• Yan, Lin
• Draine, Bruce
• Choi, Phil
• Frayer, Dave
• Armus, Lee
• Heckman, Tim
• Sajina, Anna
• Teplitz, Harry
• Fadda, Dario

Abstract

With its exquisite sensitivity, the 24um band has yielded the most valuable data on obscured star formation at cosmological distances, and the IRS has demonstrated its diagnostic power by detecting Aromatic Features out to z ~ 2 (Yan et al 2005). Understanding the 24um population can only be achieved with systematic spectroscopy at the mid-IR, coupled with secure redshifts and diagnostics from optical spectra. We propose IRS spectroscopy at 7-38um of an unbiased sample of 159 sources from the First Look Survey (FLS) for which optical spectra are or will be available. These targets have 24um flux density greater than 0.9mJy, and are selected to be representive of infrared galaxies over a wide redshift range. The proposed spectra will provide an essential library for interpreting enormous amount of mid-IR imaging data from Spitzer, then WISE and JWST; we waive the proprietary period, and will release the reduced 1D specrta to the public archive. This unbiased datset will allow us to determine how the energy output from PAH emission in dusty starbursts changes as a function of luminosity and redshift. We will also estimate the relative frequencies of AGN, starburst and composite systems, thus deriving the true obscured star formation density. Utilizing a rich variety of mid-IR spectral diagnostics, including continuum slopes, line and PAH ratios, the strength of PAH emission and silicate absorption, we will study in detail the physical conditions of the ISM in galaxies with intense star formation and AGN activities in early cosmological epochs, and understand the dust emission processes which build both galaxies and blackholes....

Topics

• density
• strength
• composite
• spectroscopy