Observations Of Feedback Between Protostars And Their Natal Clouds

Joel Green, Dan M. Watson
2009 Zenodo  
In this thesis we explore the relationship between the formation of protostars, and the influence of protostellar outflows on their environment using Infrared Spectrograph onboard the Spitzer Space Telescope. First we introduce the modern understanding of protostellar development advanced by the IRS_Disks guaranteed time program. Next we explore the FU Orionis phenomenon, an IRS_Disks dataset of flaring stars undergoing a burst accretion event. Finally we present a suite of data on Herbig Haro
more » ... lows in Cepheus A to determine whether protostellar outflows can dissociate a wide angle cavity in their natal cloud. We present 5-35 um spectra, taken with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope, of five FU Orionis objects: FU Ori, V1515 Cyg, V1057 Cyg, BBW 76, and V346 Nor. All but V346 Nor reveal amorphous silicate grains in emission at 10 um and 20 um, and show water-vapor absorption bands at 5.8 and 6.8 um and SiO or possibly methane absorption at 8 um. These absorption features closely match these bands in model stellar photospheres--signs of the gaseous photospheres of the inner regions of these objects' accretion disks. The continuum emission at 5-8 mm is also consistent with such disks, and, for FU Orionis and BBW 76, longer-wavelength emission may be fit by a model which includes moderate disk flaring. V1057 Cyg and V1515 Cyg have much more emission at longer wavelengths than the others, perhaps evidence of substantial remnant of their natal, infalling envelopes. This indicates that FU Orionis events can briefly raise outflow rates sufficiently high to dispel their surrounding envelopes and open swaths of the ambient medium via compression waves. Herbig Haro objects are small emission nebulae that signify the interaction between both broad and collimated outflows from young stellar objects and the ambient molecular cloud material. GGD37 is suspected to be an amalgamation of at least two superposed flows (including HH 168) traveling in different directions on the sky. Weaker shocks (less [...]
doi:10.5281/zenodo.55380 fatcat:iz6y34mrobde5gcsecwj5owtxq