The radio properties of optically obscured Spitzer sources

Details The radio properties of optically obscured Spitzer sources The radio properties of optically obscured Spitzer sources

2007-10-11

arxiv.org/abs/0710.2343v1

Astronomy and Astrophysics

Astrophysics

18 pages, 16 figures, to appear in MNRAS

Scientific paper

10.1111/j.1365-2966.2007.12576.x

This paper analyses the radio properties of a subsample of optically obscured (R>25.5) galaxies observed at 24um by the Spitzer Space Telescope within the First Look Survey. 96 F[24um]>0.35 mJy objects out of 510 are found to have a radio counterpart at 1.4 GHz, 610 MHz or at both frequencies respectively down to ~40uJy and ~200uJy. IRAC photometry sets the majority of them in the redshift interval z [1-3] and allows for a broad distinction between AGN-dominated galaxies (~47% of the radio-identified sample) and systems powered by intense star-formation (~13%), the remaining objects being impossible to classify. The percentage of radio identifications is a strong function of 24um flux. The radio number counts at both radio frequencies suggest that the physical process(es) responsible for radio activity in these objects have a common origin regardless of whether the source shows mid-IR emission compatible with being an obscured AGN or a star-forming galaxy. We also find that both candidate AGN and star-forming systems follow (although with a large scatter) the relationship between 1.4 GHz and 24um fluxes reported by Appleton et al. (2004) which identifies sources undergoing intense star formation activity. On the other hand, the inferred radio spectral indices alpha indicate that a large fraction of objects in our sample (~60% of all galaxies with estimated alpha) may belong to the population of Ultra Steep Spectrum (USS) Sources, typically 'frustrated' radio-loud AGN. We interpret our findings as a strong indication for concurrent AGN and star-forming activity, whereby the 1.4 GHz flux is of thermal origin, while that at 610 GHz mainly stems from the nuclear source.

Affiliated with

Also associated with

No associations

Rating

The radio properties of optically obscured Spitzer sources does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The radio properties of optically obscured Spitzer sources, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The radio properties of optically obscured Spitzer sources will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-402492