星形成ゼミ
SF newsletter 358#29 - #42(#34と#37の紹介)
川邊
2023年2月3日

Vertical structure: one of keys towards understanding of planet formation in PPDs
- current observational constraints rely on indirect methods
Directly tracing vertical location of emitting regions using method by Pinte+2018- CO isotopologues (various Ju) & HCN, CN, H2CO, H2CO, C2H and c-C3H2 from “MAPS”- MAPS sources + Elias2-27, Wa Oph6
- newly implemented an accurate masking of channel emission
to recover the vertical location even at large radial distanceand for low-SNR lines- Parametric methods used to model the emission surface and vertical structure
Results- HD163296: vertical location of mitting regions in 10 different molecules and transitions- rest of the sample: 4-7 lines- Brightness temp profile obtained for all sample for all CO isotopologues- IM Lup, HD163296, & MWC480: 12CO, 13CO show modulation of height as radius=> coincident with dust gap locations and kinematic perturbations- vertical locations of CO isotopologues agree with the physical-chemical models:
wide range of vertical heights z/r =0.05-0.5 (in CO the location inversely related to Mstar)- z/r < 0.15 for other molecular lines- HCN&H2CO in HD163296 tracing s similar intermediate layer expected by the models- the results are in good agreement with model in some sources, but need dedicatedphysical-chemical models to understand the diversity

MAPS’s images: 12CO 2-1 & 1.3mm (DSHARP+)

https://alma-maps.info/disks.html

MethodPinte+2018

Following Pinte+2018
右図の楕円上の点F, Nより(各ch. Mapで)(x軸: disk major axis)- Continuum Mapからmajor axisを求め、mapを回転させる- Pinte-based “DISKSURF” (Teague+2021):
blind search of emission maxima allows
correct results for only higher SNR regions- Masking after visual inspection => canavoid contamination from lower surface.

HD163296

Vertical Profiles
Different vertical extent
and radial extent
Scale height :inversely proportional
to stellar mass?

Gaussian fit “modulation” extraction from vertical profiles
Comparison with dust gap/ring,+ Kinematical residualRelation btw Tb and “modulation”?

Gas pressure scale height
12CO: optically thick, tracing tau=1 surface, z(CO)Nco, critical : 5 x 10^16 cm^-2 (tau~ 1)
Assuming constant CO abundanceGas pressure scale heightRobustness test: 2D thermochemical models
2D models: DARI (Brudere 2013)
Gas surface density prescription by Zhang+ (2021)
Mock 12CO 2-1 channel maps used to apply methodology to derive gas pressure heightOther molecular lines

The European Physical Journal Plus

BDs & VLMS (M-dwarfs wit a mass 0.1-0.2 Msun)- a significant fraction of 15-20 % in our Galaxy- Higher Frequency of Earth-size planets in habitable zones around M-dwarfs- Freq of giant planets ?: less than 2% of detected exoplanets(ALMA can provide new insights on planet formation?)Protoplanetary disks (PPDs) in BDs & VLMS
- NIR excess observed indicating the existence of PPDs
- (sub-)millimeter detections in nearby star forming regions; typicaly < 1 mJy=> typical Disk mass~ a few M(Earth)=> dust-growth to mm-size & pebbles alive for 1-5 Myr timescale(cf. planetary mass object, OTS44, associated with dusty disk, 0.1 mJy at B6; Bayo+2017)- “radial-drift barrier” for mm-dust a strong hurdle for planet formation in BDs & VLMS=> angular momentum loss and radial drift inward: very fast (< 1000 yrs)
- pressure bump can reduce such high radial drift, leading ring/gap structure- planet with a Saturn-mass or higher can open the gap in BDs & VLMS, but pebble
accretion model difficult to form such giant planets & GI models seem to be neededState-of-art ALMA observations of BDs & VLMS presented and revisit “radial drift barrier”

Rich earth-like & poor giant planets in M-dwarfs

Gillon+ 2016, Nature

ALMA unveiled substructures in M-dwarf disks
Disks is smaller than disks aroundsolar-type stars (~25 au vs 80 au),
showing similar substructures
Note: limited number of sources
observed with high-resolution

asymmetry

下線substructure

Inner hole?

6 disks: more compact & substructure is not clear

Mdust-Mstar relation：”scaling-law”

youngeroldererDrift velocity as a func of time
faster in lower mass star

Mdust mass evolution

Disk radius evolution

Simulation using “Dustpy” (ver 0.50)- transport of grains and dust growth calculated
Mstar = 1.0 vs 0.1 Msun
- demonstrating fast dust drift in 0.1 Msun Dwarf

Crida+ (2006)

Gap opening criterion

H: disk scale height: cs/Ω (<= Temp distr)
RH: Hill radius
Re: Reynolds Number,(ν: disk viscosity)
q: planet-to-star mass ratio
thermal criterion (RH > H) + viscos criterion ( t(gap opening) < t(viscosity) )cf) Minimum planet mass for gap opening(e.g., Rosotti+ 2016)=> rp < 40 au

FARGO3D によるhydrodynamical simulation- 0.1 Msun のPPD
- 1.7 Msaturn mass planet at r=40 au- after 2000 orbits
Gap formed in gas and dust; gap at 1 mm wider- asymmetric structure due to dust traps?

From web siteLong+2022

Dust trap at
L4 Lagrangian point?

Compiled light curves for 379 TTS in the Lagoon Nebula (VVVX survey in Ks)
Classified light curves in periodicity and asymmetry
For 126 stars, magnetically active regions remain stable for several years

High-resolution 3D radiation-hydrodynamic simulation
for young massive stars formed from collapsing 100 Msun MCs with sppinnig“Steller wobbling” (excursion of the central star) slows down the gravitational instability
and reduce accretion-driven outburst
Comparison with M17MIR observed by ALMA