Detection of PAH and nbL features in planetary nebulae NGC 7027 and BD +30° 3639 with TIRCAM2 instrument on 3.6 m DOT

Abstract

High resolution infrared imaging observations of the young planetary nebulae (PNe) NGC 7027 and BD +30° 3639, taken with the newly installed TIFR near infrared camera-II (TIRCAM2) on 3.6 m Devasthal optical telescope (DOT), ARIES, Nainital, are being reported. The images are acquired in J, H, K, polycyclic aromatic hydrocarbon (PAH) and narrow-band L (nbL) filters. The observations show emission from warm dust and PAHs in the circumstellar shells. The imaging of the two objects are among the first observations in PAH and nbL bands using TIRCAM2 on DOT. The NGC 7027 images in all bands show similar elliptical morphology with $\sim$6$^{\prime \prime }$.7 and $\sim$4$^{\prime \prime }$.5 semi-major and semi-minor axes. Considering size up to 10% of peak value the nebula extends upto 8$^{\prime \prime }$ from the central star revealing a multipolar evolution. The relatively cooler BD +30° 3639 shows a rectangular-ring shaped nebula. In J and H bands it shows an angular diameter of $\sim$8$^{\prime \prime }$, while a smaller $\sim$6$^{\prime \prime }$.9 size is observed in K, PAH and nbL bands. The 3.28 $\mu$m emission indicates presence of PAHs at about 6000 and 5000 AU from the central stars in NGC 7027 and BD +30° 3639 respectively. Analysis suggests domination of neutral PAHs in BD +30° 3639, while in NGC 7027 there is higher ionization and more processed PAH population.