suggest that 51 Eri b has an effective temperature ranging between
605-737 K, a solar metallicity, a surface gravity of (g) = 3.5-4.0 dex,
and the atmosphere requires a patchy cloud atmosphere to model the SED. From
the model atmospheres, we infer a luminosity for the planet of -5.83 to -5.93
(), leaving 51 Eri b in the unique position as being one of
the only directly imaged planet consistent with having formed via cold-start
scenario. Comparisons of the planet SED against warm-start models indicates
that the planet luminosity is best reproduced by a planet formed via core
accretion with a core mass between 15 and 127 M.Comment: 27 pages, 19 figures, Accepted for publication in The Astronomical
Journa
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