EPoS Contribution
EPoS Contribution
The Herschel Orion Protostar Survey (HOPS)

S. Thomas Megeath
University of Toledo, Toledo, Ohio, USA
The Orion molecular cloud complex is the most active region of star formation within 500 pc of the Sun, with over 400 protostars identified by Spitzer in a diverse range of environments. We are now collecting extensive observations on 280 Orion protostars, including 5-40 um Spitzer spectroscopy, near-IR imaging and spectroscopy with Hubble and ground-based telescopes, and a Herschel open time key project of PACS far-IR imaging and spectroscopy. With these data we can determine the fundamental properties (multiplicity, gas infall rate, bolometric luminosity, outflow cavity geometry) of a large sample of protostars in a single cloud complex. We are additionally obtaining data on the temperature, turbulence and column density of the surrounding molecular gas from a number of ground-based telescopes. This program will provide new insights into protostellar evolution and how protostars are influenced by their surrounding environment (molecular gas properties, density of stars, radiation fields). Current results include:
Binarity: Using Hubble, we have identified companions to protostars with separations down to 100 AU. We find the mean surface density of companions follows a broken power law similar to that found in Taurus, but with the power-law break at 1000 AU instead of the 10,000 AU found in Taurus. We interpret the break as the division between multiple systems and clustering on larger scales.
SED modeling: We have acquired Herschel 70 and 160 um images of a group of four protostars associated with the Herbig-Haro complex HH1-2. With these and other data, we constructed 1-160 micron SEDs and fit them to model SEDs generated with radiative transfer codes. The inferred mass infall rates vary by 3 orders of magnitude between the protostars, hinting at a sharp decrease in the infall rate over time. We plan to include the analysis of additional protostars that are expected to be observed by Herschel in early 2010.
Outer Envelope structure: The Herschel 160 micron maps show extended emission toward the protostars. We are using this emission to examine the structure of the cold gas and dust surrounding the protostars.
Caption: Top: HST image of edge-on protostar found in the Lynds 1641 region. Bottom: Herschel PACS 70 (blue) and 160 (red) micron image of the HH 1-2 region (also in Lynds 1641). The three brightest point sources are protostars. By inverting the image, one can also see the face of satan.
Collaborators:
The HOPS team
Key publication

Suggested Session: Herschel