Spectral Analysis of Protoplanetary Disks
Sara Vannah, Wellesley College ’17 and Colette Salyk (Astronomy)
We present a spectral analysis of three protoplanetary disks: W3 IRS5, V1057 Cygni and IRAS 19110+1045. Analyses of the spectra of these sources reveal the structure and features of the components producing the spectra. Data from the NIRSPEC high-resolution infrared spectrograph at the W. M. Keck Observatory allowed us to analyze carbon monoxide (CO) P- and R-branch rovibrational absorption lines, as well as the hydrogen Pf-beta emission line. These lines act as tracers of disk evolution and accretion, respectively. Using the HITRAN database, we estimated the column density, temperature and Doppler shift of the absorbing gas in each source. V1057 Cygni, a FU Orionis source, presents a very hot absorption spectrum, while W3 IRS5 and IRAS 19110+1045 demonstrate cooler temperatures, though hotter than a typical molecular cloud. Measured Doppler shifts for V1057 Cygni and W3 IRS5 demonstrate large blueshifts, while IRAS 19110+1045 demonstrates a small redshift. Analysis reveals a strong Pf-beta line in IRAS 19110+1045, indicating a high accretion rate of disk material onto the star. No Pf-beta line was observed in V1057 Cygni or W3 IRS5. All three sources are optically thick in 12CO at low energy levels, but V1057 Cygni tentatively appears to have the highest column density, followed by W3 IRS5, then IRAS 19110+1045. We tentatively conclude that the absorption spectra in V1057 Cygni and W3 IRS5 are from outflow components, as supported by their high blueshifts and temperatures. We furthermore suggest that the lack of blueshift in the IRAS+1045 absorption spectrum indicates that the spectrum is seen through the disk as it is heated by accretion.