Colloquium: Brian Svoboda (Host: Moire Prescott)
Sep 6 @ 3:15 pm – 4:15 pm
Colloquium: Brian Svoboda (Host: Moire Prescott) @ BX102

Starless clumps and the earliest phases of high-mass star formation in the Milky Way

Brian Svoboda, NRAO Jansky Fellow

High-mass stars are key to regulating the interstellar medium, star formation activity, and overall evolution of galaxies, but their formation remains an open problem in astrophysics. In order to understand the physical conditions during the earliest phases of high-mass star formation, I will present observational studies we have carried out on dense starless clump candidates (SCCs) that show no signatures of star formation activity. We identify 2223 SCCs from the 1.1 mm Bolocam Galactic Plane Survey, systematically analyse their physical properties, and show that the starless phase is not represented by a single timescale, but evolves more rapidly with increasing clump mass. To investigate the sub-structure in SCCs at high spatial resolution, we investigate the 12 most high-mass SCCs within 5 kpc using ALMA. We find previously undetected low-luminosity protostars in 11 out of 12 SCCs, fragmentation equal to the thermal Jeans length of the clump, and no starless cores exceeding 30 solar masses. While uncertainties remain concerning the star formation efficiency in this sample, these observational facts are consistent with models where high-mass stars form from initially low- to intermediate-mass protostars that accrete most of their mass from the surrounding clump. I will also present on-going research studying gas inflow signatures with GBT/Argus and ALMA, and the dense core mass function with the JVLA.

(note:slide overlay error)


Colloquium: Raja GuhaThakurta (Host: Rene Walterbos)
Oct 4 @ 3:15 pm – 4:15 pm
Colloquium: Raja GuhaThakurta (Host: Rene Walterbos) @ BX102

The SPLASH Survey of the Andromeda Galaxy

Raja Guhathurkurta, University of California, Santa Cruz

Our nearest large spiral galaxy neighbor, the Andromeda galaxy (M31),
and its dwarf satellites, offer a panoramic yet detailed view of
galaxy formation and evolution in our astronomical backyard. This
system also serves as an excellent laboratory for the study of stellar
populations because the stars are all practically at the same distance
from us. I will present results from the SPLASH (Spectroscopic and
Photometric Landscape of Andromeda’s Stellar Halo) survey, the
backbone of which was a large Keck DEIMOS spectroscopic survey of
evolved stars in M31. Most of the SPLASH spectroscopic targets in
M31’s disk were selected from the PHAT (Panchromatic Hubble Andromeda
Treasury) survey, a wide-field 6-filter Hubble Space Telescope mosaic
image of a portion of the disk of M31. The talk will cover a range of
science topics including: Local Group dynamics, structure/substructure
and metallicity of M31’s stellar halo, satellite tidal interactions,
disk/halo interface, dynamical heating of the disk, and rare stellar