Spectral Energy Distributions of Low-luminosity Radio Galaxies at z ~1-3: A High-z View of the Host/AGN Connection

Sparks, William B.; Deustua, Susana; Rodríguez-Zaurín, J.; Capetti, Alessandro; Chiaberge, Marco; Baldi, Ranieri D.
Bibliographical reference

The Astrophysical Journal, Volume 762, Issue 1, article id. 30, 18 pp. (2013).

Advertised on:
1
2013
Number of authors
6
IAC number of authors
1
Citations
14
Refereed citations
11
Description
We study the spectral energy distributions, SEDs (from FUV to MIR bands), of the first sizeable sample of 34 low-luminosity radio galaxies at high redshifts, selected in the COSMOS field. To model the SEDs, we use two different template-fitting techniques: (1) the Hyperz code that only considers single stellar templates and (2) our own developed technique 2SPD that also includes the contribution from a young stellar population and dust emission. The resulting photometric redshifts range from z ~ 0.7 to 3 and are in substantial agreement with measurements from earlier work, but significantly more accurate. The SED of most objects is consistent with a dominant contribution from an old stellar population with an age ~1-3 × 109 years. The inferred total stellar mass range is ~1010-1012 M ☉. Dust emission is needed to account for the 24 μm emission in 15 objects. Estimates of the dust luminosity yield values in the range L dust ~ 1043.5-1045.5 erg s–1. The global dust temperature, crudely estimated for the sources with an MIR excess, is ~300-850 K. A UV excess is often observed with a luminosity in the range ~1042-1044 erg s–1 at 2000 Å rest frame. Our results show that the hosts of these high-z low-luminosity radio sources are old massive galaxies, similar to the local FR Is. However, the UV and MIR excesses indicate the possible significant contribution from star formation and/or nuclear activity in such bands, not seen in low-z FR Is. Our sources display a wide variety of properties: from possible quasars at the highest luminosities to low-luminosity old galaxies.
Related projects
Project Image
Starbursts in Galaxies GEFE
Starsbursts play a key role in the cosmic evolution of galaxies, and thus in the star formation (SF) history of the universe, the production of metals, and the feedback coupling galaxies with the cosmic web. Extreme SF conditions prevail early on during the formation of the first stars and galaxies, therefore, the starburst phenomenon constitutes a
Casiana
Muñoz Tuñón