Search for sub-mm, mm and radio continuum emission from extremely red objects

¹ Raman Research Institute, C.V. Raman Avenue, Sadashivanagar, Bangalore 560080, India
² Joint Astronomy Program, Department of Physics, Indian Institute of Science, Bangalore 560012, India
³ Osservatorio Astrofisico di Arcetri, Largo Fermi 5, 50125 Firenze, Italy
⁴ Sterrewacht Leiden, Sterrewacht, Postbus 9513, Leiden 2300 RA, The Netherlands
⁵ Max-Planck Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching bei Muenchen, Germany
⁶ Osservatorio Astronomico di Padova, vicolo dell' Osservatorio 5, 35122 Padova, Italy
⁷ Dip. Astronomia, Universita' di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy
⁸ Joint Astronomy Centre, 660 N. Aohoku Place, Hilo, HI 96720, USA
⁹ NRAO, PO Box 0, Socorro NM, 87801, USA
¹⁰ Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, L-413, PO Box 808, Livermore, CA 94550, USA

Corresponding author: N. R. Mohan, niruj@rri.res.in

Accepted: 5 December 2001

Abstract

We present the results of sub-mm, mm (850 μm, 450 μm and 1250 μm) and radio (1.4 and 4.8 GHz) continuum observations of a sample of 27 K-selected Extremely Red Objects, or EROs, (14 of which form a complete sample with and ) aimed at detecting dusty starbursts, deriving the fraction of UltraLuminous Infrared Galaxies (ULIGs) in ERO samples, and constraining their redshifts using the radio-FIR correlation. One ERO was tentatively detected at 1250 μm and two were detected at 1.4 GHz, one of which has a less secure identification as an ERO counterpart. Limits on their redshifts and their star forming properties are derived and discussed. We stacked the observations of the undetected objects at 850 μm, 1250 μm and 4.8 GHz in order to search for possible statistical emission from the ERO population as a whole, but no significant detections were derived either for the whole sample or as a function of the average NIR colours. These results strongly suggest that the dominant population of EROs with is not comprised of ULIGs like HR 10, but is probably made of radio-quiet ellipticals and weaker starburst galaxies with 10¹²  and few hundred  yr^-1.