Low-Mass Star Formation:
For low-mass star formation (i.e., stars that form like our sun), I am particularly interested in studying how angular momentum is transferred into and out of these systems, and I particularly focus on their outflows and magnetic fields.
One of my favorite low-mass star-forming source is L1157-mm, which has a prolific outflow. L1157-mm
represents how the sun probably looked like during its first stages. Observations of L1157-mm magnetic field morphology
shows a beautiful hourglass morphology centered about the outflow, as seen below:
Figure from Stephens et al. (2013). Polarimetric maps (with polarization vectors rotated by 90º to show the inferred magnetic field orientation) of L1157-mm with the grayscale background
showing a log-scale map of Spitzer 8 μm emission (Looney et al. 2007). Magnetic field vectors are shown for P > 2σ. Left: SHARP continuum
contours and vectors are shown in green and blue respectively. Cyan shows the 2σ intensity detections from CARMA. The length of the vectors is proportional to ′′
P. SHARP contour levels range from 10% to 90% in 10% increments of the peak flux. Right: cyan (red) contours (vectors) are the combined CARMA data at 2.1 resolution and the central blue vector is from SHARP.
At Harvard-Smithsonian Center for Astrophysics, I am Co-PI with Mike Dunham on a project mapping all 75 of the young protostars (younger than ~1 Million years) in the Perseus Molecular Cloud (located 235 pc or 750 light years away).
This project, called the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES), is using an interferometer called the Submillimeter Array
to map molecular lines and continuum at high resolution (~1 arcsecond) about all these sources. Examples of the outflows and continuum of these sources are seen below.
Outflows from Stephens et al. (2018). Black contours show the 1.3 mm continuum, red contours show red-shifted CO(2-1) emission, and blue contours show
blue-shifted CO(2-1) emission.
In Stephens et al. (2017), I used the MASSES survey to investigate whether protostars inherit their angular momentum from their natal filamentary environment.
In doing so, I compared the position angles of filaments with the position angles of outflows. I found with over 99% confidence that they are not always parallel or always perpendicular.
Indeed, the alignment between filaments and outflows appears to be random, which may suggest that turbulent fragmentation occurs at scales smaller than 10000 AU.