ALMA Fellow Report: Radiation Transfer Modeling of Star and Disk - - PowerPoint PPT Presentation

ALMA Fellow Report:

“Radiation Transfer Modeling of Star and Disk Formation for ALMA”

Department of Earth & Space Science, Osaka University

Kengo TOMIDA Kei TANAKA

ALMA Users’ Meeting 2018/12/26

The Goal of Our Project

• Develop a post-processing radiation transfer code

based on the Athena++ framework for synthetic

• bservations (mainly) for ALMA
• Use synthetic observations for proposing and

interpreting observations of star and disk formation

• Bridge the gap between observations and simulations

to understand star/disk formation more quantitatively This is a half theory, half observation project.

(Athena++: a public astrophysical MHD code we are developing.)

The First Year Achievements

The Project started from January 1st, 2018.

• 1. ALMA Cycle-6 proposals
• 2. Theoretical models for massive star formation
• 3. Collaboration with observers
• 4. RT code development (in progress)

Cycle-6 Proposals

We submitted 2 PI proposals and 16 (incl. 2 LP) Co-I proposals. Both PI proposals are accepted (for the first time for both of us).

• 1. Tanaka et al. 2018.1.01656.S, “Resolving the Accretion Disk

with Photoionized Outflow in O-Star Formation” (Grade B)

• 2. Tomida et al. 2018.1.01389.S, “Mapping Magnetic Fields in the

Molecular Cloud Cores Harboring Class-0 Objects” (Grade C) Also, 5 Co-I proposals are accepted.

(Feel free to call us observers.)

Photo-Ionized Outflows (Tanaka+)

Goal: Reveal the radiation feedback and its effect on the disk. → Is massive star formation similar to low-mass star formation?

Top-left: Our target. High resolution imaging is proposed toward the protostar Top-right: SED model and observations Bottom: Theoretical prediction. The spectral index map elucidates the

• utflow and disk

structures.

B-Fields at Core Scale (Tomida+)

• Inclination produces complicated polarization patterns.
• need large MRS rather than resolution to capture the core scale

→ quantify the significance of magnetic fields in star formation

Hull+ Cycle-2 Based on Fujishiro-san’s senior thesis

Model for Massive Star Formation

(T anaka+ 2018, ApJ)

Semi-analytic prescription for star formation including various feedback processes in different environments

• MHD wind is most significant even

in massive star formation

• Photoevaporation becomes effective

in lower-metallicty environments, but does not set the upper mass limit.

Photo-evaporation from an O-star

Zhang, Tanaka+ in prep. G45.47+0.05

Top: Observations of continuum with ALMA Band 6 and VLA Band Q Bottom: Theoretical models

• f continuum

emission. The model can predict the properties of the massive protostar, such as flow velocity (~50km/s), outflow rate (3x10-5 Ms/yr), etc.

Disk + Outflow around a massive protostar G339.88-1.26

Multiple line observations (SiO, SO2, H2S, CH3OH, and H2CO) → Massive star formation is a scale-up version of low-mass SF

Zhang, T an, Sakai, T anaka+ submitted

RT code development

MHD simulation of molecular cloud formation (Iwasaki+ 2019)

Dust polarization simulation

As the first step for general radiation transfer code, we start from dust polarization RT simulation based on the Athena++ result. → Relation between magnetic fields and cloud structure

Summary

• 1. ALMA Cycle-6 proposals

2 PI proposals and 5 co-I proposals are accepted.

• 2. Theoretical models for massive star formation

useful for estimating properties of massive YSOs

• 3. Collaboration with observers

Providing theoretical models for observations

• 4. RT code development (in progress)

Dust continuum in progress, line transfer will follow