Bulletin of the American Physical Society
Mid-Atlantic Section Meeting 2021
Volume 66, Number 18
Friday–Sunday, December 3–5, 2021; Rutgers University, New Brunswick, New Jersey
Session B03: Astrophysics I |
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Chair: Andrew Baker, Rutgers University Room: 202A |
Friday, December 3, 2021 5:00PM - 5:36PM |
B03.00001: Turbulent Beginnings: A Predictive Theory of Star Formation in the Interstellar Medium Invited Speaker: Blakesley Burkhart In this talk, I will focus on how interstellar magnetohydrodynamic turbulence and stellar feedback processes affect the long-standing problem of star formation. From scales of giant molecular clouds (GMCs), I will demonstrate how the star formation efficiency and collapsing gas fraction can be analytically calculated from our understanding of how turbulence, gravity, and stellar feedback induce density fluctuations in the ISM via a probability distribution function analysis. This analytic calculation predicts star formation rates from pc size scales (GMCs) to kpc size scales in galaxies, can be observationally tested, and be used to develop sub-grid recipes for dense gas and star formation in cosmological simulations. [Preview Abstract] |
Friday, December 3, 2021 5:36PM - 5:48PM |
B03.00002: The Effects of Magnetic Fields and Outflow Feedback on the Shape and Evolution of the Density PDF in Turbulent Star-Forming Clouds Sabrina Appel, Blakesley Burkhart, Vadim Semenov, Christoph Federrath, Anna Rosen In this talk, I will describe how we use a suite of 3D hydrodynamical simulations of star-forming molecular clouds to investigate how the density probability distribution function (PDF) changes when including gravity, turbulence, magnetic fields, and protostellar outflows and heating. We find that the density PDF is not lognormal when outflows and self-gravity are considered. Self-gravity produces a power-law tail at high densities and the inclusion of stellar feedback from protostellar outflows and heating produces significant time-varying deviations from a lognormal distribution at the low densities. The simulation with outflows has an excess of diffuse gas compared to the simulations without outflows and maintains a slower star formation rate over the entire duration of the run. We study the mass transfer between the diffuse gas in the lognormal peak of the PDF, the collapsing gas in the power-law tail, and the stars. We find that the mass fraction in the power-law tail is constant, such that the stars form out of the power-law gas at the same rate at which the gas from the lognormal part replenishes the power-law. We find that turbulence does not provide significant support in the dense gas associated with the power-law tail.~ [Preview Abstract] |
Friday, December 3, 2021 5:48PM - 6:00PM |
B03.00003: Fitting Methods for Column Density PDFs of Turbulent Star-forming Clouds Avery Kiihne, Sabrina Appel, Blakelsey Burkhart Density probability distribution functions (PDFs) are used as analytic tools for studying star formation. The PDF of star forming regions takes on a lognormal form at low density with transition to a power law form at high density. The power law form indicates where self-gravity becomes dominant over supportive motions in the cloud, and understanding how the slope of the tail and the transition density depends on environment is of interest to observers and theorists alike. We study column density PDFs for a suite of four 3D hydrodynamical simulations of star forming regions of molecular clouds. These simulations include different physical processes, starting with just self-gravity and adding turbulence, magnetic fields, and protostellar outflows. We fit an analytic form to the simulated column density PDFs in order to compare to analytic models. We demonstrate a novel fitting method using spline to fit the curve of the column density and measure the width of the lognormal, the slope of the power law tail, and the transition column density between lognormal and power law portions of the PDF. We find agreement between this method and two other more traditional least squares fitting methods. Future research will be conducted to apply our results to observation. [Preview Abstract] |
Friday, December 3, 2021 6:00PM - 6:12PM |
B03.00004: Supernova-driven Superbubbles: Turbulence or Outflows from Clustered Feedback in Galaxies Matthew Orr, Drummond Fielding, Christopher Hayward, Blakesley Burkhart In this talk, I will compare an analytic model for supernova-driven superbubbles with observations of local and high-redshift star-forming galaxies. Beginning with a summary of the theoretic model, this talk will span a discussion of clustered supernova feedback itself to its consequences in galaxies. Our model correctly predicts the presence of superwinds in local galaxies and the ubiquity of outflows near $z \sim 2$. We find that high-redshift galaxies may `capture' a large fraction of their feedback momentum in the dense interstellar medium (ISM), driving supersonic turbulence in the dense gas directly, whereas local galaxies may contain $\lesssim$10\% of their feedback momentum from the central starburst. I will discuss our prediction that most superbubbles stall and fragment \emph{within} the ISM, and that this occurs at or near the scale height of gas in galaxies. Lastly, I will compare our predicted bubble properties with observed HI bubbles/holes in local galaxies. [Preview Abstract] |
Friday, December 3, 2021 6:12PM - 6:24PM |
B03.00005: Age Gradients of Simulated Dwarf Galaxies Claire Riggs, Alyson Brooks, Ferah Munshi Dwarf galaxies are observed to have negative age gradients, with younger stars closer to the center of the galaxy and older stars near the outskirts of the galaxy. Possible explanations for this trend fall into two groups. The first explanation is that stars stay where they are formed, resulting in an “outside-in” scenario. The second possibility is that stars are reshuffled over time via stellar feedback, mergers, or dark matter core creation. Using cosmological simulations, we investigate the origin of the age gradients in dwarf galaxies. Our galaxy sample incorporates both field and satellite galaxies, and includes dwarf galaxies with a wide range of stellar masses (from $\sim 10^{4.5} -10^{9.6}\text{ M}_\odot$). We find that stars tend to be reshuffled in dwarf galaxies, with stars being pushed out gradually over time. Preliminary results show that galaxies with dark matter cores can span a range of age gradients, and that for field dwarfs with cored dark matter profiles, the galaxy’s star formation history will predict the slope of the age gradient. As a result, there are a variety of mechanisms that can determine age gradients in dwarf galaxies, and these processes vary with respect to mass, star formation history, and environment. [Preview Abstract] |
Friday, December 3, 2021 6:24PM - 6:36PM |
B03.00006: A New Non-parametric Method for Reconstructing the Kinematics of Lensed Galaxies Anthony Young, Charles Keeton, Andrew Baker Studying the evolution of galaxies in the high-redshift universe can prove difficult because of their low fluxes and small sizes. The bending of light rays by gravitational lenses magnifies the images of these objects, allowing us to study them in more detail. However, studying lensed sources requires careful modeling of both the lensing mass distribution and the extended source emission. This modeling becomes even more challenging when working with integral field spectroscopy, which measures the spatial distribution of emission within a series of narrow velocity channels. The additional velocity information allows us to derive kinematic and other galaxy properties that aid in understanding the processes that drive the evolution of galaxies at high redshifts. We will present an improved non-parametric modeling strategy that better reconstructs the full 3D intensity distribution without placing strong priors on the kinematics or morphology of the source. This approach uses a new physically motivated regularization scheme that is better suited to the 3D nature of the data than previous approaches that model emission at different velocities independently. We will then compare the different approaches for reconstructing sources using mock observations of dusty star-forming galaxies. [Preview Abstract] |
Friday, December 3, 2021 6:36PM - 6:48PM |
B03.00007: First observations for the LADUMA HI survey Amir Kazemi-Moridani, Andrew Baker, Sarah Blyth, Benne Holwerda Understanding the properties of neutral atomic gas reservoirs in galaxies over a significant fraction of the age of the universe is a key input to understanding the cosmic evolution of galaxies. The Looking At the Distant Universe with the MeerKAT Array (LADUMA) survey, aiming to extend the study of HI emission to when the universe was only a third (z = 1.4) of its current age, observes a region of the sky covering the Chandra Deep Field South in two frequency bands. In addition, LADUMA observations will make it possible to study the cosmic history of OH megamasers (a probe of gas-rich mergers) to z = 1.8. This talk will provide an update on LADUMA's observations, and data processing, along with a first look at new HI and OH detections. This work has been supported by the National Science Foundation through grant AST-1814421. [Preview Abstract] |
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