Tracing Star Formation around QSOs with PAHs
Lawrence Bilton
The Open University
Jeronimo Bernard-Salas (The Open University), Stephen Serjeant (The Open University)
The feedback processes linking quasar activity to galaxy stellar mass growth are not well understood. If star formation is closely causally linked to black hole accretion we may expect star formation confined to nuclear regions rather than extended over several kpc scales. Since Polycyclic Aromatic Hydrocarbon emission features (PAH) are widely used as tracers of stellar formation, it is possible to use PAH features detected around QSOs to help resolve this question. We present PAH data from a sample of 63 QSOs procured from the Spitzer Space Telescope’s Infrared Spectrograph (IRS), employing the Spectroscopic Modelling Analysis and Reduction Tool’s (SMART) Advanced Optimal (AdOpt) extraction routines. A composite spectrum was also produced to help determine the average conditions and compositions of star forming regions. We find, from our high redshift (z>1) sample of QSOs, a marginally significant extended star formation on average of 12 kpc scales. At low redshift the median extension after deconvolving the instrumental point spread function is 1.9 kpc. We also present a tentative detection of water vapour emission from the gravitationally lensed Einstein Cross quasar, QSO J2237+0305, suggesting a strong molecular outflow possibly driven by the active nucleus.