Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21535008c&link_type=abstract
American Astronomical Society, AAS Meeting #215, #350.08; Bulletin of the American Astronomical Society, Vol. 42, p.533
Astronomy and Astrophysics
Astronomy
Scientific paper
The selection of submillimeter-bright, ultraluminous infrared galaxies (ULIRGs) at high redshift is more strongly biased towards colder dust temperatures (Tdust 35K) than local ULIRG selection. This bias potentially excludes a large fraction of high redshift ULIRGs with hotter dust temperatures (Tdust>40K) from current submillimeter galaxy (SMG) surveys and, as a result, their subsequent analyses. We have shown that z>1 submillimetre-faint radio galaxies (SFRGs) with rest-UV spectra consistent with starbursts are good representatives of the hot-dust ULIRG population. These galaxies share many properties with SMGs and local ULIRGs: high stellar masses, similar radio luminosities, and comparable AGN content. A sub-sample of the SFRG population has been detected at 70um, confirming that they represent z>1 ULIRGs with hotter dust temperatures (Tdust = 52+-10K) than SMGs of similar luminosities. The 70um detected SFRGs have significant implications for future observations from the Herschel Space Observatory and SCUBA2, which will routinely select high redshift ULIRGs with less selection bias. We can attribute the SFRGs' radio emission to star formation since high-resolution MERLIN radio maps show extended emission regions (with radii of 2-3kpc), which are unlikely to be generated by AGN activity. Both X-ray observations and mid-IR spectral analysis confirm that the population is not dominated by luminous AGN. Observations of SFRGs in CO molecular gas (from the IRAM Plateau de Bure) indicate that the population has similar star formation efficiencies to CO-observed SMGs yet SFRGs are about three times less luminous. SFRGs also exhibit narrower CO line widths than SMGs, hinting that their high star formation rates are less likely to be generated by major mergers. These hotter-dust galaxies may substantially increase the volume density of known ULIRGs at z 2, thus changing our view of galaxy evolution and the role of high-luminosity, dust-obscured systems.
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