Proof of shock-excited H2 in low-ionization structure of PNe

11th Pacific Rim Conference on Stellar Astrophysics: Physics and Chemistry of the Late Stages of Stellar Evolution

物理学;天文学

Akras, Stavros^1 ; Gonçalves, Denise R.^1 ; Ramos-Larios, Gerardo^2

Observatório Do Valongo, Universidade Federal Do Rio de Janeiro, Ladeira Pedro Antonio 43, Rio de Janeiro

20080-090, Brazil^1

Instituto de Astronomía y Meteorología, Av. Vallarta No. 2602, Col. Arcos Vallarta, Guadalajara, Jalisco

CP 44130, Mexico^2

关键词: Bipolar structure;    High angular resolutions;    High velocity;    Lateral expansion;    Line emissions;    Molecular gas;    Planetary nebulae;    Shock interactions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/728/3/032003/pdf
DOI  :  10.1088/1742-6596/728/3/032003

学科分类：天文学(综合)

来源: IOP

【 摘 要 】

We report the detection of near-IR H2line emission from the low-ionization structures (LISs) in planetary nebulae. The deepest, high-angular resolution H21-0 S(1) at 2.122 μm, and H22-1 S(1) at 2.248 μm images of K 4-47 and NGC 7662, obtained using NIRI@Gemini-North, are presented here. K 4-47 reveals a remarkable high-collimated bipolar structure, with the H2emission emanating from the walls of the outflows and a pair of knots at the tips of these outflows. The H21-0 S(1)/2-1 S(1) line ratio is ∼7-8 which indicates shock interaction due to both the lateral expansion of the gas and the high-velocity knots. The strongest line, H2v=1-0 S(1), is also detected in several LISs located at the periphery of the outer shell of the elliptical PN NGC 7662, whereas only four knots are detected in the H2v = 2-1 S(1) line. These knots have H2v = 1-0 S(1)/v = 2-1 S(1) values between 3 and 5. These data confirm the presence of molecular gas in both highly (K 4-47) and slowly moving LISs (NGC 7662). The H2emission in K 4-47 is powered by shocks, whereas in NGC 7662 is due to photo-ionization by the central star. Moreover, a likely correlation is found between the H2v = 1-0 S(1)/H2v = 2-1 S(1) and [N II]/Hα line ratios.