Periodic Reporting for period 2 - InAndOut (Towards a complete understanding of young embedded disks)
Okres sprawozdawczy: 2022-09-01 do 2023-08-31
Existing models of disk formation typically underestimate the possibility of replenishing the mass reservoir of the disk via infall from the larger-scale birth environment. Moreover, the ionization level of the gas differs in different protostellar environments. My project tackles these issues by applying cutting-edge computational tools to investigate the small-scale effects in disks, while consistently accounting for the properties provided by the protostellar environment.
I How does the degree of ionization affect the properties of embedded disks and their outflows?
II How do dust polarization and Zeeman splitting trace the magnetic field in embedded disks?
III What is the probability that gas and dust return to the disk after being ejected by an outflow?
IV How does gas and dust (chemically) evolve from infall onto the disk until accretion and/or outflow
Conclusion:
In summary, I discovered that under otherwise identical conditions, an increase of the ionization level can potentially reduce the disk size around protostars. Therefore, stars in highly ionized regions are likely born smaller on average than in regions of lower ionization. Dust polarization is a good tracer of the magnetic fields beyond the disk scale, while it remains difficult to trace the B-field in disks observationally. There are strong preliminary indications for a return of gas and tiny dust particles that are ejected through an outflow. Considering the evolution of material, my research has shown that stars can be fed with material a substantial amount of material that is initially not bound to the collapsing pre stellar core and thereby star-disk systems can be fed by material from regions of varying chemical compositions.
I How does the degree of ionization affect the properties of embedded disks and their outflows?
II How do dust polarization and Zeeman splitting trace the magnetic field in embedded disks?
III What is the probability that gas and dust return to the disk after being ejected by an outflow?
IV How does gas and dust (chemically) evolve from infall onto the disk until accretion and/or outflow
Conclusion:
In summary, I discovered that under otherwise identical conditions, an increase of the ionization level can potentially reduce the disk size around protostars. Therefore, stars in highly ionized regions are likely born smaller on average than in regions of lower ionization. Dust polarization is a good tracer of the magnetic fields beyond the disk scale, while it remains difficult to trace the B-field in disks observationally. There are strong preliminary indications for a return of gas and tiny dust particles that are ejected through an outflow. Considering the evolution of material, my research has shown that stars can be fed with material a substantial amount of material that is initially not bound to the collapsing pre stellar core and thereby star-disk systems can be fed by material from regions of varying chemical compositions.
In the first phase of the project, I conducted a mix of carrying out magnetohydrodynamical simulations, code development, simulation analysis, synthetic observations of linear polarization of dust emission, supervision and mentoring. The goal is to better constrain the properties of infall and outflow during the embedded disk stage by also accounting for the fact that the gas is ionized. To realize this ambitious goal, I am using a state-of-the-art computational tool. Setting up these simulations involved code development.
Taking data from these molecular cloud simulations in which protostars form, I used them as input for post-processing with a radiative transfer code. The code allows me to produce polarization maps by considering mechanisms of grain alignment due to magnetic field. In this way, it is possible to compare the results of the models with observations by telescope facilities such as ALMA or SOFIA HAWC+. Related to this, I also supervised together two research projects for undergraduate students that carried out radiative transfer simulations with this code. A major result of the study is that at higher column densities within ~1000 AU of the forming protostar, multi-wavelength observations at ~100 micrometer wavelength with the SOFIA telescope (HAWC+) confirm a flip in polarization pattern because the signal is either dominated by absorption or emission.
Moreover, post-processing the simulation data with a radiative transfer code allows me to produce synthetic maps of dust continuum emission. My colleagues at UVA and MPE provided useful help in succeeding in this task as they have used and built a pipeline to more efficiently post-process (magneto-)hydrodynamical data. Using data from the models I can show that (late) infall onto stars can lead to cases where an older protostar might be classified as younger objects than prior to infall. Late infall can make the star more embedded again and hence it is classified as a younger object after infall when it is de facto older than prior to infall. The analysis also shows that the orientation of star-disk systems is substantially affected by infall as the infalling material often has a different angular momentum direction than the star-disk system at the particular stage.
The dependency of disk sizes on the ionization level was already published in a paper prior to the official start of the project, but tightly connected to the proposal.
The results were also presented at conferences and workshops including an invited talk at Arcetri Observatory in November 2022.
Linear dust polarization traces the magnetic field structure on scales beyond the disk as I found out in another paper that was written and published in between the time of application submission and the official project start.
Moreover, I published a paper that illustrated the influence of infall in potentially leading to the formation of misaligned disks. I also published results the possibility of rejuvenating evolved young stellar objects through infall in an invited paper earlier this year.
Furthermore, I contributed a decadal review to the prestigious book as part of the conference series Protostars and Planets VII. The book is currently in press and it will be shipped and distributed soon.
In addition, my collaborator Gupta found by studying reflection nebulae that more stars are likely to have experienced late infall events in the past, which is consistent with my modeling results. The results were published in form of a letter led by Gupta.
I presented results related to infall as the meeting of the American Astronomical Society in 2022, colloquia in Heidelberg and Munich, or at the EAS meeting in Krakow 2023. Also I am co-author on four currently reviewed articles led by Gupta, Cacciapuoti, Krieger and Pineda that show observational constraints related to my modeling work carried out as part of my InAndOut project.
Taking data from these molecular cloud simulations in which protostars form, I used them as input for post-processing with a radiative transfer code. The code allows me to produce polarization maps by considering mechanisms of grain alignment due to magnetic field. In this way, it is possible to compare the results of the models with observations by telescope facilities such as ALMA or SOFIA HAWC+. Related to this, I also supervised together two research projects for undergraduate students that carried out radiative transfer simulations with this code. A major result of the study is that at higher column densities within ~1000 AU of the forming protostar, multi-wavelength observations at ~100 micrometer wavelength with the SOFIA telescope (HAWC+) confirm a flip in polarization pattern because the signal is either dominated by absorption or emission.
Moreover, post-processing the simulation data with a radiative transfer code allows me to produce synthetic maps of dust continuum emission. My colleagues at UVA and MPE provided useful help in succeeding in this task as they have used and built a pipeline to more efficiently post-process (magneto-)hydrodynamical data. Using data from the models I can show that (late) infall onto stars can lead to cases where an older protostar might be classified as younger objects than prior to infall. Late infall can make the star more embedded again and hence it is classified as a younger object after infall when it is de facto older than prior to infall. The analysis also shows that the orientation of star-disk systems is substantially affected by infall as the infalling material often has a different angular momentum direction than the star-disk system at the particular stage.
The dependency of disk sizes on the ionization level was already published in a paper prior to the official start of the project, but tightly connected to the proposal.
The results were also presented at conferences and workshops including an invited talk at Arcetri Observatory in November 2022.
Linear dust polarization traces the magnetic field structure on scales beyond the disk as I found out in another paper that was written and published in between the time of application submission and the official project start.
Moreover, I published a paper that illustrated the influence of infall in potentially leading to the formation of misaligned disks. I also published results the possibility of rejuvenating evolved young stellar objects through infall in an invited paper earlier this year.
Furthermore, I contributed a decadal review to the prestigious book as part of the conference series Protostars and Planets VII. The book is currently in press and it will be shipped and distributed soon.
In addition, my collaborator Gupta found by studying reflection nebulae that more stars are likely to have experienced late infall events in the past, which is consistent with my modeling results. The results were published in form of a letter led by Gupta.
I presented results related to infall as the meeting of the American Astronomical Society in 2022, colloquia in Heidelberg and Munich, or at the EAS meeting in Krakow 2023. Also I am co-author on four currently reviewed articles led by Gupta, Cacciapuoti, Krieger and Pineda that show observational constraints related to my modeling work carried out as part of my InAndOut project.
The importance of the role of cosmic-ray ionization on the properties of disk sizes is increasingly recognized in the community. Moreover, infall onto star-disk systems is increasingly considered when interpreting observational features of shadows in disks. The analysis of a set of my simulations revealed that infalling material can lead to the formation a new outer disk that is misaligned with respect to the existing inner disk. This result is exciting as it can explain recent observations of systems such as SU Aur. Ultimately, we now have a more dynamical picture of star and planet formation in mind, in which the process of star formation has deeper implications on the properties of planets than we previously thought. In particular, my models demonstrate that infall can rejuvenate protostars and lead to the formation of shadows. This implies that the mass reservoir for planet formation can be replenished and misaligned disks might be the explanation for exoplanetary systems with highly inclined orbits. As infall can lead to the formation of misaligned inner and outer disks, this result is of fundamental societal impact as it opens the window in understanding the formation of planets and exoplanets that orbit their host stars in different orbital planes (including the planets in the solar system around the Sun). It contributes to a deeper understanding of society about "our roots" in the universe.