Prof. Dimitra Rigopoulou

Abstract:

A Spitzer Space Telescope survey in the NOAO Deep Wide Field in Bootes provides a complete, 8 μm-selected sample of galaxies to a limiting (Vega) magnitude of 13.5. In the 6.88 deg2 field sampled, 79% of the 4867 galaxies have spectroscopic redshifts, allowing an accurate determination of the local (z < 0.3) galaxy luminosity function. Stellar and dust emission can be separated on the basis of observed galaxy colors. Dust emission (mostly PAH) accounts for 80% of the 8 μm luminosity, stellar photospheres account for 19%, and AGN emission accounts for roughly 1%. A subsample of the 8 μm-selected galaxies have blue, early-type colors, but even most of these have significant PAH emission. The luminosity functions for the total 8 μm luminosity and for the dust emission alone are both well fit by Schechter functions. For the 8 μm luminosity function, the characteristic luminosity is νLν*;(8.0 μm) = 1.8 × 1010 L ⊙, while for the dust emission alone it is 1.6 × 10 10 L⊙. The average 8 μm luminosity density at z < 0.3 is 3.1 × 107 L⊙ Mpc-3, and the average luminosity density from dust alone is 2.5 × 107 L⊙ Mpc-3. This luminosity arises predominantly from galaxies with 8 μm luminosities (νLν) between 2 × 109 and 2 × 1010 L⊙, i.e., normal galaxies, not luminous or ultraluminous infrared galaxies (LIRGs/ULIRGs). © 2007. The American Astronomical Society. All rights reserved.

Abstract:

We study 87 extremely red objects (EROs), selected both to have color redder than R - [3.6] = 4.0 and to have confirmed spectroscopic redshifts. Together, these two constraints result in this sample populating a fairly narrow redshift range at 0.76 < z < 1.42. The key new ingredient included here is deep Spitzer Space Telescope Infrared Array Camera (IRAC) data. Based on [3.6] - [8.0] color, we demonstrate that it is possible to classify EROs as early-type galaxies, dusty starburst galaxies, or active galactic nuclei (AGNs; power-law types). We present ultraviolet-to-mid-infrared spectral energy distributions (SEDs) and Advanced Camera for Surveys (ACS) images, both of which support our simple IRAC color classification. © 2007. The American Astronomical Society. All rights reserved.