On the Selection of High-z Quasars Using LOFAR Observations

Frontiers in Astronomy and Space Sciences

Rö¹  Retana-Montenegro, Edwin¹ 

[1] Leiden Observatory, Leiden University, Netherlands

关键词: quasars;    active galactic nuclei;    surveys;    Radio;    extragalactic astronomy;    Photometry;    spectroscopy;   

DOI  :  10.3389/fspas.2018.00005

学科分类：空间科学

来源: Frontiers

【 摘 要 】

We present a method to identify candidate quasars which combines optical/infrared color selection with radio detections from the Low Frequency ARray (LOFAR) at 150MHz. We apply this {method} in a region of 9 square degrees located in the Bo\"{o}tes field, with a wealth of multi-wavelength data. Our LOFAR imaging in the central region reaches a rms noise of $\sim50\mu$Jy with a resolution of $5''$. This is so deep that we also routinely, `radio-quiet' quasars. We use quasar spectroscopy from the literature to calculate the completeness and efficiency of our selection method. We conduct our analysis in two redshift intervals, $1-1.0$ sources can be detected in the WSRT-Bo\"{o}tes map, we find that the spectral index distribution of the 21 quasars in the resulting sample is steeper than the general LOFAR-WSRT spectral index distribution with a median of $\alpha=-0.80\pm0.06$. As the upcoming LOFAR wide area surveys are much deeper than the traditional 1.4GHz surveys like NVSS and FIRST, this indicates that LOFAR in combination with optical and infrared will be an excellent fishing ground to obtain large samples of quasars.

【 授权许可】

CC BY