Repository logo
 

Karl G. Jansky very large array observations of cold dust and molecular gas in starbursting quasar host galaxies at z ∼ 4.5


Type

Article

Change log

Authors

Wagg, J 
Carilli, CL 
Aravena, M 
Cox, P 
Lentati, L 

Abstract

We present Karl G. Jansky Very Large Array (VLA) observations of 44 GHz continuum and CO J=2-1 line emission in BR1202-0725 at z=4.7 (a starburst galaxy and quasar pair) and BRI1335-0417 at z=4.4 (also hosting a quasar). With the full 8 GHz bandwidth capabilities of the upgraded VLA, we study the (rest-frame) 250 GHz thermal dust continuum emission for the first time along with the cold molecular gas traced by the Low-J CO line emission. The measured CO J=2-1 line luminosities of BR1202-0725 are L'(CO) = (8.7+/-0.8)x10^10 K km/s pc^2 and L'(CO) = (6.0+/-0.5)x10^10 K km/s pc^2 for the submm galaxy (SMG) and quasar, which are equal to previous measurements of the CO J=5-4 line luminosities implying thermalized line emission and we estimate a combined cold molecular gas mass of ~9x10^10 Msun. In BRI1335-0417 we measure L'(CO) = (7.3+/-0.6)x10^10 K km/s pc^2. We detect continuum emission in the SMG BR1202-0725 North (S(44GHz) = 51+/-6 microJy), while the quasar is detected with S(44GHz) = 24+/-6 microJy and in BRI1335-0417 we measure S(44GHz) = 40+/-7 microJy. Combining our continuum observations with previous data at (rest-frame) far-infrared and cm-wavelengths, we fit three component models in order to estimate the star-formation rates. This spectral energy distribution fitting suggests that the dominant contribution to the observed 44~GHz continuum is thermal dust emission, while either thermal free-free or synchrotron emission contributes less than 30%.

Description

Keywords

cosmology: observations, early universe, galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: starburst

Journal Title

Astrophysical Journal

Conference Name

Journal ISSN

0004-637X
1538-4357

Volume Title

783

Publisher

American Astronomical Society
Sponsorship
Science and Technology Facilities Council (ST/J00152X/1)
Science and Technology Facilities Council (ST/K003119/1)
Science and Technology Facilities Council (ST/L001381/1)
This work was co-funded under the Marie Curie Actions of the European Commission (FP7-COFUND). We thank all those involved in the VLA project for making these observations possible (project code 13A-012).