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This talk is based on•

Nakatani & Yoshida (arXiv:1811.00297; Submitted to ApJ)

(and Nakatani et al. (ApJ, 857, 57, 2018); Nakatani et al. (ApJ, 865, 75, 2018))

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(a)GMC, Dark CloudGalaxies

https://simple.wikipedia.org/wiki/Galaxy#/media/File:The_Pinwheel_Galaxy__M101.jpg

Clump

Gravitationa
l contraction

CoreClumps
(c)

(d)
(e)

(b)

PMS star

Jet
Accretion

Protoplanetary disk
Nakatani et al. (2018a,b)
PMS star + Disk

Protostar + Disk + Envelope© R.Nakatani

https://apod.nasa.gov/apod/ap180805.html

Orion Molecular Cloud

Trapezium cluster

GMC

https://en.wikipedia.org/wiki/Orion_Molecular_Cloud_Complex#/media/File:Orion_Head_to_Toe.jpg

Intense UV from OB stars can destructambient cores/clumps.

GMC
Vulpecula OB1 association

NGC 6823 (Open cluster)NGC 6820(Molecular clouds)

https://apod.nasa.gov/apod/ap141008.html

This situation is observed in many other GMCs.

• Erode clouds throughZeta Puppis (O4 star) inthis direction (~ 70 pc)~ 0.14 pc• Cometary structure• Radiation-driven

Reipurth (1983)

FIR~4.4 pc

opticalMass functions of cores, clumps, and stars can be s affected

Imai et al. (2017)

W5-W (O7-star)André et al. 2010

Core mass function(CMF) resembles stellar
IMF in GMCs
Massive star radiation
may affect to someextent

Ø LMC (lower metallicity; strong UV field) has similar
Clump MF (e.g., Brunetti & Wilson 2018) → Is there any
metallicity effectsØ What about other low-metallicity environment
(protogalaxies, high-z galaxies, outer Galaxy.)UV radiation

Core
Massive stars

Corresponding distance: O-type star at 0.1 pc.

• 3D Hydrodynamics + Radiation transfer (ray-tracing) + Chemistry• Metallicity is varied over a range of 10−3 < Z/Zsun < 1Initial Condition

Cometary structure formation

0.2 pcDirection of UV radiation field
Shock development

Rocket effect• Mass loss is higher with high cross-section, inefficient in the cometary phase• Lifetime is 105 years for !⊙ core↑ Forms cometary structure↑ Disappears very soon

• Faster disapperance for lower-Z cores

Strong Shock0.1 pcLine/continuumemission
Strong Shock0.1 pc

Temperatures are
NOT reduced
Lower metallicity clumps remain larger in launch surface

RedBlue• Lifetime is ~104 years for ! = 10&' !⊙Metal-poor coresdisperse fasterAlmost constantat very low-Z~10 times difference

Would be necessary to gravitationally collapse.

○○○

Compression shortens
the free fall timeMarginal××

Photoevaporation isvery efficient

Massive stars have potential to significantly
suppress star formation in nearby cores withlow metallicities.

• Aims:
Metallicity dependence of the lifetimes of cores
illuminated by external massive stars.
• Results:
The lifetime is 100,000 years for solar-metallicity cores, andis shorter with metal-poor cores.
The lifetime is 10,000 years for very low-metallicity cores.
• Conclusion:- the gas metallicity strongly affects the core lifetime andthus determines the strength of feedback from massive
stars in star-forming regions.
- star formation could be significantly suppressed in lowmetallicity environments.
• Future prospects:- Parameter study (metallicity, flux, core density, size)- Postprocess study in the context of galaxy evolutionLifetimes are almost
constant for very
low-Z clumps