First Results from the ISO-IRAS Faint Galaxy Survey

September 1998 • 1998ApJ...504...64L

Authors • Levine, Deborah A. • Lonsdale, Carol J. • Hurt, Robert L. • Smith, Harding E. • Helou, George • Beichman, Charles • Cesarsky, Catherine • Elbaz, David • Klaas, Ulrich • Laureijs, Rene • Lemke, Detrich • Lord, Steven • McMahon, Richard • Moshir, Mehrdad • Neugebauer, Gerry • Soifer, B. T. • Van Buren, Dave • Wehrle, Ann • Wolstencroft, Ray

Abstract • We present the first results from the ISO-IRAS Faint Galaxy Survey (IIFGS), a program designed to obtain ISO observations of the most distant and luminous galaxies in the IRAS Faint Source Survey by filling short gaps in the ISO observing schedule with pairs of 12 μm ISOCAM and 90 μm ISOPHOT observations. As of 1997 October, over 500 sources have been observed, with an ISOCAM detection rate over 80%, covering over 1.25 deg² of sky to an 11.5 μm point-source completeness limit of approximately 1.0 mJy (corresponding to a ~10 σ detection sensitivity). Observations are presented for nine sources detected by ISOPHOT and ISOCAM early in the survey for which we have ground-based G- and I-band images and optical spectroscopy. The ground-based data confirm that the IIFGS strategy efficiently detects moderate-redshift (z = 0.11-0.38 for this small sample) strong emission line galaxies with L_{60 μm} >~ 10¹¹ L_⊙ one of our sample has L_{60 μm} > 10¹² L_⊙ (H₀ = 75 km s^-1 Mpc^-1, Ω = 1). The infrared-optical spectral energy distributions are comparable to those of nearby luminous infrared galaxies, which span the range from pure starburst (e.g., Arp 220) to infrared QSO (Mrk 231). Two of the systems show signs of strong interaction, and four show active galactic nucleus (AGN)-like excitation; one of the AGNs, F15390+6038, which shows a high excitation Seyfert 2 spectrum, has an unusually warm far- to mid-infrared color and may be an obscured QSO. The IIFGS sample is one of the largest and deepest samples of infrared-luminous galaxies available, promising to be a rich sample for studying infrared-luminous galaxies up to z ~ 1 and for understanding the evolution of infrared galaxies and the star formation rate in the universe.

ISO is an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

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George Helou

IPAC Executive Director