Changes between Version 13 and Version 14 of TriggeredStarFormation
- Timestamp:
- 01/07/14 18:54:24 (11 years ago)
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TriggeredStarFormation
v13 v14 1 '''Intro'''[[BR]] 1 ''' 2 == Intro == 3 '''[[BR]] 2 4 Triggered star formation, in which winds generated from supernova blasts or wind-blown bubbles enters a clumpy region and compresses the clumps into dense cores that can violate local Jean's criterion and trigger gravitational collapse, is one of the mechanisms used to explain star forming regions such as Cygnus Loop, and more importantly, the Solar System. The triggering mechanism provides a natural way of forming stars while at the same time injecting SLRI's into the star and its disk. Recent years' literature has seen a noticeable increase in the amount of numerical works dedicated to this topic, as projects lead by Boss (Boss et al 2008) carried out pioneering work on the study of the shock condition of such successful triggering and mixing. In the general cases, the higher the Mach number of the shock, the more difficult it is to trigger collapse. From an intuitive point of view, the shock being too fast will shred the clump material away at a shorter time scale compared to the time scale for collapse. At the mean time, faster shock speed allows better mixing because of the enhanced Rayleigh-Taylor instability growth rate. 3 5 [[BR]][[BR]] … … 5 7 [[BR]][[BR]] 6 8 In this project, we study the shock-induced triggering of a stable Bonnor-Ebert cloud following, for the first time, the long-term evolution of the flow after a star has formed. We will be focusing on the triggering event as well as the post-triggering evolution of the star. We will impose initial rotation as well as internal magnetic field to study their influence on the post-triggering evolution. 7 [[BR]][[BR]] 9 [[BR]][[BR]][[BR]][[BR]] 8 10 9 '''Hydro Triggering with Initial Rotation'''[[BR]] 11 ''' 12 == Hydro Triggering with Initial Rotation == 13 '''[[BR]] 10 14 We setup an initial marginally stable Bonnor-Ebert sphere as the triggering target. The cloud has 1 $M_{\odot}$ and radius of $0.058 pc$, with central density $6.3\times10^{-19} g/cc$ and edge density of $3.6\times 10^{-20} g/cc$. The cloud has a uniform interior temperature at $10K$. The ambient medium is setup to satisfy the pressure balancing at the cloud edge, with density $3.6\times 10^{-22} g/cc$ and temperature of $1000 K$. We have performed simulations to check the stability of the cloud, and found that the initial cloud breathes at a time scale of about $10$ cloud crushing time scales (here after $t_{cc}$), which is longer than the time span of our simulation ($4t_{cc}$). $t_{cc}$ is defined as the time for the transmitted shock to pass the cloud, which is estimated to be $t_{cc} \approx 276 kyrs$. The free-fall time of the cloud is $t_{ff} \approx 84 kyrs$. 11 15 [[BR]][[BR]] … … 51 55 We can study important physics quantities by line plots. The first set of line plots are 1. star mass formed by triggering, 2. accretion rate, 3. mixing ratio of the wind material onto the star, 4. bounded mass (basically the mass of the disk for the rotation cases. for the non-rotating cases, the bounded material evaporates very fast after stage I. [[BR]] 52 56 [[Image(fig4.png,60%)]] 53 [[BR]][[BR]] 57 [[BR]][[BR]][[BR]][[BR]] 54 58 55 '''Choice of Algorithm'''[[BR]] 59 ''' 60 == Choice of Algorithm == 61 '''[[BR]] 56 62 We implement Krumholz's (Krumholz et al 2006) sink particle algorithm apart from Federrath et al 2010. The differences in the two algorithms are summarized in the following papers:[[BR]] 57 63 http://arxiv.org/pdf/astro-ph/0312612v1.pdf … … 96 102 There is also a difference in asymptotic star mass due to the difference in accretion routines. [[BR]][[BR]] 97 103 [[Image(http://www.pas.rochester.edu/~shuleli/0520/starmass.png,30%)]] 104 [[BR]][[BR]][[BR]][[BR]] 98 105 99 '''MHD Triggering'''[[BR]] 106 ''' 107 == MHD Triggering == 108 '''[[BR]] 100 109 When added magnetic field to the cloud, the triggering behavior can be very different. Here, we suppose the initial rotation to be zero first, and look at the case where there is a global uniform magnetic field along the vertical axis. We assume Mach = 3, and the magnetic field has beta of 4. The density slice looks like:[[BR]][[BR]] 101 110 1 cloud crushing time: [[BR]] … … 125 134 http://www.pas.rochester.edu/~shuleli/mhdtsf/tsftor.gif 126 135 [[BR]] 127 128 129 130 131 132
