Distributions of molecules in the circumnuclear disk and surrounding starburst ring in the Seyfert galaxy NGC 1068 observed with ALMA

• Published in: Publications of the Astronomical Society of Japan Vol. 66; no. 4
• Main Authors: Takano, Shuro, Nakajima, Taku, Kohno, Kotaro, Harada, Nanase, Herbst, Eric, Tamura, Yoichi, Izumi, Takuma, Taniguchi, Akio, Tosaki, Tomoka
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.08.2014
• Subjects: radio lines: galaxies; galaxies: Seyfert; galaxies: starburst; galaxies: individual (NGC 1068); line: identification
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/psu052

Sensitive observations with the Atacama Large Millimeter/submillimeter Array (ALMA) allow astronomers to observe the detailed distributions of molecules with relatively weak intensity in nearby galaxies. In particular, we report distributions of several molecular transitions including shock and dust related species (13CO J = 1–0, C18O J = 1–0, 13CN N = 1–0, CS J = 2–1, SO J N  = 32–21, HNCO J Ka,Kc  = 50,5–40,4, HC3N J = 11–10, 12–11, CH3OH J K  = 2 K –1 K , and CH3CN J K  = 6 K –5 K ) in the nearby Seyfert 2 galaxy NGC 1068 observed with the ALMA early science program. The central ∼ 1′(∼ 4.3 kpc) of this galaxy was observed in the 100-GHz region covering ∼ 96–100 GHz and ∼ 108–111 GHz with an angular resolution of ∼ 4′′ × 2′′ (290 pc × 140 pc) to study the effects of an active galactic nucleus and its surrounding starburst ring on molecular abundances. Here, we present images and report a classification of molecular distributions into three main categories: (1) molecules concentrated in the circumnuclear disk (CND) (SO J N  = 32–21, HC3N J = 11–10, 12–11, and CH3CN J K  = 6 K –5 K ), (2) molecules distributed both in the CND and the starburst ring (CS J = 2–1 and CH3OH J K  = 2 K –1 K ), and (3) molecules distributed mainly in the starburst ring (13CO J = 1–0 and C18O J = 1–0). Since most of the molecules such as HC3N observed in the CND are easily dissociated by UV photons and X-rays, our results indicate that these molecules must be effectively shielded. In the starburst ring, the relative intensity of methanol at each clumpy region is not consistent with those of 13CO, C18O, or CS. This difference is probably caused by the unique formation and destruction mechanisms of CH3OH.