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Turbulent, Molecular Clouds Regulate...

Raskutti, Sudhir.

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Turbulent, Molecular Clouds Regulated by Radiation Feedback.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Turbulent, Molecular Clouds Regulated by Radiation Feedback./
Author:	Raskutti, Sudhir.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2016,
Description:	247 p.
Notes:	Source: Dissertation Abstracts International, Volume: 78-04(E), Section: B.
Contained By:	Dissertation Abstracts International78-04B(E).
Subject:	Astrophysics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10167607
ISBN:	9781369219555

Turbulent, Molecular Clouds Regulated by Radiation Feedback.
Raskutti, Sudhir.

Turbulent, Molecular Clouds Regulated by Radiation Feedback. - Ann Arbor : ProQuest Dissertations & Theses, 2016 - 247 p.

Source: Dissertation Abstracts International, Volume: 78-04(E), Section: B.

Thesis (Ph.D.)--Princeton University, 2016.

Radiation feedback from stellar clusters is expected to play a key role in setting the rate and efficiency of star formation in giant molecular clouds (GMCs) and across whole galaxies. In particular, stellar radiation may quench star formation by driving outflows and unbinding stellar clusters. To investigate how radiation forces influence realistic clouds, we have conducted a series of simulations employing the Hyperion radiation hydrodynamics solver, considering the regime that is optically thick to ultraviolet and optically thin to infrared radiation. Our model clouds cover initial surface densities between Sigmacl,0 &sim; 10--300 M[special character omitted] pc-2, with varying initial turbulence and magnetic field strength (Bz,0). We follow them through turbulent, self-gravitating collapse, formation of star clusters, and cloud dispersal by stellar radiation. All our models display a lognormal distribution of gas surface density Sigma as seen by both the observer and the central cluster. For an initial virial parameter alphavir,0 = 2$, the lognormal standard deviation is sigmalnSigma = 1--1.5 and the star formation rate (SFR) coefficient epsilonff,rho = 0.3--0.5, both of which are sensitive to turbulence, and magnetic fields, but not radiation feedback. Embedded stars are more centrally concentrated than the gas so that above Sigmacl,0 &sim; 60 M[special character omitted] pc-2, the star cluster remains intact even when surrounding gas is dispersed. The net star formation efficiency depends primarily on the distribution of Eddington ratios in the cloud and therefore increases with Sigmacl,0 and decreases with both alpha vir,0 and Bz,0. This also has implications for outflows, since low surface density regions may be driven outwards to nearly 10 times their initial escape speed (vesc). However, the overall efficiency of momentum injection to the gas is reduced because much of the radiation escapes and irrespective of Sigmacl,0 , the mean outflow velocity is approximately twice v esc. Unless GMCs are highly magnetized and turbulent, the lognormal structure of gas modulates the effect of radiative feedback in disrupting clouds, so that it cannot alone explain the low observed galactic SFR.

ISBN: 9781369219555Subjects--Topical Terms:

535904
Astrophysics.

Turbulent, Molecular Clouds Regulated by Radiation Feedback.
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245 1 0 $a Turbulent, Molecular Clouds Regulated by Radiation Feedback.
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300 $a 247 p.
500 $a Source: Dissertation Abstracts International, Volume: 78-04(E), Section: B.
500 $a Adviser: Eve C. Ostriker.
502 $a Thesis (Ph.D.)--Princeton University, 2016.
520 $a Radiation feedback from stellar clusters is expected to play a key role in setting the rate and efficiency of star formation in giant molecular clouds (GMCs) and across whole galaxies. In particular, stellar radiation may quench star formation by driving outflows and unbinding stellar clusters. To investigate how radiation forces influence realistic clouds, we have conducted a series of simulations employing the Hyperion radiation hydrodynamics solver, considering the regime that is optically thick to ultraviolet and optically thin to infrared radiation. Our model clouds cover initial surface densities between Sigmacl,0 &sim; 10--300 M[special character omitted] pc-2, with varying initial turbulence and magnetic field strength (Bz,0). We follow them through turbulent, self-gravitating collapse, formation of star clusters, and cloud dispersal by stellar radiation. All our models display a lognormal distribution of gas surface density Sigma as seen by both the observer and the central cluster. For an initial virial parameter alphavir,0 = 2$, the lognormal standard deviation is sigmalnSigma = 1--1.5 and the star formation rate (SFR) coefficient epsilonff,rho = 0.3--0.5, both of which are sensitive to turbulence, and magnetic fields, but not radiation feedback. Embedded stars are more centrally concentrated than the gas so that above Sigmacl,0 &sim; 60 M[special character omitted] pc-2, the star cluster remains intact even when surrounding gas is dispersed. The net star formation efficiency depends primarily on the distribution of Eddington ratios in the cloud and therefore increases with Sigmacl,0 and decreases with both alpha vir,0 and Bz,0. This also has implications for outflows, since low surface density regions may be driven outwards to nearly 10 times their initial escape speed (vesc). However, the overall efficiency of momentum injection to the gas is reduced because much of the radiation escapes and irrespective of Sigmacl,0 , the mean outflow velocity is approximately twice v esc. Unless GMCs are highly magnetized and turbulent, the lognormal structure of gas modulates the effect of radiative feedback in disrupting clouds, so that it cannot alone explain the low observed galactic SFR.
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