2025A&A...698A..52M

Aims. We present high-contrast imaging observations of seven protoplanetary disks at 4 μm using the Enhanced Resolution Imager and Spectrograph (ERIS) on the Very Large Telescope. This study focuses on detecting scattered light from micron-sized dust particles and assessing the potential of the grating vector Apodizing Phase Plat (gvAPP) coronagraph for disk and planet characterization.
Methods. Observations were performed in pupil-stabilized mode with the vAPP coronagraph. Data were reduced using reference differential imaging and angular differential imaging techniques, incorporating principal component analysis for point-source detection. Contrast curves and detection limits were computed for planetary companions and disk features.
Results. The infrared disk signal was resolved in all systems, with first-time 4 μm detections around AS 209 and Elias 2-24, revealing mostly axisymmetric structures extending up to 60 au. Two gaps were detected in the radial profiles of TW Hya (22 au, 35 au) and AS 209 (50 au, 100 au). For Elias 2-24, scattered light emission matched ALMA observations of inner disk structures, marking their first mid-infrared detection. In the case of HD 100546, the vAPP uncovered flared disk structures and faint spiral arms consistent with previous observations. HD 163296 shows a bright inner dust ring, confirming disk asymmetries and features, but we did not detect any planet candidate within the achieved contrast limits. The disk around PDS 70 exhibits clear features, with faint structures detected within the cavity. The observations achieved contrasts enabling the detection of planets down to 800 K, but no companions were detected, implying either low-mass planets, cooler formation scenarios, or a large dust extinction of A_V ≳ 20 mag.
Conclusions. The vAPP performed robustly for imaging structures in protoplanetary disks at 4 μm, providing critical insights into disk morphology and constraints on planet formation processes. No planetary-mass companions with temperatures >1000 K are present in our sample.