Chemical evolution of N2H+ in massive star-forming regions 喻耐平 王俊杰 徐金龙 July 2018 Kunming 中德亚毫米波望远镜

Content 1. Massive star formation 2. Properties of N2H+ 3. Data analysis 4. Summary 5. Subsequent work

Massive star formation IRDCs(starless cores) Hot cores HII regions O B clusters

Massive star formation 恒星演化 物理环境 化学性质

Properties of N2H+ Trace dense and cold gas + N Caselli et al. 1995

Properties of N2H+ Lee et al. (2004): Bonner-Ebert sphere + inside-outside collapse Formation: H3+ + N2 → N2H+ + H2 Destroy(T > 20K): N2H+ + CO → HCO+ + N2

Properties of N2H+ N2H+ + e- → N2 + H or NH (Vigren et al. 2012) Yu et al. 2015 MNRAS Yu et al. 2016 ApJ

Properties of N2H+ X(N2H+) Tdust ~20 K ~30 K Early stage Middle stage Late stage Tdust

Data analysis Data set: 1. MALT90 (~90 GHz) 2. Hi-GAL (70, 160, 250, 350, and 500 μm)

Data analysis Molecular data: MALT90 (Foster et al. 2011) From MALT90 home page

Data analysis N2H+ (1-0) N2H+ (1-0)

Data analysis CN148

Data analysis S36

Data analysis G326.432+0.916

Data analysis G326.641+0.612

Data analysis SED method using Hi-GAL (70, 160, 250, 350, and 500 μm): (Wang et al. 2015 MNRAS) 1. Remove the background emissions; 2. smooth and rebin to the beam and pixel sizes of 500 μm; 3. SED N(H2) Tdust Where ,

Data analysis SED result: N(H2) Tdust

Data analysis N(H2) Tdust Abundance map

Data analysis

Data analysis Tdust ~ 27 K

Data analysis Compared with chemical models of low-mass star formation: X(N2H+) ~20 K ~30 K Early stage Middle stage Late stage Tdust

Higher resolution observations are needed! Data analysis Three reasons: 1. Beam dilution; core: ~0.1 pc clump: ~1 pc 2. Chemical model may be not accurate; 3. Massive star formation process. Higher resolution observations are needed!

Summary 1. A method to study chemical properties; 2. When the dust temperature is below 27 K, the abundance of N2H+ increases with dust temperature; 3. When the dust temperature is above 27 K, the abundance of N2H+ begins to drop.

Subsequent work HC3N C2H

The end Thanks