Direct Imaging And Spectroscopy Of Exoplanets With The ELT/HARMONI High-contrast Module

Results of our detection simulation based on population synthesis models, using the H-high configuration, on a semi-major axis/mass space (left) and separation/contrast space (right). Blue to red filled dots are the simulated companions, colored according to their S/N. The transition from blue to red is set at 5σ to highlight the detection limit. The companions detected over 5σ are further circled in black for clarity, and the green empty dots show the remaining companions of the population that were not simulated (see text for details). Some known companions are included for comparison. We show as well in the left plot the 10% and 50% detection probability curves of the VLT/SPHERE SHINE survey from Vigan et al. (2020). In the right plot we overlay the T-type detection limit in H-high from Fig. 5.

Combining high-contrast imaging with medium-resolution spectroscopy has been shown to significantly boost the direct detection of exoplanets.

HARMONI, one of the first-light instruments to be mounted on ESO's ELT, will be equipped with a single-conjugated adaptive optics system to reach the diffraction limit of the ELT in H and K bands, a high-contrast module dedicated to exoplanet imaging, and a medium-resolution (up to R = 17 000) optical and near-infrared integral field spectrograph. Combined together, these systems will provide unprecedented contrast limits at separations between 50 and 400 mas. In this paper, we estimate the capabilities of the HARMONI high-contrast module for the direct detection of young giant exoplanets.

We use an end-to-end model of the instrument to simulate observations based on realistic observing scenarios and conditions. We analyze these data with the so-called "molecule mapping" technique combined to a matched-filter approach, in order to disentangle the companions from the host star and tellurics, and increase the S/N of the planetary signal.

We detect planets above 5-sigma at contrasts up to 16 mag and separations down to 75 mas in several spectral configurations of the instrument. We show that molecule mapping allows the detection of companions up to 2.5 mag fainter compared to state-of-the-art high-contrast imaging techniques based on angular differential imaging.

We also demonstrate that the performance is not strongly affected by the spectral type of the host star, and that we reach close sensitivities for the best three quartiles of observing conditions at Armazones, which means that HARMONI could be used in near-critical observations during 60 to 70% of telescope time at the ELT. Finally, we simulate planets from population synthesis models to further explore the parameter space that HARMONI and its high-contrast module will soon open.

Mathis Houllé, Arthur Vigan, Alexis Carlotti, Élodie Choquet, Faustine Cantalloube, Mark W. Phillips, Jean-François Sauvage, Noah Schwartz, Gilles P. P. L. Otten, Isabelle Baraffe, Alexandre Emsenhuber, Christoph Mordasini

Comments: Accepted for publication in A&A (14 pages, 9 figures)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2104.11251 [astro-ph.EP] (or arXiv:2104.11251v1 [astro-ph.EP] for this version)
Submission history
From: Mathis Houllé
[v1] Thu, 22 Apr 2021 18:00:04 UTC (570 KB)

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