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Multi-Scale Star Formation: From Fil...

Hsieh, Cheng-Han,

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Multi-Scale Star Formation: From Filaments to Protostellar Disk Substructures /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Multi-Scale Star Formation: From Filaments to Protostellar Disk Substructures // Cheng-Han Hsieh.
作者:	Hsieh, Cheng-Han,
面頁冊數:	1 electronic resource (300 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-08, Section: B.
Contained By:	Dissertations Abstracts International86-08B.
標題:	Astronomy. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31561203
ISBN:	9798302885050

Multi-Scale Star Formation: From Filaments to Protostellar Disk Substructures /
Hsieh, Cheng-Han,

Multi-Scale Star Formation: From Filaments to Protostellar Disk Substructures /Cheng-Han Hsieh. - 1 electronic resource (300 pages)

Source: Dissertations Abstracts International, Volume: 86-08, Section: B.

Stars are the fundamental constituents of galaxies and serve as hosts of planetary systems. Understanding the process of star formation is essential for unraveling galaxy evolution and comprehending the mechanisms behind planet formation. Until today, there is no complete theory of star formation due to the complex physics involved (e.g., gravity, turbulence, magnetic fields, radiation, and stellar feedback).This thesis focused on the data-driven demographic study of multi-scale star formation covering spatial scales across seven orders of magnitude: filaments (105 au), protostellar cores (103 − 104 au), protostellar disks (102 au), protostellar disk substructures (10 au), and protostars (0.01 au). This thesis addresses five major problems in the field of star formation: (1) The angular momentum problem of star formation and the origin of the protostellar cores' specific angular momentum, (2) The magnetic braking problem and the formation of protostellar disks, (3) The star formation efficiency and the problem of feedback, (4) The emergence of protostellar disk substructures and the onset of planet formation, and (5) The lack of observational constraints for macroscopic star formation and the protostellar mass function.In this thesis, we present the first measurement of the specific angular momentum of filament at parsec scales. We developed a new method to derive the first 2D protostellar outflow rate maps which enables us to quantify protostellar outflows' role in core dispersal. We found protostellar outflows have high mass-loss rates, which suggests that protostellar cores are not the primary reservoir of stellar mass, and cores are continuously replenished by accretion from larger scales.We surveyed nearly all the Class 0/I and Flat-spectrum protostellar disks in 7 nearby molecular clouds and found that hydrodynamical models without consideration of magnetic fields cannot explain the disk size distribution for the youngest protostars. We found that protostellar disk formation must be magnetically regulated. In addition, we used this large sample to conduct the first uniform, high angular resolution (< 15 au) search for substructures in the Class 0/I protostellar disks in nearby star-forming regions within 200 pc. We discovered 2 populations of disk substructures, which we named the "C-type" and "F-type" disk substructures. We discovered that most protostellar disks have 2 to 3 au-sized substructures when the bolometric temperature of the protostar reaches ∼ 210 K or at age ∼ 0.2 − 0.3 Myr. Our study pushed the onset of planet formation to the much earlier protostellar phase and showed that planet formation occurs at the same time when the central protostar is still accreting its mass.In this thesis, we developed and pioneered a new method to measure the protostellar mass function (PMF), the mass distribution of protostars. PMF is an important quantity on par with the IMF, however, it has never been measured. From our pilot study, we showed the link between the Class 0 molecular bullet mass-loss rates and the protostar accretion holds the key to the protostellar mass function (PMF).

English

ISBN: 9798302885050Subjects--Topical Terms:

517668
Astronomy.
Subjects--Index Terms:

Disk substructures

Multi-Scale Star Formation: From Filaments to Protostellar Disk Substructures /
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520 $a Stars are the fundamental constituents of galaxies and serve as hosts of planetary systems. Understanding the process of star formation is essential for unraveling galaxy evolution and comprehending the mechanisms behind planet formation. Until today, there is no complete theory of star formation due to the complex physics involved (e.g., gravity, turbulence, magnetic fields, radiation, and stellar feedback).This thesis focused on the data-driven demographic study of multi-scale star formation covering spatial scales across seven orders of magnitude: filaments (105 au), protostellar cores (103 − 104 au), protostellar disks (102 au), protostellar disk substructures (10 au), and protostars (0.01 au). This thesis addresses five major problems in the field of star formation: (1) The angular momentum problem of star formation and the origin of the protostellar cores' specific angular momentum, (2) The magnetic braking problem and the formation of protostellar disks, (3) The star formation efficiency and the problem of feedback, (4) The emergence of protostellar disk substructures and the onset of planet formation, and (5) The lack of observational constraints for macroscopic star formation and the protostellar mass function.In this thesis, we present the first measurement of the specific angular momentum of filament at parsec scales. We developed a new method to derive the first 2D protostellar outflow rate maps which enables us to quantify protostellar outflows' role in core dispersal. We found protostellar outflows have high mass-loss rates, which suggests that protostellar cores are not the primary reservoir of stellar mass, and cores are continuously replenished by accretion from larger scales.We surveyed nearly all the Class 0/I and Flat-spectrum protostellar disks in 7 nearby molecular clouds and found that hydrodynamical models without consideration of magnetic fields cannot explain the disk size distribution for the youngest protostars. We found that protostellar disk formation must be magnetically regulated. In addition, we used this large sample to conduct the first uniform, high angular resolution (< 15 au) search for substructures in the Class 0/I protostellar disks in nearby star-forming regions within 200 pc. We discovered 2 populations of disk substructures, which we named the "C-type" and "F-type" disk substructures. We discovered that most protostellar disks have 2 to 3 au-sized substructures when the bolometric temperature of the protostar reaches ∼ 210 K or at age ∼ 0.2 − 0.3 Myr. Our study pushed the onset of planet formation to the much earlier protostellar phase and showed that planet formation occurs at the same time when the central protostar is still accreting its mass.In this thesis, we developed and pioneered a new method to measure the protostellar mass function (PMF), the mass distribution of protostars. PMF is an important quantity on par with the IMF, however, it has never been measured. From our pilot study, we showed the link between the Class 0 molecular bullet mass-loss rates and the protostar accretion holds the key to the protostellar mass function (PMF).
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590 $a School code: 0265
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650 4 $a Astrophysics. $3 535904
650 4 $a Planetology. $3 546174
653 $a Disk substructures
653 $a Planet formation
653 $a Protostellar disk
653 $a Protostellar mass function
653 $a Protostellar outflows
653 $a Star formation
690 $a 0606
690 $a 0596
690 $a 0590
710 2 $a Yale University. $b Astronomy. $e degree granting institution. $3 3823486
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